28-homobrassinolide supplementation modulates the physiological mechanism and yield in Phaseolus vulgaris L. under sodium fluoride stress.

Abstract

In the modern era, anthropogenic activities have led to an alarming increase in soil salinity, posing significant challenges to agriculture. Salinity not only adversely affects crop growth but also contributes to water pollution. Na stress reduces plant growth through osmotic effects, limiting water uptake and causing ion toxicity and oxidative damage. Brassinosteroids, a class of plant steroids, are well known for their roles in plant development and enhancing tolerance to various environmental stressors. This study aimed to investigate the impact of 28-homobrassinolide (28-HBL) application, both through seed priming and foliar application on Phaseolus vulgaris L. (common beans) subjected to sodium fluoride (NaF) stress. In pot experiments, soil was treated with 200 ppm NaF via aqueous solution 15 days before sowing followed by seed priming and foliar application with two concentrations of 28-HBL (40 and 60 ppm). Seed priming with 28-HBL enhanced total phenolic content and facilitated the uptake of essential mineral nutrients (K⁺, Zn²⁺, and Mg²⁺), counteracting the adverse effects of NaF on plant growth. Furthermore, the combined treatment of seed priming and foliar application of 28-HBL significantly increased protein content (24%) and proline content (61%), with the highest levels observed in the 28-HBL SP+FS-60 ppm group. Gas exchange characteristics, chlorophyll a (66%), chlorophyll b (65%), and carotenoids (75%) were all significantly improved in plants subjected to SP+FS-60 ppm 28-HBL treatment compared to those treated solely with NaF stress. 28-HBL effectively mitigated NaF induced stress by modulating ascorbic acid content and DPPH and enhancing the plant's antioxidant system, improving growth and biomass production. Additionally, the study investigated the antioxidant capacity of 28-HBL under salt stress, highlighting its potential as a valuable tool for enhancing P. vulgaris cultivation in fluoride-polluted soil. These findings underscore the potential of 28-homobrassinolide as a promising strategy for addressing soil salinity stress in agricultural settings.