Abstract: 【Aim】To explore the effects of heavy metal lead (Pb) and herbivore feeding stress on the nutrients and defense compounds in pakchoi (Brassica chinensis), and the growth and development of Spodoptera litura. 【Methods】The plants of pakchoi variety Zhengwangda 88 were subjected to the stress of Pb (400 mg/kg), S. litura larval feeding (feeding density: 3 individuals/leaf; feeding area: 30%) and their combination, the contents of soluble sugar, trypsin protease inhibitor and Pb, and the activities of protective enzymes including peroxidase, superoxide dismutase and catalase in pakchoi leaves were detected using biochemical methods, and the larval survival rate, larval duration, pupal duration, emergence rate, and adult dry weight of S. litura were counted. 【Results】The combined effects of 400 mg/kg Pb stress and S. litura larval feeding significantly affected the contents of soluble sugar and trypsin protease inhibitor, and the activities of peroxidase, catalase and superoxide dismutase in pakchoi leaves. The larval survival rate, larval duration, pupal duration, emergence rate, and adult dry weight were also significantly affected by Pb stress, S. litura larval feeding, and their combinations. Compared with the control group, Pb stress, S. litura larval feeding, and their combinations decreased the soluble sugar contents in pakchoi leaves by 10.5%, 9.3% and 38.1%, respectively, and increased the trypsin protease inhibitor contents by 51.6%, 90.1% and 103.0%, respectively; and increased the peroxidase activities by 136.1%, 46.6% and 243.8%, respectively, the superoxide dismutase activities by 43.1%, 16.4% and 91.1%, respectively, and the catalase activities by 68.6%, 17.3% and 139.0%, respectively. In addition, Pb stress, S. litura larval feeding, and their combinations decreased the larval survival rates of S. litura by 28.2%, 31.3% and 43.9%, respectively; extended the larval duration by 4.28, 3.78 and 8.41 d, respectively, and the pupal duration by 2.69, 2.13 and 5.11 d, respectively; and decreased the emergence rates by 33.4%, 46.7% and 60.0%, respectively, and the adult dry weight by 7.98, 3.61 and 12.39 mg, respectively, compared to the control group. 【Conclusion】The results suggest that Pb stress, S. litura larval feeding and their combinations have negative effects on the growth and development of pakchoi. The accumulation of heavy metal Pb in pakchoi plants can produce a superposition or synergistic effect on the phytochemical defense mediated by S. litura, inducing the pakchoi resistance to increase and nutrient content to decrease, and further inhibiting the growth and development of S. litura.

Key words:  Spodoptera litura, lead, pakchoi, nutrient content, phytochemical defense, life history