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1

Electronic Resource

Optimum experimental design for Free-Air Carbon dioxide Enrichment (FACE) studies (2000)

Filion, Mathieu ; Dutilleul, Pierre ; Potvin, Catherine

Oxford, UK : Blackwell Science Ltd

Global change biology 6 (2000), S. 0

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ISSN: 1365-2486

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography

Notes: This article presents the logical reasoning underlying the optimal design of an experiment. We used Free-Air Carbon dioxide Enrichment (FACE) experiments to illustrate this trade-off as such experiments are particularly costly. On a theoretical basis, two-way nested designs and split-plot designs have similar power in testing carbon dioxide (CO2) main effects. If researchers have the choice of adding two replicate rings or two control plots to their experiment, our results show that both options provide a substantial gain in statistical power, with a slightly greater gain in the former case and at reduced financial cost in the latter. The former option, however, provides an insurance against possible ring failure.On an empirical basis, we analysed a preliminary FACE photosynthesis dataset collected at Duke University. The experiment was designed as a split-plot design to test the effects of growth environment (GROWTH) and measurement CO2 concentration (MEAS) on photosynthetic rates of loblolly pine. Although a significant effect of MEAS was observed, we failed to detect a significant main effect of GROWTH. Power analysis was used to understand why the GROWTH main effect was not significant. The minimum detectable difference between treatment means that we calculated for GROWTH in this experiment was 4.04 μmol CO2 m−2 s−1 for a statistical power of 0.90, whereas the observed difference was 0.16 μmol CO2 m−2 s−1.Our recommendations for the design of FACE experiments are: (i) consider a second treatment factor with many levels within each ring in order to obtain a split-plot design that provides a powerful test of interaction between treatment factors; (ii) add control plots, unless financial constrictions disallow for necessary personnel; (3) pool the data of FACE experiments conducted in comparable ecosystems (e.g. forests or grasslands), with two rings per treatment level at each site.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2486.2000.00353.x

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2

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Differences in photosynthetic characteristics among northern and southern C4 plants (1987)

Potvin, Catherine

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 69 (1987), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Both responses to short-term changes of temperature and to chilling under high light were analyzed in populations of Echinochloa crus-galli var. crus-galli (L.) Beauv. from Québec. North Carolina and Mississippi to improve the understanding of C4 photosynthesis at low temperature. Comparison also included plants of Eleusine indica (L.) Gaertn. from Mississippi to provide for differences among species and populations. Plants were grown at two thermoperiods (28/22°C, 21/15°C). After transfer from cool (21/15°C) to warm (28/22°C) growth conditions, Echinochloa from Mississippi achieved the highest photosynthetic rates. Plants from Québec maintained the highest rates of CO2 uptake upon transfer to cool conditions. Exposure to 7°C for 3 days at a photon fluence rate of 1000 μmol m−2s−1 resulted in a reduction in the growth rates of all populations. This reduction was paralleled by a decrease in net photosynthesis and in stomatal conductance. Following chilling under hight light, the reduction in growth parameters was less important for plants from Québec than for the other populations. It suggests that, among other characteristics, northern plants had developed a certain tolerance to chilling under light.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb01981.x

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3

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Effect of low temperature on the photosynthetic metabolism of the C4 grass Echinochloa crus-galli (1986)

Potvin, Catherine ; Simon, Jean-Pierre ; Strain, Boyd R.

Springer

Oecologia 69 (1986), S. 499-506

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary CO2 curves of photosynthesis and activities of the four C4 enzymes and Ribulose bisphosphate carboxylase (RUBPc) were compared in two populations of the C4 grass Echinochloa crus-galli from contrasting thermal environments (Québec and Mississippi). Analyses were conducted both before and after 14 h of chilling at 7°C under high light conditions. This comparison provides the opportunity to assess which steps of the C4 pathway are more susceptible to become limiting at low temperatures. Both populations maintained, after chilling, a pattern of CO2 fixation typical of C4 plants with photosynthesis saturating at low external CO2 concentrations. However, the chilling treatment led to reductions in carbon uptake and in the activities of the C4 enzymes. RUBPc activity was not significantly affected by chilling. Reductions in photosynthesis and in C4 enzyme activities following the chilling treatment were significantly larger for plants of the Mississippi population. The enzyme data suggest that two steps of the C4 pathway, NADP+-malate dehydrogenase and pyruvate Pi dikinase, are likely to be associated with the reduction of CO2 uptake in C4 plants under cool conditions. When the experiment was replicated under enriched atmospheric CO2 (675 μl l-1 CO2), similar differences were observed between the two populations. CO2 enrichment resulted in an increase of activity for phospho-enol-pyruvate carboxylase and NADP+-malate dehydrogenase while activities of phospho-enol-pyruvate carboxylase and NADP+-malic enzyme were less reduced following chilling. Such an interaction was not observed for gas exchange parameters but net photosynthesis was lower when plants were grown under enriched CO2.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00410354

