Sink Traits And Its Regulation Mechanism Of Inferior Kernels Of Maize Under Intense Crowding

Clarifying the relationship of sink capacity and/or sink activity with kernel abortion and/or filling stagnation of inferior kernels and its physiological basis and exploring the mechanism of cultivation mearsures on the impact of the library feature, are of great importance for closing the yield gap by improving the grain filling of inferior kernels of maize. In this present study, two typical commercial maize hybrids Zhengdan 958 and Xianyu 335 were planted at two lacations, Comparing the difference between the sink capacity, sink activity and grain filling parameters of the two pollination treatments, incomplete pollination (ICP) and completely pollination(CP) respectively, and analysing the relationship of library features and Grain Endogenous hormones and polyamines, and under the nitrogen fertilizer and density interaction conditions to study the physiological mechanism of the library feature of inferior grains response to cultivation measures. The main results are as follows:1. The endosperm cell division progress and the maximum endosperm cell number of inferior kernels showed no difference between ICP and CP treatments, while the soluble acid invertase activity of ICP was significant higher than that of CP, by 12.6% in avera and 21.8% in maximum. Futhermore, the actual 100-kernel weight, the stimulated final kernel weight, the maximum kernel-filling rate anf the mean kernel-filling rate of ICP treatment were also higher than of CP. The results proved that the major limited factors of the abortion and/or filling stagnation of inferior kernels of maize was not its sink capacity, the sink activity was the primary limited factor.2. There was closely relationship between grain capacity and endogenous hormone content. During endosperm cells actively proliferating stage, inferior grains zeatin (Z+ZR), auxin (IAA), gibberellin (GA3) and abscisic acid (ABA) showed no significant difference between the two control pollination, and the endosperm cells proliferation rate and kernel-filling rate had extremely significantly difference with Z+ZR, IAA content and significantly negatively difference with GA3 content.The results indicats that No significant difference between endogenous hormone of two control pollination was the important internal reasons of no significant difference between its grain capacity.3. The balance relationship between polyamine and ethylene in the inferior kernel affected the sink activity level, and ultimately determined whether inferior kernel could develop successfully. In the inferior kernels, SAI activity was significantly positively correlated with polyamine content, but significantly negative correlated with ethylene production rate, besides polyamine content had a negative correlation with ethylene production rate. It showed that polyamine synthesis inhibited ethylene synthesis and release, as to improve the grain sink activity (SAI activity), so the photosynthetic material unloaded to grain successfully. The inferior kernel completion and full grouting were realized.4. Nitrogen and planting density combination had a significant impact on SAI activity and individual sink capacity, and overall performance for low density and high nitrogen condition was that SAI activity was higher but the abortion rate was lower. Effect of Nitrogen and planting density on the inferior kernel abortion mainly related to plant nitrogen accumulation rate before and after silking stage, and affected greatly by planting density.In summary, the sink activity was the core limiting factor of inferior kernel abortion or the grain filling restriction. Inferior kernel sink activity was regulated by the balance between polyamine and ethylene. An adequate supply of sugar, synthesis of a large number of polyamine inhibited ethylene release, promoted SAI activity and unloading sugar to grain, so that the inferior kernel was successfully completed; sugar supply was insufficient, polyamine synthesis was limited, but ethylene was synthesized much, the SAI activity was inhibited, reducing sugar unloading was blocked, inferior kernel abortion or grouting was limited. Nitrogen and planting density combination regulated grain sink activity to affect the individual sink capacity, and was mainly influenced by the density, and it had relation with the plant nitrogen accumulation rate of the before and after silking stage.