Pedosphere 22(4): 497--507, 2012
ISSN 1002-0160/CN 32-1315/P
©2012 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Cellular tolerance, accumulation and distribution of cadmium in leaves of hyperaccumulator Picris divaricata |
HU Peng-Jie1, GAN Yuan-Yuan1, TANG Ye-Tao1,2, ZHANG Quan-Fang3, JIANG Dan4, YAO Nan3 and QIU Rong-Liang1 |
1 School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China);
2 Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275 (China);
3 School of Life Sciences, Sun Yat-sen University, Guangzhou 510275 (China);
4 Instrumental Analysis and Research Center, Sun Yat-sen University, Guangzhou 510275 (China) |
| ABSTRACT |
| Knowledge of cellular metal homeostasis will provide a better understanding of the mechanisms involved in metal tolerance and hyperaccumulation in metal-hyperaccumulating plants. Energy dispersive X-ray spectrometry (EDS) was used to determine the localization of cadmium (Cd) in leaves of the Zn/Cd hyperaccumulator Picris divaricata which had a shoot Cd concentration of 565 mg kg-1 after 2 weeks of growth in solution culture supplying 10 μmol L-1 CdCl2. The results indicated that Cd was distributed mainly in the trichomes, upper and lower epidermis and bundle sheath cells, with a relatively low level of Cd in mesophyll cells. Mesophyll protoplasts isolated from leaves remained viable after 24 h exposure to CdCl2 at a concentration up to 1 mmol L-1, indicating their high tolerance to Cd. The intracellular Cd was visualized by staining with Leadmium Green dye, a cellular permeable Cd fluorescence probe. The results showed that the majority of protoplasts (> 82%) did not accumulate Cd, with only a minority (< 18%) showing Cd accumulation. In the Cd-accumulating protoplasts, Cd accumulation was depressed by the addition of Fe2+, Mn2+ and the metabolic inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP), but not by Ca2+ or Zn2+. Furthermore, the entire process of Cd uptake from external solution into the cytoplasm and subsequent sequestration into vacuoles was successfully recorded by confocal images. These results suggested that reduced cellular Cd accumulation and efficient Cd vacuolar sequestration in mesophyll cells might be responsible for cellular Cd tolerance and distribution in the leaves of P. divaricata. |
| Key Words: confocal images, fluorescence probe, mesophyll, protoplast, vacuolar |
| Citation: Hu, P. J., Gan, Y. Y., Tang, Y. T., Zhang, Q. F., Jiang, D., Yao, N. and Qiu, R. L. 2012. Cellular tolerance, accumulation and distribution of cadmium in leaves of hyperaccumulator Picris divaricata. Pedosphere. 22(4): 497-507. |
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