Study On The Effect Of Water Stress On Corn WUE And Its Appraisal Indices During Ear Period

The experiment was conducted under the drought - resistance plastic canopy in Chinese Academy of Agricultural Science weather graduate school during 2004 to 2005. In order to research the changing rule of the growth and development, the morphological and physiological indexes and the water use efficiency, six materials that had great response to water were researched under normal water supply condition, mild drought stress and moderate drought stress during ear period. The aim was to select out, institute the appraisal indices of corn WUE during ear period by setpwise regression analysis. The results followed:1. The grain yield WUE of varieties had great variances under different water supply treatments. The GYWUE of Zhengdan958, Jidan209, Zhengdan19, Ludan981 was the highest under normal water condition. The GYWUE of Sidan19 and Longdan13 was the highest under mild water stress. The GYWUE of six varieties was the lowest under moderate water stress.2. The experiment showed that the variance of GYWUE was obvious among 6 varieties. Zhengdan958 was a high grain yield, high water consumption and high GYWUE variety. Jidan209 was a moderate grain yield, moderate water consumption and high GYWUE variety. Zhengdan19 had a character with moderate grain yield, high water consumption and moderate GYWUE.Sidan19,Longdan13 both had the same characters with low grain yield, low water consumption and low GYWUE. Ludan981 was a low grain yield, high water consumption and low GYWUE variety.3. The appraisal indices of GYWUE had great variance under different period and water stress. In spinning silk period, the variety with little root volume, little EC, little breath of stoma in under leaf had high GYWUE; In matured period , the variety with high grain-leaf ratio ,high harvest index , big coronal, had high GYWUE. The appraisal indices to judge GYWUE in matured period were more convenient and credible than those in spinning silk period.4. The appraisal indices under normal water supply condition could judge GYWUE under water stress. In spinning silk period , the variety that showed little cubage of root, low minimal chlorophy II fluorescence had a potential of high GYWUE under mild drought stress, and the variety that showed high 12 hour water-losing ratio, high ratio of the variable to maximal fluorescence, high plant height inclined to having high GYWUEunder moderate water stress. In matured period, the variety of having little root-shoot ratio, big minimal chlorophy II fluorescence, high grain-leaf ratio could show the ability of high GYWUE under slight water stress, and the variety of having high grain-leaf ratio, big root ,bigh ear height ratio had the potential of high GYWUE under moderate water stress.5. The varieties with high GYWUE had better drought resistance. Under mild and moderate water stress, the coefficient of correlation between HI and GYWUE were 0.905 and 0.869 and those were extremely significant positive correlation. The varieties with high GYWUE had high grain yield, the coefficient of correlation between GY and GYWUE was 0.958 and it was extremely significant positive correlation.6. In matured period, correlation between TYWUE and GYWUE was extremely significant positive correlation. The harvest index was the primary cause making the difference order between TYWUE and GYWUE.7. In spinning silk period, the leaf water use efficiency of varieties under mild water stress was the highest. That under normal water supply condition followed and the LWUE of varieties under moderate water stress was lowest. In matured period, the LWUE of varieties under normal water supply condition was highest. The coefficient of correlation between stomatal conductance and transpiration rate was bigger than one between stomatal conductance and photosynthetic rate. All showed that the degree which water deficit affected to transpiration was greater than that to photosynthesis. It was not appropriate to use LWUE to appraisal GYWUE.