Effects Of UV-B On Physiological Characteristics And Secondary Metabolites Content Of The Atropa Belladonna L

In this paper, we take Atropa belladonna as plant material, investigated the response of physiological characteristics and secondary metabolites to different doses of UV-B radiation. Four groups of UV-B radiation were set in the experiment which included: natural light control(0μW·cm-2), LU(5μW·cm-2), MU(10μW·cm-2), HU(15μW·cm-2). The physiological indicators, photosynthesis character and the key enzyme gene expression and alkaloid content of Atropa belladonna tropane alkaloid metabolic pathways were measured under different UV-B radiation. Results are as follows:1. Compare the response of photosynthetic pigment content and chlorophyll fluorescence parameters of Atropa belladonna leaves to different doses of UV-B radiation and the days of treatment on. Results showed that 5μW·cm-2 UV-B radiation increased the contents of chlorophyll a, chlorophyll b and carotenoid. The contents of chlorophyll a, chlorophyll b and carotenoid decreased with the increase of treatment days under 10μW·cm-2 and 15μW·cm-2 UV-B radiation. With the increase of UV-B radiation and treatment days, F0 and q N increased, but Fv/Fm, Yield, q P and ETR decreased. These results suggest that UV-B radiation destroyed the center of photosynthesis, which inhibition the photosynthesis of Atropa belladonna.2. UV-B radiation changed the activities of antioxidant enzymes( SOD, POD, CAT), the contents of osmotic adjustment substances( free praline, soluble sugar) and MDA. With the increase of UV-B radiation, MDA content increased, CK<LU<MU<HU, all treatment higher than that of control. With the increase of treatment days, SOD and CAT activities rose firstly then down, POD activity increased. 5μW·m-2 radiation only slightly increased the activities of SOD, POD, and CAT. The contents of free praline and soluble sugar rose firstly then down with the increase of treatment days, 10μW·cm-2 and 15μW·cm-2 UV-B radiation significantly increased the contents of free praline and soluble sugar. These results suggest that low-intensity of UV-B radiation has little effects on the growth of Atropa belladonna, high intensity of UV-B radiation injured the growth of Atropa belladonna and led to metabolic disorders.3. The response of nitrogen metabolism, alkaloid content, key enzyme gene expression of tropane alkaloid metabolic pathways to UV-B radiation were investigated. With the increase of UV-B radiation and treatment days, nitrate nitrogen content higher than that of control under 5μW·cm-2, 10μW·cm-2 and 15μW·cm-2 UV-B radiation treatment. Meanwhile, the activity of GS and GDH rose firstly then down, even were higher than control. UV-B radiation decreased the hyoscyamine and scopolamine contents in leaves and stems of Atropa belladonna. Furthermore, the expression of pmt and h6 h genes showed tissue specific. The main pmt gene expression in tissues is the root, in leaves and stems almost no expression. The expression of pmt gene higher than that of control under 5μW·cm-2 UV-B radiation treatment, but lower than that of control under 10μW·cm-2 and 15μW·cm-2 UV-B radiation treatment. The main expression of h6 h gene in tissues is the root, and the expression of h6 h gene decreased gradually with the increase of UV-B radiation. The expression of tr1 gene in leaves higher than other tissues and the expression of tr1 gene in other tissues very low. The expression of tr1 gene increased with the increase of UV-B radiation. These results suggest that low-intensity of UV-B radiation promoted the nitrogen metabolism and self-protection of Atropa belladonna. UV-B radiation also influenced the expression of key enzyme gene, but not increased the contents of hyoscyamine and hyoscine.Taken together, 5μW·cm-2 UV-B radiation has little effect on the regulation of plant physiological characteristics and secondary metabolites, 10μW·cm-2 and 15μW·cm-2 UV-B radiation destroyed the center of photosynthesis and inhibition the photosynthesis of Atropa belladonna, which was correlated with the oxidative damage. Meanwhile, 10μW·cm-2 and 15μW·cm-2 UV-B radiation have negative effect on the accumulation of the secondary metabolites, and decreased the contents of the hyoscyamine and scopolamine. So the plantation of Atropa belladonna should avoid high intensity UV-B radiation area.