Studies On The Relationship Between Maize Kernel Development And Pedicel Unloading

The experiment was conducted in the teaching and experimental station of Agricultural university of hebei using maize hybrid zhengdan 958 as material during 2006～2007. The relationship between maize kernel development and kernel pedicel unloading was studied. The changes of maize kernel development and the physiological and biochemical index were mensurated at different ear positions, and the advanced "seed cup" technique was used to study the assimilation substance unloading of the kernel pedicel. The results were showed as follows:1. After silking, the trends of kernel development at different ear positions were similar and the results showed that middle kernels were better than upper kernels on length of ovary, fresh and dry weight and volume.2. The changes of the soluble sugar and starch in the upper kernels and middle kernels were measured. From the comparison it could be found that within the 16 day after silking (DAS) the middle kernels were better than upper kernels on soluble sugar but insignificantly on starch. The high soluble sugar content in the former period could be used for the starch accumulation in the latter period. From 16 DAS , the middle kernels were lower than upper kernels on soluble sugar but higher on starch, as the soluble sugar transformed to the starch in rapid filling stage. The content of the soluble sugar and starch in cob showed a rising trend, the content of soluble sugar in middle cob was similar in the upper cob, but the starch content was higher. So the nutrition supply ability of middle cob was better than the upper cob.3. By comparing the activity of theα-amylase and the soluble acid invertase(SAI) in the kernel and the pedicel, the trend of theα-amylase activity in the kernel and the pedicel showed a peak, theα-amylase activity was high in the early stage, it could promoted amylolysis, supply the nutrition for the kernel development; theα-amylase activity was low in the rapid filling stage, it was in favorable to the starch accumulation. The upper kernels had higherα-amylase activity than middle kernels, so the upper starch accumulation was low. Study on the SAI activity of kernel showed that the middle kernels were better than upper kernels, that meant the sink strength of kernels were better than upper kernels, and it was in favor of filling. The SAI activity of pedicel was measured and the reasult showed that the unloading ability of middle pedicel was better than that of upper pedicel.4. Studies on the change rate of kernel development and the material accumulation showed that the fresh weight change rate of the kernels were rising as the kernel development, the middle kernels were better than the upper kernels. The volume change rate of the kernels appeared one peek, the upper peek point higher than that obviously, and the peek was delayed for 4 days. The dry weight change rate of the kernels were rising rapidly then maintained the level after 16DAS, the middle kernels were better than the upper kernels. The trend of the soluble sugar in the middle kernels were rising then declined, the peek appeared at 12 DAS, the trend of the upper kernel was not obviously. The accumulation rate of starch in the kernel appeared one peek, the middle kernels were better than the upper kernels.5. The "seed cup" technique experiment showed that the unloading ability of middle kernel was better than that of the upper kernel. That meant without pull of sink strength, the supply of middle kernels was better than that of the upper kernels. The upper kernels developed baddly due to the weak of sink strength, the lack of assimilation supply ability was also an important factor.