Abstract: In order to select excellent Morus albaL. varieties suitable for the windy and sandy area of northwestern Liaoning, three Morus alba clones, “Shensang No. 1” selected by Shenyang Agricultural University (SS), Morus alba superior clone in Zhangwu County, Fuxin City, Liaoning Province (ZW) and Morus alba superior clone from Ji’an County, Tonghua City, Jilin Province (JS), and “Longsang No. 1”, the main cultivar in Northeast China (LS), were used as test materials. The drought resistance of differentMorus alba clones was studied by measuring photosynthetic pigment content, light response curve, the influence of light intensity on gas exchange parameters and the change of photosystem Ⅱ (PSⅡ) under drought stress. Under drought stress, photosynthetic pigment content of all clones decreased, with ZW changing the least, followed by LS, and JS and SS decreasing greatly. Under drought stress, the net photosynthetic rate of Morus alba clones decreased, stomatal conductance, intercellular CO₂ concentration and transpiration rate decreased to varying degrees, while water use efficiency increased. The reduction of parameters of light response curves strengthened with the order of ZW, LS, JS and SS. Drought stress destroyed the activity of PSⅡ reaction center of Morus alba clones, inhibited electron transfer, leading to QA^- accumulation and photosynthetic apparatus damage. Comparing the parameters of four clones under drought conditions, ZW was least affected by drought stress, followed by LS, while JS and SS had poor photosynthetic capacity. Collectively, ZW has the strongest drought resistance, which would be more suitable for planting and cultivating in the windy and sandy area of northwestern Liaoning.

Key words: Morus alba L., photosynthesis, drought resistance, photosystem Ⅱ, variety selection.