| The study was carried out on root characteristics of different wheat cultivars and root adjustment in Zhengzhou by combining field experiment with pot experiment from 1999 to 2001. The results are as follows:1.Under population conditions, the high-yield cultivars ( Yumai49, Zhoumail3 ) had less secondary root number per plant but more root amount in the soil. The activity of its root was higher with a wide changeable range. High quality cultivars (Yumai34, NeixianglSS and Lankao906) have more secondary roots but less root amount than the high-yield cultivars. The root activity of high-quality cultivars was higher in the early stages of wheat development, but in the later stage, it was a little weaker with a small variety YumaiSO, a soft-quality wheat, had more secondary roots, but it didn't develop very well. The root activity of Yumai50 was higher in the middle stage of wheat development, but would decrease obviously in the late development stages. Difference was also found among the cultivars that were regarded as the same type of wheat.2. Closely relationship was found among the yield components and root characteristics. The result indicated that the secondary root number was negative related to theyield, lOOOgrain Wt and the grain number per spike in the early and middle stages of wheat development, but was positive related to these factors in the later stage. It was positive related to the spike number per area in the early and middle stages, but was negative related to the spike number in later stage. Root dry Wt and fresh Wt were positive related to the yield and spike number. They were also found to be negative related to lOOOgrain Wt and the grain number per spike in the early stages, but in later stage the correlation was positive. The study also showed that the physiological characteristics of root had a much more closely relationship with yield components than that of ecological characteristics of root. The root activity had a significant positive relationship to grain yield and spike number in the middle stage of wheat development. The MDA content of root was positive related to the yield and yield components. Both the SOD activity and the POD activity of root were negative related to the yield and yield components in the middle stage, but in the late stage, the relationship was positive. It indicated that higher root activity and lower SOD and POD activity in the early and middle stages of wheat development was beneficial to the plant for acquiring high yield of wheat, but in the later stage, strong root system with higher SOD and POD activity would delay the plant senescence and increase the grain yield obviously.3. The result also indicated that nitrogen application with different amount and method and application of regulators had a significant effect on root adjustment. Under the condition of equal amount ofnitrogen application, both the root amount and secondary root number would increased by 13% to the CK if nitrogen was applied or sprayed in the later stage. The root activity and POD activity would increase by 70% and 16% to CK, respectively. The effect of nitrogen spraying during flowering stage is better than that applied in jointing stage. Spraying regulator in flowering stage increased the root activity significantly, which enhanced the root POD activity 31% and decreased its MDA content 26%, respectively. Thus it enhanced the plant adaptation to adverse conditions and increased the grain Wt.4. Different measures should be taken according to the features of different cultivars. For high-yield cultivars, the seedling number should be decreased reasonably and the technique for nitrogen application in later stage be applied to promote the development of the root and seedling. For soft-quality wheat Yumai50, management measures should be taken in the early stages to promote root development, but control the height of plant and adjust the root development at jointing stage, spray nitrogen and regulators to the plant in the later stage to enhance root activity. Regarding the...
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