ALBERT

Notes: Abstract The impact of the grape leafhopper,Empoasca vitis, on leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves of the grapevines,Vitis vinifera L., was studied. Gas exchange was measured on the discolored (red) and the green parts of infested main leaves and on leaves from uninfested vines. Photosynthesis and mesophyll conductance were severely reduced on main leaves showing leafhopper feeding symptoms. The stomatal conductance of the red leaf section of infested main leaves was lower than on undamaged control leaves. Additionally, the red leaf section of infested main leaves showed lower transpiration rates when compared to the green parts of the same leaves and to undamaged control leaves. Gas exchange processes of lateral leaves were not affected by leafhopper feeding. Leafhopperload on main leaves was correlated to visual damage symptoms. At 71.8 leafhopper-days per leaf up to 40% of the main leaf area of the infested plants was discolored from the borders towards the center. Lateral leaves showed no feeding symptoms. Shoot diameter, pruning weight and carbohydrate reserves in the wood were not affected by leafhoppers. Lateral leaf area growth was significantly stimulated on plants infested by leafhoppers. No decrease in yield and fruit quality with leafhopper-loads up to 71.8 leafhopper-days per leaf were observed.

Notes: Abstract This study concerns the inhibitory effects of acid pH and nickel on growth, nutrient (NO3 - and NH4 +) uptake, carbon fixation, O2 evolution, electron transport chain and enzyme (nitrate reductase and ATPase) activities of acid tolerant and wild-type strains of Chlorella vulgaris. Though a general reduction in all these variables was noticed with decreasing pH, the tolerant strain was found to be metabolically more active than the wild-type. A reduced cation (NH4 +, Na+, K+ and Ca2+) uptake, coupled with a facilitated influx of anions (NH4 +, PO4 3- and HCO3 -), suggested the development of a positive membrane potential in acid tolerant Chlorella. Nevertheless, a tremendous increase in ATPase activity at decreasing pH revealed the involvement of superactive ATPase in exporting H+ ions and keeping the internal pH neutral. A difference in Na+ and K+ efflux of the two strains at decreasing pH suggests there is a difference in membrane permeability. The low toxicity of Ni in the acid tolerant strain may be due to the low Ni uptake brought about by a change in membrane potential as well as in permeability. Hence, the development of superactive ATPase and a change in both membrane potential and permeability not only offers protection against acidity, but also co-tolerance to metals.

Notes: Abstract This tutorial was designed for nonbiologists requiring an introduction to the nature and general timescales of phytoplankton responses to physical forcing in aquatic environments. As such, an effort was made to highlight biological markers which might assist in identifying, measuring and/or validating physical processes controlling the variability in the distribution, abundance, composition and activity of phytoplankton communities. Given the recent advances in environmental optics and remote sensing capabilities, a special emphasis was placed on the nature and utility of phytoplankton optical properties in current bio-optical modelling efforts to predict temporal and spatial variability in phytoplankton productivity and growth.

Notes: Summary Six-year-old Norway spruce trees of the same clone were exposed for 10 weeks at the edge of a highway and compared with controls kept in an unpolluted area within 15 km of the first site. Significant differences could be observed with respect to growth, photosynthesis and transpiration rate, all of which were reduced after exposure at the highway.

Notes: Abstract Toxicological responses of the filamentous N2-fixing cyanobacteriumNostoc calcicola Bréb. towards Hg2+ were studied to enumerate the decisive lethal events. In low-dose, long-term experiments (0.05–0.25 μm Hg2+, 10 days), photoautotrophic growth was severely inhibited with concurrent loss of photosynthetic pigments (phycocyanin〉chlorophyll α〉carotenoids) and nucleic acids. The termination of growth after a day 4 exposure to 0.25 μm Hg2+ has been attributed to the complete inhibition ofin vivo photosynthetic activity in the cyanobacterium (O2 evolution〉14CO2 incorporation). The elevated Hg2+ concentrations irreversibly damaged the cell membrance as observed under light microscopy, and as indicated by the leakage of intracellular electrolytes and phycocyanin. In high-dose, short-term experiments (0.5–20.0 μm Hg2+, up to 6 h), thein vivo activities of selected enzymes (glutamine synthetase 〉 nitrate reductase 〉 nitrogenase) were less inhibited by Hg2+ than the uptake of nutrient ions (NH 4 + 〉NO 3 − 〉PO 4 3− ).

Notes: Abstract Stomatal conductance, mesophyll conductance, transpiration and photosynthesis varied considerably by within-plant locations on celery (Apium graveolens L.), but specific opposite leaves proved equivalent. Using such comparable leaves, feeding damage by Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) larvae or adults was found to reduce significantly the capacity of celery for photosynthetic activity. In field trials where populations of L. trifolii were manipulated with pesticides, numbers of leaves, plant height, and numbers of petioles per plant were significantly greater in treatments with low leafminer densities. In treatments where L. trifolii was encouraged, harvest was delayed by up to 3 weeks. Related laboratory studies indicated that the pesticides used in the field trial neither promoted nor slowed celery growth. None of the physiological parameters measured at either 1.5 h or 7 days post-treatment was significantly affected.

Notes: Abstract 1. The world consumption of energy is roughly 250 EJ. It increases with the level of technology and gross national product of a country. More than 83% of world energy consumption is used by the industrialized countries with one third of the world population; not quite 17% is used by the developing countries with two thirds of the world population. The world's resources of fossil fuels are estimated at 364,560 EJ; about 5–13% of this, and 31% in the case of natural gas, are considered reserves that are economically recoverable and utilizable with current technologies. 2. Agriculture's share of the economy's energy consumption in the Federal Republic of Germany is about 3.4%. It was five times higher per hectare of agricultural land in 1975 than in 1880, but the productivity of the energy was only half as high because of the enormous increase in productivity per unit of labor and area. In absolute terms, however, energy production per unit area increased tremendously, with gross agricultural production two and a half times its earlier size. 3. As a producer of plant material, agriculture qualifies as an energy producer, while as a producer of livestock it also is an energy consumer. In fact, through plant production agriculture becomes the only branch of our economic system that produces more energy than it consumes as fossil energy. Agriculture uses about 40% of its energy requirement for fuel, about 20% for machinery repair and replacement, 30% for mineral fertilizers, about 10% for electricity, and 1–2% for chemical crop protection. Forestry can be evaluated as particularly favorable from the energy viewpoint, while hothouse crops are very unfavorable. Agricultural chemicals support the energy output of green plants; agriculture as a whole is on balance energetically. 4. Solar energy and photosynthesis are the primary sources of energy to our plant. About 3 million EJ solar energy are radiated to the earth annually; 3000 EJ are fixed photosynthetically (2 ⋅ 1011 tons vegetable matter); the food requirement of 4 billion people is 15EJ. Another item of interest on the periphery of the energy balance is the enrichment of our atmosphere with oxygen, which has been accomplished for millions of years solely by the photosynthesis of green plants. 5. Through their additional yield effect, mineral fertilizers increase the energy output of plants more strongly than just the equivalent of the energy input. They cause the plant to produce more foliage and thereby promote more intensive assimilation, which means that mineral fertilizers enable the plant to utilize free solar energy better. A calculation of the energy involved in long-term field trials in cereals disclosed energy input: energy output ratios of 1:5.8 and 1:6.1. 6. Chemical crop protection has a similar effect since it protects against loss of plantproduced energy. Based on an average energy expenditure of 263 MJ ha−1 per kg ha−1 ‘typical’ active ingredient for a crop protection product, additional yields of only 4–4.5% — or considerably less in the case of high-energy crops such as cereals or sugar beets — would be sufficient to cover the energy expenditure; as a rule, however, the productivity of the chemical crop protectants is higher. The biological potential of our crops to utilize solar energy also has been improved considerably compared to earlier times — with cereals, for example, from 0.25% per unit area during the Middle Ages to 1.5% today; theoretically 4% is possible. The thesis that agrochemical aids in agriculture and horticulture are a waste of energy is unjustified. 7. Biomass also creates energy. Experts estimate the utilizable annual production of biomass in the Federal Republic of Germany to be 30 million tons mineral coal units (1 coal unit = 29.3 MJ), whereby undersized and refuse wood, straw and biogas are of special significance. Especially “fuel forests' of, for example, willows, poplars and alders could produce the equivalent of 486,000 MJ by way of 30 tha−1 biomass, contributing sizably to the fuel supply of the nation; at the moment, the conventional form of forestry produces only 30,240 MJ. It is considered feasible in Sweden to supply the entire energy requirement of the country from 93,000 km2 of ‘fuel forest’, and it must be remembered that mineral fertilization could be used to increase the productivity of land used for this purpose relatively quickly if the need were to become acute. The extraction of alcohol from crops offers other interesting aspects; the currently highest yield fuel crops (sugar beet, sugarcane and cassava) produce between 4,900 and 10,700 l ha−1 alcohol. 8. The energy problem of modern economies will not find its complete answer in the green plant. Prudent and well contemplated use of the green plant, however, may eventually do much to take the edge off today's energy dilemma.

Notes: Abstract A one-year study of phytoplankton, primary production and related physical and chemical factors was made in a Swiss basin of Lake Lugano (Lago di Lugano). The chlorophylls and 12 carotenoids were analyzed with a TLC technique. The carotenoid monitoring was considered to be particularly interesting, because the role of these pigments in freshwater algae is still very poorly documented by field studies. The dependence of photosynthesis on several factors was statistically evaluated. Evidence was found of light-adaptation phenomena. The variations of photosynthetic activity and efficiency largely depended on the light regime in the few days before the field observations and on the cellular content of chlorophylls and single carotenoids, whose concentrations in their turn were closely linked with light, temperature, average cell size, and with the actual species assemblage.

Notes: Summary The growth and photosynethetic responses to atmospheric CO2 enrichment of 4 species of C4 grasses grown at two levels of irradiance were studied. We sought to determine whether CO2 enrichment would yield proportionally greater growth enhancement in the C4 grasses when they were grown at low irradiance than when grown at high irradiance. The species studied were Echinochloa crusgalli, Digitaria sanguinalis, Eleusine indica, and Setaria faberi. Plants were grown in controlled environment chambers at 350, 675 and 1,000 μl 1-1 CO2 and 1,000 or 150 μmol m-2 s-1 photosynthetic photon flux density (PPFD). An increase in CO2 concentration and PPFD significantly affected net photosynthesis and total biomass production of all plants. Plants grown at low PPFD had significantly lower rates of photosynthesis, produced less biomass, and had reduced responses to increases in CO2. Plants grown in CO2-enriched atmosphere had lower photosynthetic capacity relative to the low CO2 grown plants when exposed to lower CO2 concentration at the time of measurement, but had greater rate of photosynthesis when exposed to increasing PPFD. The light level under which the plants were growing did not influence the CO2 compensation point for photosynthesis.

Notes: Abstract The phase transitional behaviour of bilayers of the phospholipid l-α-ditridecanoylphos-phatidylcholine is studied as a function of protein content for the reaction center (RC) and an antenna protein (LHCP) of the bacterial photosynthetic apparatus. As membrane and protein are structurally well characterized the experimental results can be quantitatively compared with those of calculations based upon elastic models within the Landaude Gennes-theory. Agreement between theory and experiment demonstrates that dominant elastic forces result from a mismatch of hydrophobic regions of membrane and protein. The data also indicate that RC are present in a monomeric form and LHCP in a highly aggregated form. In addition, the latter protein responds to changes in the lipid environment.

