Enhancing drought resilience in Brassica campestris: Antioxidant and physiological benefits of Ascophyllum nodosum extract and alginic acid

Abstract

Global climate change is the reason behind extreme dry weather, which is the primary factor behind reduced crop growth and yield. To mitigate the detrimental effect of drought, biostimulants like Ascophyllum nodosum extract (ANE) and alginic acid (AA) are increasingly used, as they have demonstrated growth-promoting effects on plant. This study was designed to delve into the role of ANE and AA on drought affected rapeseed (Brassica campestris cv. BARI Sarisha-17). Moreover, the study gives a comparative illustration of ANE and one of its principal polysaccharide components AA and explores AA's ability to mimic or surpass the effects of the complete extract. Drought was applied from 15 days after sowing (DAS) by keeping soil moisture level at 25 % field capacity. The control plants were irrigated as per requirement with water. Foliar spraying of ANE (0.02 %) and AA (0.02 %) were initiated after plant establishment. Data on different morphophysiological and biochemical parameters were collected at 35 DAS. Water deficit condition reduced plant growth, biomass accumulation, water balance and chlorophyll pigments. It notably increased oxidative damage by increasing lipid peroxidation, hydrogen peroxide content, proline content, electrolyte leakage, and disrupting glyoxalase system which elevated reactive oxygen species in plants by suppressing antioxidants enzyme activities. Conversely, application of ANE and AA substantially alleviated the detrimental consequences of drought stress with AA being slightly more effective than ANE, by uplifting water balance and redox levels of ascorbate and glutathione. The activities of antioxidant defense and glyoxalase pathway enzymes were also enhanced by exogenous ANE and AA. Both ANE and AA enhanced drought tolerance but it was observed that foliar spraying of AA performed better by reducing oxidative damage and improving antioxidant enzyme activities over plants treated with ANE. These improvements play a crucial role in strengthening rapeseed's resistance to drought conditions.

Keywords: Abiotic stress; Ascorbate-glutathione pathway; Biostimulants; Osmotic stress; Reactive oxygen species; Stress elicitor.