Adverse effects of shading on the tea yield and the restorative effects of exogenously applied brassinolide

Shading during cultivation leads to increased tea quality, but its effect on tea yield remains unclear. In this study, shading decreased the tea plant yield because it resulted in the production of thin leaves and shortened internodes as well as a decreased photosynthetic rate. The exogenous application of brassinolide (BL), which is a novel phytohormone, recovered some of the lost yield caused by shading by increasing the leaf area, promoting internode elongation, and increasing the photosynthetic rate. Moreover, BL did not affect the enhancement effect of shading on tea quality. The exogenous application of BL could increase the content of total amino acid (AA), geraniol, chlorophyll and carotenoid, and reduce polyphenols-to-amino acids ratio (P/A) in green tea processed from shaded tea leaves. Our findings have clarified the effects of shading on tea plants and explored measures to address shading-induced yield losses without affecting the enhancement of quality, which have potential implications for limiting shading-induced yield losses in tea plants.