Notes: Abstract The phosphate metabolism of Platymonas subcordiformis was investigated by 31P-NMR spectroscopy with special attention on the effect of external pH. Glycolyzing cells and cells energized by respiration or photosynthesis gave spectra dependent upon their metabolic state. The transition from deenergized to energized states is accompanied by a shift of cytoplasmic pH from 7.1–7.4, an increase of ATP level and-in well energized cells-the appearance of a new signal tentatively assigned to phosphoarginine. The spectra remain stable over a wide range of external pH. Cytoplasmic pH is well regulated in respiring cells for external pH in the range 5.3–12.3. The typical 0.4 units difference of internal pH in energized as compared to deenergized cells is not affected by external pH in the range 6–12. The intensity of a signal attributed to PEP is markedly increased at high external pH. pH regulation is less efficient below external pH of 6 in deenergized cells. Below pH 3.8 oxidative phosphorylation ceases. Upon raising cytoplasmic pH to 7.4 in deenergized cells polyphosphate chains start to disintegrate.

Notes: Summary In a plastid genome (plastome) mutation of Oenothera hookeri, at least two of the plastome-coded polypeptides (the β and ε subunits) of the chloroplast ATP synthase are directly affected. As in other plastid chromosomes, the genes for the β and ε subunits are located next to each other on the Oenothera ptDNA molecule and are cotranscribed. Immunoanalysis and peptide mapping of in vivo products suggests that a fusion of the two genes may have occurred in the plastome mutant. In contrast to the in vivo data, in vitro translation of the RNA using a heterologous system results in polypeptides which cannot be distinguished from those of wild-type. In addition, neither the mRNA sizes nor plastid DNA restriction fragment patterns differ from wild-type. To reconcile the paradox of these results, it is suggested that either a defect in a translational signal or some other post-transcriptional event is responsible for the mutant phenotype.

Notes: Abstract The effect of SO2 on the photosynthesis ofClethra barbinervis collected from a smoke-polluted area near the Ashio copper smelter in Tochigi Prefecture was compared withC. barbinervis collected from a nonpolluted district in Tsukuba, Ibaraki Prefecture andQuercus mongolica var.grosseserrata grown in a nonpolluted field in Nagano Prefecture. The plants were exposed to 0.5–1.5 p.p.m. SO2 for 90 min (short-term) and to 0.3 p.p.m. SO2 for 31–39 days (long-term). TheClethra plants from both sites had a lower intrinsic stomatal conductance and photosynthetic rate thanQuercus plants. Short-and long-term fumigation caused stomatal closure inQuercus plants, but had little effect on the stomatal conductance ofClethra plants. Under short-term fumigation, nonstomatal photosynthetic inhibition per unit of absorbed SO2 was smallest inClethra plants from Ashio. Long-term fumigation caused photosynthetic decline and visible foliar injury toQuercus plants, but had no effect onClethra plants from Ashio. Consequently,Clethra plants from Ashio had a higher photosynthetic rate thanQuercus plants after long-term fumigation. These results suggest thatC. barbinervis populations in the smoke-polluted area of Ashio had evolved high SO2 resistance connected with SO2 detoxification ability in mesophyll cells.

Notes: Cherry (Prunus avium L.) saplings were grown under natural sunlight (controls) or moderate shading (up to 30%, depending on the incident light intensity and the hour of the day). Reduced light intensity increased the dry mass of each of the plant components studied. Consequently, the total dry mass of shaded plants was significantly greater than that of controls at the end of the growing season. However, the diurnal trend in the level of photosynthesis (per unit of leaf area) of shaded plants was similar to the controls in August, but lower in September. As the growing season proceeded, reduced photosynthetic rates, thinner mesophyll and larger specific leaf area in the shaded plants indicated that leaf development had adapted to shaded conditions throughout the growing season. It is suggested that increased growth of shaded plants was caused by a higher initial relative growth rate and a greater whole-plant photosynthesis. Shading consistently reduced transpiration over the season, therefore improving water use efficiency of shaded leaves. Our results suggest that a moderate reduction in light intensity can be a useful method for improving growth and saving water in hot and dry environments.

Notes: Abstract Light saturated net photosynthesis was measured in bracts and leaves ofCarpinus laxiflora, the major species in secondary forests in cool and intermediate temperate zones in Japan. The maximum net photosynthesis of leaves and bracts was essentially constant from May to early August and decreased gradually thereafter. For bracts, it was 3.2 μmol m−2s−1, approximately half that for the leaves. The photosynthesis of bracts would thus appear to contribute significantly to seed maturity. The estimated production of bract based on the photosynthesis would make seeds (3 mg dry weight) mature for 37 days, assuming all photosynthate of the bracts to have been distributed in the seeds only. This was quite consistent with the growth curve for the seeds. A mast year phenomenon is discussed in relation to bract photosynthesis and leaf number.

Notes: Abstract Aucuba japonica varieties are common evergreen understory shrubs in Japan.Aucuba japonica var.borealis is distributed on the Sea of Japan side of Honshu and Hokkaido where heavy snow cover lasts for more than 3 months in winter.Aucuba japonica var.japonica is distributed in areas with shallow or no snow on the Pacific Ocean side of Honshu and Shikoku. The ecophysiological characteristics of var.borealis were compared with those of var.japonica to examine the effects of heavy and long-term snow cover on the life cycle of var.borealis. Shoots of both varieties were shaded in crushed ice for 110 days, but their photosynthetic activities, chlorophyll contents and the chlorophylla/b ratio was not affected. The leaves of var.borealis were no less frost tolerant than those of var.japonica. In spite of the difference in environmental factors, both varieties had similar characteristics in seasonal changes of photosynthesis, respiration and chlorophylla/b ratio. These results suggest that var.japonica could survive in areas with heavy snow where it does not normally occur. Leaf net production (LNP) was estimated based on the microclimatic data and seasonal photosynthetic and respiration rates. The difference in the annual LNP between the two varieties was equivalent to the difference in the LNP during the snow season. One of the major effects of snow cover is to interrupt and reduce the production period of var.borealis.

Notes: Abstract The impacts of juglone on plant growth and several other physiological functions were evaluated in this study. Juglone inhibitedLemna minor growth, chlorophyll content, and net photosynthesis at treatments between 10 and 40μM. Soybean leaf disks vacuum infiltrated with as little as 10μM juglone had reduced photosynthesis. Oxygen evolution by chloroplasts isolated fromPisum sativum was inhibited by juglone with an I50 of 2μM. Micromolar treatments of juglone stimulated oxygen uptake in mitochondria isolated fromGlycine max. These data suggest perturbations of chloroplast and mitochondrial functions may contribute to plant growth reductions observed in juglone-mediated allelopathy.

Notes: Abstract A second locus (Lhb1B) encoding Photosystem II Type I chlorophyll a/b-binding (CAB) polypeptides was identified in Arabidopsis thaliana. This locus carries two genes in an inverted orientation. The predicted sequences of the polypeptides encoded by these two genes show substantial divergence in their amino termini relative to each other and to the proteins encoded by the three Lhb1 CAB genes previously characterized [10], but little divergence within the predicted primary structure of the mature protein. DNA probes derived from seven additional types of tomato CAB genes, encoding chlorophyll a/b-binding polypeptides of several antenna systems of the photosynthetic apparatus, were tested against A. thaliana. Each of these hybridized in Southern blots to unique DNA fragment(s), demonstrating the existence of each of these different types of CAB genes in the genome of A. thaliana. The number of genes encoding each CAB type in A. thaliana was estimated to be similar to that of tomato.

Notes: Abstract The activity and location of carbonic anhydrase has been modified by transformation of tobacco with antisense and over-expression constructs. Antisense expression resulted in the inhibition of up to 99% of carbonic anhydrase activity but had no significant impact on net CO2 assimilation. Stomatal conductance and susceptibility to water stress appeared to increase in response to the decline in carbonic anhydrase activity. An over-expression construct designed to increase cytosolic carbonic anhydrase abundance resulted in a significant increase in net activity, a small increase in stomatal conductance but little impact on CO2 assimilation. Chloroplastic carbonic anhydrase activity was enhanced by the expression of an additional construct which targeted the polypeptide to the organelle. The increase in chloroplastic carbonic anhydrase appeared to be accompanied by a concomitant increase in Rubisco activity.

Notes: Abstract The genes encoding the photosynthetic cytochrome b 6 (petB) and subunit 4 (petD) have been cloned and sequenced from the unicellular, photoheterotrophic, transformable cyanobacterium Synechococcus sp. PCC 7002, formerly designated Agmenellum quadruplicatum. The gene arrangement was found to be similar to that reported in the cyanobacterium Nostoc PCC 7906. The DNA and derived protein sequences were compared to chloroplast and the other cyanobacterial sequences. By pulsed-field electrophoresis, the petBD operon and the petCA operon, encoding the Rieske iron-sulfur protein and cytochrome f, were found to be located on separate, unlinked,Not I-digested DNA fragments. ThepetBD operon was found on the third largest Not I fragment (NC-325) while the petCA operon was found on the second largest Not I fragment (NB-370). These results suggest the two operons are not in proximity. The 1.35 kb transcript was shown to be light-regulated. Transcripts from cells grown under constant illumination showed a decrease in petB transcript levels to undetectable levels within 2 h after the cells were placed in the dark. Upon reillumination, transcript levels rose to three-fold over that seen initially under constant illumination.

Notes: Abstract Detailed molecular mechanisms of electron transfer-driven translocation of ions and of the generation of electric fields across biological membranes are beginning to emerge. The ideas inherent in the early formulations of the chemiosmotic hypothesis have provided the framework for this understanding and have also been seminal in promoting many of the experimental approaches which have been successfully used. This article is an attempt to review present understanding of the structures and mechanisms of several osmoenzymes of central importance and to identify and define the underlying features which might be of general relevance to the study of chemiosmotic devices.

Notes: Abstract We first describe the history and methods of membrane protein crystallization, and show how the structure of the photosynthetic reaction centre from the purple bacteriumRhodopseudomonas viridis was solved. The structure of this membrane protein complex is correlated with its function as a light-driven electron pump across the photosynthetic membrane. Finally we draw conclusions on the structure of the photosystem II reaction centre from plants and discuss the aspects of membrane protein structure.

Notes: Abstract We report here the isolation and nucleotide sequence of a cDNA clone encoding a phtosystem I polypeptide that is recognized by a polyclonal antibody prepared against subunit II of the photosystem I reaction center. The transit peptide processing site was determined to occur after Met50 by N terminal sequencing. The decuced sequence of this protein predicts that the polypeptide has a net positive charge (pI=9.6) and no membrane spanning regions are evident from the hydropathy plot. Based on these considerations and the fact that subunit II is solubilized by alkali treatment of thylakoids, we concluded that subunit II is an extrinsic membrane protein. The absence of hydrophobic regions characteristic of thylakoid transfer domains furthermore implies that subunit II is localized on the stromal side of the membrane.

Notes: Abstract A mutant strain of the cyanobacterium Synechocystis sp. PCC (Pasteur Culture Collection) 6803 has been developed in which psbB, the gene coding for the chlorophyl a-binding protein CP47 in Photosystem II (PSII), has been deleted. This deletion mutant can be used for the reintroduction of modified psbB into the cyanobacterium. To study the role of a large hydrophilic region in CP47, presumably located on the lumenal side of the thylakoid membrane between the fifth and sixth membrane-spanning regions, specific deletions have been introduced in psbB coding for regions within this domain. One psbB mutation leads to deletion of Gly-351 to Thr-365 in CP47, another psbB mutation was targeted towards deletion of Arg-384 to Val-392 in this protein. The deletion from Gly-351 to Thr-365 results in a loss of PSII activity and of photoautotrophic growth of the mutant, but the deletion between Arg-384 and Val-392 retains PSII activity and the ability to grow photoautotrophically. The mutant strain with the deletion from Gly-351 to Thr-365 does not assemble a stable PSII reaction center complex in its thylakoid membranes, and exhibits diminished levels of CP47 and of the reaction center proteins D1 and D2. In contrast to the Arg-384 to Val-392 portion of this domain, the region between Gly-351 and Thr-365 appears essential for the normal structure and function of photosystem II.