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4

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Thermal adaptation and acclimation of higher plants at the enzyme level: kinetic properties of NAD malate dehydrogenase and glutamate oxaloacetate transaminase in two genotypes of Arabidopsis thaliana (Brassicaceae) (1983)

Simon, Jean-Pierre ; Potvin, Catherine ; Blanchard, Marie-Hélène

Springer

Oecologia 60 (1983), S. 143-148

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Kinetic properties of NAD malate dehydrogenase (MDH) and glutamate oxaloacetate transaminase (GOT) were analyzed in two genotypes of Arabidopsis thaliana collected in two sites of contrasting climates. Plants from each genotype were acclimated under controlled conditions at four different thermoperiods: 5–10° C, 7–15° C, 15–25° C and 25–28° C. Apparent energy of activation for MDH of the cold adapted genotype were significantly lower at low temperatures of acclimation, while for GOT, significant differences were found but no clear patterns emerge from the data. No differences of significance between the two genotypes were observed for apparent K m and K cat of both enzymes. For MDH, apparent K ms for oxaloacetic acid increased as a positive function of assay temperature but for GOT, K ms for α-oxoglutaric acid did not vary significantly over the 10–35° C assay temperature range. K cat values for both enzymes increased about 2 fold for every 10° C raise in assay temperature. Concentrations of both enzymes significantly increased in plants of both genotypes acclimated to the coldest thermoperiod. The concentration of GOT was signficantly higher in plants of the cold adapted genotype acclimated to 5–10° C and 7–15° C. Results suggest that MDH and GOT from the cold adapted genotype are more efficient in the modulation of catalysis at low temperatures, while the opposite is found for plants of the warm-adapted genotype through enhanced thermostability of the mitochondrial fraction of MDH.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00379515

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5

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Evolutionary consequences of simulated global change: genetic adaptation or adaptive phenotypic plasticity (1996)

Potvin, Catherine ; Tousignant, Denise

Springer

Oecologia 108 (1996), S. 683-693

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ISSN: 1432-1939

Keywords: Artificial selection ; Brassica juncea ; Global change ; Inbreeding depression ; Evolutionary changes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract During the next century, natural and agricultural systems might need to adjust to a rapid increase in atmospheric CO2 concentration and global temperature. Evolution of genotypes adapted to this global change could play a central role in plants' response. The main purpose of this study was to determine the relative importance of phenotypic and genotypic responses of plants to global change. To do so, we selected two populations of the short-lived Brassica juncea, one under ambient conditions and another one under conditions simulating global change. After seven generations of selection, differences between the two populations were examined using a reciprocal transplant garden. We monitored 14 different traits and found evidence for genetic adaptation only once, for vegetative biomass early in the growth cycle. Of the 14 traits, 11 responded plastically to the environment, but only one of these plastic changes had a possible adaptive value. Overall, the long-term evolutionary consequences of global change will depend on the response of fitness-related traits. None of the five reproductive traits measured showed any evolutionary responses. The main conclusion of our study is that Brassica juncea was apparently unable to respond evolutionarily to simulated global change either by genetic adaptation or by adaptive phenotypic plasticity. The limit to selection was apparently due to inbreeding depression induced by the harsh conditions of the “predicted” environment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00329043

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6

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Effects of temperature and CO2 enrichment on kinetic properties of phospho-enol-pyruvate carboxylase in two ecotypes of Echinochloa crus-galli (L.) Beauv., a C4 weed grass species (1984)

Simon, Jean-Pierre ; Potvin, Catherine ; Strain, Boyd R.

Springer

Oecologia 63 (1984), S. 145-152

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Two populations of Echinochloa crus-galli (Québec, Mississippi) were grown at the Duke University Phytotron under 2 thermoperiods (28°/22°C, 21°/15°C day/night) and 2 CO2 regimes (350 and 675 μl l-1). Thermostability, energy of activation (E a ),K m (PEP), K m (Mg++), and specific activity of phospho-enol-pyruvate carboxylase (PEPc) were analyzed in partially purified enzyme preparations of plants grown for 5 weeks. Thermostability of PEPc from extracts (in vitro) and leaves (in situ) was significantly higher in Mississippi plants. In vitro denaturation was not appreciably modified by thermal acclimation but CO2 enrichment elicited higher thermostability of PEPc. In situ thermostability was significantly higher than that of in vitro assays and was higher in Mississippi plants acclimated at 28°/22°C and in plants of the two ecotypes grown at 675 μl l-1 CO2. E a (Q 10 30°/20°C) for PEPc was significantly lower in Québec plants as compared to Mississippi and no acclimatory shifts were observed. Significantly higher K m's (PEP) in 20°C assays were obtained for Mississippi as compared to Québec plants but values were similar at 30°C and 40°C assays. K m (Mg++) decreased at higher assay temperatures and were significantly lower for PEPc of the Québec ecotype. No significant changes in K m (Mg++) values were associated with modifications in temperature on CO2 regimes. PEPc activity measured at 30°C was significantly higher for Québec plants when measured on a leaf fresh weight, leaf area or protein basis but not on a chlorophyll basis. Significantly higher PEPc activity for both genotypes was observed for plants acclimated at 21°/15°C or grown at 675 μl l-1 CO2. Net photosynthesis (Ps) and net assimilation rates (NAR) were higher in Québec plants and were enhanced by CO2 enrichment. NAR was higher in plants acclimated at low temperature, while an opposite trend was observed for Ps. PEPc activities were always in excess of the amounts required to support observed rates of CO2 assimilation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00379870

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7

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Effects of temperature and CO2 enrichment on kinetic properties of NADP+-malate dehydrogenase in two ecotypes of Barnyard grass (Echinochloa crus-galli (L.) Beauv.) from contrasting climates (1989)

Simon, Jean-Pierre ; Potvin, Catherine ; Strain, Boyd R.

