2017 ASHS Annual Conference

Abstract: Ultraviolet-B radiation (UV-B) radiation is a key environmental signal for plant growth and development. An excess or lack of UV-B can affect plant growth, resistance, yield and quality. However, the appropriate dose of UV-B for cucumber seedlings growth in plant factories is not well understood. Cucumber seedlings (C. sativus L. cv. Chinese long 9930) were used as the test material in this study, when the sixth leaf had expanded, the plants were moved into a controlled chamber with a 14 hours photoperiod, 28/20℃, 60% relative humidity and 150 μmol•m-2•s-1 photon flux density (400–700 nm) supplemented with high-pressure sodium lamps from 6:00 AM to 8:00 PM. After the cucumber seedlings were moved into a controlled chamber for three days, they were exposed to biologically effective UV-B irradiance for 4 hours (11:00 AM–2:00 PM). The experiments included five different doses: 0(CK), 10(T1), 20(T2), 30(T3) and 40(T4) μw•cm-2. The physiological indexes of cucumber plants were determined every seven days. The result showed that UV-B radiation effectively decreased the cucumber seedlings by 4.2–32.0%, and decreased soluble protein content in cucumber leaves. Stem diameter growth, soluble sugar content, total ascorbic acid (AsA) and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly promoted by about 15.9-33.3%, 31.3-51.4%, 31.5-36.3%, 27.7-31.5%, 31.6-44.7% and 33.3-42.8% in cucumber seedlings by 20μW•cm-2 UV-B. By contrast, these characteristics were inhibited by 40 μW•cm-2 UV-B. 20 μW•cm-2 UV-B had no significant influence on hydrogen peroxide(H2O2) and malondialdehyde (MDA) content in cucumber leaves, whereas high intensity UV-B (30 or 40 μW•cm-2) led to increase in MDA and H2O2 levels. Low and medium intensity UV-B (10 or 20 μW•cm-2) had no influence on the net photosynthetic rate of cucumber leaves after 7 days of treatment, while high intensity UV-B (30 or 40 μW•cm-2) reduced it. In addition, the UV-B radiation had no effect on the biomass accumulation of cucumber plants after 28 days of the treatment. Therefore, we conclude that the growth of cucumber seedlings are promoted by 20μW•cm-2 UV-B, and 20 μW•cm-2 UV-B increased the anti-oxidase activities and AsA content of cucumber seedlings in the biotron. The results of this study indicates that supplied 20μW•cm-2 UV-B to promote the growth and improve stress resistance of cucumber plants in plant factory.