Notes: Abstract We studied assembly of the PsaE subunit of photosystem I into photosynthetic membranes of cyanobacterial mutant strains that lack specific photosystem I subunits. Radiolabeled PsaE was incubated with photosynthetic membranes, and their binding and assembly were assayed by resistance to removal by chaotropic agents and proteolytic digestion. PsaE incorporated into the wild-type membranes was resistant to these treatments. In the absence of PsaD, it was resistant to proteolytic digestion, but was removed by NaBr. When the membranes were isolated from a mutant strain in which the psaF and psaJ genes have been inactivated, PsaE assembled in vitro could not be removed. PsaE could associate with the membranes of the strain DF in which the psaD, psaJ and psaF genes have been mutated. However, the radiolabeled PsaE associated with these membranes was removed both by the proteolytic as well as by the chaotropic agents. Characterization of PsaE present in vivo revealed similar results. These observations suggest that PsaD and PsaF/J may interact with PsaE and stabilize it in the photosystem I complex.

Notes: Abstract The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI Q repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 μmol photons m-2 s-1 in the presence of 40 or 80 μg/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 μg/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI Q system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.

Notes: Abstract The extrinsic 33 kDa polypeptide of the water-oxidizing complex has been extracted from pea photosystem II particles by washing with alkaline-Tris and purified by ion-exchange chromatography. The N-terminal amino acid sequence has been determined, and specific antisera have been raised in rabbits and used to screen a pea leaf cDNA library in λgt11. Determination of the nucleotide sequence of positive clones revealed an essentially full-length cDNA for the 33 kDa polypeptide, the deduced amino acid sequence showing it to code for a mature protein of 248 amino acids with an N-terminal transit peptide of 81 amino acids. The protein showed a high degree of conservation with previously reported sequences for the 33 kDa protein from other species and the sequence contained a putative Ca2+-binding site with homology to mammalian intestinal calcium-binding proteins. Northern analysis of total pea RNA indicated a message of approximately 1.4 kb, in good agreement with the size of the cDNA obtained at 1.3 kbp. Southern blots of genomic DNA probed with the labelled cDNA give rise to several bands suggesting that the 33 kDa polypeptide is coded by a multi-gene family.

Notes: Abstract The two operons atp1 and atp2, encoding the subunits of the FOF1 ATP-synthase, have been cloned and sequenced from the cyanobacterium Synechocystis sp. PCC 6803. The organization of the different genes in the operons have been found to resemble that of the cyanobacteria Synechococcus sp. PCC 6301 and Anabaena sp. PCC 7120. The Synechocystis FOF1 ATP-synthase has nine subunits. A tenth open reading frame with unknown function was detected at the 5′ end of atp1, coding for a putative gene product similar to uncI in Escherichia coli. A promoter structure was inferred for the Synechocystis atp operons and compared to other known promoters of cyanobacteria. Even though the operon structure of atp1 and atp2 in Synechocystis resembles the corresponding operons of Synechococcus, the amino acid sequences of individual gene products show marked differences. Genetic distances between cyanobacterial genes and genes for ATP-synthase subunits from other species have been calculated and compiled into evolutionary trees.

Notes: Abstract The 23 kDa polypeptide of the oxygen-evolving complex of photosystem II has been extracted from pea photosystem II particles by washing with 1 M NaCl and purified by anion-exchange chromatography. The N-terminal amino acid sequence has been determined and specific antisera have been raised in rabbits and used to screen a pea-leaf cDNA library in λgt11. Determination of the nucleotide sequence of two clones provided the nucleotide sequence for the full 23 kDa polypeptide. The deduced amino acid sequence showed it to code for a mature protein of 186 amino acid residues with an N-terminal presequence of 73 amino acid residues showing a high degree of conservation with previously reported 23 kDa sequences from spinach and Chlamydomonas. Southern blots of genomic DNA from pea probed with the labelled cDNA gave rise to only one band suggesting that the protein is encoded by a single gene. Northern blots of RNA extracted from various organs indicated a message of approximately 1.1 kb, in good agreement with the size of the cDNA, in all chlorophyll-containing tissues. Western blots of protein extracted from the same organs indicated that the 23 kDa polypeptide was present in all major organs of the plant except the roots.

Notes: Abstract The levels of chlorophyll a/b-binding protein (Cab) gene polysomal poly(A)+ mRNA were quantitated throughout the development of Glycine max L. Cab mRNAs were abundant in young expanding leaves, representing 6.1% of the leaf mRNA population. Lower Cab mRNA levels were present in embryos, stems, and cotyledons of developing seedlings; the lowest levels were found in roots where they accounted for 0.04% of the polysomal poly(A)+ mRNA of this organ. To determine the contribution of different members of the Cab gene family to the Cab mRNA populations, a quantitative S1 nuclease reconstruction assay was developed. Cab3, Cab4, and Cab5 mRNAs were detected in all stages examined during soybean development but their levels underwent differential changes. Cab3 encodes the most abundant Cab mRNA in young leaves, developing embryos, and in Stage VII cotyledons from the developing soybean seedling. The levels of Cab mRNAs were compared to the levels of ribulose-1,5-bisphosphate carboxylase small subunit gene mRNA and differences in their patterns of accumulation were noted. Collectively these data indicate that during soybean embryogenesis developmental control mechanisms supersede light-regulatory signals.

Notes: Summary The region of the chloroplast genome of Chlamydomonas reinhardii containing the gene of the thylakoid polypeptide D2 (psbD) has been sequenced. A unique open reading frame of 350 codons exists in this region. Because the first ATG is followed 11 codons downstream by a second one, the D2 polypeptide consists of either 339 or 350 amino acids. Comparison of the sequences of D2 and the 32K dalton polypeptides, both of which are associated with photosystem II, reveals partial homology. Although, the overall homology of these two polypeptides is only 27%, they contain several related regions and their hydropathic profiles are strikingly similar. These data suggest that the two polypeptides may have related functions and/or that their genes may have originated from a common ancestor. Alternatively, convergent evolution of these polypeptides may be due to structural constraints in the thylakoid membrane. Limited sequence homology is also observed between the D2 polypeptide and some of the subunits of the reaction centers of photosynthetic bacteria.

Notes: Summary The effect of the pore-forming antibiotic gramicidin on pure lipid membranes is well characterized. We studied its action in protein-rich thylakoid membranes that contain less than 25% (wt/wt) acyl lipids. A transmembrane voltage was induced by flashing light, and its decay was measured and interpreted to yield the distribution of gramicidin over thylakoids, its dimerization constant and its single-channel conductance in this membrane. The distribution of gramicidin over the ensemble of thylakoids was immediately homogeneous when the antibiotic was added under stirring, while it became homogeneous only after 20 min in a stirred suspension that was initially heterogeneous. The dimerization constant, 5×1014 cm2/mol, was about 10 times larger than in pure lipid membranes. This was attributed to the upconcentration of gramicidin in the small fractional area of protein free lipid bilayer and further by a preference of gramicidin for stacked portions of the membrane. The latter bears important consequences with regard to bioenergetic studies with this ionophore. As gramicidin was largely dimerized from a concentration of 1 nm (in the suspension) on, the membrane's conductance then increased linearly as a function of added gramicidin. When the negative surface potential at the thylakoid membrane was screened, the conductance of a single gramicidin dimer agreed well with figures reported for bilayers from neutral lipid (about 0.5 pS at 10 mm NaCl). The modulation of the conductance by the surface potential in spinach versus pea thylakoids and between different preparations is discussed in detail.

Notes: Summary The rate of inorganic carbon uptake and its steadystate accumulation ratio (intracellular/extracellular concentration) was determined in the cyanobacteriumAnabaena variabilis as a function of extracellular pH. The free energy of protons ( $$\Delta \overline \mu _{H^ - }$$ ) across the plasmalemma was calculated from determinations of membrane potential, and intracellular pH, as a function of the extracellular pH. While inward proton motive force decreased with increasing extracellular pH from 6.5 to 9.5, rate of HCO 3 − influx and its accumulation ration increased. The latter is several times larger than would be expected should HCO 3 − influx be driven by $$\Delta \overline \mu _{H^ + }$$ . It is concluded that HCO 3 − transport in cyanobacteria is not driven by the proton motive force.

Notes: Summary The proton-driven ATP synthase of chloroplasts is composed of two elements, CF0 and CF1. The membrane bound CF0 conducts protons and the peripheral CF1 interacts with nucleotides. By flash spectrophotometric techniques applied to thylakoid membranes from which about 50% of total CF1 was removed, we have previously determined the protonic (timeaveraged) single-channel conductance of CF0. Being in the order of 1 pS, it was sufficiently large to support the proposed role of CF0 as a low-impedance access for protons to the coupling site in CF0CF1. On the other hand, it was too large to be readily reconciled with current concepts of proton supply to and proton conduction through the channel. We studied the time-averaged single-channel conductance of CF0 under variation of pH, pD, ionic composition, temperature, and water/membrane structure with the following results: (i) CF0 was proton-specific even against a background of 300mm monovalent or 30mm divalent catins. (ii) While the conductance of CF0 was pH/pD-independent in the range from 5.6–8.0, in D2O it was lower by a constant factor of 1.7 than in H2O (iii) Addition of glycerol diminished the conductance and abolished the isotope effect. (iv) The Arrhenius activation energy was 42 kJ/mol and thus intermediate between the ones found for the water-filled pore, gramicidin (30 kJ/mol), and the mobile carrier, valinomycin (65 kJ/mol). The results implied that CF0 is endowed with an extremely proton-specific (107-fold) selectivity filter. Its conductance is very high, and its conduction cycle is not necessarily rate limited by a protolytic reaction. The mechanisms of rapid proton supply to the channel mouth and of proton conduction remained enigmatic.

Notes: Summary Relations between measurements of the slow kinetics of chlorophyll fluorescence and growth and yield were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Drought reduced total dry matter production and yields and increased tuber dry matter concentration. Drought increased harvest index in cv. Spunta, but decreased it in cv. Pentland Crown. Total dry matter production was correlated with each of constant fluorescence, variable fluorescence and the half life of the decay in variable fluorescence. These correlations were determined largely by the effect of treatment, and did not discriminate effectively between genotypes within a treatment.

Notes: Summary The slow kinetics of chlorophyll fluorescence were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Constant and variable fluorescence (F o andF v respectively) declined with time in plants from both irrigated and droughted treatments, but the decline was greater in droughted than irrigated plants. However, the yield of variable fluorescence (F v/(F o+F v)) was unaffected by the drought treatment. The main effect of drought was upon the quenching of variable fluorescence. Both the half life of the decay of variable fluorescence (q1/2) and the secondary maximum (M) were significantly greater in the droughted plants than in those from the irrigated treatment. Significant differences between genotypes were found forF v/(F o+F v),M andq 1/2. Genotype-by-treatment interactions were non-significant for all the variables examined. Changes in chlorophyll fluorescence transients were not closely related to changes in leaf water potential.

Notes: Abstract We analyzed the recent data on the distribution of the photosynthetic energy of zooxanthellae in corals and the models of interactions between the plant and animal cells in the course of matter and energy exchange developed based on this information. The models of energy exchange of animals symbiotic with zooxanthellae are characterized by the following features: (1) A flow chart of carbon or energy fluxes is the main form of representation of the energetics in native symbiotic organisms. (2) The relations between the symbionts are relatively adequately revealed and correspond to the modern notions; however, the intensities of the energy fluxes ascribed to these relations are dependent on the experimental and design methods used by the authors. (3) The inputs into the energy budget consist of the autotrophic production of zooxanthellae and the heterotrophy of the polyp. The energy expenditures comprise excretion, respiration, development, and growth of the animal and algae. (4) The differences between the species, genera, and phyla of animals that develop symbiotic relations with zooxanthellae are confined to the absolute values of energy fluxes in the organism.

