| The reduction of stratospheric ozone results in the increase of solar UV-B radiation on the earth's surface. UV-B radiation has an effect on secondary metabolism processes in plants. Most of the medically active ingredients in medicinal plants are secondary metabolites while the contents of active ingredients are not high enough. Previous results indicated that enhanced UV-B radiation could significantly prompt secondary metabolism processes in postharvest medical plants organs. However the scientists are just beginning to study UV-B effects on isolated organs of medicinal plants. So more works should be done for better evaluation of the application of UV-B radiation in medicinal plants. The paper, medical chrysanthemum as tested materials, mainly studied:(1) the effects of enhanced UV-B radiation on biochemical traits and quality of postharvest chrysanthemum inflorescence during the different development stages(2) the effects of different drying technologies on nutritional and active ingredients in chrysanthemum inflorescence treated by UV-B radiation, in order to determining the best harvest stage and drying methods according to the content of nutritional and active ingredients in chrysanthemum inflorescence. This will be helpful for further research about the application of UV-B radiation on medicinal plants. The results as followed:1. The effects of enhanced UV-B radiation on biochemical traits during the floral development of medicinal chrysanthemum. The experiment included two levels of UV-B radiation(0 and 400 ?W cm-2). The harvest flowers were divided into four stages according to floral development: jumi, taiju, youju and quanju, and were immediately treated with UV-B radiation for 60 min. The physiological traits of chrysanthemum flowers at different stages had evident differences and the physiological activity of flowers at jumi and taiju stages was more vigorous. Enhanced UV-B radiation significantly increased the activities of phenylalanine ammonia lyase(PAL), cinnamic acid-4-hydroxylase(C4H) and 4-coumarate Co A ligase(4CL), and the contents of H2O2, UV-B absorbing compounds, chlorophyll, carotenoids, soluble sugar, amino acid, vitamin C, flavonoid and chlorogenic acid in medical chrysanthemum flowers. The results indicated that enhanced UV-B radiation could significantly promoted physiological activity and secondary metabolic processes during floral development of medical chrysanthemum.2. The effects of enhanced UV-B radiation on nutritional and active ingredients contents during the floral development of medicinal chrysanthemum. The contents of soluble sugar,free amino acid and vitamin C were significantly increased with the floral development. The contents of flavonoids and chlorogenic acid were significantly different in the four stages of floral development, and their highest contents were found in the jumi stage. Enhanced UV-B radiation significantly affected the active and nutritional ingredients during the floral development of medicinal chrysanthemum. Comprehensive analysis revealed that the best harvest stage of chrysanthemum flowers was between the taiju and youju stages.3. The effects of different drying technologies on nutritional and active ingredients in chrysanthemum inflorescence treated by UV-B radiation. The drying methods were employed in the experiment: microwave drying, drying after steaming, stoving drying, sun-drying, fixing drying and shade-drying. Drying methods have significant differences on active and nutritional ingredients in flowers treated by enhanced UV-B radiation. The contents of flavonoids and chlorogenic acid were higher in the samples of microwave drying and drying after steaming, and flowers have intense perfume and better brilliant color and flower shape by the microwave drying method.The study broadens the field of UV-B radiation, and furthers extent and improves the research about the application of UV-B radiation technology on medical plants. This will effectively promote the development of medicinal plant resources. |
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