Cyclic electron flow, NPQ and photorespiration are crucial for the establishment of young plants of Ricinus communis and Jatropha curcas exposed to drought

Abstract

Although plant physiological responses to drought have been widely studied, the interaction between photoprotection, photorespiration and antioxidant metabolism in water-stressed plants is scarcely addressed. This study aimed to evaluate the physiological adjustments preserving photosynthesis and growth in two plant species with different tolerance to drought: Jatropha curcas and Ricinus communis. We measured stress indicators, gas exchange, photochemistry of PSII and PSI, antioxidant enzymes, cyclic electron flow and photorespiration. Physiological stress indicators associated with reduction in growth confirmed R. communis as sensitive and J. curcas as tolerant to drought. Drought induced loss of photosynthesis in R. communis, whereas J. curcas maintained higher leaf gas exchange and photochemistry under drought. In addition, J. curcas showed higher dissipation of excess energy and presented higher cyclic electron flow when exposed to drought. Although none of these mechanisms have been triggered in R. communis, this species showed increases in photorespiration. R. communis displayed loss of Rubisco content while the Rubisco relative abundance did not change in J. curcas under drought. Accordingly, the in vivo maximum Rubisco carboxylation rate (V ) and the maximum photosynthetic electron transport rate driving RuBP regeneration (J ) were less affected in J. curcas. Both species displayed an efficient antioxidant mechanism by increasing activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD). Overall, we suggest that the modulation of different photoprotective mechanisms is crucial to mitigate the effects caused by excess energy, maintaining photosynthetic apparatus efficiency and promoting the establishment of young plants of these two species under drought.

Mitochondrial Biogenesis in Diverse Cauliflower Cultivars under Mild and Severe Drought. Impaired Coordination of Selected Transcript and Proteomic Responses, and Regulation of Various Multifunctional Proteins

“…In contrast to that, the visible increase of PhR rate in the mild treatment in “ P ” is known among drought-tolerant species [ 61 ]. Notably, the general trend in PhR response could be reversed at the early vegetative stage in some species with varying drought tolerance [ 62 ]. In drought-tolerant and drought-sensitive cultivars of Malus domestica , even moderate drought resulted in major PhR decline [ 63 ].…”

Functioning of potassium and magnesium in photosynthesis, photosynthate translocation and photoprotection

“…Besides carboxylation, Rubisco catalyzes the oxygenation of RuBP, resulting in photorespiration. Photorespiration is considered an important photoprotective mechanism that can alleviate over‐reduction of the electron transport chain and thus helps to prevent photoinhibition and excessive ROS formation (Lima Neto et al ). In cotton, the response of photorespiration to K deficiency was variety‐specific and resulted in an increase of photorespiration in the K‐efficient var.…”

Unraveling the roles of brassinosteroids in alleviating drought stress in young Eucalyptus urophylla plants: Implications on redox homeostasis and photosynthetic apparatus

“…Higher values of F v /F m revealed that EBR increased the photochemical efficiency of the reaction center linked to PSII, attenuating the photoinhibition due to water deficit. The reductions in F 0 and increase in F m indicated that EBR application reduced the photooxidative damage caused by water deficit on the structure and function of the primary PQ acceptor in the reaction center of PSII, increasing the cyclic electron flow in the photosystems (Huang et al, 2012;Lima Neto et al, 2017). Wang, Zheng, et al (2015) F I G U R E 4 Leaf dry matter (LDM), root dry matter (RDM), stem dry matter (SDM) and total dry matter (TDM) in Eucalyptus urophylla plants sprayed with 24-epibrassinolide (EBR) and exposed to water deficit.…”