Sorghum bicolor prioritizes the recovery of its photosynthetic activity when re‐watered after severe drought stress, while manages to preserve it under elevated CO₂ and drought

Abstract

Understanding plant response and resilience to drought under a high CO2 environment will be crucial to ensure crop production in the future. Sorghum bicolor is a C4 plant that resists drought better than other crops, which could make it a good alternative to be grown under future climatic conditions. Here, we analyse the physiological response of sorghum under 350 ppm CO2 (aCO2) or 700 ppm CO2 (eCO2) with drought (D) or without drought (WW) for 9, 13 and 16 days; as well as its resilience under long (R1: 9D + 7R) or short (R2: 13D + 3R) recovery treatments. Sorghum showed elevated rates of gs under aCO2 and WW, which resulted in a significant decrease in Ψw, gs, E, ΦPSII, Fv’/Fm′ when exposed to drought. Consequently, A was greatly decreased. When re‐watered, both re‐watering treatments prioritized A recovery by restoring photosynthetic machinery under aCO2, whereas under eCO2 plants required little recovery since plant were hardly affected by drought. However, sorghum growth rate for aboveground organs did not reach control values, indicating a slower long‐term recovery. Overall, these results provide information about the resilience of sorghum and its utility as a suitable candidate for the drought episodes of the future.

Precision Phenotyping of Agro-Physiological Responses and Water Use of Sorghum under Different Drought Scenarios

“…This reasoning was also given by Devnarain et al [55] in their study of five African sorghum varieties, which were able to maintain chlorophyll and carotenoid levels upon rehydration after drought stress. Moreover, Martínez-Goñi et al [12], studying the ability of sorghum to adapt to drought combined with elevated and ambient CO 2 , observed that after being subjected to drought, sorghum prioritized recovery of its photosynthesis activity upon rehydration mainly by rapidly opening its stomata and increasing the transpiration rate. They also observed that sorghum required more than 7 days of rehydration to fully recover from drought stress.…”

“…Early drought stress is reported to induce changes in sorghum physiology by decreasing stomatal conductance, which can lead to the reduction of CO 2 uptake and the leaf transpiration rate [11]. It has also been shown to reduce leaf water potential and the maximum quantum efficiency of photosystem II [12,13]. However, the leaf area temperature was found to be increased under drought [14].…”

“…Jedmowski et al [13] observed good recovery for leaf relative water content, whereas the recovery of leaf fluorescence parameters (Fv/Fm and performance index) were genotype-dependent. Moreover, Martínez-Goñi et al [12] showed that plants prioritized the recovery of the net photosynthetic rate under ambient CO 2 compared to elevated CO 2 . Therefore, since there is still a knowledge gap on sorghum recovery from drought stress after rehydration, there is a need for more investigation.…”

Elevated CO2 increases biomass of Sorghum bicolor green prop roots under drought conditions via soluble sugar accumulation and photosynthetic activity

“…Although previous studies have described the combined effect of distinct drought intensity and E[CO 2 ] on stomatal conductance, the transpiration rate, net photosynthetic CO 2 assimilation and growth levels of sorghum plants (AbdElgawad et al, 2015;Gleadow et al, 2016;Martínez-Goñi et al, 2022), as well as molecular responses under water stress (AbdElgawad et al, 2015;Abdel-Ghany et al, 2020;Fracasso et al, 2016;Varoquaux et al, 2019) At 90 DAP, the entire plant was carefully dissected to harvest its distinct components, including roots, prop roots, leaves, culms, and grains, in separate collections, which corresponds to the grain-filling stage, at which time the grains are immature. The roots correspond to the main roots and secondary and belowground white prop roots, whereas the GPRs prop roots correspond to the aboveground prop roots.…”

“…Although previous studies have described the combined effect of distinct drought intensity and E[CO 2 ] on stomatal conductance, the transpiration rate, net photosynthetic CO 2 assimilation and growth levels of sorghum plants (AbdElgawad et al, 2015; Gleadow et al, 2016; Martínez‐Goñi et al, 2022), as well as molecular responses under water stress (AbdElgawad et al, 2015; Abdel‐Ghany et al, 2020; Fracasso et al, 2016; Varoquaux et al, 2019), none of the studies have reported findings on the transcriptional effects of E[CO 2 ] under drought in this species. Moreover, despite the importance of GPRs for monocots, little is known about the molecular responses of these organs to E[CO 2 ] and drought stress.…”