The regulation of P700 is an important photoprotective mechanism to NaCl‐salinity in Jatropha curcas

Abstract

Salinity commonly affects photosynthesis and crop production worldwide. Salt stress disrupts the fine balance between photosynthetic electron transport and the Calvin cycle reactions, leading to over‐reduction and excess energy within the thylakoids. The excess energy triggers reactive oxygen species (ROS) overproduction that causes photoinhibition in both photosystems (PS) I and II. However, the role of PSI photoinhibition and its physiological mechanisms for photoprotection have not yet been fully elucidated. In the present study, we analyzed the effects of 15 consecutive days of 100 mM NaCl in Jatropha curcas plants, primarily focusing on the photosynthetic electron flow at PSI level. We found that J. curcas plants have important photoprotective mechanisms to cope with the harmful effects of salinity. We show that maintaining P700 in an oxidized state is an important photoprotector mechanism, avoiding ROS burst in J. curcas exposed to salinity. In addition, upon photoinhibition of PSI, the highly reduced electron transport chain triggers a significant increase in H2O2 content which can lead to the production of hydroxyl radical by Mehler reactions in chloroplast, thereby increasing PSI photoinhibition.

Comparative analysis of salt-induced changes in the leaves proteome of two contrasting Jatropha curcas genotypes

“…Recently, some studies [10][11][12] have been described J. curcas genotypes more tolerant do salinity than others. Although, J. curcas is a relatively drought-tolerant plant [15][16][17], it is also considered a salt-sensitive one [12,18,19], while others classify it as moderately tolerant to salt stress [13]. Such contrasting results can be explained by the fact that J. curcas is still in the domestication stage [20].…”

Salt-tolerance induced by leaf spraying with H2O2 in sunflower is related to the ion homeostasis balance and reduction of oxidative damage

“…The increase observed at 35 days in the carotenoid content in plants under salt stress ( Figure 2 D) occurred as a plant protection mechanism, dissipating the excess energy accumulated by stress in the form of heat through the xanthophyll cycle. Salt stress disrupts the balance between photosynthetic electron transport and Calvin-Benson's cycle reactions, leading to over-reduction and excess energy within of the thylakoids ( Cerqueira et al., 2019 ). Carotenoids are integral constituents of thylakoid membranes acting as accessory pigments in the capture of light and as photoprotective agents in the dissipation of excess absorbed light ( Maoka, 2020 ).…”

Physiological and morphological features denote that salt stress in Stevia rebaudiana is based on nonstomatic instead of stomatic limitation

“…The fact that under salt stress P N has been reduced to a greater extent than ETR is an indication that alternative electron sinks were increased due to the stressful conditions caused by salinity (Hussin et al, 2017;Cerqueira et al, 2019;Fonseca-Pereira et al, 2019). This pattern led us to speculate that the reduction of P N should be attributed rather to nonstomatal limitations than to stomatic ones.…”

“…Under optimum conditions, P N is the main sink; however, under stress P N is more sensitive and decreases faster than ETR, promoting the ratio increase and indicating an energy impairment that can be associated to ROS production (Fonseca-Pereira et al, 2019). This is an indication that alternative electron sinks were increased due to the stressful conditions (Cerqueira et al, 2019). This combined with high irradiance can lead to the loss of coordination between light reaction and Calvin cycle due to insufficient supply of the electron and proton acceptor (CO 2 ).…”