Field experiment was conducted,using maize hybrid Zhengdan958 as experimental variety during 2005-2006.Effects of microelement fertilizers including B,Mn and Zn on the silk growth and development and kernel setting rate of summer maize were studied by plant spring method.The result showed that the development of repro-ductive organ was affected by treatment of microelement fertilizers,the growth and development of silk was promoted and the number of aborted flower and kernel was decreased,and the kernel setting rate was increased.The physiological and chemical mechanism of reproductive organ promoted by microelement fertilizers still need further study.

Studies on the biochemical and physiological characteristics of kernel and cob development were conducted with summer maize hybrids Zhengdan 958 both in the field and lab measurement.The results showed as follows:the length of the ovary,fresh weight,dry matter accumulation and volume of kernels at the middle of ear were better than those of the upper part.The content of soluble sugar,protein and starch of the kernel and cob in different parts of the ear had different change trends,but the 12 day after anthesis(DAA) is a key day of the physiology characteristics,all of the three indexes had changed after 12DAA.This study is of some scientific meaning for summer maize kernel development and high and quality maize production.

Maize kernel development of different models was studied under culture in vitro. Kernel volume,kernel weight,content of soluble sugar,starch,protein and kernel respiration were also measured.The result was showed that the model of kernel∶ cob as 3∶10 was the best.Kernel development under cultured in vitro was the same as the field grow maize.This culture technique can be generally used in maize physiology study.

The effects of temperature on kernel development were studied in vitro,with maize hybrids Nongdan 5 and Nongda 108.The rate of kernel abortion,kernel weight,and the content of soluble sugar,starch were also measured.The result showed that the effects of temperature on 2 hybrids were showed the same trend: the rate of kernel abortion was lowest and kernel weight was highest at 28℃ compared with the 18℃ and 38℃.Content of soluble sugar was high and starch was low at both 18℃ and 38℃.Condition of 28℃ was most suit for kernel development.

The distribution of ~(14)C-assimilates in plant organs and different positions of ear in maize(Zea mays L.) was studied by feeding the ear leaf with ~(14)CO_2 at early period of kernel development.The results showed that ear was the main sink organ during kernel filling period,but the distribution of ~(14)C-assimilates was uneven in different parts of ear.The distribution of ~(14)C-assimilates in cob ranked as basal>middle>upper part,while the amount of ~(14)C-assimilates in kernel sequenced as middle>basal>upper part of the ear.The sugar concentration in upper cob was not less(P>0.05) than that in middle part,but the content of reducing sugar in aborted kernels was significantly higher(P<0.05) than that in kernels at middle part of ear.It suggests the main reason of kernel abortion at ear tip in maizewould be low sink strength in kernels instead of assimilate deficiency.