Yield response of field‐grown soybean exposed to heat waves under current and elevated [CO₂]

Abstract

Elevated atmospheric CO2 concentration ([CO2]) generally enhances C3 plant productivity, whereas acute heat stress, which occurs during heat waves, generally elicits the opposite response. However, little is known about the interaction of these two variables, especially during key reproductive phases in important temperate food crops, such as soybean (Glycine max). Here, we grew soybean under elevated [CO2] and imposed high‐ (+9°C) and low‐ (+5°C) intensity heat waves during key temperature‐sensitive reproductive stages (R1, flowering; R5, pod‐filling) to determine how elevated [CO2] will interact with heat waves to influence soybean yield. High‐intensity heat waves, which resulted in canopy temperatures that exceeded optimal growth temperatures for soybean, reduced yield compared to ambient conditions even under elevated [CO2]. This was largely due to heat stress on reproductive processes, especially during R5. Low‐intensity heat waves did not affect yields when applied during R1 but increased yields when applied during R5 likely due to relatively lower canopy temperatures and higher soil moisture, which uncoupled the negative effects of heating on cellular‐ and leaf‐level processes from plant‐level carbon assimilation. Modeling soybean yields based on carbon assimilation alone underestimated yield loss with high‐intensity heat waves and overestimated yield loss with low‐intensity heat waves, thus supporting the influence of direct heat stress on reproductive processes in determining yield. These results have implications for rain‐fed cropping systems and point toward a climatic tipping point for soybean yield when future heat waves exceed optimum temperature.

Rapid temperature responses of photosystem II efficiency forecast genotypic variation in rice vegetative heat tolerance

“…Assessing heat tolerance across many genotypes is constrained by issues related to space for growing plants and facilities and equipment for experimentally increasing the temperature, both in controlled (Wang et al ., 2012) and field environments (Thomey et al ., 2019). Here we detail a rapid methodology for assaying heat tolerance that does not require substantial space to grow plants and that is correlated with independent estimates of heat tolerance in genetically diverse adult rice plants.…”

“…From the A n – c i response measurements, we modelled V cmax and J max to gauge the efficiency of carboxylation by Rubisco and the rate of electron transport, respectively. These parameters are frequently assessed to determine the photo‐physiological response to heat stress (Perdomo et al ., 2016; Haworth et al ., 2018; Thomey et al ., 2019; Chen et al ., 2019); however, we believe that this is the first instance of genetic variation in these parameters being tested under heat stress in rice in a substantial and genetically diverse set of lines. All accessions demonstrated a downregulation in V cmax (Figure 8a), which is likely to be linked to Rubisco activase thermosensitivity (Feller et al ., 1998; Makino and Sage, 2007), as well the degradation of other Calvin‐cycle enzymes (Sharkey, 2005) and general metabolic reprogramming in the chloroplasts (Wang et al ., 2018).…”

Consequences and Mitigation Strategies of Heat Stress for Sustainability of Soybean (Glycine maxL. Merr.) Production under the Changing Climate

“…Such conditions do not support harvestable moisture levels for soybean growth with the final aim to get the high-quality seed. Modeling soybean yields based on carbon assimilation alone underestimated yield loss with high-intensity heat-wave and overestimated yield loss with low-intensity heat-wave, thus supporting the influence of direct HT stress on reproductive processes in determining yield [65]. The uniformity of seed development within the crop is a major factor that depends on production practices and growing conditions.…”

Physiological and Defense Responses of Tea Plants to Elevated CO2: A Review

“…This raises the question of how tea plants increase the photosynthetic rate under reduced stomatal conductance. In C 3 plants, the activity of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO) is critical for CO 2 assimilation (Eisenhut et al, 2019;Thomey et al, 2019). Elevated CO 2 increases maximum carboxylation rate of RuBisCO and maximum rates of RuBP regeneration in tea plants (Li et al, 2017), thus facilitating carboxylation over oxygenation of RuBP (Amthor, 1997;Li et al, 2013), which potentially contributes to increased CO 2 assimilation in tea leaves (Li et al, 2017).…”