Salicylic acid-functionalised chitosan nanoparticles restore impaired sucrose metabolism in the developing anther of cotton (Gossypium hirsutum) under heat stress

Abstract

Nanotechnology provides tremendous potential in agriculture, mitigating climate change impact and improving abiotic stress management strategy. Chitosan nanoparticles (NCS) were synthesised using the ion gelation method and characterised for size (75.5 nm in particle size analyser), shape (spherical under scanning electron microscopy) and stability (132.2 mV zeta potential). Further, salicylic acid was incorporated into NCS to craft salicylic acid-functionalised chitosan nanoparticles (SA-NCS) and illustrated for size (517 nm), shape (spherical) and stability (197.1 mV). The influence of the exogenous application of SA-NCS (0.08%) was studied at the reproductive stage of three genotypes of cotton (Gossypium hirsutum): (1) heat-tolerant Solar-651 BGII; (2) moderately heat-tolerant Solar-701 BGII; and (3) heat-susceptible Solar-805 BGII, exposed to different temperature regimes: (1) H1 (optimal), 32/20 ± 2°C; (2) H2 (sub-optimal), 38/24 ± 2°C; H3 (supra-optimal), 45/30 ± 2°C. Heat stress significantly reduces carbon-fixing Rubisco, enzymes related to sucrose metabolism and pollen tube length. Considering three genotypes and reproductive stages (sepal and anther tissues), activities of Rubisco (sepals), invertase (sepals), sucrose phosphate synthase (anthers), sucrose content (sepals) and pollen tube length were elevated under high-temperature regimes, signifying better source to sink transposition of sucrose influenced by SA-NCS. The study provides new insights into SA-NCS to improve source–sink imbalance and restore sucrose metabolism for better growth of reproductive structure under heat stress in cotton.