| Spring wheat cultivars of different drought resistance ecotypes were planted under the diferent water supply conditions, eg. sufficient water supply, water stress in potted plant during booting stage and heading stage respectively, and natural drought condition in field , effects of different water supplies on the physiecological traits and difference of spring wheat ecotypes were carried out, which will be available for selection of drought resistance genetypes and high efficient use of water under limitted water conditions, also, will deepen recognization to drought resistance and its mechanism of difference among drought resistance ecotypes,main results are as following: 1. Under sufficient water supply condition in potted plant, yield and WUE of the wet ecotype and the middle ecotype were obviously higher than those of the drought resistance ecotype, which indicated that the wet ecotype and the intermediate ecotype had the advantage of high yield and water use efficiency under sufficient water supply.The cause of high yield of the wet ecotype and the intermediate ecotype was that they had a great deal of grains per ear, while there was no significant divergence among ecotypes. Plant height of the drought resistance ecotype and the intermediate ecotype was obviously higher than the wet ecotype. But under natural drought condition in field, yield of the intermediate type was usually higher than the wet ecotype, mean of yield was 14.74 kilogram higher than the wet ecotype, increasing 13.48 percentage averagely, while 50.6 percentage maximally.The intermediate ecotype was being the mainly cultivated ecotype in the dry land at present.Contrasted by the sufficient water supply,under the water stress whether at booting or heading stage,yield,dry matter,WUEW,WUEY,thousand kernel weight, weight of spike, grains weight, numbers of grain per ear of all kinds of ecotypes were all decreased,Water stress treatment during booting stage had greatly heavier effects on those traits than that during heading stage.Compared to the contrast,yield, dry matter,WUEY,WUEW were reduced to 53.42,36.66,18.53,19.92 percentage separately under water stress during booting stage,but under water stress during heading stage ,those traits were forced to 19.31,13.89,6.12,0.93 percentage separately,the degree of drop of those traits under water stress during booting stage was 1.77,1.63,4.03,20.4 times higher than that during heading stage separately.The yield decent degree of the wet ecotype, under water stress during booting stage, was the largest, which of the intermediate ecotype was the second,and which of the drought resistance ecotype was the smallest, it was 69.19, 49.44, 41.64 percentage successively,yet the divergence scope was also great among cultivars of the same type,but under Water stress during booting stage,the decreasing scope of yield among three types was narrow.2. Under water stress condition, photosynthetic rate (Pn), stomata conductance (Cd) and transpiration (Tr) were all subjected to repressing of distinct degree. Against the sufficient water supply, under water stress during booting stage,it was the lightest that Pn was repressed in it,Tr took second place,Cd was the heaviest, the relative magnitudes of Pn,Tr,Cd were 57.44,46.87, 36.03 percentage separately. During heading stage homologous, they were 56.52, 46.28, 37.40 percentage respectively, the repressing degrees of three traits under two water stress treatments were similar.No matter which kind of treatments,along with processing of water stress, by means of adaptable regulation,the value of Pn,Cd,Tr was coming to the regular ones(CK),which was one kind of adaptive reaction of the plant by means of initiative regulation to adapt to water stress. After stress, the initiatively recovery capability of Cd was the biggest, next, Tr, Pn was the smallest. The relative magnitudes of three traits against the contrast moved upward ,and the scope was 51.7,40.43,22.87 percentage successively,by contrast among ecotypes ,the upward scope of Cd and Tr of the in...
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