Does the exogenous application of brassinosteroids affect the photosynthetic, morphological characteristics, and THC concentrations of Cannabis sativa L. under drought stress?

Abstract

Drought stress represents a significant constraint on the productivity of crops globally. The application of plant growth regulators, particularly brassinosteroids (BRs), has demonstrated potential in enhancing plant tolerance to drought conditions. This study aimed to examine the effects of exogenous BR application on the photosynthetic and morphological characteristics, as well as the concentrations of Delta-9-Tetrahydrocannabinol (THC), in Cannabis sativa subjected to drought stress. A split-plot experimental design was implemented over two growing seasons, with the primary factor being the planting date (May 20, June 5, June 20) and the secondary factor being the irrigation level (80–100 %, 50–60 %, and 30–40 % of field capacity). Exogenous BR treatments (0, 200, and 400 μg/L) were applied as the tertiary factor. The results indicated that drought stress significantly diminished photosynthetic efficiency, plant growth, and THC concentrations in C. sativa. Conversely, the exogenous application of BRs alleviated the adverse effects of drought, leading to enhanced photosynthetic performance, improved morphological traits, and increased THC levels compared to drought-stressed plants that did not receive BR treatment. These findings suggest that the exogenous application of BRs may serve as a promising strategy to improve drought tolerance and the medicinal properties of C. sativa. The study offers valuable insights into the role of plant growth regulators in modulating the physiological and biochemical responses of this important medicinal plant under conditions of water limitation.