Effects of nitrogen nutrition and inoculation with Colletotrichum higginsianum on anthracnose resistance physiology in Flowering Chinese Cabbage Ⅱ.The effects of nitrogen nutrition on anthracnose and membrane lipid peroxidation in Flowering Chinese Cabba

The effects of six nitrogen(N) levels and inoculation with Colletotrichum higginsianum on plas-malemma permeability, polyphenoloxidase(PPO)activity, the content of ascorbic acid (AsA) and malonialde-hyde(MDA)in Flowering Chinese Cabbage (Brassica parachinensis) , and the relationship between membrane lipid peroxidation and incidence of anthracnose were studied. The results showed that anthrax fungi could enhance the degradation of AsA, and the degradative effect of low N was more significant than that of high N. PPO activity of leaves was increased after inoculation with C. higginsianum. Compared with high, low N levels and non-fertilization, the suitable N level could significantly strengthen PPO activity. The integrity of cell membrane of leaves was gradually injured after infected with C. higginsianum in all N treatments, permeability of cell membrane augmented rapidly, but the cell membrane of the suitable N level was less injured than that of high N and non-fertilization treatments. With lastingness of the infection with C. higginsianum, MDA content in the leaves increased consistently, the results indicated that after the plant infected with C. higginsianum , membrane lipid peroxidation was strengthened and product of lipid peroxidation was increased. Low and suitable N treatments would accelerate the level of lipid peroxidation in early stage after the plant infected with C. higginsianum, but inhibition effect in the later, while the effect of non-fertilization or high N level was contrary.