The Disaster Grades Index Of Low Temperature And Sparse Sunlight For Watermelon Cultivation In Plastic Greenhouse In Haikou

With unique ecological environment and climate advantages, Hainan become an important production base of cucurbits and vegetables in winter, and perennial planting area of greenhouse vegetables is about12,000hectares. Low temperature and sparse sunlight caused by strong cold air, which is unfavorable for the growth of vegetables, has become a major meteorological disasters for greenhouse cultivation of vegetables. To build the disaster grades index of low temperature and sparse sunlight for vegetables cultivation in plastic greenhouse is necessary for government agencies, agricultural sector quickly grasp the disaster information, develop appropriate disaster mitigation measures, minimize the damage and losses caused by meteorological disasters. It is also provide a favorable protection for safe and efficient production of greenhouse vegetables in Hainan.This paper combined laboratory with field experiments to construct disaster grades index of low temperature and sparse sunlight for greenhouses watermelon. Laboratory experiment is to study the effects of low temperature and low light on physiology and morphology of watermelon seedlings, and determined the injury grades. Field trials used the historical weather data to obtain integrated climate index (HI), and combined integrated index (HI) of low temperature and sparse sunlight with damage of watermelon to construct disaster grades index. To establish meteorological data model between stations and greenhouses, finally build disaster grades index of low temperature and sparse sunlight for watermelon cultivation in greenhouse. Then use the historical data to validate the index. The main conclusions of this study are as follows:(1) Low temperature and low light slowed the growth of hypocotyl, stem diameter and leaf area, and inhibited the leaf photosynthesis and caused damage to photosynthetic apparatus. SOD and POD activity were induced to increase after treatment, and has a positive effect for elimination of excessive reactive oxygen species in plant. Whereas, with the temperature and light stress sustained, the synthesis pathway of antioxidant enzyme is inhibited. Low temperature and low light led an increase in MDA content, and caused peroxidation injury in cell membrane lipid. In addition, low light had a positive effect on hypocotyl elongation and leaf area growth, and could alleviate the oxidative damage caused to leaves under low temperatures.(2) Based on the physiological and morphological variation and mechanisms of resistance of watermelon seedlings under low temperature and low light, the damage of watermelon seedlings grow in temperature15/10?. light intensity100?mol m-2s-1for6d,6?12d, more than12d was defined into mild, moderate and serious disaster, respectively. (3) Choose the minimum temperature X1,?15?duration time X2, chilling accumulation X3and sunless time X4as the main disaster-inducing factors, and used the historical weather data from1998to2008to obtain integrated index (HI). Research the damage and yield reduction rate of watermelon suffered different intensity low temperature and sparse sunlight disaster in winter from2012to2013, on the basis of integrated index HI values defined the disaster grade:0-5.3was mild disaster,5.3to23was moderate disaster, more than23was serious disaster.(4) By building meteorological data model between stations and greenhouses, constructed the disaster grades index of low temperature and sparse sunlight for watermelon cultivation in greenhouse. The HI value was used to define the disaster grade:2-8was mild disaster,8to32was moderate disaster, and more than32was serious disaster. In addition, by selecting daily maximum temperature difference, average daily temperature and sunshine duration to establish a regression model to achieve the forecast of sunshine duration of future weather.(5) Analyze the disaster of watermelon for different cultivation methods in historical year indicated that compared with the open cultivation, built greenhouses in winter increased resistance to meteorological disasters, and could effectively reduce the damage and losses of watermelon caused by disaster weather.