Individual and Joint Effects of Lead and Mercury on the Viability of Root Border Cells in Mung Bean (Vigna Radiata)

摘要

Root border cells (RBCs) are detach from the growing root cap. RBCs serve both physical and biological roles in the rhizosphere. Lead (Pb) and mercury (Hg) are assuredly toxic to higher plants. Effects of Pb and Hg on the release and viability of RBCs can intuitionistic represent their phytotoxicity and provide information of mechanism for the rhizosphere tolerance of heavy metals. We used mung bean to investigate the development of RBCs and the individual and joint effect of Pb and Hg on the viability of RBCs. The results showed that mung bean could be observed and collected more than 300 RBCs when the root was 5 mm long, and the maximum was about 1000 as 20-25 mm in length. Meantime, RBCs synchronously had relative high harvest and strongly biotic livingness when roots grew to 20 mm. The viability of RBCs decreased as the exposure time increased at all designed treatment levels. Through analysis respective EC50 value, Hg was more toxic than Pb on the viability of detached RBCs from 20 mm length roots, having a toxic level of about 3 orders of magnitude higher than that of Pb. And the joint effect of Pb and Hg on the viability of RBCs in vitro suggested an additive or potentiation relationship. Also, mechanisms of plants resisting the toxic effects of metal ions were discussed in detail.