Abstract：This paper studied the influence of different draught stress period to the heart leaf of cowpea〔Vigna unguiculata（L.）Walp.〕seedlings and mature leaves and roots．The results showed that the micro-structures of heart leaf and mature leaves were both changed under draught stress．The palisade tissue cells became shorter than CK，and were arranged orderly in the early stressed stage，then the cells became dehydrated，deformed and disordered in the later stressed stage．The changes in heart leaf were larger than the mature leaves．The transverse section of root showed that the influence of drought stress to root came earlier than to leaves．The root morphology and all column cells shrank and became smaller，then deformed．The cortical parenchyma cells in root were atrophy and withered under severe stress and only left the column cells stood．
