Brassinolide improves the tolerance of Malus hupehensis to alkaline stress

Abstract

Malus hupehensis is one of the most widely used apple rootstocks in china but is severely damaged by alkaline soil. Alkaline stress can cause more serious harmful effects on apple plants than salt stress because it also induces high pH stress except for ion toxicity, osmotic stress, and oxidative damage. Brassinolide (BL) plays important roles in plant responses to salt stress. However, its role and function mechanism in apple plants in response to alkaline stress has never been reported. This study showed that applying exogenous 0.2 mg/L BL significantly enhanced the resistance of M. hupehensis seedlings to alkaline stress. The main functional mechanisms were also explored. First, exogenous BL could decrease the rhizosphere pH and promote Ca2+ and Mg2+ absorption by regulating malic acid and citric acid contents and increasing H+ excretion. Second, exogenous BL could alleviate ion toxicity caused by alkaline stress through enhancing Na+ efflux and inhibiting K+ expel and vacuole compartmentalization. Last, exogenous BL could balance osmotic stress by accumulating proline and reduce oxidative damage through increasing the activities of antioxidant enzymes and antioxidants contents. This study provides an important theoretical basis for further analyzing the mechanism of exogenous BL in improving alkaline tolerance of apple plants.

Enhanced Seedling Growth and Physiological Performances of Melia azedarach L. by Foliar Application of 24-Epibrassinolide under Salt Stress

“…On the other hand, the application of EBR, especially at higher concentrations, had a positive impact, resulting in a relative growth increment in the indicators measured in the present study (Tables 1-3). The application a plant growth regulator is one of the most efficient techniques for alleviating abiotic stress because hormones play significant roles in plant growth and development under environmental stress [14]. In the study of Dong et al [42], EBR application at a low concentration significantly increased the plantgrowth-related parameters of wheat seedlings under 120 mM NaCl treatment, and 10 nM was found as the most effective dosage of EBR under saline conditions.…”

“…Consequently, the use of growth regulators has commonly been employed as an effective approach to enhance the performance of plants under stress [12]. Exogenously applying plant growth regulators is an effective way to reduce abiotic stress as hormones are essential for a plant's growth, development, and reaction to environmental stress [14]. One of them, the application of brassinosteroids (BRs), has been found to have beneficial effects in supporting growth and alleviating the negative effects of salt stress [15].…”