小麦颖果韧皮部细胞ATPase活性及其与籽粒光合同化物积累关系

The ATPase Activity in Phloem Cells and Its Relation to the Accumulation of Photo-Assimilates in Developing Caryopsis During Wheat Grain Filling

【目的】探明韧皮部细胞ATPase分布规律,分析韧皮部细胞ATPase活性与籽粒光合同化物量之间的关系。【方法】在小麦(Triticum aestivum L.)灌浆不同阶段,采用蒽酮法测定籽粒光合同化物积累量;运用显微细胞化学技术对颖果韧皮部和胚乳细胞的多糖进行定位,同时对韧皮部细胞ATPase进行超微细胞化学定位。对籽粒光合同化物积累量与韧皮部细胞ATPase活性产物量进行相关分析和线性回归分析。【结果】(1)在灌浆渐增期,籽粒积累的光合同化物主要是可溶性糖。约在花后14d,籽粒可溶性糖和淀粉积累量含量相等。以后,籽粒以积累淀粉为主。在整个灌浆期,籽粒可溶性糖和淀粉量的变化呈现彼此消长,但籽粒总糖含量一直呈"S"型增长。在灌浆渐增期和快增期,韧皮部筛分子(Sieveelement,SE)的细胞壁和胚乳细胞的淀粉粒均被锡夫试剂染成鲜红色;但在灌浆缓增期,上述细胞染色明显变浅(。2)在SE、中间细胞(Intermediary Cell,IC)、伴胞(Companion Cell,CC)和韧皮薄壁细胞(Phloem Parenchyma Cell,PPC)中,ATPase活性产物主要分布于质膜、细胞内壁和靠近质膜的囊泡上。在SE内的P型-质体和线粒体的双层膜上、SE和IC之间分枝状的胞间连丝上也有较强ATPase活性。在灌浆渐增期和快增期,SE的ATPase活性高,而在缓增期,IC的ATPase活性较SE高。(3)SE中ATPase酶活性产物与籽粒可溶糖呈显著负相关;与籽粒淀粉含量呈极显著正相关;与籽粒总糖呈显著正相关,且ATPase活性产物与光合同化物积累量之间有明显的线性关系。IC中ATPase活性产物只与籽粒可溶糖呈极显著正相关。【结论】在灌浆过程中,籽粒中可溶性糖和淀粉量的增加彼此消长,但总糖含量一直增加。籽粒光合同化物积累量与SE和IC中ATPase活性产物量之间有显著或极显著的相关关系。韧皮部细胞ATPase活性产物呈现出动态的时空变化。SE在灌浆前2个阶段起主要的同化物运输作用,而IC主要在灌浆第3阶段起主导作用。上述结果为小麦籽粒灌浆生理研究提供了细胞学基础。

[ Objective ] The objective of this study was to determine the distribution of ATPase in phloem cells and to analyze the relationships between the ATPase active products in phloem cells and the accumulation of photo-assimilates in grain during grain filling. [Method] During grain filling of wheat （Triticum aestivum L.）, different photo-assimilates in grain were determined by Anthrone＇s method, the positions of polysaccharide in phloem and endosperm of caryopsis were located by microscopic cyto-chemical technology and the ATPase activity in phloem were located by ultracytochemical technology. Meanwhile, correlation analysis and linear regression analysis were done between ATPase active products in phloem cells and accumulation of photo-assimilates in grain. [Result] At early stage of grain filling, the photo-assimilates of grain were mainly soluble sugar. At around 14 d after flowering, the contents of soluble sugar and starch of grain were basically equal and then starch became the main form of photo-assimilates. During the whole filling stage, the changes of soluble sugar and starch showed mutual growth and decline, but the total sugar of grain showed a ＂S＂-type growth. The cell wall of SE and the starch granules in endosperm were dyed bright red by PAS reaction during gradual increasing period and fast increasing period, but they showed light red during slight increasing period. In the SE, IC, CC and PPC, ATPase active products mainly distributed on the plasma membrane, the cell wall and the vesicles around plasma membrane. The P-type plastids, double-layer membrane of mitochondria in SE and the branches of the plasmodesmata between SE and IC also had a strong ATPase activity. The ATPase activity in SE was higher than that in IC during gradual increasing period and fast increasing period, but the ATPase activity in IC was higher than that in SE during slight increasing period. There was a significant negative correlation between the soluble sugar contents of grain and the ATPase active products of the SE, a very significant positive correlation between the starch contents and the ATPase active products and a significant positive correlation between the total sugar contents and the ATPase active products. Otherwise, there was a clear linear relationship between the ATPase active products and the photo-assimilates contents. The soluble sugar contents of grain and the ATPase active products of the IC also had a highly significant positive correlation. [ Conclusion ] In the grain filling process, the changes of grain soluble sugar and starch showed mutual growth and decline, but the total sugar content was still increased. The contents of different photo-assimilates of grain and the ATPase active products of SE and IC had significant or very significant correlations. The distribution of ATPase active in phloem showed a dynamic changes in time and space. The SE played a leading role at the first and second filling stages, but IC played a leading role at the third filling stages. This result has provided a cytological basis for the physiological study of wheat grain filling