Both AB-toxin and Alternaria brassicae could stimulate the activity of phenylalanine ammonialyase (PAL) and peroxidase(PO) in leave cells of Brassica chinensis.There were two PAL activity peaks in resistant cv. Shandong No.4 and susceptible cv. Xiaoza 56 under AB-toxin stress.The PAL activity peaks of Xiaoza 56 (2 h,12 h) appeared earlier than those of Shandong No.4(12 h,48 h). There were two PO activity peaks(12 h,60 h) in Shandong No.4,but only one evident PO activity peak(12 h) appeared in Xiaoza 56 unde...