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1

Electronic Resource

Effects of temperature and irradiance on non-structural carbohydrate accumulation in barley primary leaves (1986)

Sicher, Richard C. ; Kremer, Diane F.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 66 (1986), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Non-structural storage carbohydrates were measured in 9-day-old barley (Hordeum vulgare L. cv. Brant) primary leaves. Accumulation rates of starch, sucrose and total non-structural carbohydrates (TNC) were approximately linear when measured between 2- and 12-h of light. Progressively higher TNC accumulation rates were observed at higher irradiance levels (i.e., comparing 250, 550 and 1050 ·mol m−2 s−1). Synthesis of a low-molecular-weight fructan also was enhanced by high irradiances. Low irradiance treatments decreased leaf sucrose levels and there was a corresponding increase in the lag period preceding starch synthesis in the light. Increased starch accumulation rates were usually observed when sucrose concentrations were high. These and other results suggested that cytosolic sucrose concentrations affected starch metabolism in the chloroplast. However, sucrose accumulation rates increased and starch storage decreased when barley seedlings were transferred from 20 to 10°C during the light period. Lowering the night temperature from 20 to 10°C for a single dark period 8-days after planting increased the TNC content of barley primary leaves at the beginning of day nine. In this experiment, TNC accumulation rates of treated and untreated leaves were similar. Changes in the accumulation rate of TNC were usually observed within 2- to 4-h after barley seedlings were exposed to altered environmental conditions. Monitoring rapid changes in leaf carbohydrate levels is a sensitive method for assessing the effects of environmental treatments on photosynthetic metabolism.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb05936.x

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2

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Responses of Nicotiana tabacum to CO2 enrichment at low-photon flux density (1994)

Sicher, Richard C. ; Kremer, Diane F.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 92 (1994), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Effects of CO2 enrichment on photosynthesis and on dry matter allocation were examined in two tobacco (Nicotiana tabaum L.) genotypes. Samsun and W38. Plants were grown from seed in controlled environment chambers at a photosynthetic photon flux density of 450 μmol m−2 s−1. Averaged over the 9 day study, net photosynthesis rates were 14.2±0.5 and 13.0±0.4 μmol m−2 s−1 in elevated (70 Pa) and in ambient (35 Pal CO2 air. respectively, when measured at the irradiance and CO2 partial pressure employed for plant growth. However. photosynthesis rates of plants grown in elevated CO2 were 50% less than those of the ambient controls on the last day of treatment, when measured al 70 Pa CO2 air and an irradiance of 900 μmol m−2 s−1 Total plant dry weight and specific leaf weight were greater (P 〈 0.051 in enriched-CO2-grown than in ambient-CO2-grown plants. Leaf starch, measured during the first hour of the photoperiod. increased over 7 days of treatment in elevaled-CO2-grown but not in ambient-CO2-grown plants. Ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) activities of tobacco plants grown at 35 and 70 Pa CO2 air were 58.5±4.5 and 48.5±3.7 umol m−2 s−1. respectively, between days 0 and 9 of the study. Rubisco activation state. Rubisco protein concentration. soluble protein and total chlorophyll were unaffected by CO2 enrichment. The above findings demonstrated that photosynthesis was down regulated in tobacco plants after 7 to 9 days of CO2 enrichment at low photosynthetic photon flxu density, but less than at moderate irradiances.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb08825.x

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3

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Photosynthate partitioning in diploid and autotetraploid barley (Hordeum vulgare) (1984)

Sicher, Richard C. ; Kremer, Diane F. ; Harris, William G. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 60 (1984), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Net rates of carbon assimilation per unit leaf area by fully expanded, vegetative leaves of diploid (2x) and autotetraploid (4x) barley (Hordeum vulgare L. cultivars OAC-21 and Brant) were not significantly different (90% level) when measured under controlled environment conditions with air levels of CO2 and either 2 or 20% O2. Leaf thickness increased with ploidy so that net photosynthetic rates measured on single leaves were lower for 4x than 2x barley varieties when compared on a dry or fresh weight basis. Rates of 14CO2 fixation by isolated mesophyll protoplasts prepared from seedlings were also lower for 4x than 2x varieties [about 108 and 125 μmol (mg ChI)−1 h−1, respectively]. Carbohydrate accumulation in leaves of 5-weekold plants averaged 28% (2x) and 47% (4x) of the total photosynthetic weight gain during the first 9 h of the light period. Estimated photoassimilate export from leaves was 15% (OAC-21) and 38% (Brant) lower for 4x compared to 2x isolines. The sucrose and oligofructan content of 4x compared to 2x leaves increased as a result of decreased photosynthate transport.Total tiller dry weight of plants raised in a glasshouse was greater for 4x than 2x barley varieties at ear emergence, but tiller height decreased with increasing ploidy. The nonstructural carbohydrate content of the inflorescence, leaves and lower stem organs was significantly (P≤ 0.01) higher in 4x than in 2x lines at this sampling. During the first 15 days of grain development total tiller dry weight increased by 46% (2x) compared to 8% (4x) when the results of both varieties were averaged together. The dry weight gain of the ear during this period was about 60 to 80% lower for 4x compared to 2x isolines. The nonstructural carbohydrate content of the inflorescence was also about 24% (Brant) and 51% (OAC-21) lower for 4x as compared to 2x plants 15 days post ear emergence. The above results suggested that photosynthate partitioning in autotetraploid barley was sink-limited.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb04571.x

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Control of carbohydrate metabolism in a starchless mutant of Arbidopsis thaliana (1992)

