β-carotene enhances drought tolerance in fenugreek by modulating antioxidant defense and redox homeostasis.

Abstract

Drought stress is one of the main abiotic factors that modulates the morphology and physiology of crops. This study investigated the effect of foliar application of β-carotene on the growth, physiological, and biochemical responses of fenugreek (Trigonella foenum-graecum L.) under drought stress conditions. A pot experiment was conducted using two varieties, Kasuri and Local, under two drought stress levels (control and 50% field capacity), and three β-carotene concentrations (0, 100, and 200 ppm) were applied. Drought stress significantly declined shoot fresh weight up to 35.02% and 58.04%, and shoot length to 17.12% and 17.14%, while increasing the root fresh weight by 133% and 26.2% and the root length to 109.1% and 13.4%, respectively, in the Kasuri methi and Local. Drought stress decreases the total Chl. by 55.4% and 59.3% and carotenoids 42.1% and 59.3% and increased the MDA by 6.35% and 24.2%, respectively, and the content of hydrogen peroxides increased by 12.05% and 44.2% in Kasuri and Local as compared to control. By the application of 200  ppm β-carotene, the shoot fresh weight increased by 95.06% and 66.7%, the shoot length increased by 49.6% and 44.5%, and the total Chl. increased by 194.3% and 144.3%, and carotenoids 71.6% and 63%, and MDA decreased by 14.7% and 15.8%, hydrogen peroxides 26.6% and 27.8%, in Kasuri methi and Local under drought stress conditions. Additionally, with the application of β-carotene, antioxidant enzyme activities (SOD, POD, and CAT) and osmoprotectants (total soluble proteins and sugars) improved significantly, indicating enhanced oxidative defense. Overall, foliar β-carotene application, especially at 200 ppm, proved highly effective in improving fenugreek's drought tolerance by enhancing antioxidant capacity, maintaining pigment stability, and supporting metabolic homeostasis, thereby highlighting its potential role in sustainable crop management under water-limited conditions.