The growth of soybean under free air [CO2] enrichment (FACE) stimulates photosynthesis while decreasing in vivo Rubisco capacity

Abstract

Down-regulation of light-saturated photosynthesis (A(sat)) at elevated atmospheric CO(2) concentration, [CO(2)], has been demonstrated for many C(3) species and is often associated with inability to utilize additional photosynthate and/or nitrogen limitation. In soybean, a nitrogen-fixing species, both limitations are less likely than in crops lacking an N-fixing symbiont. Prior studies have used controlled environment or field enclosures where the artificial environment can modify responses to [CO(2)]. A soybean free air [CO(2)] enrichment (FACE) facility has provided the first opportunity to analyze the effects of elevated [CO(2)] on photosynthesis under fully open-air conditions. Potential ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation (V(c,max)) and electron transport through photosystem II (J(max)) were determined from the responses of A(sat) to intercellular [CO(2)] (C(i)) throughout two growing seasons. Mesophyll conductance to CO(2) (g(m)) was determined from the responses of A(sat) and whole chain electron transport (J) to light. Elevated [CO(2)] increased A(sat) by 15-20% even though there was a small, statistically significant, decrease in V(c,max). This differs from previous studies in that V(c,max)/J(max) decreased, inferring a shift in resource investment away from Rubisco. This raised the C(i) at which the transition from Rubisco-limited to ribulose-1,5-bisphosphate regeneration-limited photosynthesis occurred. The decrease in V(c,max) was not the result of a change in g(m), which was unchanged by elevated [CO(2)]. This first analysis of limitations to soybean photosynthesis under fully open-air conditions reveals important differences to prior studies that have used enclosures to elevate [CO(2)], most significantly a smaller response of A(sat) and an apparent shift in resources away from Rubisco relative to capacity for electron transport.

Genomic basis for stimulated respiration by plants growing under elevated carbon dioxide

“…S2 A) and 22% in 2006 (Fig. 1 A), which is consistent with the observed response in soybean (11) (14); and (ii) the ability of soybean to fix N and therefore a diminished benefit from reallocating N away from the photosynthetic machinery (12 (Table S3). Each blue or yellow box represents the statistically significant treatment response (P Ͻ 0.05) of a unique transcript encoding an enzyme or protein structure (details of transcriptional response in Table S1; details about gene annotations in soybean in SI Materials and Methods).…”

Response of soybean yield components and allocation of dry matter to increased temperature and CO2 concentration

“…Meanwhile, the magnitude of changes also depend on the technology used to simulate future conditions (Ainsworth et al, 2008). In the case of soybean, CO 2 enrichment environments (between 550 and 700 molCO 2 mol -1 ) has shown increased photosynthesis by up to ~30% (Griffin and Luo, 1999;Rogers et al, 2004;Bernacchi et al, 2005;Prior et al, 2011), and yield by up to 13% Long et al, 2006). However, increases in photosynthetic rates can be smaller under longterm exposure to high CO 2 due to photosynthetic acclimation (Bernacchi et al 2005;Bloom, 2009).…”

“…In the case of soybean, CO 2 enrichment environments (between 550 and 700 molCO 2 mol -1 ) has shown increased photosynthesis by up to ~30% (Griffin and Luo, 1999;Rogers et al, 2004;Bernacchi et al, 2005;Prior et al, 2011), and yield by up to 13% Long et al, 2006). However, increases in photosynthetic rates can be smaller under longterm exposure to high CO 2 due to photosynthetic acclimation (Bernacchi et al 2005;Bloom, 2009). It should be noticed that higher photosynthesis does not necessarily indicate increased productivity because the yield depends ultimately on the biomass partitioning and harvest index (Richards, 2000).…”

Fisiologia foliar e qualidade enológica da uva em videiras infectadas por vírus

“…No detalhamento dessas restrições fotossintéticas pela infecção viral, observa-se que a radiação de saturação destas folhas sintomáticas atingiu uma redução média de 38%, sendo mais acentuada em C. Franc (-41%). Palliotti et al (2000) (Bernacchi et al, 2005). Portanto, com a redução desse limite de saturação pode-se supor que esses vírus estão limitando o "turnover" protéico/acúmulo de enzimas relacionadas com a etapa de carboxilação na fotossíntese destas cultivares.…”