Silicon differentially protects PSII and PSI photochemistry and preserves fatty acid metabolism in salt-stressed Sorghum bicolor (L.).

BACKGROUND: Silicon (Si) has been demonstrated to be an important element to enhance crop tolerance against salinity. Nevertheless, mechanisms underlying Si's mitigation of salt stress remains insufficiently explored and understood. This study aims to provide new insights into Si's impact on salt-stressed Sorghum bicolor (L.) supplied or not with 0.5 mmol L-1 of sodium silicate (Na2SiO3) by combining the assessment of photosystems performance, fatty acid metabolism as linked to membrane integrity, and molecule's chemical structure stability. RESULTS: Relative to sodium chloride (NaCl) treatment alone, Si supply enhanced biomass production; increased chlorophyll a, chlorophyll b, and carotenoid contents by 35%, 26%, and 61%, respectively (P < 0.01); and increased proline and total soluble sugar contents (P < 0.05). Notably, results shed new light into Si-optimized photochemical balance between photosystems by further enhancing photosystem II (PSII) photochemical yield (Y(II)), electron transport rate (ETR(II)) and diminished non-photochemical energy dissipation processes (Y(NPQ) and Y(NO)), while recovering photosystem I (PSI) photochemical yield (Y(I)) and electron transport rate (ETR(I)), primarily via the alleviation of the donor-side limitation (decrease in Y(ND)). Moreover, Si supplementation preserved membrane integrity, reducing malondialdehyde (MDA) levels by 15% (P < 0.01), as demonstrated by enhanced linoleic acid (C18:2) and linolenic acid (C18:3) contents (P < 0.05). Further, results showed a previously unreported observation of Si's protective effect on the chemical structure of molecules by suppressing the induced salt modifications. CONCLUSION: In summary, this study broadens our understanding of Si's enhanced salt tolerance, showing improved balance of photosystem's performance, maintaining membrane stability and fatty acid metabolism, and preserving the integrity of chemical secondary structures. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.