Nanoselenium improves drought tolerance of sorghum via reduced transpiration rate and osmolytic accumulation

• Published in: South African journal of botany 2024-09, Vol.172, p.93-108
• Main Authors: Djanaguiraman, M., Priyanka, A.S., Haripriya, S., Kalarani, M.K., Umapathi, M.
• Format: Article
• Language: English
• Subjects: antioxidant activity; drought; drought tolerance; ecotoxicology; foliar spraying; grain yield; hydrogen peroxide; leaves; Nanoselenium; Osmotic adjustment; Oxidative damage; photosynthesis; pollen; Pollen and pistil; proline; Reproductive success; seed set; seed yield; Selenium; sodium selenate; soil; Sorghum bicolor; stigma; superoxide anion; toxicity; transpiration; turgor; water content; water stress
• ISSN: 0254-6299
• DOI: 10.1016/j.sajb.2024.07.012

•Nanoselenium (n-Se) up to 20 mg L−1 did not cause toxicity at any trophic levels.•Application of n-Se at 20 mg L−1 reduced sorghum transpiration rate under drought.•Application of n-Se at 20 mg L−1 increased sorghum photosynthetic rate under drought.•During drought, n-Se enhanced seed-set by preserving reproductive tissue structures. Sorghum [Sorghum bicolor (L.) Moench] grain yield is vulnerable to drought stress. Therefore, developing appropriate technologies to mitigate drought is essential. We hypothesize that inhibition of photosynthesis and reproductive success by drought in sorghum can be improved by enhanced osmolyte accumulation and antioxidant defence system by foliar application of nanoselenium. In this study, the ecotoxicity potential and the physiological basis of drought alleviation by nanoselenium were evaluated. Nanoselenium did not cause toxicity to soil, aquatic and terrestrial organisms up to 20 mg L−1. During drought, foliar application of nanoselenium at 20 mg L−1 reduced the transpiration rate (16 %) compared to water spray. The superoxide radical content (50 %), hydrogen peroxide content (35 %), and membrane damage (26 %) were reduced, indicating antioxidant activity was exerted by nanoselenium. In contrast, the leaf turgor potential (80 %), relative water content (17 %), reducing sugars (57 %), non-reducing sugars (11 %), and proline (35 %) contents were increased by nanoselenium than water spray, indicating a higher tissue water content was maintained, which has increased the photosynthetic rate (26 %). Higher reproductive success in nanoselenium-sprayed plants under drought was associated with reproductive tissue morphology and an increased number of pollen grains attached to the stigma. Foliar application of nanoselenium at 20 mg L−1 increased seed-set percentage (21 %) and seed yield (26 %) under drought than control. A similar response was observed by foliar spray with sodium selenate. Overall, foliar application of nanoselenium at 20 mg L−1 improved the drought tolerance of sorghum by reducing the transpiration rate and increasing the antioxidant defense system.