Vol. 9, Special Issue 11, Part N (2025)

The present investigation was conducted during the rabi season of 2019-2020 at the Seed Technology Research Farm, Jawaharlal Nehru Krishi Vishwa Vidyalaya (JNKVV), Jabalpur, Madhya Pradesh, India to evaluate the effects of salicylic acid (SA) and thiourea (TU) on biochemical stress tolerance, yield performance, and seed quality attributes of wheat (Triticum aestivum L.) under normal, and late sown conditions. Two wheat varieties, JW-3211 and JW-3382, were subjected to foliar application of SA (400 and 800 ppm) and TU (200 and 400 ppm) during critical growth stages. Significant variability was observed among varieties, sowing conditions, and treatments. Terminal heat stress in late sowing caused notable reductions in plant height (21.5%), spikelet number (7%), seed setting (10%), 1000-seed weight (23%), and seed yield (38%) compared with normal sowing. Foliar application of SA @ 800 ppm markedly improved biological yield (30.52%), seed yield (16%), and 1000-seed weight (21%) over the control, while TU @ 400 ppm enhanced seed setting (6%) and vigor index II (12%). JW-3211 exhibited superior performance, recording 15% higher biological yield, 9.4% more grains per ear, and 7% higher seed setting compared to JW-3382, indicating greater thermotolerance. SA treatments effectively maintained photosynthetic stability, antioxidant protection, and assimilate partitioning under stress, whereas TU improved reproductive efficiency and seedling vigor. The results clearly demonstrate that the use of bioregulators can substantially enhance wheat growth, productivity, and seed quality under high-temperature stress, providing a physiological basis for sustainable yield improvement in changing climatic conditions.