磷饥饿胁迫下两种山核桃叶肉与根尖细胞的超微结构特征

Ultrastructural characteristics of mesophyll cells and root tip cells of hickory and pecan seedlings to phosphorus starvation

目的:解析在磷饥饿胁迫下叶肉和根尖在亚细胞层面的超微结构变化特征。方法:以半年生山核桃和薄壳山核桃幼苗为试材,采用水培方法进行磷胁迫对比处理,用透射和扫描电镜观察叶肉和根尖细胞的超微结构。结果:相比对照组,缺磷处理下,两种山核桃属植物叶肉细胞中均出现内含物增加,核质电子密度升高,常染色质与异染色质相间分布更均匀,淀粉粒膨大、叶绿体肿胀,线粒体拟核区扩大,嗜锇颗粒、蛋白-脂类复合体球、磷酸钙颗粒物质基本不可见;气孔均关闭,蜡质分泌增多。其中,山核桃叶绿体基粒片层紊乱,线粒体明显减少,多泡体结构增加,根尖细胞降解严重,而薄壳山核桃类囊体仍垛叠规则,根尖细胞完整、仅内部细胞器发生变化。结论:两种山核桃属植物在缺磷条件下的亚细胞超微结构变化相似,但薄壳山核桃亚细胞超微结构表现更稳定,表明其在缺磷胁迫下的适应能力与抗性更强。

Objective:In order to investigate the response mechanism of mesophyll cells and root tip cells of hickory and pecan seedlings on the cytological level. Method:Half-year seedlings of hickory and pecan were used as materials under contrast conditions of normal phosphorus supply(1 mmol·LKHPO,CK) and none phosphorus treatment(0 mmol·LK HPO,NP) which was controlled by hydroponic culture, then the ultrastructure of mesophyll cells and root tip cells were observed by transmission electron microscopy and scanning electron microscopy. Result:The results showed that after NP treatment, both hickory and pecan seedlings presented increasing contents in mesophyll cells, more evenly distributed chromatin as well as higher electron density in nuclei, enlarged nucleoids in mitochondria, disappearance of Osmophilic granules in chloroplast, Calcium phosphate particles in mitochondria and protein-lipid bodies in vacuoles, distinctly swollen starch grains in both mesophyll cells and root tip cells, closed stoma with increased wax secretion. However, the mesophyll cells of hickory witnessed grana lamellae disorder, diminished mitochondria, increased multivesicular body and the root tip cells of hickory suffered plasmolysis together with decomposition, while grana lamellae of pecan arranged regularly and root tip cells remained intact and distinct accompanying with growing quantities of mitochondria. Conclusion:Similar responses appeared in both under NP condition, whereas the ultrastructure of cells of pecan seedlings demonstrated higher stability which proved its superior adaptive capacity and resistance against phosphorus starvation stress.