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失水对板栗种子超微结构与生理变化及萌发的影响

Effects of Water Loss on Ultrastructure and Physiological changes and Germination of Castanea mollissima Seeds

  • 摘要: 本研究以板栗(Castanea mollissima)种子为材料,测定不同失水状态下萌发率和成苗率;利用石蜡切片和植物组织染色技术,观察胚轴显微结构和细胞中多糖及蛋白质变化,利用电子扫描显微观测胚轴超微结构变化。实验结果显示,当含水量降至30%以下,发芽率和成苗率开始迅速下降。胚轴中胚芽细胞较大且排列松散,胚根细胞排列更加密集、整齐。胚轴显微结构和超微结构均显示含水量30%的胚轴出现显著的细胞质壁分离,含水量10%的胚轴细胞质发生严重皱缩,并出现大量细胞降解。细胞中多糖和蛋白质随含水量降低呈现先聚集后分解的现象。板栗种子具有较强的脱水敏感性,细胞在失水过程中分解多糖和蛋白质以抵御脱水伤害,含水量降至10%会导致板栗胚轴细胞质严重皱缩和出现细胞降解现象,这可能是板栗种子脱水致死的主要原因之一。

     

    Abstract: Castanea mollissima seeds were used as materials to divide them for dehydration gradient treatment in this experiment. The germination rate and normal seedling rate of C. mollissima seeds under different water loss treatments were determined. The microstructure of embryonal axis and the changes of polysaccharides and proteins in cells were observed by paraffin section and plant tissue staining. The ultrastructural changes of hypocotyl were observed by electron scanning microscopy. The results showed that the germination rate and normal seedling rate of embryonal axis decreased rapidly when the water content dropped below 30%. The germ cells were larger and more loosely arranged, while the radicle cells were more densely arranged. The microstructure and ultrastructure of embryonal axis showed that significant cytoplasmic wall separation happen in the embryonal axis with 30% water content. The embryonal axis with 10% water content were found severely contracted and a large number of cells were degraded. The polysaccharides and proteins in cells aggregate first and then decompose with the decrease of water content. Castanea mollissima seeds are highly sensitive to dehydration, as cells lose water, they hydrolyzed polysaccharides and proteins to fight dehydration. The decrease of water content to 10% would lead to severe cytoplasmic collapse and even cell degradation, this may be one of the reasons for the death of Castanea mollissima seeds due to dehydration.

     

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