不同土壤水分供应下锌对玉米叶片超微结构的影响

Effect of zinc on maize leaf cell ultra-structure under different soil moistures

  • 摘要: 选择 土为供试土壤, 进行盆栽玉米试验, 设定0和5.0 mg·kg-1两个锌处理, 按土壤饱和持水量的40%~45%和70%~75%在玉米的4叶1心期实施干旱和正常水分处理。生长50 d后, 测定不同土壤水分与锌供应状况下植株生物量和锌含量, 利用透射电子显微镜观察完全伸展新叶的超微结构变化, 以期揭示不同土壤水分供应下, 植物对施锌的响应机理。结果表明: 土壤水分供应充足条件下, 与不施锌相比, 施锌玉米地上部生物量和总干重分别增加78%和52%, 根系和地上部锌含量和锌吸收量增加较多; 而干旱条件下, 施锌对玉米生物量无显著影响。干旱条件下缺锌玉米叶片维管束鞘细胞中叶绿体结构基本保持完好, 淀粉粒和基质片层清晰可见, 但叶肉细胞中叶绿体膜受损, 基质片层结构出现皱缩, 基粒片层减少; 施锌玉米叶片维管束鞘细胞中叶绿体结构保持完好, 叶绿体周围的线粒体数目较多, 叶肉细胞中叶绿体中脂肪颗粒增多, 叶片维管束鞘细胞与叶肉细胞之间可见清晰的胞间连丝。土壤水分充足处理下, 缺锌叶片细胞膜出现皱缩, 维管束鞘细胞叶绿体淀粉粒增多, 片层结构受损, 严重时维管束鞘细胞中内溶物消失, 残存的叶绿体中仅有淀粉粒和少许片层; 叶肉细胞中叶绿体可见淀粉粒, 但片层结构少, 有些出现断裂、收缩。土壤水分充足条件下, 施锌玉米维管束鞘核叶肉细胞结构清晰, 叶绿体结构完整。结论认为: 锌对干旱胁迫下玉米叶片细胞结构的破坏有一定的缓解作用; 但土壤水分正常供应下, 缺锌导致细胞结构受损程度比干旱情况下更严重。

     

    Abstract: Zinc (Zn) deficiency is a major nutrient problem in calcareous soils of the North China, where drought is also a considerable stress factor in crop production. Pot trials under greenhouse conditions were conducted using Zn-deficient cumulic cinnamon soils sampled from Shaanxi Province of the Northwest China. With two levels of Zn 0 and 5.0 mg(Zn)·kg-1(soil) and two soil moisture (40%~45% and 70%~75% of saturated soil water content) regimens, a completely randomized factorial design (2 Zn treatments × 2 water levels × 3 replicates) was set. Ultra-structure of cells of maize plant leaves under different soil water conditions and Zn doses were examined using transmission electron microscope. The objective of the study was to investigate the mechanisms of maize plants responding to Zn under different soil moisture conditions. The results showed that Zn increased plant biomass and Zn content more notably under well-watered conditions than under drought conditions. The structures of maize mesophyll and bundle sheath cells remained integrated and normal under adequate soil water and Zn supply. Under adequate soil water supply, chloroplast plasmolemma distortion, starch accumulation and thylakoid disturbance were noticed in vascular bundle sheath cells of Zn-deficient leaves. Moreover, vascular bundle sheath cells collapsed when plants were subjected to severe Zn deficiency. Thylakoid shrinking and much less lamella stacking occurred in leaf mesophyllic cells of maize plants grown under adequate soil water and severe Zn deficiency. Under drought conditions, thylakoid shrinking and much less grana stacking occurred in Zn deficient leaf mesophyllic cells. Chloroplast structure in vascular bundle sheath and mesophyllic cells of Zn-sufficient leaves remained normal. With Zn application under drought treatments, the number of mitochondria increased around the chloroplast in vascular bundle sheath cells. Also numerous plastoglobuli were noted in the chloroplast of mesophyllic cells of maize plants. It suggested that Zn application alleviated disruptions in leaf cells by drought stress conditions. However, the ultra-structures of Zn-deficient leaf cells were more easily harmed under adequate soil water supply than that under drought stress conditions.

     

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