| 15 and 9 spring wheat cultivars were chosen for field and pot experiment to investigate the effects on agronomic and eco-physiological characters of different irrigation treatment in Er-Shi-Li-Pu station, Zhangye from May. to Aug. 2004 . Three irrigation treatments (T1: irrigating 70m~3/mu at jointing stage, enthesis stage and grouting stage respectively, 120m~3/mu before soil frozen; T2: irrigating 70m~3/mu at jointing stage and enthesis stage respectively, 120m~3/mu before soil frozen; T3: irrigating 70m~3/mu at jointing stage and 120m~3/mu before soil frozen;) and four water content treatment (soil water content were 35%, 45%, 60% and 75% respectively) were designed respectively in field and pot experiments. The main results are as following: 1.Yield and water use efficiency (WUE) of T2 were improved compared to T1 and T3 and that of Tl increased 4.47% and 15.76% respectively compared to T1 and 10.24% and 25.31% respectively compared to T3.2.Thousand kernel weight was decreased by water stress and that decreased with the reduction of irrigation quantum thus had the sequence of T1>T2>T3。 The thousand-kernel weight of T2 increased 7.95% and 20.97% compared to T3, and that of T2 did 12.06 compared to T3. The spike number per mu and kernels per ear had no significant different in different treatment. 3.The effects on physiological traits of water stress on different stage were different.The varieties of photosynthesis rate (Pn) during all the growth course of spring wheat in field experiment were inevident and the minimum of all the duration appeared at enthesis stage (11/6) and the maximum of Tlappeared at the early stage of enthesis (31/5) and that of T2 and T3 appeared at grouting stage (22/6). That in pot experiment was different with the difference of treatments. Pn in 35% and 45% increased with the last of growth duration expressing as liner relations and that in 60% appeared as square relations and that in 75% demonstrated as "M".The varieties of stomata conductance (Cd) of field experiment were consistent at the early stage and appeared difference at the late stage. Cd of all treatments was decrease after a phase of increase at the early stage and that of Tl increased, T2 decreased slowly and T3 decreased rapidly. The maximum of different growth stage had no obvious orders and appeared in T2 and T3 alternatively. The tendency of Cd among different cultivars in the same treatment was similar. For the pot experiment, the tendency of Cd on different water conditions was different. That of 35% and 45% increased with the advance of growth duration expressing as liner relations, that of 60% decreased after the increase at first demonstrating as square relations, and that of 75% showed as "M".The tendency of leaf water content and leaf relative water content was consistent and the maximum of the early stage of growth appeared alternatively in the three treatments. With the advance of growth duration, that of T1 had no evident changes, and T3 decreased rapidly leading to the sequence of T1>T2>T3. Leaf bulk density decreased at first and then increased gradually with the last of growth duration and reached maximum at the late stage. The maximum of leaf bulk density of different growth stage at the early stage appeared in T1 and T2 alternatively, and that of T2 at late stage was higher than that of T1, thus that of T3 in all growth duration was lower than that of T1 and T2.4.The growth of crop had close relations with soil water content. Field experiment showed that appropriate irrigation could improve crop growth and all the agronomic traits except the third internode length under spike had the sequence of T2>T1>T3. Water treatment had most significanteffects on the first and second internode length under spike of T2 increased 13% and 18% respectively while the plant length increased 10% compared to T3. It also showed that fitable irrigation could increase the rate of one-grained and two-grained spikelet, prevent the degradation of spikelet and reduce the rate of invalid spikelet, thus lead to high economic yield.Pot experiment showed that crop growth was restrained severely with the decrease of soil water content and all the agronomic traits demonstrated as that of 75%>60%>45%>35%. The water content had most significant effects on grain weight per ear and that of 35% and 45% were only 19.12% and 29% of 75%. Dry matter and biological yield per pot were also effected greatly by water treatment and the former of 30% were 20.39% and 27% and the later were 23.93% and 32% of 75% respectively.5. Water stress could accelerate the grain-filling rate and had no evident effects on filling last time. The difference of mean filling rate of different treatments was significant and the mean filling rate decreased gradually with the decrease of irrigation quantum and that of T3 decreased 9.21% and 21.67% respectively compared to Tl and T2 and T2 did 13.73% compared to Tl. The difference of filling last time in different water treatment was significant.6. Water stress could quicken crop growth course and accelerate prematurity. The growth duration decreased with the diminishment of irrigation quantum. The mean growth duration of T3 shortened 1.33-6.33 and 5-11.33 days compared to T2 and Tl respectively.7. Correlation showed that WUE was main influenced by yield and the influenced factors were different on different water conditions. The correlation coefficients of colony WUE and yield of spring wheat was significant, and that of three treatments were 0.959**, 0.866** and 0.968**. The spike length and WUE in Tl, thousand-kernel weight, biological yield and WUE in T2, the leaf water content in booting stage and WUE in T3 correlated significantly.8. Regression showed that WUE was a trait restrained by many factors and the correlative analysis on WUE and the other traits showed that yield and WUE had significantly positive correlative relations, and the stepwise also proved the above result and considered that the varieties of WUE was controlled by YIELD over 80%. Cd of Tl and leaf water content of T2 all had close relations to WUE and the former two determined 98.6% and 97.9% respectively combined with yield while only the yield of T3 determined 100% of WUE.
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