Notes: Abstract Diurnal changes in carbohydrate content of natural phytoplankton populations differed from those found for cyanobacteria grown in continuous cultures. The carbohydrate accumulation rate was not constant during the light period. Also in contrast to results obtained using continuous cultures the photosynthetic characteristics changed during the light period. A close correlation was observed between changes in carbohydrate accumulation rate and the efficiency of photosynthesis over 24 hours. Seasonal changes in carbohydrate consumption rate over the dark period were proportional to changes in growth rate.

Notes: Abstract One hundred and eighteen algal isolates comprising seven classes were obtained from a range of sites from polluted rivers running through Cu or Zn mining regions, and from unpolluted rivers. All the isolates were tested for photosynthetic activity when exposed to Cu, Cd or Zn. The tolerance levels of Bacillariophyceae, Charophyceae, Cyanophyceae and Chlorophyceae to Cu showed significant positive correlations with Cu concentrations in the field. However the distribution of metal sensitivities of the algae from the sites with the same metal concentration was broad. Both Bacillariophyceae and Charophyceae had a number of strains whose sensitivity to Cu differed more widely in relation to Cu levels in the environment than Cyanophyceae and Chlorophyceae. Cyanophyceae were sensitive to all three metals, whether or not isolates were obtained from polluted sites, whereas Chlorophyceae tended to have high tolerance even in isolates from unpolluted sites. For Cd and Zn the correlation between tolerance levels and concentrations in the field was not so clear as for Cu. The occurrence of Cu tolerance was shown in 4 diatom species and one Charophyceae, whereas metal resistance occurred in some Chlorophyceae. Cu-tolerant isolates tended also to be Zn-tolerant in Bacillariophyceae, and Cd-resistant isolates tended also to be Zn-resistant in Chlorophyceae.

Notes: Abstract Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipette – experimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mgmL-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light(measured at 580 μmol m-2 s-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mgChl ml-1 and 0.050 mgChlml-1 can be recommended when applying the Light Pipette system in bioassays using microalgae.

Notes: Abstract The present study examined the effect of UV andphotosynthetically active radiation (PAR) onphotoinhibition and recovery in the Phaeophyte Macrocystis pyrifera, the Rhodophyte Chondruscrispus and the Chlorophyte Ulva lactuca underoutdoor culture conditions. There was an increase inphotoinhibition as a consequence of high exposure toUV-B radiation in M. pyrifera, however, highlevels of PAR accounted for most of thephotoinhibition in C. crispus and U.lactuca. Photodamage by UV-A, UV-B and PAR wascompletely repaired within 5 h and effective quantumyield reached pretreatment values in the three speciesstudied. Species were less susceptible tophotoinhibition after being incubated for 5 d underhigh exposures of natural irradiance suggesting aphotoadaptive process. The recovery of the effectivequantum yield was impaired by long exposure to highlevels of UV-B in C. crispus and UV-A, UV-B andPAR in M. pyrifera. This suggests a differentkind of damage by UV-A and PAR radiation, one to thephotosynthetic apparatus and another which affects therepair mechanism of some species. There was anincrease in UV-absorption (λ 330 nm) in M. pyrifera and C. crispus within four days ofthe initiation of the experiment suggesting that thesespecies photoprotect their photosynthetic system whenexposed to elevated UV and PAR levels.

Notes: Abstract Leafy thalli of the red algaPorphyra yezoensis Ueda, initiated from conchospores released from free-living conchocelis, were cultured using aeration with high CO2. It was found that the higher the CO2 concentration, the faster the growth of the thalli. Aeration with elevated CO2 lowered pH in dark, but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO 3 − to OH− and CO2 proceeded much faster than the dissociation of hydrated CO2 releasing H+. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO2 + HCO 3 − + CO 3 − ). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO2 by marine algae is discussed.

Notes: Abstract Photosynthetic characteristics of Dunaliella salina with high (red form) and low β-carotene (green form) concentrations were studied. D. salina growing in brine saltworks exhibited a high level of β-carotene (15 pg cell−1). The rate of oxygen evolution as a function of irradiance was higher in the red than in the green form (on chlorophyll basis). Photosynthetic inhibition of the green form was observed above 500 µmol m−2 s−1. The red form appeared more resistant to high irradiance and no inhibition in O2 evolution was observed up 2000 µmol m−2 s−1. However, when these results are expressed on a cell number basis the rate of oxygen evolution was significantly higher in the green form. Carbonic anhydrase (CA) activity (total, soluble, membrane bound) was found in red and green forms. CA was higher in the red form on a chlorophyll basis, but lower if expressed on a protein basis. The light dependent rate of oxygen evolution and photoinhibition depends on the concentration of β-carotene in D. salina cells.

Notes: Abstract The use of ‘of the shelf’ microcomputer hardware and software and a new type of laboratory style combination pH electrode with a built in preamplifier makes it possible to monitor pH shifts in a group of experimental vessels in a time frame of seconds without resorting to expensive smart switch boxes or multiple pH meters. A data acquisition system is described for monitoring pH shifts.

Notes: Abstract Iron is an essential component of electron transport in almost all living organisms. It is particularly important to phototrophs like cyanobacteria because 22–23 irons are required for a complete functional photosynthetic apparatus. Since the low solubility of Fe+++ above neutral pH in oxic ecosystems severely limits the biological availability of iron to aquatic microorganisms, cyanobacteria and other microbes have developed a number of responses to cope with iron deficiency. Cyanobacterial responses to iron stress include the synthesis of an efficient, siderophore-based system to scavenge iron and the substitution of ferredoxin with flavodoxin. An additional response in cyanobacteria involves the alteration of the light-harvesting apparatus that includes the appearance of a new, iron-stress-induced, photosystem II, chlorophyll-binding protein. Although cytochromec-553 has a potential non-iron-containing replacement in plastocyanin, a copper-containing protein, iron stress appears to favor the utilization of cytochromec-553 because siderophores also bind copper and form a complex that is excluded from the cell. This paper is intended primarily as a review of molecular and physiological responses of actively growing cyanobacterial cultures to conditions of iron stress, where iron is present but essentially insoluble, and to differentiate these responses from iron starvation, where the amount of iron in the system is not sufficient for cell growth.

Notes: Abstract As filament aggregation is responsible for heterogeneity of Laminariales gametophyte cultures, a project was conducted to obtain stable homogeneous `free-living' cultures of Laminaria digitatagametophytes. The alga was cultivated at 15 ° Cunder low light and in the presence of a cationic cellulosic polymer, JR125. With 0.1%polymer in the culture medium, the filaments were dispersed and did not adhere to the culture vessel. The absence of any effect of the closely related, but uncharged, polymer LR-250 Natrasol on filament aggregation indicated that the cationic nature of the JR125 molecule was involved in gametophyte dissociation. In the presence of JR125, the gametophytes showed active vegetative growth; the doubling time, measured as chlorophyll concentration, was 5 days. The outer surface of the cell wall was clearly modified by the polymer treatment, as observed by transmission electron microscopy, while neither the inner cell wall or cell organelles were affected. Physiological studies indicated that JR125 treatment did not disturb cell physiology, there being no effecton respiration, photosynthetic activity, sensitivity to high-light stress or modification of pigment or fluorescence characteristics. We have therefore established the conditions for maintaining a stable culture of mixed male and female Laminaria digitata gametophytes in active vegetative growth. The presence of JR 125 in the medium yields a homogeneous culture without cell physiology becoming modified.

Notes: Abstract Depending on the intensity, quality and duration ofthe illumination, necessary for viewing show caves,conditions conducive for algal growth are created. Although algae are the major component of this flora,ferns and mosses have also been recorded. Little isknown of the algae, except that they are considered anuisance in terms of discoloration and damage to thekarst formations. The occurrence and possible controlof the algal flora has been studied in the CangoCaves, one of the most important touristic sites inSouth Africa. The algal flora is sparse in speciesdiversity and primitive forms are present. They haveparticular physiological adaptations and usingmicro-oxygen liberation and fluorescence measurements,their photosynthetic characteristics were established. Environmentally friendly control measures wereinvestigated and a solution for their control is proposed.

Notes: Abstract The successful coupling between physiology andtechnology is central to the success of algalbiotechnology. Imperative is a proper understandingof the variables and their impacts on biomass and/orbiocompound production. The crux lies inphotosynthesis and the capturing of light energy atthe optimal rate for eventual maximal photochemistry(biosynthesis). It is in the hands of algalbiotechnologists to understand the dynamics andregulatory mechanisms of especially PSII (photosystemII) activity in order to advance this technologyfurther. Biophysical and technological optimisationand design aimed at maximising photon flux capture aresome of the avenues that needs be pursued. This needsto be augmented by molecular, biochemical andphysiological inputs. Unfortunately detailedsystematic analyses of the variables, theirinteraction and possible synergism have rarely beendone. The debate regarding the merits andproductivity in closed, either plate or tubular,vertical or horizontal, and open pond reactors need tobe resolved. Exciting developments regarding onlinemeasurements and feedback control for optimalproductivities are part of the solutions andapproaches that need to be followed. Multistagesystems that not only utilise autotrophic growth andstress components, but also combinedautotrophic/heterotrophic systems could providesolutions to specific production requirements. Theseand other important issues are addressed in theoverview. The challenges facing algalbiotechnologists and future research needs are also discussed.

Notes: Abstract A deterministic simulation model was developed to predict production rates of the marine prymnesiophyteIsochrysis galbana in an outdoor algal mass culture system. The model consists of photoadapation, gross photosynthesis and respiration sections. Actual physiological and biophysical laboratory data, obtained from steady state cultures grown under a wide range of irradiance levels, were used in calculating productivity. The resulting values were used to assess optimal operational parameters to maximize algal biomass production. The model predicted a yearly averaged production rate of 9.7 g C m−2d−1, which compared well with field data reported in the literature. The model evaluated the effect of pond depth and chlorophyll concentration on potential production rate in various seasons. The model predicted that a yearly averaged chlorophyll areal density of 0.65 g m−2 will yield the maximal production rate. Chlorophyll areal density should be seasonally adjusted to give maximal production. This adjustment could be done either by changing pond depth or chlorophyll concentration. The model predicted that under optimal operational conditions, the diurnal respiration losses averaged 35% of gross photosynthesis. The calculated growth rate for maximal productivity ranged between 0.15 and 0.24 d−1, suggesting an optimal hydraulic retention time of 6.7 and 4.2 d for various seasons.

Notes: Abstract The use of ‘of the shelf’ microcomputer hardware and software and a new type of laboratory style combination pH electrode with a built in preamplifier makes it possible to monitor pH shifts in a group of experimental vessels in a time frame of seconds without resorting to expensive smart switch boxes or multiple pH meters. A data acquisition system is described for monitoring pH shifts.

Notes: Abstract A flat plate, multi-pass air lift reactor (FPALR) for the culture of photosynthetic organisms was constructed from twin wall acrylic sheet and its performance characterised. When operated at an air input of 2.01 min−1 the multi-pass system had a Reynolds number of 5200 indicating fully turbulent flow. Chlorella vulgaris 211/11c was found to have a stationary phase biomass of 1.48 g 1−1 when grown in the flat plate air lift reactor (FPALR) at 100 µmol m−2s−1 compared to 1.11 g 1−1 when cultured in the continually stirred tank reactor (CSTR) at the same PFD (photon flux density). The same organism cultured at 200 µmol m−2s−1 achieved a stationary phase biomass of 1.71 g 1−1 in the FPALR. In contrast, Scenedesmus sp. produced a stationary phase biomass of 2.27 g1−1 and 1.27 g1−1, when cultured at 100 µmol m−2s−1 in the FPALR and the CSTR respectively. The growth rates of both organisms were also higher in the PFALR.

