Induction of an oxidative defence system against UV-stress and application to improve qualities of green vegetables

We investigated the utilization of UV-stress as a method to increase the contents of beta-carotene, tocopherols, and ascorbic acid in green vegetables. UV irradiation with fluorescent lamps (max. UV wave length: 310 nn) for 5 min increased alpha-tocopherol and reduced ascorbic acid in spinach cultivated in a plastic film house. Similar effects from UV irradiation were also expected in the shorter treatment beginnig about 20 days before harvest. Judging from the results obtained in the simulation examination with laminas, it appeared that the effect demands successive daily treatments until harvest time and results from the induction of the plant antioxidative system in an adaptation response to UV-stress. Our results indicate that UV irradiation could be an effective technique to improve the quality of green vegetables.