小麦小穗不同粒位粒重形成的生理特性差异

Difference of physiological characteristics of grain weight at various kernel positions in wheat spikelets

为探明小麦小穗上不同粒位籽粒粒重形成的生理机制,明确限制小穗上位弱势粒充实的主要原因,本试验选用大穗型小麦品种泰农18(TN18)和多穗型小麦品种山农20(SN20)为材料,调查检测了灌浆过程中小穗上不同粒位籽粒内源激素、可溶性糖、全氮含量的动态变化以及籽粒与籽粒柄连接处横面的组织结构与不同粒位籽粒粒重的关系。花后籽粒灌浆过程中灌浆速率与籽粒内GA和IAA含量呈极显著或显著相关,小穗基部籽粒中较高的GA和IAA含量可使蔗糖向淀粉转化开始早,籽粒分化快,灌浆速率高,是小穗基部籽粒粒重高的生理机制;扫描电镜图显示小麦籽粒灌浆初期小穗基部籽粒柄维管束横面面积明显大于上位籽粒,微观空隙小且排列较整齐,有利于同化物和生理活性物质的运输,是小穗基部籽粒粒重增长快、灌浆速率高的解剖学基础.

The object of the experiment was to explore the main physiological mechanism of heterogeneous development of grains located at the various kernel positions in wheat spikelets, further to reveal the factors restricting grain filling of inferior grains located on the distal kernel positions. Two varieties with different spike sizes of winter wheat (a large-spike cultivar Tainong 18 and a multiple-spike cultivar Shannong 20) were used to as the experimental materials. We have studied the dynamic changes of concentrations of endogenous hormones, soluble sugar and total nitrogen in grains located at different kernel positions in wheat spikelets during grain-filling period, and the microstructure of vascular bundle junction on kernel handle and kernel weight. Correlation analysis showed that the grain filling rate was significantly correlated with the contents of GA and IAA in grains. Higher GA and IAA contents in proximal kernels could make the conversion from sucrose to starch start earlier, the seed differentiate rapidly and the grain-filling rate higher, which is the physiological mechanism of the higher weight of proximal kernel in wheat spikelets. The micrograph showed that the cross-sectional area of vascular bundle of seed stalk on proximal kernels at the early stage of grain-filling period was significantly larger than that of distal kernels, and the microcosmic space was small and orderly, which is conducive to the transport of assimilates and physiological active substances, showing an anatomical basis for the rapid increase of seed weight and higher grain-filling rate in the proximal kernels of spikelets.