Studies On The Regulation Of Enhanced UV-B Radiation And Drought Stress On Carbon And Nitrogen Metabolism And Alkaloid Content In Catharanthus Roseus

In this paper we take the medicinal plants Catharanthus roseus as materials, the photosynthetic physiological, nitrogen metabolism and alkaloid metabolic process under different intensity UV-B radiation and soil drought environment were studied.We analysed the alkaloids metabolism to UV-B and drought response from the dynamic changes of carbon and nitrogen metabolism. The environmental factors to increase alkaloid content of Catharanthus roseus were also summarized and discussed. The results may provide some basic information for the research of the relationship between secondary metabolism in Catharanthus roseus and it's environment,and they also have some guidance significance in the practice of Catharanthus roseus cultivation in order to gain high alkaloid concentration. The main results are as follows:1. The stomata conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr) were reduced under enhanced UV-B radiation and drought stress. This lead to photosynthetic rate dropped significantly, and composite treatment on the influence of photosynthetic rate lower than a single factor. But Increased UV-B radiation or drought applied alone or combined increased the water utilization efficiency of leaves.2. Chlorophyll fluorescence analysis showed that all the stress treatment will lead the initial fluorescence(Fo), conversion efficiency of primary light energy (Fv/Fm) of PSⅡand the photo chemical quenching coefficient (qP) decreased significantly, and these cause photosynthetic electronic transfer rate (ETR) decline.The chlorophyll contents were decreased by enhanced UV-B radiation,drought stress and the two stresses combined had no significant impact on these pigments. Increased UV-B radiation or drought applied alone or combined caused an enhancement of carotenoids (Car.) contents, and this lead to the ratio of Chi to Car increased. It could be conclude that increased UV-B radiation damage PSⅡ, and the protective ability was strengthened under UV-B radition.3. The results suggested that N metabolism of Catharanthus roseus could be accelerated by UV-B radiation and drought stress. It can be seen from the follw index. The stress caused the free amino acid and total nitrogen content increased significantly. Increased UV-B radiation reduced nitrate reductases (NR) activity, increased UV-B and drought combined make it more drastically, but UV-B and drought composite combined treatment improve glutamine synthase (GS) activity.4. All the treatment caused the contents of vindoline(VIN) decreased. Enhance UV B radiation reduced the content of catharanthine(CAT),but drought raised the content of CAT.UV-B radiation will increased the content of vinblastine(VBL). Light UV-B radiation and drought composite processing (10μW·cm-2 ultraviolet intensity,55% 60% soil moisture) most favorable to produce vincristine (VCR). The content of VIN and CAT will decreased under all the stress treatment of Catharanthus roseus stems.The content of VBL and VCR are hightest under Light UV-B radiation and drought composite processing.To sum up, enhance the UV-B radiation and drought composite processing changed carbon and nitrogen allocation of Catharanthus roseus, thereby improving the alkaloid content of secondary metabolites.Because the VBL and VCR have more economic value.Therefore it is an efficient method to increase alkaloid centration in Catharanthus roseus that proper short-term UV-B radiation and drought stress was conducted after a period of vigorous growth.