Efects of water stress on the activities of antioxidant enzymes of Malus L．plant

The changes in activities of SOD．CAT．P0D and MDA contents in 1eaves and roots of three different species of Malus L．were studied under the water stress．The results show that the activities of S0D．CAT and POD are gradually increased under the water stress conditions． activity firstly reaches the highest point when the absolute water content of soi1 decreases to 6．5％ ．but the highest point of SOD activity is at 2．8％ ．then their activities are decreased with further increasing of water stress．an dare partly recovered by rewatering．rrhe highest point of P0D activity appears when the absolute water content of sol1 declines to 3．2％ ．declines again with further increase of water stress and stin decreases after rewatering．MDA content is gradually increased un der the water stress conditions，and arrives at the highest point when the absolute water content of soil declines to 1．8％ and decreases after rewatering．It is eoncluded that the order of an tioxidization abilities of the species is M ．sieverii> M micromalus> M ．hupehensis．