Brassinolide Promotes the Growth of Zanthixylum schinifolium by Improving Photosynthetic Efficiency and Antioxidant Capacity

As a plant growth regulator, brassinolide (BL) is essential for enhancing plant growth and development. Studies on how BL affects the growth and development of prickly ash (Zanthixylum schinifolium) are scarce, nevertheless. Thus, the purpose of this study was to investigate how Z. schinifolium growth and development were affected by the application of BL (0, 0.1, 0.2, 0.3, 0.4, and 0.5 mg/L). According to the results, the 0.4 mg/L BL treatment had improved the plant height and leaf length after 30 days of treatment, which was displayed in an increase of 8.75% and 20.48%, respectively, when compared to the control (distilled water). On day 30, Z. schinifolium’s basal diameter, leaf breadth, compound leaf length, and leaf weight all rose noticeably after treatment with 0.4 mg/L BL. Furthermore, the 0.4 mg/L BL treatment raised the levels of osmotic substances (proline, soluble sugar, and soluble protein) and photosynthesis parameters (chlorophyll a, chlorophyll b, PSII, Fv/Fm, NPQ, and qP) in Z. schinifolium compared to the control. It also decreased the levels of malonaldehyde, increased the activities of antioxidant enzymes (POD, SOD, CAT, and APX), and increased the contents of non-enzymatic antioxidants (ASA and GSH). Accordingly, these findings implied that BL might be crucial in fostering Z. schinifolium growth and development by boosting antioxidant capacity, decreasing malonaldehyde concentration, preserving water balance, and improving photosynthesis.