Notes: Abstract The influence of elevated CO2 concentrations on growth and photosynthesis ofGracilaria sp. andG. chilensis was investigated in order to procure information on the effective utilization of CO2. Growth of both was enhanced by CO2 enrichment (air + 650 ppm CO2, air + 1250 ppm CO2, the enhancement being greater inGracilaria sp. Both species increased uptake of NO3 − with CO2 enrichment. Photosynthetic inorganic carbon uptake was depressed inG. chilensis by pre-culture (15 days) with CO2 enrichment, but little affected inGracilaria sp. Mass spectrometric analysis showed that O2 uptake was higher in the light than in the dark for both species and in both cases was higher inGracilaria sp. The higher growth enhancement inGracilaria sp. was attributed to greater depression of photorespiration by the enrichment of CO2 in culture.

Notes: Abstract Chlorophyll fluorescence measurements were used to evaluate the effect of temperature on photoinhibition inSpirulina platensis cultures grown in tubular reactors outdoors. Cultures grown at 35 °C during the day time showed a lower reduction in the Fv/Fm ratio as compared to cultures grown at 25 °C. It is demonstrated that the lower temperature photoinhibited cells can undergo a complete recovery once transferred to low light and higher temperature. This recovery does not take place when 100 µg ml-1 chloramphenicol is added to cells. The recovery is light dependent and cells incubated in the dark at low temperature do not show a recovery in the Fv/Fm ratio. The data presented strongly support the hypothesis that photoinhibition takes place in outdoorSpirulina cultures. At the same time it is demonstrated that fluorescence measurements can be used as a fast reliable indication for photoinhibition in outdoor algal cultures.

Notes: Abstract Biomass production from macroalgae has been viewed as important mainly because of the need for pollution abatement. Environmental considerations will increasingly determine product and process acceptability and drive the next generation of economic opportunity. Some countries, including Japan, are actively promoting "green" technologies that will be in demand worldwide in the coming decades. Should an international agreement on CO2-reduction be ratified, its effective use for energy production would be of high priority. This report shows that macroalgae have great potential for biomass production and CO2 bioremediation. Macroalgae have high productivity, as great or greater than the most productive land plants, and do not compete with terrestrial crops for farm land. The review focuses on recent data on productivity, photosynthesis, nutrient dynamics, optimization and economics. Biomass from macroalgae promises to provide environmentally and economically feasible alternatives to fossil fuels. Nevertheless, the techniques and technologies for growing macroalgae on a large-scale and for converting feedstocks to energy carriers must be more fully developed.

Notes: Abstract The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 °C), low PPF (70–140 μmol photon m-2s-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.

Notes: Abstract A study was made of the tolerance to Cu of 11 strains of Cyanophyceae and 7 strains of eukaryotes. These had all been tested within 6 months after isolation for their photosynthetic activity when exposed to Cu (Takamuraet al., 1989) and had repeatedly been subcultured in the medium without Cu for 2 years. Photosynthetic measurements were made in two ways: precultured in medium without Cu or precultured (for one subculture) in medium containing Cu (645 μg 1−1). The results were compared with those obtained within 6 months of isolation. The tolerance of the eukaryotes did not change significantly in any case, but most strains of Cyanophyceae lost their tolerance to Cu within a few subcultures in medium without Cu; however tolerance recovered following one subculture in medium containing an intermediate level of Cu. This rapid adaptation cannot be explained by a constitutive mutation.

Notes: Abstract The net photosynthesis of the Mediterranean brown seaweedCystoseira barbata f.repens is measured according to irradiance, temperature and salinity. There is not only, a good utilization of low light intensities (light-shade adaptation), but also a specific ability to use a broad range of irradiance, which corresponds in the photosynthesis-irradiance curves to a high initial slope and an extended light saturation level from 300 to 1500 μmol photon m−2 s−1; only very high irradiances induce photoinhibition. Maximum net photosynthesis occurred at temperatures ranging from 20 °C to 30 °C. The alga tolerates not only a low level of salinity, but also a slight increase in salinity; however, at more than 47.5 g 1−1 NaCl, oxygen exchange is significantly reduced. Light, temperature and salinity requirements are discussed, taking into account ecological considerations. Yields and quality of alginic acid are presented according to the irradiance and yearly evolutionin situ in order to aid future cultivation of this species.

Notes: Abstract Leafy thalli of the red algaPorphyra yezoensis Ueda, initiated from conchospores released from free-living conchocelis, were cultured using aeration with high CO2. It was found that the higher the CO2 concentration, the faster the growth of the thalli. Aeration with elevated CO2 lowered pH in dark, but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO 3 − to OH− and CO2 proceeded much faster than the dissociation of hydrated CO2 releasing H+. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO2 + HCO 3 − + CO 3 − ). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO2 by marine algae is discussed.

Notes: Abstract A method for quantitative evaluation of light sources from the point of their suitability for algal cultivation is described. Two parameters are used for the evaluation: (1) amount of photons emitted in the spectral region absorbed by algae per consumed unit of electrical energy; (2) fraction of photons intercept by the algae that got effectively transformed into chemical energy. The value of parameter (2) depends on the emission spectrum of the light source, the absorption spectrum of the algae, quantum capacity of the algae and on conditions of cultivation. The method permits the assessment of the differences in algal productivity under light of various light sources with respect to other recent methods for comparison.

Notes: Abstract The productivity was evaluated of a strain of Chlamydomonas perigranulata isolated from the RedSea. A mutant with small light-harvesting pigments(LHC-1) was obtained by UV mutagenesis. Thechlorophylls content of the wild type was twice ashigh as that of LHC-1, and the initial slope of thephotosynthesis-irradiance curve was higher in the wildtype. However, the maximum photosynthetic activity ona per cell basis was almost the same. It isconcluded that LHC-1 is a mutant with lesslight-harvesting pigment (LHP) than the wild type. Aspreviously reported, the mutant with lower LHP contenthas a higher productivity in a continuous culturesystem, so we compared the productivity of the wildtype and the mutant. The maximum productivity of LHC-1was 1.5 times higher than that of the wild type. Itis suggested that the technique of reducing thecontent of light-harvesting pigment should be madeavailable for other organisms.

Notes: Abstract A stromatolitic microbial mat extensively covers La Solana streambed, a calcareous Mediterranean stream. This stromatolite shows remarkable biological and physiological diversity. It is mainly composed by cyanobacteria, with Rivularia and Schizothrix as the most abundant taxa. The stromatolite is photosynthetically adaptated to the high irradiances reaching the streambed. Photosynthetically active chlorophyll is present even in the lowest layers of the stromatolite, indicating the presence of well-preserved cyanobacteria in that part. Diffusion of gases and nutrients within the stromatolite can be possible because of the high porosity of the crust. It has been experimentally established that the stromatolite recovers heterotrophic and autotrophic activities in a few hours, after being desiccated for long periods. Recovery after desiccation is indicative of the high resilience of this community to environmental extremes, which are common in Mediterranean climatic regimes. The stromatolitic community is adapted to nutrient limitation, both to low availability of inorganic phosphorus and nitrogen (that constrain growth of primary producers), and to low dissolved organic carbon (mainly affecting heterotrophs). Stromatolitic heterotrophs mainly rely on the organic carbon stored in the crust as the main organic carbon source. These strategies are the direct response of the stromatolite to oligotrophy, and justify the restricted occurrence in stream systems affected by organic pollution.

Notes: Abstract We measured underwater light penetration, phytoplankton biomass and photosynthetic activity during three years (1987–1990) in Lake Xolotlán (L. Managua), Nicaragua. Phytoplankton biomass governed the light climate of the photic zone, but as biomass also was composed of a varying proportion of dead algae, light availability for the potential biomass of actively photosynthesizing algae (170 mg Chl-a.m−2) was reduced. The concentration of chlorophyll-a within the photic zone was thus lower and ranged between 58 and 141 mg Chl-a.m−2. Still, photosynthetic activity was high (2,162 mg 02.m-2.h−1) due to an extremely high specific rate of photosynthesis; light was the only factor that limited growth. As also other conditions in Lake Xolotlán, beside light limitation, met with the requirements of the models that have been used to analyse production and photosynthetic characteristics in tropical lakes there was a striking agreement between observed and predicted values.

Notes: Abstract A strain selection procedure using Gracilaria verrucosa gametophytic sporelings was found to be an efficient tool for the improvement of Gracilaria strains. Two strains, C-2 and A-18, which were isolated and grown clonally, showed higher growth rates under high and low temperature conditions, respectively, than the local Gracilaria conferta. Growth rate, photosynthesis and chlorophyll, which were measured under different temperature and photon flux densities, demonstrated an overall advantage of the selected strains over the wild type strains of both G. verrucosa and G. conferta. Growth rates were also generally in positive correlation with the carboxylase activity of Rubisco. The G. verrucosa wild type also had a 40% higher agar content than G. conferta. The selected strains thus showed higher potential for outdoor cultivation than local wild type populations.

Notes: Abstract In mass algal cultures, some form of agitation is usually provided; among other effects, this moves the organisms though an optically dense profile and provides mixing. During this transport, medium frequency fluctuations in the light energy supply are perceived by the algae, which are of the order of 1 Hz and less. It has been suggested that turbulence with the resultant light/dark cycles of medium frequency enhances productivity. However, turbulence has two major influences in a well mixed system: it facilitates fluctuating light regimes and increases the transfer rates between the growth medium and the cultured organism. An estimation of productivity as oxygen liberation was measured under laminar and turbulent flow rates, and varying light/dark ratios. Increased turbulence, which increased exchange rates of nutrients and metabolites between the cells and their growth medium, together with increased light/dark frequencies, increased productivity and photosynthetic efficiency.

Notes: Abstract Chemical techniques were investigated in order to eradicate Caulerpa taxifolia, a green alga spreading at a remarkable rate in the Mediterranean Sea. The action of copper, potassium and sodium ions on survival rates and photosynthetic parameters was compared, in order to optimise the conditions of further in situ treatments. The lethal doses were determined and the impact of the studied cations on photosynthesis and respiration rates and PSII photochemistry was analysed from measurements of net oxygen exchanges and chlorophyll fluorescence. The Cu2+ concentrations required to obtain 100% mortality were 15 × 102 to 104 times lower than those of K+ and Na+. Respiration was slightly affected whatever the salt concentration,while photosynthesis could be totally inhibited depending on the applied treatment. Changes in the structure of the Ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO, EC: 4.1.1.39) were also detected when C. taxifolia under went cation treatments (10 mg L-1 Cu2+, 1h; 20 gL-1 K+, 3 h; 20 g L-1 Na+, 1 h). Given the high concentration and long incubation periods required with K+ and Na+ ions, these cations are not suitable to be used in situ. Our results make possible the utilisation of copper cations following technical approaches such asion-exchange textile covers, which allows a controlled release of cupric ions without dissemination in the marine environment.

Notes: Abstract Laboratory and field studies on aphid damage in wheat are described. Both direct and indirect effects of aphids on the behaviour of the crop were studied. In the laboratory a clear effect of honeydew and yeasts on photosynthesis was found. This effect could not be demonstrated under field conditions, since even at yield loss levels of 700 kg ha−1 the size of this effect may be undetectable with crop enclosures reaching an accuracy of 10%. The effect of honeydew on ageing, measured in the laboratory trials was also found in the field and may form a major cause of the yield losses found in the field. Yield losses under field conditions reached 700 kg ha−1 and were for 72% due to direct sucking damage of the 35 aphids, found maximally per culm, and direct and indirect honeydew effects. Saprophytic and possibly also some necrotrophic fungi caused 28% of the yield losses. The exact contribution of each of the damage factors was not revealed but it was demonstrated that direct and indirect effects contribute to the final yield losses.

