Heat Stress Mitigation through Exogenous Glycine Betaine in Brassica rapa subsp. chinensis under Controlled Environments

Abstract

Heat stress is a major abiotic constraint affecting growth, physiological performance, and yield of leafy vegetables under controlled and open-field conditions. This study evaluates the potential of exogenous glycine betaine application to mitigate heat stress effects in Brassica rapa subsp. chinensis. A controlled environment experiment was conducted using foliar application of glycine betaine at varying concentrations under elevated temperature regimes to assess plant growth, physiological responses, and stress tolerance. The results demonstrated that heat stress significantly reduced biomass accumulation, chlorophyll content, and overall plant vigor. However, exogenous application of glycine betaine alleviated stress effects by enhancing osmotic adjustment, stabilizing cellular membranes, and improving photosynthetic efficiency. Treated plants exhibited higher chlorophyll retention, better water status, and increased antioxidant activity, leading to improved growth and yield performance under heat stress conditions. Moderate application levels were found to be most effective, while excessive concentrations did not provide additional benefits. The protective role of glycine betaine was associated with improved metabolic stability and reduced oxidative damage. While analytical techniques were used to quantify physiological and biochemical responses, the primary focus remained on crop stress management and agronomic performance. The findings highlight the potential of glycine betaine as a practical strategy for enhancing heat tolerance in Brassica rapa subsp. chinensis. This study contributes to sustainable agriculture by supporting climate-resilient crop production through improved stress adaptation and resource-use efficiency.