Regulatory effects of brassinolide on the physiological characteristics of Festuca arundinacea, a slope protection plant, under drought stress

Tall fescue (Festuca arundinacea) was used as experimental material in this study to explore the mechanism by which brassinolide enhances its drought resistance when grown in vegetation concrete under drought stress. A pot experiment was conducted to investigate the effects of brassinolide on plant height, biomass, photosynthetic characteristics, and certain osmotic adjustment substances and antioxidants of tall fescue under drought stress by setting treatments with three water gradients (well water, mild drought, and severe drought) and four concentrations of brassinolide (0, 0.05, 0.2, and 0.5 mg·L⁻¹). The results showed that the growth of tall fescue was inhibited, and the physiological performance decreased with the aggravation of drought stress and prolongation of stress time in vegetation concrete. Brassinolide treatment significantly increased (P < 0.05) the plant height, biomass, net photosynthetic rate, transpiration rate, stomatal conductance, and proline content of tall fescue under drought stress, reduced the intercellular CO₂ concentration and malondialdehyde content in the leaves of tall fescue, effectively improved the drought resistance of tall fescue grown in vegetation concrete, and had a significant concentration effect. Spraying 0.2 mg·L⁻¹ brassinolide under normal water and mild drought stress had the best effect on the growth of tall fescue, while spraying 0.05 mg·L⁻¹ brassinolide under severe drought stress had the best effect. This preliminary study revealed the effect of brassinolide on the physiological characteristics of tall fescue under drought stress, providing a research basis for using the exogenous phytohormone brassinolide in the ecological slope restoration of vegetation concrete.