| In this paper, Different genotypes spring soybean of xinjiang for the test materials,Comparative study of the drought on different growth stages of soybean photosynthetic characteristics, chlorophyll fluorescence, chlorophyll value and yield.Main results are as follows:1. The change of Photosynthetic characteristicsUnder natural conditions,the use of Li-6400 portable detector photosynthesis,in flowering period,the podding and the seed-filling period of different genotypes of soybeans for photosynthesis,the results show that: the growth period under drought stress,The change of gas exchange parameters Net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) showed a downward trend and the decline in the varieties (lines).flowering and podding period under drought stress,the parameters of 03NKZ16 the smallest decline,the xindadou NO.1 at seed-filling period of drought of the smallest decline.Three soybeans of intercellular CO2 concentration (Ci) at different growth stages are different change,the flowering period and the podding of the different genotypes of soybeans under drought stress decline,photosynthetic rate of decline was mainly due to stomatal factors,and the xindadou NO.1 at seed-filling period under drought of the Ci increased photosynthetic rate of decline has been due mainly to non-stomatal factors limit, 03NKZ19 and 03NKZ16 t at seed-filling drought of Ci decline,the photosynthetic rate of decline is still stomatal factors.Under drought stress,the photosynthetic characteristics vary with the normal irrigation,but significant differences or not between species and period.2. The change of chlorophyll fluorescence parametersDuring the time of measuring photosynthesis of soybeans,the portable chlorophyll fluorescence system of OS5-FL,which is made in USA,were used to measure changes of chlorophyll fluorescence of the different genotypes soybeans. The results showed that: the growth period of different genotypes soybean of chlorophyll fluorescence parameters optimal/ minimal (Fv/Fm), optimal/maximal (Fv/F0),have decreased significantly, the initial reaction process that photosynthesis Inhibited,Photosystem II (PSII) potential damage to the active center.moreover, non-photochemical quenching coefficient (NPQ) and photochemical quenching coefficient (qP) have different degrees of lowering that PSII accepted by the centre for the excess stimulate consumption can not to in the form of heat dissipation,the protection of the photosynthetic capacity fell by a greater impact on drought stress.Different growth stages of soybean genotypes of the Electron transfer rate (ETR) value under drought stress has significantly increased,and significantly,that in dealing with drought,soybean genotypes reflect the strengthening of the Centre for electronic capture efficiency,in order to maintain a higher rate of electron transfer and enhance light respiration, better protection of the photosynthetic apparatus.Comprehensive can be drawn from different growth stages ,different genotypes soybean of chlorophyll fluorescence indicators under drought stress,compared with normal irrigation to achieve significant and very significant difference,therefore,chlorophyll fluorescence Parameters can be used as identification of soybean drought resistance of supporting indicators.After rewater some Indicators higher than normal water irrigation,possible rehabilitation of water to crop growth may have compensation or excited,"bounce-back" phenomenon. Soybean currently under drought stress on the effect of compensation is not enough depth,pending further study.3. chlorophyll production values and yieldFrom the value of chlorophyll,plant height,the number of main stem,above ground biomass production,root weight and yield,the different growth stages of soybean under drought stress than normal water production decreased, In addition,the strong correlation between the indicators, the impact on each other to jointly resist drought stress.
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