（Key Laboratory of Horticultural Crops Genetic Improvement，Ministry of Agriculture，Institute of Vegetables and Flowers，
Chinese Academy of Agricultural Sciences，Beijing 100081，China）
Abstract：In order to investigate the effect of chlorocholine chloride（ CCC） on cucumber seedling hypocotyl strench，seeds of cucumber（Cucumis sativus L．）variety‘Zhongnong 203’were soaked with 3 000 mg·L-1 CCC to test the morphological index of cucumber seedling hypocotyl growth．And transmission electron microscope was adopted to observe the changes in the submicroscopic structure of its hypocotyl cortical cell．The results showed that the length of hypocotyl was reduced and dry matter accumulation was promoted by CCC treatment．Compared with the contrast，cell wall of cucumber seedling hypocotyl cortical cell was obviously thickened，the number of vacuoles was increased，and the volume became smaller．The chloroplast morphology and structure were altered．The grana content and number of starch bodies were increased．
