Elevated CO2 concentration induces photosynthetic down-regulation with changes in leaf structure, non-structural carbohydrates and nitrogen content of soybean

Abstract

Background Understanding the mechanisms of crops in response to elevated CO 2 concentrations is pivotal to estimating the impacts of climate change on the global agricultural production. Based on earlier results of the “doubling-CO 2 concentration” experiments, many current climate models may overestimate the CO 2 fertilization effect on crops, and meanwhile, underestimate the potential impacts of future climate change on global agriculture ecosystem when the atmospheric CO 2 concentration goes beyond the optimal levels for crop growth. Results This study examined the photosynthetic response of soybean ( Glycine max (L.) Merr.) to elevated CO 2 concentration associated with changes in leaf structure, non-structural carbohydrates and nitrogen content with environmental growth chambers where the CO 2 concentration was controlled at 400, 600, 800, 1000, 1200, 1400, 1600 ppm. We found CO 2 -induced down-regulation of leaf photosynthesis as evidenced by the consistently declined leaf net photosynthetic rate ( A n ) with elevated CO 2 concentrations. This down-regulation of leaf photosynthesis was evident in biochemical and photochemical processes since the maximum carboxylation rate ( V cmax ) and the maximum electron transport rate ( J max ) were dramatically decreased at higher CO 2 concentrations exceeding their optimal values of about 600 ppm and 400 ppm, respectively. Moreover, the down-regulation of leaf photosynthesis at high CO 2 concentration was partially attributed to the reduced stomatal conductance ( G s ) as demonstrated by the declines in stomatal density and stomatal area as well as the changes in the spatial distribution pattern of stomata. In addition, the smaller total mesophyll size (palisade and spongy tissues) and the lower nitrogen availability may also contribute to the down-regulation of leaf photosynthesis when soybean subjected to high CO 2 concentration environment. Conclusions Down-regulation of leaf photosynthesis associated with the changes in stomatal traits, mesophyll tissue size, non-structural carbohydrates, and nitrogen availability of soybean in response to future high atmospheric CO 2 concentration and climate change.

Will rising atmospheric CO2 concentration inhibit nitrate assimilation in shoots but enhance it in roots of C3 plants?

“…The increase in total plant DW relative to total plant N and the resultant decrease in tissue N per unit DW at elevated CO 2 has been termed ‘N dilution’ and has been linked to increased accumulation of non‐structural carbohydrates and plant secondary compounds (Taub and Wang ). In some cases, elevated CO 2 can increase photosynthesis in the short term, but if photosynthate utilisation is inadequate, a source sink imbalance can arise, leading to end‐product (carbohydrate) accumulation and subsequent down‐regulation of photosynthesis linked to lower ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) concentration and activity (Ainsworth and Rogers , Zheng et al , Beechey‐Gradwell et al ). In their Summary, Bloom et al () stated that ‘hundreds of papers’ support their proposal that rising atmospheric CO 2 concentrations inhibit malate production in chloroplasts and thus impede assimilation of NO 3 − into protein in shoots of C 3 plants.…”

CO<sub>2</sub> fertilization effect can cause rainfall decrease as strong as large-scale deforestation in the Amazon

“…variety of plant species with instantaneous measurements [e.g. (Domingues et al, 2014;Zheng et al, 2019)], although longterm (beyond the execution time of FACE experiments) acclimation changes of gs to eCO2 are yet poorly known (Xu et al, 2016).…”

High Nitrate or Ammonium Applications Alleviated Photosynthetic Decline of Phoebe bournei Seedlings under Elevated Carbon Dioxide

“…Chlorophyll has the function of absorbing and transferring light energy, which is essential for photosynthesis [38].We explored the mechanism of nitrogen regulation from the aspects of photosynthetic chlorophyll content, which can reflect the photosynthetic capacity of plant leaves and has been shown to be significantly positively correlated with the net photosynthetic rate (Pn) [39].We also determined rubisco and rubisco activase (RCA) content because rubisco is the core enzyme in the Calvin cycle and RCA increases the proportion of active rubisco in photosynthetic cells [40]. The response of plants to eCO 2 is basically mediated by leaf photosynthesis, which is closely related to changes in leaf structure and chemical composition [41]. Furthermore, leaf anatomical structures best reflect the effects of environmental factors on plants and the adaptation strategies of plants to the environment [42].…”