Establishment Of Grasses Indexes Evaluation System Of Water Competitive Ability

In order to study water competitive ability of five grasses ,a neighbourhood experiment was conducted under three water conditions. 15 different physiology and morphological indices were researched,a comprehensive evaluation system of grasses water competitive ability was established based on principal component analysis and subordinate function.The system was acceptable because the results of comprehensive evaluation and directive evaluation using relative growth rate had a well consistent with each other. Accordingly, this study suggested that the model be a new method with more external way for competitive theory, at the same time,other varieties' position and dynamic change can be forecasted by using the best regressive function .The main findings are as follows:(1)The water competitive ability grades of five grasses were:Agropyron desertorum.>Festuca rubra L.>Bromus inermis Leyss.>Stipa capillata L.>Lolium perenne L.(2)Through regression analysis, an integrated identification index including the relative tissue water content, relative root length, relative MDA content which were significantly correlated with the grasses water competitive ability.From the distribution of indexes,there were morphlogical index,water physiology index and water stress index,which was reasonable and comprehensive.(3)Established the grasses indexes evaluation system of water competitive ability: Y=1.61+0.403X1-1.855X2+0.137X3. In this equation, X1, X2 and X3 respectively representthe relative tissue water content, relative root length, relative MDA content .The competitive results of evaluation system and directive evaluation using relative growth rate had a well consistent with each other,the correlation coefficient was 0.90. Verification by experiment tested by experiment, the evaluation system was suitable Elymus dahuricus Turcz.and Agropyron smithii.(4)Through the dynamic change analysis of grasses water competitive indexes , the species with strong water competitive ability germinated early and had well developed root system,which was helpful to acquiring more rasources. Otherwise,these species were tolerant to drought,which can maintain a higher metabolizable level under water stress.(5)Through the research of photosynthesis and water use characteristics of five grasses under ware stress,we found that Pn, Tr and WUE changed obviously under different water conditions.But change range varied according to water competitive ability of species. Species with strong water competitive ability were higher than species with weak water competitive ability at Pn and WUE,which showed that light utilization was consistent with water competitive ability.