Notes: Abstract A simple simulation model is described to account for the rates at which plants take up nitrate and reduce it to protein. It is based on the pump and leak principle, with the pump working at a constant rate per unit sap volume provided that there is an adequate concentration of nitrate at the root surface. The rate of leakage is assumed to be proportional to the concentration difference between the inside and the outside of the plant. Nitrogen is removed from the plant nitrate pool (the ‘buffer’) at a constant fraction of the photosynthesis rate. When applied to data for the diurnal variation in nitrate uptake by ryegrass, the model predicts an uptake pattern similar to that actually observed, with a time lag of about 5 hours between photosynthesis and uptake.

Notes: Abstract The electron transport rates of photosystems II and I, amounts of electron carriers, coupling factor activity and photosynthetic rates were investigated in thylakoids isolated from pea plants grown under a wide range of light intensities (16 h light-8 h dark). The electron transport rates of PS II and PS I, as partial reactions or in whole chain, and coupling factor activity on a unit chlorophyll basis, all increased as the light intensity available for growth was altered from a very low intensity of 10 μE m-2s-1 to a high intensity of 840 μE m-2s-1. Similarly, there were increases in the amounts of atrazine binding sites, plastoquinine, cytochrome f and P700 per unit chlorophyll; significantly, the amounts of reaction centres of PS II and PS I were not equal at any light intensity. The rate of change of all parameters with respect to light intensity could be represented by two straight lines of different slopes which met at a transition point corresponding to approximately 200 μE m-2s-1 during growth. These photoadaptations were similar to those observed for both the relative distribution of chlorophyll in chlorophyll-protein complexes and the chl a/chl b ratios [Leong and Anderson, 1984, Photosynthesis Research 5:117–128]. Since these thylakoid components and functions were affected in the same direction by light intensity during growth and all show linear relationships with chl a/chl b ratios, it indicates that they are closely regulated and markedly well co-ordinated. Plants compensate for the limited amount of low light intensities by drastically increasing the light-harvesting antenna unit size of photosystem II and to a lesser extent that of photosystem I. Changes in the composition of the thylakoid membranes exert a regulatory effect on the overall photosynthetic rate up to approximately 450 μE m-2s-1.

Notes: Abstract Field observations were conducted to examine the processes governing the phytoplankton distribution and photosynthetic activity in and around a tidal front formed in Iyo Nada, the Seto Inland Sea, Japan. The existence of a middle layer intrusion, which, it has been suggested, moves from the mixed region to the stratified region of the tidal front, was ascertained by the phytoplankton distribution in addition to a T-S diagram. Skeletonema costatum, which originally inhabited the mixed region, was used as the indicator to reveal the intrusion. However, the tip of water containing the S. costatum population did not extend deeply into the stratified region. The velocity of the intrusion seemed to be slow enough to make biological processes, such as nutrient uptake by phytoplankton and subsequent growth, as well as the decrease in cell density due to zooplankton grazing, dominate during the transportation. The patchy distribution of copepod nauplii implied that grazing has an influence on the distribution pattern of phytoplankton. The location of high photosynthetic activity did not coincide spatially with the center of high phytoplankton biomass, suggesting the importance of these biological processes. Therefore, it is considered that the middle layer intrusion plays a role as an inducer of subsequent biological processes at the tidal front by not only supplying nutrients from the mixed region but also by increasing the vertical diffusivity.

Notes: Abstract Potato (Solanum tuberosum L.) plants cv.Saturna were subjected to infection withVerticillium dahliae and drought stress. At the early stages of growth, stomatal conductance, transpiration and net photosynthesis were measured at light saturation (PAR〉300 m−2) on individual leaves and with mobile field equipment with the aid of field enclosures. No significant changes in stomatal conductance and gas exchange characteristics occurred as a result ofV. dahliae instomatal conductance, transpiration and and photosynthetic rates, especially on older leaves and on plants exposed to direct sunlight for a longer period of time. In combination with drought,V. dahliae only occasionally showed interaction; their effects being less than additive. High values of coefficients of variatoon necessitated a high number of measurements per treatment; the more so in the inoculated plants which shows thatV. dahliae seems to affect certain leaves while not affecting others early in growth. Crop photosynthesis was less reduced byV. dahliae than individual leaf photosynthesis due to the levelling effect of integration over the whole canopy and possibly through a stimulation of the top leaves. The upper non-affected leaves are responsible for the bulk of photosynthetic crop activity. The results indicate that following an infection withV. dahliae photosynthesis is reduced early in growth as a result of drought stress in the leaves.

Notes: Abstract A method of measuring CO2gas exchange (caused, for example, by microalgal photosynthesis on emersed tidal mudflats) using open flow IR gas analyzers is described. The analyzers are integrated in a conventional portable photosynthesis system (LI-6400, LI-COR, Nebraska, USA), which allows manipulation and automatic recording of environmental parameters at the field site. Special bottomless measuring chambers are placed directly on the surface sediment. Measurements are performed under natural light conditions and ambient CO2concentrations, as well as under different CO2concentrations in air, and various PAR radiation levels produced by a LED light source built into one of the measurement chambers. First results from tidal channel banks in a north Brazilian mangrove system at Bragança (Pará, Brazil) under controlled conditions show a marked response of CO2assimilation to CO2concentration and to irradiance. Photosynthesis at 100 μmol mol−1CO2in air in one sample of a well-developed algal mat was saturated at 309 μmol photons m−2s−1, but increased with increasing ambient CO2concentrations (350 and 1000 μmol mol−1CO2) in the measuring chamber. Net CO2assimilation was 0.8 μmol CO2 m−2s−1at 100 μmol mol−1CO2, 5.9 μmol CO2m−2s−1at 350 μmol mol−1CO2and 9.8 μmol CO2m−2s−1at 1000 μmol mol−1CO2. Compensation irradiance decreased and apparent photon yield increased with ambient CO2concentration. Measurements under natural conditions resulted in a quick response of CO2exchange rates when light conditions changed. We recommend the measuring system for rapid estimations of benthic primary production and as a valuable field research tool in connection with certain ecophysiological aspects under changing environmental conditions.

Notes: Abstract In order to understand more clearly the dynamics of rice (Oryza sativa L.) yield development in relation to N fertilization, a field experiment was conducted in Laguna, Philippines. The soil, a Maahas clay (Aquic Hapludalf), was flooded, puddled, and then planted with 20-day-old seedlings of IR64 rice. Treatments were six combinations of N fertilizer timing and method: (1) 0 N control; (2) prilled urea broadcast at 15 and 60 days after transplanting (DAT) (BR-LATE); (3) prilled urea injected with a spring auger applicator at 15 DAT and broadcast at 60 DAT (INJ-LATE); (4) prilled urea broadcast and incorporated at 0 DAT and broadcast at 40 DAT (BR-EARLY); (5) urea super granules (USG) manually deep-placed at 3 DAT and prilled urea broadcast at 40 DAT (DP-EARLY); and (6) USG manually deep-placed at 3 DAT (DP). Except for the control, all treatments received a total of 58 kg N ha-1. Yield results were consistent with those of other experiments, namely, DP had the highest yields, the early-split treatments (BR-EARLY and DP-EARLY) were second best, followed by the late-split treatments (BR-LATE and INJ-LATE), with the control having the lowest yield. Sequential harvest results showed that the advantages of DP in terms of dry matter assimilation, tillering, and leaf area index (LAI) were expressed later in the season. For all treatments, midday net CO2 assimilation (Ac) peaked around 48 DAT, approximately panicle initiation. Grain yield was highly correlated with midday Ac at panicle initiation and flowering but not at other growth periods. Rates of midday Ac and night respiration depended strongly on shoot N content. We conclude that N application method and timing should be designed to give high shoot N content at panicle initiation and flowering, and that DP satisfied this requirement best among the treatments tested.

Notes: Abstract We tested a conceptual model describing the influence of elevated atmospheric CO2 on plant production, soil microorganisms, and the cycling of C and N in the plant-soil system. Our model is based on the observation that in nutrient-poor soils, plants (C3) grown in an elevated CO2 atmosphere often increase production and allocation to belowground structures. We predicted that greater belowground C inputs at elevated CO2 should elicit an increase in soil microbial biomass and increased rates of organic matter turnover and nitrogen availability. We measured photosynthesis, biomass production, and C allocation of Populus grandidentata Michx. grown in nutrient-poor soil for one field season at ambient and twice-ambient (i.e., elevated) atmospheric CO2 concentrations. Plants were grown in a sandy subsurface soil i) at ambient CO2 with no open top chamber, ii) at ambient CO2 in an open top chamber, and iii) at twice-ambient CO2 in an open top chamber. Plants were fertilized with 4.5 g N m−2 over a 47 d period midway through the growing season. Following 152 d of growth, we quantified microbial biomass and the availabilities of C and N in rhizosphere and bulk soil. We tested for a significant CO2 effect on plant growth and soil C and N dynamics by comparing the means of the chambered ambient and chambered elevated CO2 treatments. Rates of photosynthesis in plants grown at elevated CO2 were significantly greater than those measured under ambient conditions. The number of roots, root length, and root length increment were also substantially greater at elevated CO2. Total and belowground biomass were significantly greater at elevated CO2. Under N-limited conditions, plants allocated 50–70% of their biomass to roots. Labile C in the rhizosphere of elevated-grown plants was significantly greater than that measured in the ambient treatments; there were no significant differences between labile C pools in the bulk soil of ambient and elevated-grown plants. Microbial biomass C was significantly greater in the rhizosphere and bulk soil of plants grown at elevated CO2 compared to that in the ambient treatment. Moreover, a short-term laboratory assay of N mineralization indicated that N availability was significantly greater in the bulk soil of the elevated-grown plants. Our results suggest that elevated atmospheric CO2 concentrations can have a positive feedback effect on soil C and N dynamics producing greater N availability. Experiments conducted for longer periods of time will be necessary to test the potential for negative feedback due to altered leaf litter chemistry. ei]{gnH}{fnLambers} ei]{gnA C}{fnBorstlap}

Notes: Abstract Four pigeon pea [Cajanus cajan (L.) Mill sp.] cultivars were studied during two cycles of development of water stress and recovery. During these two cycles the genetic variation in vegetative development, leaf water potential, relative water content, photosynthesis, and stomatal conductance was followed. Plants were grown in a greenhouse and irrigated every seventh day. On two occasions (30 days and 80 days from sowing) water was withheld for 13 days in one group of plants and 16 days in another. Control plants were irrigated as usual. The four cultivars differed in their response to drought, with ICPL 215 being the most tolerant cultivar. In the plants exposed to the 13-day water stress, the first stress cycle resulted in preconditioning of plants such that higher values for carbon dioxide exchange rate and relative water content were observed in the second stress cycle. The longer stress period (16 days) resulted in some damage to the photosynthetic capacity and in a slow recovery rate in both cycles. During the second drought cycle the plants retained a water content above the critical value, possibly due to osmotic adjustment. It seems that water status parameters, especially relative water content, may serve as indicators of drought tolerance in pigeon pea varieties and may be useful in breeding programs for cultivation of pigeon pea under semiarid conditions.

