Mycobiogenic silver nanoparticles enhance sorghum growth and salinity tolerance by modulating photosynthesis and oxidative responses

Abstract

Adverse environmental conditions, including salinity, significantly threaten crop production worldwide, necessitating innovative strategies to improve plant resilience. This study comprehensively compared the effects of mycobiogenic (AgNP b ) and synthetic (AgNP s ) silver nanoparticles with ionic silver (AgNO 3 ) on sorghum growth and physiology. We also evaluated AgNP b seed priming to mitigate salinity effects, hypothesizing that salinity tolerance conferred by this priming is mediated by optimizing photosynthesis and enhancement of the antioxidant defense system, leading to reduced oxidative damage. In an initial experiment, sorghum seeds were treated with 0, 1.1 mg L -1 , or 10.8 mg L -1 of each silver form. AgNO₃ at 10.8 mg L -1 proved highly phytotoxic, inhibiting germination, reducing biomass, and inducing severe oxidative imbalance (elevated H₂O₂ and TBARS). In contrast, AgNP b exhibited lower toxicity and, at 10.8 mg L -1 , promoted sorghum growth and increased photosynthetic performance. Synthetic AgNP s showed intermediate effects. Crucially, in a subsequent experiment, AgNP b seed priming (1.1 mg L -1 ) successfully mitigated salinity effects (100 mM NaCl), improving photosynthetic efficiency and reducing oxidative damage markers in salt-exposed seedlings compared to non-primed controls. Our findings demonstrate that the form of silver (ionic vs. NP; biogenic vs. synthetic) is a critical determinant of phytotoxicity. Mycobiogenic AgNPs show significant potential for both growth promotion and, via priming, enhancement of salinity tolerance.

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