Sicher, Richard C. ; Kremer, Diane F.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 85 (1992), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The biochemical regulation of photosynthate partitioning was investigated in a starchless mutant (TC7) of Arabidopsts thaliana (L.) Henyh, that was deficient in chloroplast phosphoglucomutase (Caspar et al. 1985. Plant Physiol. 79: 11–17). Plants were raised at 20°C with a 20 h light and 4 h dark period, so that the growth rates of the mutant and wild type were similar. Two or 3 isoforms of phosphoglucomutase were separated by ion-exchange chromatography using mutant and wild type leaf preparations, respectively. Initial rate kinetics of all isoforms were similar. Light-saturated photosynthetic oxygen evolution rates of the mutant and wild type were 224 and 302 nmol g-1 chlorophyll h-1, respectively. Starch, sucrose and hexose concentrations were unchanged in wild type leaves after a dark to light transition, whereas sucrose and hexose increased in mutant leaves. Hexose-phosphates accumulated in both genotypes in the light, although the steady-state leaf concentrations of glucose 6-phosphate were 3-fold higher in mutant than in wild type samples. Fructose 2,6-bisphosphate and glucose 1,6-bisphosphate were lower in the mutant than in the wild type at the end of the dark period when mutant leaves were depleted of carbohydrates. Levels of UTP were lower in the mutant than in the wild type, possibly indicating that growth conditions had induced phosphate limited photosynthesis. These results are discussed in relation to the regulation of photosynthetic carbon metabolism.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb05810.x

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5

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Reversibility of photosynthetic acclimation of swiss chard and sugarbeet grown at elevated concentrations of CO2 (1995)

Ziska, Lewis H. ; Sicher, Richard C. ; Kremer, Diane F.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 95 (1995), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Although leaf photosynthesis and plant growth are initially stimulated by elevated CO2 concentrations, increasing insensitivity to CO2 (acclimation) is a frequent occurrence. In order to examine the acclimation process, we studied photosynthesis and whole plant development in swiss chard (Beta vulgaris L. Koch ssp. ciela) and sugarbeet (Beta vulgaris L. ssp. vulgaris) grown at either ambient or twice ambient concentrations of CO2. In an initial controlled environment study, photosynthetic acclimation to elevated CO2 levels was observed in both subspecies 24 days after sowing (DAS) but was not observed at 42 and 49 DAS for sugarbeet or at 49 DAS for swiss chard. Although sugarbeet and swiss chard differed in root size and morphology, this was not a factor in the onset of photosynthetic acclimation. The reversal of photosynthetic acclimation that was observed in older plants grown at elevated CO2, concentrations was associated with a rapid increase in root development (i.e. increased root: shoot [R/S] ratio), increased sucrose levels in sinks (roots) and no differences in total soluble leaf protein of either subspecies relative to the ambient CO2 condition. In a second set of experiments, swiss chard and sugarbeet were grown in outdoor Plexiglass chambers at different times of the year (i.e. summer and early fall). Average 24-h temperature was 30.7 and 19.4°C for the summer and fall plantings, respectively. In agreement with the controlled environment study, lack of photosynthetic acclimation, determined from the response of photosynthesic rate to internal CO2 concentration, was correlated with increased root biomass and sucrose concentration relative to the ambient condition. However, photo-synthetic acclimation was observed depending on the season, i.e. summer (swiss chard) or fall (sugarbeet), suggesting that acclimation was affected by environmental factors, such as temperature. Data from both experiments suggest that continued long-term photosynthetic stimulation may be dependent upon the ability of increased CO2 to stimulate new sink development which would allow full utilization of the additional carbon made available in a high CO2 environment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00849.x

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6

Electronic Resource

Photosynthetic acclimation and photosynthate partitioning in soybean leaves in response to carbon dioxide enrichment (1995)

Sicher, Richard C. ; Kremer, Diane F. ; Bunce, James A.

Springer

Photosynthesis research 46 (1995), S. 409-417

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ISSN: 1573-5079

Keywords: sink-limited photosynthesis ; starch ; carbohydrate metabolism ; Glycine max ; Rubisco

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Photosynthetic rates and photosynthate partitioning were studied in three-week-old soybean [Glycine max (L.) Merr. cv. Williams] plants exposed to either ambient (35 Pa) or elevated (70 Pa) CO2 in controlled environment chambers. Ambient CO2-grown plants also were given a single 24 h treatment with 70 Pa CO2 1 d prior to sampling. Photosynthetic rates of ambient CO2-grown plants initially increased 36% when the measurement CO2 was doubled from 35 to 70 Pa. Photosynthetic rates of the third trifoliolate leaf, both after 1 and 21 d of elevated CO2 treatment, were 30 to 45% below those of ambient CO2-grown plants when measured at 35 Pa CO2. These reduced photosynthetic rates were not due to increased stomatal resistance and were observed for 2 to 8 h after plants given 1 d of CO2 enrichment were returned to ambient CO2. Initial and total ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activities, percent activation, Rubisco protein, soluble protein and leaf chlorophyll content were similar in all CO2 treatments. Quantum yields of photosynthesis, determined at limiting irradiances and at 35 Pa CO2, were 0.049±0.003 and 0.038±0.005 mol CO2 fixed per mol quanta for ambient and elevated CO2-grown plants, respectively (p〈0.05). Leaf starch and sucrose levels were greater in plants grown at 70 than at 35 Pa CO2. Starch accumulation rates during the day were greater in ambient CO2-grown plants than in plants exposed to elevated CO2 for either 1 or 21 d. However, the percentage of C partitioned to starch relative to total C fixed was unaffected by 1 d of CO2 enrichment. The above results showed that both photosynthetic and starch accumulation rates of soybean leaflets measured at 35 Pa CO2 were temporarily reduced after 1 and 21 d of CO2 enrichment. The biochemical mechanism affecting these responses was not identified.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00032295

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