EFFECT OF Ca ADDITION ON ALLEVIATING Cd INDUCED CYTO-TOXICITY IN Salix matsudana KOIDZ ROOT-TIP CELLS

In order to study the toxic effect of Cd on the root tip cells of Salix matsudana Koidz and the alleviating effect of Ca on Cd cytotoxicity, Cd absorption, cell damage, cell division and nucleoli structure changes of S. matsudana root tip cells were studied by using LeadmiumTM Green AM dye fluorescence observation, Propidium iodide (PI) staining, carbol fuchsin and silver dyeing technology. The results of Cd specific probe showed that Cd ions firstly entered and accumulated mostly in meristem zone, then extended up to the elongation zone and mature zone as treatment time increased. Cd absorption was reduced significantly by Ca addition when compared with the Cd absorption between 50 Cd+5 mmol/L Ca treatment and 50 molIL Cd treatment alone. PI staining results showed Cd stress increased the red fluorescence intensity of S. matsudana roots, while Ca addition reduced the red fluorescence intensity. The mitotic index (MI) decreased and the frequencies of abnormal dividing cells increased with the Cd concentration increasing and treatment time prolonging. Some types of chromosome aberrations, such as c -mitosis, chromosome bridges, chromosome stickiness and lagging chromosomes were induced by Cd. In addition, Cd stress can induce the nucleolus materials move slowly outward from the nucleolus to the nucleoplasm and even to cytoplasm. Nevertheless the inhibition of MI and nucleolus materials' outward movement was mitigated partly after Ca addition. Therefore 5 mmol/L Ca addition reduced Cd absorption and decreased the above cytotoxicity in S. matsudana root tips.