Springer

Oecologia 81 (1989), S. 138-144

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ISSN: 1432-1939

Keywords: Echinochloa crus-galli ; Ecotypes ; Temperature ; CO2 enrichment ; C4 metabolism ; NADP+-malate dehydrogenase ; Energy of activation ; K m, V max/K m

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The apparent energy of activation (E a), Michaelis-Menten constant (K mfor oxaloacetate), V max/K mratios and specific activities of NADP+-malate dehydrogenase (NADP+-MDH; EC 1.1.1.82) were analyzed in plants of Barnyard grass from Québec (QUE) and Mississippi (MISS) acclimated to two thermoperiods 28/22°C, 21/15°C, and grown under two CO2 concentrations, 350 μl l-1 and 675 μl l-1. E avalues of NADP+-MDH extracted from QUE plants were significantly lower than those of MISS plants. K mvalues and V max/K mratios of the enzyme from both ecotypes were similar over the range of 10–30°C but reduced V max/K mratios were found for the enzyme of QUE plants at 30 and 40°C assays. MISS plants had higher enzyme activities when measured on a chlorophyll basis but this trend was reversed when activities were expressed per fresh weight leaf or per leaf surface area. Activities were significantly higher in plants of both populations acclimated to 22/28°C. CO2 enrichment did not modify appreciably the catalytic properties of NADP+-MDH and did not have a compensatory effect upon catalysis or enzyme activity under cool acclimatory conditions. NADP+-MDH activities were always in excess of the amount required to support observed rates of CO2 assimilation and these two parameters were significantly correlated. The enhanced photosynthetic performance of QUE plants under cold temperature conditions, as compared to that of MISS plants, cannot be attributed to kinetic differences of NADP+-malate dehydrogenase among these ecotypes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00377023

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8

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Maternally-induced modification of progeny phenotypes in the C4 weed Echinochloa crus-galli: An analysis of seed constituents and performance (1993)

Charest, Christiane ; Potvin, Catherine

Springer

Oecologia 93 (1993), S. 383-388

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ISSN: 1432-1939

Keywords: Maternal effects ; Seed mass ; Germination ; Mineral content ; Reserve constituents

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract To clarify the physiological basis of maternal inheritance we examined the effect of the thermal environment of mother plants of Echinochloa crus-galli on subsequent seed mass, content and quality. The same plants were grown in a warm and a cold environment until seeds were produced and, since E. crus-galli is a highly inbred species, the observed variation in seed production was a purely plastic response to the environment. When mother plants were grown at high temperature, average seed mass, variance and germinability were low. Cold maturation led to the production of more large seeds than warm maturing temperature. The latter seeds were deprived of reserve constituents. Seeds matured at high temperature had high concentrations of K+ and Mn2+ but lower concentrations of starch and protein.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00317882

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9

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Natural pasture community response to enriched carbon dioxide atmosphere (1998)

Vasseur, Liette ; Potvin, Catherine

Springer

Plant ecology 135 (1998), S. 31-41

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ISSN: 1573-5052

Keywords: Canonical correspondence analysis ; CO2 ; Multivariate analysis ; Open-top chambers ; Plant community ; Succession

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We examined the response of a pasture community in southern Quebec (Canada) to long-term exposure of enriched atmospheric CO2 conditions. The study was conducted using open-top growth chambers directly placed on top of the natural pasture community. To investigate the change in the overall species composition in time and space, we used canonical correspondence analysis, a direct ordination method. Over the three years, the overall community responded significantly to enriched CO2. The analyses show that, after three years, CO2 was the most important environmental variable affecting the species composition. Initially the presence of the wall of the chambers influenced the composition but CO2 became more important by the third year. Soil and air temperatures only slightly influenced the community composition. The first two axes of the canonical correspondence analysis explained a large proportion of the variation in the three years and these trends appeared to increase with time. Species such as Agropyron repens appeared to be positively influenced by the presence of the wall (slightly warmer conditions). However, the analyses suggest that Phleum pratense and Trifolium repens, for example, were favored by the increase in atmospheric CO2. The variation in species composition in enriched versus ambient CO2 chambers suggests that the effect of the environmental factors, particularly CO2, were important in affecting the rate and pattern of succession. Furthermore, the temporal increase in importance of the variable CO2 in the present analyses indicates that there might be a time-lag in response to atmospheric enrichment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009753403246

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