Evaluating the effect of exogenous application of salicylic acid on heat stress tolerance in wheat (Triticum aestivum L.)

Abstract

Heat stress is a major abiotic constraint that impairs photosynthesis, disrupt cellular homeostasis, and reduce grain yield in wheat. Salicylic acid (SA), an important signalling molecule, enhances tolerance to several abiotic stresses, but its role in improving wheat performance under heat stress remains insufficiently explored. Therefore this research study was was conducted to evaluate the effect of exogenous salicylic acid (SA; 5 mM) on heat stress tolerance in wheat (Triticum aestivum L., cv. FSD-2002). Plants were exposed to >32 °C after 45 days of seedling growth and treated with SA as a foliar spray, soil supplementation, or both. ANOVA showed significant (p < 0.05) improvements in all growth and yield traits. Under control conditions, shoot and root lengths increased from 59 and 33 cm in untreated plants to 87 and 52 cm with combined SA treatment, while under heat stress they rose from 49 and 26 cm to 71 and 45 cm, respectively. Shoot and root fresh weights improved from 5.6 and 1.5 g to 8.7 and 3.1 g under control, and from 4.5 and 1.3 g to 7.7 and 2.2 g under stress. SA enhanced physiological traits, raising SPAD values from 34.2 to 46.1 (control) and 27.5 to 39.4 (stress), and leaf area from 21.5 to 35.6 cm² and 16.4 to 29.3 cm², respectively. Yield traits improved markedly: spikes from 8 to 15, spikelets from 20 to 35, grains per spike from 35 to 52, and 1000-grain weight from 35 to 59 g under control; corresponding stressed values rose from 5 to 11 spikes, 12 to 26 spikelets, 22 to 38 grains, and 30 to 51 g. Mineral nutrition was enhanced, with shoot calcium increasing from 8.1 to 11.5 mg/g DW (control) and 7.2 to 9.8 mg/g DW (stress), sulphate from 6.9 to 11.1 and 6.1 to 9.6 µg/g DW, and phosphate from 7.5 to 10.3 and 7.0 to 9.7 µg/g DW. These findings demonstrate that SA plays a key role in strengthening heat stress tolerance in wheat by sustaining biomass production, improving mineral nutrition, and preserving chlorophyll and photosynthetic capacity under thermal stress. © 2025 The Author(s)