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Foliar sprays of 1-MCP, CPPU, or KNO3 improve mango physiology following chilling by promoting stomatal opening
Silicon-induced photosynthetic adaptations in common buckwheat under salt stress revealed by prompt chlorophyll a fluorescence analysis
Abstract This study aimed at investigating the protective role of silicon (Si) in mitigating salt-induced damage in common buckwheat plants (Fagopyrum esculentum cv. Smuga). Twenty one-day-old seedlings were subjected to salt stress by irrigating 50 mM sodium chloride solutions for seven days, with or without Si (two foliar applications with 1 mM sodium metasilicate nonahydrate). Salt stress significantly altered the chlorophyll a fluorescence transient (OJIP) curve, disrupting energy flow and electron transport in photosystem II (PSII), as reflected in the O-J, J-I, and I-P phases, along with the emergence of a positive K-band indicating damage to the oxygen-evolving complex (OEC). Silicon application mitigated these effects, stabilizing the OEC and thylakoid membrane integrity while improving JIP test parameters and reducing excessive energy absorption, dissipation, and unregulated energy loss per reaction center. Silicon-treated plants under salt stress exhibited enhanced photochemical quenching, reduced regulatory energy dissipation, and decreased photosystem I (PSI) over-reduction. A significant increase in open PSI centers was observed, improving the balance and functionality between PSI and photosystem II. The application of Si resulted in significant photosynthetic improvements, which were also paired with enhanced morphological traits, such as increased root length and leaf thickness in saline conditions. Overall, findings indicate that exogenous Si helps to reduce salt-induced stress by enhancing photosynthetic efficiency in plants, positioning it as a promising strategy for improving crop performance in saline environments.
Enhancing UV-B Tolerance in Radish and Mung Bean Plants Using Magnetic Iron Oxide Nanoparticles Foliar Application
ABSTRACTThis study investigates the potential of magnetic iron oxide nanoparticles (MIONPs) in mitigating ultraviolet‐B radiation (UV‐B) induced physiological damage in radish (Raphanus sativus L.) and mung bean (Vigna radiata). Screening of the seed vigour indices identified 1500 mg L−1 MIONPs as the optimal concentration for radish and 100 mg L−1 for mung bean for seed vigour improvement. After the first true leaf appeared (~15 days), plants were exposed to different UV‐B intensities: control (UV0, 0 mW m−2), moderate (UV1, 26 mW m−2), and high (UV2, 53 mW m−2), with or without foliar MIONPs application. Results showed that UV‐B significantly decreased the net photosynthesis rate (Pn) by 32% in radish and 65% in mung bean after UV2 exposure. Fluorescence parameters, including photosystem II (PSII) efficiency and photosynthetic performance (PIabs), were also impaired by UV‐B. UV‐B stress led to a decline in plant growth, leaf area, biomass accumulation, and chlorophyll content while increasing antioxidant enzyme activities, flavonoids, anthocyanins, malondialdehyde (MDA), and hydrogen peroxide (H2O2) levels. However, MIONPs treatment enhanced UV‐B tolerance by improving pigment content, PSII efficiency, Pn, leaf area, and biomass accumulation while reducing MDA and H2O2 levels, thus improving overall plant physiological health. In the leaf model of energy flux, MIONPs‐treated plants showed more active reaction centers and improved electron transport. The OJIP curves differed under UV‐B stress, with increasing UV‐B stress showing decreased fluorescence intensity at the IP phase. However, plants treated with MIONPs showed higher fluorescence intensity specifically at the IP phase, suggesting their protective effect. The UV sensitivity index (UV‐SI) revealed that mung bean is more UV‐sensitive than radish. MIONPs treatment increased UV‐SI values and enhanced the plant tolerance towards UV‐B. The results suggest that the application of MIONPs could improve UV‐B resistance in future agricultural practices.