Does the response of Rubisco and photosynthesis to elevated [CO2] change with unfavourable environmental conditions?

Abstract

Climate change due to anthropogenic CO2 emissions affects plant performance globally. To improve crop resilience, we need to understand the effects of elevated CO2 concentration (e[CO2]) on CO2 assimilation and Rubisco biochemistry. However, the interactive effects of e[CO2] and abiotic stress are especially unclear. This study examined the CO2 effect on photosynthetic capacity under different water availability and temperature conditions in 42 different crop species, varying in functional group, photosynthetic pathway, and phenological stage. We analysed close to 3000 data points extracted from 120 published papers. For C3 species, e[CO2] increased net photosynthesis and intercellular [CO2], while reducing stomatal conductance and transpiration. Maximum carboxylation rate and Rubisco in vitro extractable maximal activity and content also decreased with e[CO2] in C3 species, while C4 crops are less responsive to e[CO2]. The interaction with drought and/or heat stress did not significantly alter these photosynthetic responses, indicating that the photosynthetic capacity of stressed plants responded to e[CO2]. Moreover, e[CO2] had a strong effect on the photosynthetic capacity of grasses mainly in the final stages of development. This study provides insight into the intricate interactions within the plant photosynthetic apparatus under the influence of climate change, enhancing the understanding of mechanisms governing plant responses to environmental parameters.

Keywords: Drought; Rubisco; elevated CO2; heat stress; phenology; photosynthesis; plant functional groups.

Fig. 1.

Comparative photosynthetic responses of plants subjected to elevated CO₂ concentration (e[CO₂]) alone and plants subjected to a combination of e[CO₂] and abiotic stresses. (A) The effect of e[CO₂] versus e[CO₂]×stress (drought, heat stress, or their combination). (B) The effect of e[CO₂] at well-watered (Ww) conditions versus e[CO₂]×drought. (C) The effect of e[CO₂] at ambient temperature (aT) versus e[CO₂]×heat stress. Response variables: A_n, net CO₂ assimilation; C_i, intercellular CO₂ concentration; E, transpiration rate; g_s, stomatal conductance. The results are presented as the mean percentage change at e[CO₂] relative to a[CO₂]. The error bars represent 95% CI. The response to e[CO₂] was considered significant when the 95% CI did not overlap with zero. The asterisks indicate significant between group heterogeneity (Q_B) for control and stress conditions (**P<0.01). The number of observations for each response variable is indicated on the left. Number of species and effect sizes for each variable are given in Supplementary Table S3.

Fig. 2.

Comparative Rubisco responses of plants subjected to elevated CO₂ concentration (e[CO₂]) alone and plants subjected to a combination of e[CO₂] and abiotic stresses. (A) The effect of e[CO₂] versus e[CO₂]×stress (drought, heat stress, or their combination). (B) The effect of e[CO₂] at well-watered (Ww) conditions versus e[CO₂]×drought. (C) The effect of e[CO₂] at ambient temperature (aT) versus e[CO₂]×heat stress. Response variables: J_max, maximum electron transport rate; Leaf N, leaf nitrogen; [Rubisco], Rubisco content; Rub. activation, Rubisco activation state; Rub. initial act., Rubisco initial activity; Rub. total act., Rubisco total activity; TSP, total soluble protein; V_max^c, maximum carboxylation rate. The results are presented as the mean percentage change at e[CO₂] relative to a[CO₂]. The error bars represent 95% CI. The response to e[CO₂] was considered significant when the 95% CI did not overlap with zero. The asterisks indicate significant between group heterogeneity (Q_B) for control and stress conditions (*P<0.05). The number of observations for each response variable is indicated on the left. Number of species and effect sizes for each variable are given in Supplementary Table S3.

Fig. 3.

Response of the components of C assimilation to elevated CO₂ concentration (e[CO₂]) and interactions with abiotic stress in different plant groups. Comparative photosynthetic and Rubisco responses of different plant groups to e[CO₂] alone (black symbols) or a combination of e[CO₂]×stress (grey symbols). Response variables: A_n, net CO₂ assimilation; C_i, intercellular CO₂ concentration; E, transpiration rate; g_s, stomatal conductance; J_max, maximum electron transport rate; Leaf N, leaf nitrogen; [Rubisco], Rubisco content; Rub. activation, Rubisco activation state; Rub. initial act., Rubisco initial activity; Rub. total act., Rubisco total activity; TSP, total soluble protein; V_max^c, maximum carboxylation rate. The results are presented as the mean percentage change at e[CO₂] relative to a[CO₂]. The error bars represent 95% CI. The response to e[CO₂] was considered significant when the 95% CI did not overlap with zero. The asterisks indicate significant between group heterogeneity (Q_B) among plant groups (*P<0.05, **P<0.01, ***P≤0.001). The number of observations for each variable is indicated on the left. Some variables corresponding to some plant groups are not represented due to insufficient available data. Number of species and effect sizes for each variable are given in Supplementary Table S3.

Fig. 4.

Response of the components of C assimilation to elevated CO₂ concentration (e[CO₂]) and interactions with abiotic stress in different phenological stages. Comparative photosynthetic and Rubisco responses of different phenological stages of grasses to e[CO₂] alone (black symbols) or a combination of e[CO₂]×stress (grey symbols). Response variables: A_n, net CO₂ assimilation; C_i, intercellular CO₂ concentration; E, transpiration rate; g_s, stomatal conductance; J_max, maximum electron transport rate; Leaf N, leaf nitrogen; [Rubisco], Rubisco content; Rub. activation, Rubisco activation state; Rub. initial act., Rubisco initial activity; Rub. total act., Rubisco total activity; TSP, total soluble protein; V_max^c, maximum carboxylation rate. The results are presented as the mean percentage change at e[CO₂] relative to a[CO₂]. The error bars represent 95% CI. The response to e[CO₂] was considered significant when the 95% CI did not overlap with zero. The asterisks indicate significant between group heterogeneity (Q_B) among plant groups (*P<0.05, **P<0.01, ***P≤0.001). The number of observations for each variable is indicated on the left. Some variables corresponding to some phenological stages are not represented due to insufficient available data. Number of species and effect sizes for each variable are given in Supplementary Table S3.