Photochemical Efficiency of Photosystem II in Inverted Leaves of Soybean [Glycine max (L.) Merr.] Affected by Elevated Temperature and High Light

Abstract

In summer, high light and elevated temperature are the most common abiotic stresses. The frequent occurrence of monsoon exposes the abaxial surface of soybean [Glycine max (L.) Merr.] leaves to direct solar radiation, resulting in irreversible damage to plant photosynthesis. In this study, chlorophyll a fluorescence was used to evaluate the functional status of photosystem II (PSII) in inverted leaves under elevated temperature and high light. In two consecutive growing seasons, we tested the fluorescence and gas exchange parameters of soybean leaves for 10 days and 15 days (5 days after recovery). Inverted leaves had lower tolerance compared to normal leaves and exhibited lower photosynthetic performance, quantum yield, and electron transport efficiency under combined elevated temperature and high light stress, along with a significant increase in absorption flux per reaction center (RC) and the energy dissipation of the RC, resulting in significantly lower performance indexes (PIABS and PItotal) and net photosynthetic rate (Pn) in inverted leaves. High light and elevated temperature caused irreversible membrane damage in inverted leaves, as photosynthetic performance parameters (Pn, PIABS, and PItotal) did not return to control levels after inverted leaves recovered. In conclusion, inverted leaves exhibited lower photosynthetic performance and PSII activity under elevated temperature and high light stress compared to normal leaves.

The Exogenous Application of Brassinosteroids Confers Tolerance to Heat Stress by Increasing Antioxidant Capacity in Soybeans

“…Accordingly, heat stress treatment significantly decreased the leaf net photosynthesis rate and plant biomass during the recovery stage (Figure 5). These results were consistent with the previous studies that determined that heat stress significantly increased ROS levels and decreased the photosynthetic capacity and grain yield [36][37][38]. Although the activity of antioxidant enzymes (SOD, CAT, and POD) and contents of antioxidant substances (ASA and GSH) were enhanced, the accumulation level of ROS was still significantly increased under heat stress, suggesting that the production rate of ROS under heat stress exceeded its clear rate in this study.…”

Growth, photosynthetic function, and stomatal characteristics of Persian walnut explants in vitro under different light spectra

“…The increase in F v /F m indicates the increase in photochemical efficiency of photosystem II (Guidi et al, 2019). Plants absorb blue and red-light spectra more than green and yellow light spectra (Wang et al, 2022). Different absorption for different lights may partially explain the difference in CO 2 absorption of plants growing under different light spectra (Aalifar et al, 2020a;Aalifar et al, 2020b;Javadi Asayesh et al, 2021).…”

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