Notes: Abstract In most cases, rice production is associated with flooding irrigation and the efficiency of irrigated water use (WUEi) is generally lower for production of rice than for other crops. We have examined the effects of various irrigation regimes on water consumption in a well-puddled paddy field, as well as on dry matter production, grain yield and physiological responses of the plants. Four sets of conditions were studied, with two replications, in the well-puddled paddy field: Continuous flooding irrigation treatment (CSF); three intermittent irrigation treatments, designated II-0, II-1 and II-2, in which plants were re-irrigated when the water potential of the soil fell below 0, –10, and –20 kPa at a depth of 5 cm, respectively. Water consumption was lower during II-0 than during CSF because the percolation rate was reduced by the reduction in the hydraulic head of the ponded water. Intermittent irrigation led to the repeated shrinking and swelling of soil during II-1 and II-2 and, therefore, soil cracks developed rapidly. Since they became the major routes of water percolation, these soil cracks increased water consumption during II-1 and II-2 above that during CSF and II-0. There were no significant differences in dry matter production and grain yield between CSF and II-0, but both were significantly greater than in the case of II-1 and II-2. Therefore, WUEi increased in the following order: II-0, CSF, II-2, II-1, although the difference was very small between II-1 and II-2. A lower crop growth rate (CGR) resulted from a decrease in the net assimilation rate (NAR) during II-1 and II-2, and there was also a reduction in the leaf area index (LAI) during II-2. Early senescence with ripening and water stress around midday decreased the rate of photosynthesis in leaves, causing the lower NAR. These physiological responses of the plants were responsible for the reduction on the dry matter production and grain yield in the intermittent irrigation.

Notes: Abstract A CO2 assay circuit adapted to in vitro culture was designed to investigate CO2 exchanges in test tube-grown Vitis rupestris plantlets. The CO2 concentration of the air in culture tubes was measured by injection of samples in the open circuit. It was observed under the culture conditions used that the CO2 content stabilized during the light phase at 3 times the CO2 compensation point. Measurements of dark respiration under closed circuit conditions at every two-hour interval during the night did not reveal any limiting by lack of the substrate under mixotrophic culture conditions. A mathematical model of the influence of ambient CO2 concentration on net CO2 uptake rates under closed circuit conditions was devised and used to compare net photosynthesis at different lighting levels. Measurement of CO2 evolution into CO2-free air under open circuit conditions revealed a post-illumination burst characteristic of photorespiration which increased with the temperature.

Notes: Summary The responses of six wheat genotypes to water stress were analysed. Soil moisture (H), leaf water potential (Ψw), photosynthesis (PN), stomatal resistance (rs) and transpiration (T) were measured during a water stress. The genotypes investigated differed in their stress avoidance (Ψw-H relationship) and their stress tolerance (PN-Ψw and rs-Ψw relationships). The most important differences observed concern the mechanisms of tolerance at low leaf water potential: two varieties, Haurani 27 and Baalback, can then maintain a high photosynthetic activity. These observations are in agreement with the drought resistance characteristics already known for these genotypes. Possible applications to wheat breeding are considered

Notes: Summary Net photosynthesis and dark respiration of sixteen selected tomato genotypes grown under low light intensity and low night temperatures were measured. Differences between genotypes in net photosynthesis and dark respiration were present. In all genotypes an increase of net photosynthesis with time was observed. Significant genotypic differences in this respect were established. The rate of dark respiration remained constant throughout the experimental period. The photosynthesis on a leaf area basis and dark respiration were not affected by the night temperature. Net photosynthesis on a fresh weight basis was lower under the lower night temperatures.

Notes: Summary The photosynthetic characteristics of the penultimate leaf in barley genotypes (reciprocal F1 combinations and varieties) were studied at the flowering stage in order to analyze the relationship between these traits and the biological yield and the economic yield. The biological yield was correlated with the leaf area whereas the economic yield was more dependent on the green area duration of the leaf or the combination of the two factors, leaf area and green area duration. The net photosynthesis per unit leaf area, determined at anthesis, was not a factor of productivity. On the other hand, the chlorophyll fluorescence (P), which was negatively correlated with the leaf area (+0.5) and with the combination of leaf area and green area duration (+0.5), was found to be a good marker of the economic yield. In view of its high heritability, it may provide an effective selection criterion.

Notes: Summary A durum wheat cultivar Langdon (LDN) and fourteen disomic D genome chromosome substitution lines of Langdon, where A or B genome chromosomes were replaced with homoeologous D genome chromosomes of Chinese Spring (CS), were used to assess the compensatory effect of the D genome chromosomes on photosynthetic rates at tetraploid level. The LDN 1D(1B) and LDN 3D(3B) lines showed significantly higher photosynthetic rates than ‘Langdon’, whereas LDN 1D(1A) and LDN 3D(3A) lines were not greatly different from ‘Langdon’. It appears that chromosomes 1B and 3B decrease photosynthesis. This suggests the differentiation of the effects on the photosynthesis within the first and third homoeologous groups. Substitution with the 2D chromosomes did not compensate the effects of either 2A or 2B chromosomes as it reduced photosynthetic rate compared to plant with either chromosomes 2A or 2B. Tetra CS had a higher photosynthetic rate than CS and Penta CS. The photosynthetic rate of CS was similar to that of Penta CS, which lacked one set of D genome. The results suggest that it may be possible to increase photosynthesis, if both sets of the D genome were entirely removed from hexaploid wheat. However, it is difficult to conclude that the lower rate of photosynthesis of the hexaploids was mainly attributable to D genome chromosome effects, because we did not find a dose dependent effect of D genome. Homoeologous differentiation of chromosomes may be involved in photosynthesis.

Notes: Abstract A newly developed fluorescence measuring system is employed for the recording of chlorophyll fluorescence induction kinetics (Kautsky-effect) and for the continuous determination of the photochemical and non-photochemical components of fluorescence quenching. The measuring system, which is based on a pulse modulation principle, selectively monitors the fluorescence yield of a weak measuring beam and is not affected even by extremely high intensities of actinic light. By repetitive application of short light pulses of saturating intensity, the fluorescence yield at complete suppression of photochemical quenching is repetitively recorded, allowing the determination of continuous plots of photochemical quenching and non-photochemical quenching. Such plots are compared with the time courses of variable fluorescence at different intensities of actinic illumination. The differences between the observed kinetics are discussed. It is shown that the modulation fluorometer, in combination with the application of saturating light pulses, provides essential information beyond that obtained with conventional chlorophyll fluorometers.

Notes: Abstract Excitation energy distribution in Porphyridium cruentum in state 1 and state 2 was investigated by time resolved 77 K fluorescence emission spectroscopy. The fluorescence rise times of phycoerythrin, phycocyanin and allophycocyanin (in cells in state 1 and state 2) were very similar in contrast to the emission from chlorophyll a (Chl a) associated with the two photosystems. In state 2 photosystem II (PSII) Chl a fluorescence emission rose faster than the PSI Chl a emission and decayed more rapidly, and the converse was observed in state 1. These kinetic data support the concept of increased energy transfer from PSII Chl a to PSI Chl a in state 2 in P. cruentum.

Notes: Abstract The nature of the different processes of O2 uptake involved in the light in the red macroalga Chondrus crispus Stackhouse (Rhodophyta, Gigartinales) was investigated. At limiting CO2, INH (2.5 mM) did not alter the O2 uptake rate. Glycolate was not excreted and did not accumulate within the cells. KCN reduced the rate of O2 uptake in the light by 76% at limiting CO2 and by 43% at saturating CO2, but caused 〉 95% inhibition of O2 evolution. DCMU (5 μM) totally blocked the photosynthetic electron transport chain, but allowed a residual O2 uptake of 3.0±0.6 μmol O2 .h−1.g−1 FW, irrespective of the CO2 concentration. In saturating CO2, a high light intensity pretreatment significantly stimulated the rate of O2 uptake compared to net O2 evolution, suggesting the persistence, in the light, of mitochondrial respiration. Irrespective of the CO2 concentration, the optimum temperature for O2 evolution was 17°C whereas dark O2 uptake increased linearly with temperature. In contrast, O2 uptake in the light showed an optimum at 17°C in limiting CO2, and 21–25° C in saturating CO2; its Q10 was 2.4 at limiting CO2, a value close to that of RuBP oxygenase, and 3.1 at saturating CO2, a value close to that of dark respiration. It is concluded that: 1) mitochondrial respiration and Mehler reaction are both involved at all CO2 concentrations, 2) RuBP oxygenase activity cannot account for more than 45%, and Mehler reaction for less than 20%, of the total O2 uptake observed in the light at limiting CO2.

Notes: Abstract Nearest neighbour relationships within the LHC2-PS2 complex were investigated by using the reversible crosslinking agent dithiobis(succinimidyl propionate) (DSP). This was accomplished by treating PS2-enriched membranes, prepared from chloroplasts of Pisum sativum, with the crosslinker followed by diagonal electrophoresis of the solubilised polypeptides. Analysis of the off-diagonal spot patterns produced by crosslinker cleavage and second dimension electrophoresis was made on the basis of: staining with Coomassie blue or silver, labelling with [35S]-methionine, and sensitivity to 1 M NaCl washing. It was concluded that LHC2 polypeptides crosslinked with several components of the PS2 complex and that the extrinsic polypeptides associated with water oxidation, having approximate molecular weights of 16 and 23 kDa, crosslink to form homodimers. The latter finding suggests that there may be more than one copy of each of these polypeptides per PS2 complex.

Notes: Abstract An immunological method for quantitative determination of photosynthetic fructose-1,6-bisphosphatase in crude extracts of leaves is proposed. It is based on the ELISA technique, and offers two modifications. A non-competitive technique has a higher sensitivity and is the right option for samples of low fructose-1,6-bisphosphatase content. However, this method is not sufficiently specific when the total protein is higher than 5 μg/cm3; so, despite its lower sensitivity, in these circumstances a competitive technique is more suitable. Thus photosynthetic fructose-1,6-bisphosphatase can be measured without interferences from the gluconeogenic cytosolic enzyme of the photosynthetic cell or from a non-specific phosphatase present in the chloroplast.

Notes: Abstract Light-saturated photosynthetic rates at air levels of carbon dioxide were measured about weekly in upper canopy leaves of two soybean cultivars grown at stand densities of 40 and 100 plants per square meter. Early in the season, when leaf area indices differed between stand densities, plants of both cultivars grown at high stand density had photosynthetic rates which averaged 23% lower than plants at low stand density. Later in the season, when there were no differences in leaf area index between stand densities, there were no differences in photosynthetic rates in the cultivar Kent, but rate differences of about 14% persisted in the cultivar Williams. In Williams mainstem leaves emerged into full sunlight later in their development at high than at low stand density. In both cultivars the oldest fully exposed leaves were photosynthetically immature for much of the season, as higher rates could be achieved by lower leaves which were shaded in situ. The results identify shading of young developing leaves and photosynthetic immaturity of fully exposed leaves as factors limiting canopy photosynthesis in soybeans, and indicate cultivar differences in how much high stand density reduces photosynthetic capacity.

Notes: Abstract Effects of rising atmospheric CO2 concentrations on gas exchange, growth and productivity were investigated on an important grassland species, Trifolium repens L. cv. Blanca. Pure stands of this species were cultivated over an entire growing season in small acrylic greenhouses with an artificial atmosphere of ±367 or ±620 ppm CO2, respectively. Effects on growth and development were examined in a functional growth analysis, while consequences for gas exchange were determined by photosynthesis and transpiration measurements on canopy level. The stands were regularly clipped for production assessment. Canopies grown at high CO2 levels showed an average increase in productivity of almost 75%. Growth analysis indicated development of a larger foliage area as the major cause, particularly in the first days of regrowth after cutting. The growth advantage that began in this stage was maintained or bettered during the following weeks. The difference between gas exchange measurements expressed per unit leaf area and per unit ground area suggested that changes in net photosynthesis and respiration did not contribute to the increase in total yield. Transpiration declined under high CO2 if expressed on a leaf area basis but total canopy transpiration was at least as large as in ambient CO2 due to the larger leaf area. Water-use efficiency calculations on the summer data indicated a 35% improvement with a doubling of CO2 concentration.

