Response on Morphology and Growth of Seedlings of Liriodendron tulipifera Under Submergence

In order to explore the different resistance of Liriodendron tulipifera under submergence, the study made 2yearold potting Liriodendron tulipifera seedling, from 3 families of 3 provenances（Louis （L）, Kent （K） and Penn （P）） as material and treated by submergence, studied the variation of lenticels, knee roots and leaves of seedlings. The results showed that, knee roots formation was a stress response for Liriodendron tulipifera to adapt to submergence. In a same family, the length and coarseness of knee roots were increased with aggravated submergence height, while knee roots increment existed differences in different families, such as knee roots of L family was the longest and thinnest, the thickening of P family was fastest, while K family was in the medium. Lenticels formation increased the resistance of Liriodendron tulipifera under submergence, the order of lenticel quantity from high to low were L family, K family and P family. Under submergence condition, plants withered and green leaves reduced, but different families existed differences, and green leaves quantity were the most. The growth of living roots under water improved the ratio of aboveground and underground part, expanded superficial area for oxygen absorbed, and then increased the resistance to submergence, and therefore, it was a stress response. According to index, the order of resistance to submergence in three families was L＞K＞P. Knee roots length and lenticels quantity were direct correlation with submergence tolerance of Liriodendron tulipifera