Change of Superficial Shape and Cell Microstructure of Milk-vetch (Astragalus L. ) Root under Simulated Cu Pollution in a Red Soil
红壤模拟铜污染下紫云英根表形态及其组织和细胞结构变化

This study carried out experiments to investigate changes of shape, inter-structures and cell microstructures of milk-vetch root under simulated Cu stress at non- or contaminated levels in a red soil using observation and bio-microscopic technique. It resulted that when Cu concentration ranged from 0 to 40mg·kg-1 soil, the milk-vetch grew well and it had a whole root which worked normally. When Cu concentration reached 50mg·kg-1 soil, the growth of milk-vetch began to get influence with decline of biomass, the taproot crooked and was less branched, root became short and hazel and had fewer shorter hairs, tubby appeared, epidermis began to shrink and cell wall cockled slightly and unevenly, the boundary between plasmalemma and organelle blurred as well. When treatment concentration reaching to 200mg·kg-1 soil, milk-vetch roots became rotted and black, the cell wall broke and cytoplasm shrank so severely that plasmolysis happened and the plant died. So the critical Cu concentration in experimented soil was 50mg·kg-1 soil, and the resistance of milk-vetch root to Cu contamination buildup with the growth of aboveground part, and cell wall was the main part to Cu tolerance.