Notes: Abstract Manipulation of the CO2 concentration of the atmosphere allows the selection of photorespiratory mutants from populations of seeds treated with powerful mutagens such as sodium azide. So far, barley lines deficient in activity of phosphoglycolate phosphatase, catalase, the glycine to serine conversion, glutamine synthetase, glutamate synthase, 2-oxoglutarate uptake and serine: glyoxylate aminotransferase have been isolated. In addition one line of pea lacking glutamate synthase activity and one barley line containing reduced levels of Rubisco are available. The characteristics of these mutations are described and compared with similar mutants isolated from populations of Arabidopsis. As yet, no mutant lacking glutamine synthetase activity has been isolated from Arabidopsis and possible reasons for this difference between barley and Arabidopsis are discussed. The value of these mutant plants in the elucidation of the mechanism of photorespiration and its relationships with CO2 fixation and amino acid metabolism are highlighted.

Notes: Abstract In order to understand more fully chloroplast genetic systems, we have determined the complete nucleotide sequence (155, 844 bp) of tobacco (Nicotiana tabacum var. Bright Yellow 4) chloroplast DNA. It contains two copies of an identical 25,339 bp inverted repeat, which are separated by 86, 684 bp and 18,482 bp single-copy regions. The genes for 4 different rRNAs, 30 different tRNAs, 44 different proteins and 9 other predicted protein-coding genes have been located. Fifteen different genes contain introns. Twenty-two genes for components of the photosynthetic apparatus have so far been identified. Most of the genes (except the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase) code for thylakoid membrane proteins. Twenty of them are located in the large single-copy region and one gene for a 9-kd polypeptide of photosystem I is located in the small single-copy region. The gene for the 32-kd protein of photosystem II as well as the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase have strong promoters and are transcribed monocistronically while the other genes are transcribed polycistronically. We have found that the predicted amino acid sequences of six DNA sequences resemble those of components of the respiratory-chain NADH dehydrogenase from human mitochondria. As these six sequences are highly transcribed in tobacco chloroplasts, they are probably genes for components of a chloroplast NADH dehydrogenase. These observations suggest the existence of a respiratory-chain in the chloroplast of higher plants.

Notes: Abstract The presence of four photosystem II proteins, CP47, CP43, D1 and D2, was monitored in mutants of Synechocystis sp. PCC 6803 that have modified or inactivated genes for CP47, CP43, or D2. It was observed that: (1) thylakoids from mutants without a functional gene encoding CP47 are also depleted in D1 and D2; (2) inactivation of the gene for CP43 leads to decreased but significant levels of CP47, D1 and D2; (3) deletion of part of both genes encoding D2, together with deletion of part of the CP43-encoding gene causes a complete loss of CP47 and D1; (4) thylakoids from a site-directed mutant in which the His-214 residue of D2 has been replaced by asparagine do not contain detectable photosystem II core proteins. However, in another site-directed mutant, in which His-197 has been replaced by tyrosine, some CP47 as well as breakdown products of CP43, but no D1 and D2, can be detected. These data could indicate a central function of CP47 and D2 in stable assembly of the photosystem II complex. CP43, however, is somewhat less critical for formation of the core complex, although CP43 is required for a physiologically functional photosystem II unit. A possible model for the assembly of the photosystem II core complex is proposed.

Notes: Abstract Two methods (whole-plant growth analysis and gas exchange) were used to measure the response of Psophocarpus tetragonolobus (L.) DC cultivar ‘UPS 99’ to the environment. This plant had an optimal temperature for root growth of 25°C, its rate of acetylene reduction (when inoculated with Rhizobium, strain ‘RRIM 56’) was maximal at 30°C and it required an atmospheric temperature of about 35°C for optimal shoot growth. Maximum water-use efficiency was ca. 33 mg CO2·g H2O-1. The rate of photosynthesis reached a plateau at 900 vpm CO2-this condition also gave the lowest rate of transpiration. Under normal conditions, the light compensation point was at 1.7 klx, while that for CO2 was 60 vpm. Photorespiration diminished gross photosynthesis of P. tetragonolobus by forty percent. Water stress (as measured by sensitivity to slightly increased CO2 levels) caused rapid closure of stomata, and the response was ‘remembered’ for up to five days.

Notes: Abstract The time courses of some Photosystem II (PS II) parameters have been monitored during in-vivo and in-vitro photoinhibition of spinach chloroplasts, at room temperature and at 10 °C or 0 °C. Exposing leaf discs of low-light grown spinach at 25 °C to high light led to photoinhibition of chloroplasts in-vivo as manifested by a parallel decrease in the number of functional PS II centres, the variable chlorophyll fluorescence at 77K (F v /F m ), and the number of atrazine-binding sites. When the photoinhibitory treatment was given at 10 °C, the former two parameters declined in parallel but the loss of atrazine-binding sites occurred more slowly and to a lesser extent. During in-vitro photoinhibition of chloroplast thylakoids at 25 °C, the loss of functional PS II centres proceeded slightly more rapidly than the loss of atrazine-binding sites, and this difference in rate was further increased when the thylakoids were photoinhibited at 0 °C. During the recovery phase of leaf discs (up to 9 h) the increases in F v /F m preceded that of the number of functional PS II centres, while only a further decline in the number of atrazine-binding sites was observed. The recovery of variable chlorophyll fluorescence and the concentration of functional PS II centres occurred more rapidly at 25 °C than at 10 °C. These results suggest that the photoinhibition of PS II function is a relatively temperature-independent early photochemical event, whereas the changes in the concentration of herbicide-binding sites appear to be a more complex biochemical process which can occur with a delayed time course.

Notes: Abstract Recovery from photoinhibition of photosynthesis in intact Lemna gibba was studied in presence of the protein synthesis inhibitors chloramphenicol and cycloheximide. Exposure to an irradiance of 1000 μmol m-2s-1 in N2 for 90 min induced 80% photoinhibition. The plants recovered photosynthesis when transfered to normal irradiances (210 μmol m-2s-1) and air. Chloramphenicol added to the medium was taken up by the plant and reduced photosynthesis slightly. Recovery from photoinhibition was more inhibited than photosynthesis. Cycloheximide was also taken up by the plants and reduced synthesis of light harvesting chlorophyll protein: however, neither photosynthesis nor recovery were much affected. Synthesis of 32-kD chloroplast protein during recovery was inhibited by chloramphenicol, but not by cycloheximide. Synthesis of 32-kD protein was enhanced by 20–210 μmol m-2s-1 light. The results support the hypothesis that synthesis of 32-kD protein is important for recovery of photosynthesis after photoinhibition.

Notes: Abstract Inhibition of electron flow from H2O to methylviologen by 3-(3′4′ dichlorophenyl)-1,1 dimethyl urea (DCMU), yields a biphasic curve — an initial high sensitivity phase and a subsequent low sensitivity phase. The two phases of electron flow have a different pH dependence and differ in the light intensity required for saturation. Preincubation of chloroplasts with ferricyanide causes an inhibition of the high sensitivity phase, but has no effect on the low sensitivity phase. The extent of inhibition increases as the redox potential during preincubation becomes more positive. Tris-treatment, contrary to preincubation with ferricyanide, affects, to a much greater extent, the low sensitivity phase. Trypsin digestion of chloroplasts is known to block electron flow between Q A and Q B, allowing electron flow to ferricyanide, in a DCMU insensitive reaction. We have found that in trypsinated chloroplasts, electron flow becomes progressively inhibited by DCMU with increase in pH, and that DCMU acts as a competitive inhibitor with respect to [H+]. The sensitivity to DCMU rises when a more negative redox potential is maintained during trypsin treatment. Under these conditions, only the high sensitivity, but not the low sensitivity phase is inhibited by DCMU. The above results indicate the existence of two types of electron transport chains. One type, in which electron flow is more sensitive to DCMU contains, presumably Fe in a Q A Fe complex and is affected by its oxidation state, i.e., when Fe is reduced, it allows electron flow to Q B in a DCMU sensitive step; and a second type, in which electron transport is less sensitive to DCMU, where Fe is either absent or, if present in its oxidized state, is inaccessible to reducing agents.

Notes: Abstract Membranes and PS II particles retaining high rates of O2-evolving activity have been isolated from the transformable cyanobacterium, Synechocystis sp. PCC6803. Membranes from cells grown under red light exhibit rates of O2-evolution ranging from 500–700 μmole O2/mg chl/h. PS II particles are prepared by a simple procedure involving DEAE column chromatography of detergent extracts obtained by simultaneous treatment of membranes with octylglucoside and dodecylmaltoside. The isolated PS II fraction is enriched in polypeptides immunologically cross-reactive with polypeptides present in core reaction center preparations of spinach, exhibits 77 K fluorescence emission maxima at 685 and 696 nm, but not emission and absorption due to phycobilines and is capable of rates of O2-evolution exceeding 1000 μmole O2/mg chl/h.

Notes: Abstract The membrane-bound photooxidizable cytochrome c-554 from Chloroflexus aurantiacus has been purified. The purified protein runs as a single heme staining band on SDS-PAGE with an apparent molecular mass of 43 000 daltons. An extinction coefficient of 28 ± 1 mM−1 cm−1 per heme at 554 nm was found for the dithionite-reduced protein. The potentiometric titration of the hemes takes place over an extended range, showing clearly that the protein does not contain a single heme in a well-defined site. The titration can be fit to a Nernst curve with midpoint potentials at 0, +120, +220 and +300 mV vs the standard hydrogen electrode. Pyridine hemochrome analysis combined with a Lowry protein assay and the SDS-PAGE molecular weight indicates that there are a minimum of three, and probably four hemes per peptide. Amino acid analysis shows 5 histidine residues and 29% hydrophobic residues in the protein. This cytochrome appears to be functionally similar to the bound cytochrome from Rhodopseudomonas viridis. Both cytochrome c-554 from C. aurantiacus and the four-heme cytochrome c-558-553 from R. viridis appear to act as direct electron donors to the special bacteriochlorophyll pair of the photosynthetic reaction center. They have a similar content of hydrophobic amino acids, but differ in isoelectric point, thermodynamic characteristics, spectral properties, and in their ability to be photooxidized at low temperature.

Notes: Abstract This study investigated the basis of the negative relationship between leaf size and photosynthetic rate per unit of area among five cultivars of soybeans. Exposure of developing mainstem leaves to light, and sizes and light saturated photosynthesis rates of those leaves at maturity were compared in cultivars grown in field plots for two years at Beltsville, Maryland, USA. Plants were grown both in stands at 2.5 cm by 1 m spacing and as isolated plants. While cultivar differences in leaf size were large and consistent in both planting arrangements, significant cultivar differences in light saturated photosynthetic rates were found only in plants grown in stands. Similarly, leaf size was significantly correlated with specific leaf weight only for plants grown in stands. The mainstem apex and developing mainstem leaves experienced more severe shading in large-leaved cultivars than in small-leaved cultivars when plants were grown in stands. Thus, cultivar differences in photosynthetic capacity were probably a consequence of differences in the exposure of developing leaves to light.

Notes: Abstract The photosynthetic energy storage yield of uncoupled thylakoid membranes was monitored by photoacoustic spectroscopy at various measuring beam intensities. The energy storage rate as evaluated by the half-saturation measuring beam intensity (i50) was inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea, by heat inactivation or by artificial electron acceptors specific for photosystem I or photosystem II; and was activated by electron donors to photosystem I. The reactions involving both photosystems were all characterized by a similar maximal energy storage yield of 16±2 percent. The data could be interpreted if we assumed that the energy storage elicited by the photosystems at 35 Hz is detected at the level of the plastoquinone pool.