花青素是决定梨果皮颜色的重要成分。研究发现褪黑素可以影响花青素代谢，但褪黑素采前处理对果实着色的作用尚不清楚。本试验以‘南红梨’为材料，研究了50、200 μM褪黑素采前喷施梨果实，对果皮着色、酚类物质含量及相关基因表达的影响。结果表明，褪黑素采前喷施可以显著影响梨果实着色，提高果皮中花青素和黄酮醇的含量，降低羟基肉桂酸和黄烷醇的含量，同时增加多数花青素合成基因和相关转录因子的相对表达量。此外，外源褪黑素处理促进了褪黑素合成相关基因的表达，从而增加果皮中内源褪黑素的含量。试验结果为探索褪黑素调控果实花青素代谢提供了新的思路，并有助于外源褪黑素在农业上的应用。

The effects of light intensity on photosynthesis and photoprotective mechanisms under progressive drought were studied on apple trees (Malus domestica Borkh.) Fuji. The potted trees were exposed to drought stress for 12 days and different light conditions (100, 60 and 25% sunlight). During the progressive drought, the relative water content (RWC) in leaf declined and was faster in full light than in 60 and 25% sunlight. However, the decrease in the net photosynthetic rate (Pn), stomatal conductance (Gs) and Rubisco activity were slower under 100% sunlight condition than other light conditions. After the 6 days of drought, the maximum PSII quantum yield (Fv/Fm), the capacity of electrons move beyond QA − (1–VJ) and electron move from intersystem to PSI acceptor side (1–VI)/(1–VJ) decreased, with greater decline extent in brighter light. While RWCs were >75%, the variations in different light intensities of Gs and Rubisco activity at identical RWC, suggested the direct effects of light. While the little difference in the state of photosynthetic electron transport chain among tested light intensities indicates the results of faster water loss rate of light. Our results also demonstrated that the enhancement the de-epoxidations of xanthophyll cycle, activities of ascorbate peroxidase (APX) and catalase (CAT) were directly regulated by light intensity. While the higher photorespiration rate (Pr) under stronger light condition was mainly caused by faster water loss rate of light.