Study On The Physiological Responds And Ecological Compatibility Of Medicago Sativa L.cv.xingjing Daye Under Water Stress

Medicago sativa L.cv.Xinjiang Daye as experimental materials were treated by 4 treatments,namely: Fully water supply (TA)(water content is 80-90% of the maximum field water-holding capacity);Light soil water stress (TB)(water content is 70-80% of the maximum field water-holding capacity);Medium soil water stress (TC) (water content is 60-70% of the maximum field water-holdingcapacity);severe soil water stress (TD)( water content is 50-60% of the maximum fieldwater-holding capacity),this study mainly measured some water indices, photosynthesis indices, biochemical indices and morphological indices characteristics of Medicago sativa L.cv.Xinjiang Daye under different soil water condition at seedling period,branching period and flowering period. The author expects to discover the adaptability of Medicago sativa L.cv.Xinjiang Daye under different soil water stress conditions and wants to provide the science instruction for saving water cultivation. The research result shows:1 Under water stress,free water (Va) content of Medicago sativa L.cv.Xinjiang Daye decreased,while the bound water(Vs) content and Vs/Va increased. RWC decreased and WSD increased,the leave water potential of Medicago sativa L.cv.Xinjiang Daye and its water-holding capacity increased.Va decreased17.1%,27.6%,34.0%,44.8%, respectively,while the Vs increased 16.9% ,17.5%,25.5%,25.7% and Vs/Va increased 41.1%,62.4%,90.0%,127.6% at branching period than it at seedling period, respectively.The more severe the water stress was,the biger the decreasing scale of Va and the increasing scale of Vs/Va were.At seedling period, the changing rule of RWC was fully water supply >light water stress>medium water stress>severe water stress;and the changing rule of WSD was fully water supply <light water stress<medium water stress<severe water stress.During the branching and flowering periods , the changing rule of RWC was light water stress>medium water stress> fully water supply >severe water stress.With the decreasing of soil water content,the daily course of leave water potential appeares an obvious characteristic of"W"curve and the leave water potential decreased rapidly at the same time.2.Under soil water stress conditions, the transpiration rate and the photosynthetic rate of Medicago sativa L.cv.Xinjiang Daye declined .the LS and ci raised and the WUE raisedWith the decling of soil water content , the transpiration rate declined .At seedling period, The daily course of transpiration rate of light,medium and severe water stress appeared an obvious characteristics of bimodal curve except fully water supply,while at the branching period, they all became bimodal curve and they have unimodal curves characteristics at flowering period.Along with the soil water stress's aggravating, the photosynthetic rate presents the obvious declining trend. The daily courses of photosynthetic rate of all treatments were bimodal curves,they all had"midday rest"phenomenon. the severer the water stress was ,the lower the value of photosynthetic rate was .From seedling period to branching period,the main reason of the decling of photosynthetic rate was the transform from the stomatal restriction to the non-stomatal restriction,at flowering period,the main reason of the decling of photosynthetic rate was the non-stomatal restriction.Under soil water stress conditions, the order of average daily WUE under four soil water stress was severe water stress>medium water stress> light water stress >fully water supply;that is to say ,the more severe the water stress was ,the higher the WUE of Medicago sativa L.cv.Xinjiang Daye was.3 Under soil water stress conditions, the Epicyte Permeability and MDA content of Medicago sativa raised, Proline and WSS content increased and the activity of SOD and POD raised,while the chlorophyll content decreased.With the decling of soil water content,the Epicyte Permeability raised differently. With the enhancement and lasting of water stress,the Proline and WSS content increased.The Pro concent was more under medium and severe water stress and it was the maxium under severe water stress.With the lasting of soil water stress,The chlorophyll content under all treatments declined,the chlorophyll content flowering period decrease48%,56%,64%,and 72% than it at seedling,respectively.4 Under soil water stress, The growth was limited and the biomass of Medicago sativa L.cv.Xinjiang Daye reduced. The ratio between root and stem increased.The order of growthing quantity of seedling height and basic diameter was that light water stress>medium water stress>fully water supply>severe water stress, The growth was limited by water stress,the more severe the stress was,the more slowly the Medicago sativa L.cv.Xinjiang Daye growed .With the enhancement and lasting of water stress,except light water stress,leaves,branch and Lateral root reduced and the main root was the longest under severe water stress.With the enhancement of water stress, the ratio becomes higher. the ratio between root and stem of fresh weight and dry weight under all kinds of treatments was 0.81and0.63,0.92 and 0.81,1.09 and 0.91,1.34 and 1.31.