High-resolution dissection of photosystem II electron transport reveals differential response to water deficit and heat stress in isolation and combination in pearl millet [Pennisetum glaucum (L.) R. Br.]

Abstract

Heat and Water Deficit Stress (WDS) tend to impede and restrict the efficiency of photosynthesis, chlorophyll fluorescence, and maximum photochemical quantum yield in plants based on their characteristic ability to interfere with the electron transport system in photosystem II. Dissection of the electron transport pathway in Photosystem II (PSII) under water deficit and Heat Stress (HS) can be insightful in gaining knowledge on the various attributes of the photosynthetic performance of a plant. We attempt a high-resolution dissection of electron transport in PSII with studies on chlorophyll a fast fluorescence kinetics and non-photochemical quenching (NPQ) as a response to and recovery from these stresses in pearl millet [Pennisetum glaucum (L.) R. Br.] in isolation and combination. In this study, we bring out the mechanisms by which both heat and water stress, in isolation and in combination, affect the photosynthetic electron transport in Photosystem II. Our results indicate that oxygen evolution complex (OEC) damage is the primary effect of heat stress and is not seen with the same intensity in the water-stressed plants. Low exciton absorption flux in heat stress and combined stress was seen due to OEC damage, and this caused an electron transport traffic jam in the donor side of PS II. Both the specific energy flux model and the phenomenological flux model developed from the derived values in our study show that water deficit stress in combination with heat stress has a much stronger effect than the stresses in isolation on the overall electron transport pathway of the PS II in pearl millet plants.

Adaptive Responses of Biofortified Common Bean Lines to Acidic Soil and High Temperature in the Amazon Region of Colombia

“…When we look at the ability to regulate leaf temperature, we find that in general all lines manage to adjust the temperature below the ambient temperature (negative values of LTD). This mechanism is possibly triggered by the higher loss of water at the leaf surface allowing to keep the leaf surface cooler, managing to maintain an optimal metabolism [76], and as mentioned by Shanker et al [77] a decrease in the vapor pressure deficit within the leaf. It is possible that heat stressed plants are trying to minimize the irreversible damage that can be caused by the combined stress.…”

“…The identification of these mechanisms is important because: 1) photosynthesis is the process that contributes most to CB production; 2) an adequate mechanism in energy dissipation is related to a better translocation of assimilates (PHI and HI for pod and grain formation); 3) variations in electron transport due to heat stress can be reflected in the yield obtained also [77,[87][88][89][90]. Based on the results of this study, we found that nine biofortified common bean lines [F5: 859, 805, 865, 657, 653; F4: 2853, 2796, 2815, 3730], have traits with potential for adaptation to the combined stress of acid soils and high temperatures.…”

Adaptive Responses of Biofortified Common Bean Lines to Acidic Soil and High Temperatures in the Colombian Amazon Region

“…When we look at the ability to regulate leaf temperature, we find that in general, all lines manage to adjust the temperature below the ambient temperature (negative values of LTD). This mechanism is possibly triggered by the higher loss of water at the leaf surface, allowing the leaf surface to be cooler, managing to maintain an optimal metabolism [73], and, as mentioned by Shanker et al [74], a decrease in the vapor pressure deficit within the leaf. It is possible that heat-stressed plants are trying to minimize the irreversible damage that can be caused by the combined stress.…”

Metabolic pathways engineering for drought or/and heat tolerance in cereals

“…Br.] ( Shanker et al., 2022 ). The damage to the oxygen evolution complex (OEC) was predominant in heat-stressed, but not in drought-stressed plants.…”

“…The damage to the oxygen evolution complex (OEC) was predominant in heat-stressed, but not in drought-stressed plants. Additionally, OEC damage-induced low exciton absorption flux was evident in HS and H+D stress, causing electron transport congestion in the donor side of PSII ( Shanker et al., 2022 ). These results showed that combined D+H stress was more dominant than the individual stresses on the overall electron transport pathway of the PSII ( Shanker et al., 2022 ).…”