Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8579, Japan.
Planta. 2011 Dec;234(6):1275-84. doi: 10.1007/s00425-011-1480-2. Epub 2011 Jul 26.
In some plant species, various arsenic (As) species have been reported to efflux from the roots. However, the details of As efflux by the As hyperaccumulator Pteris vittata remain unknown. In this study, root As efflux was investigated for different phosphorus (P) supply conditions during or after a 24-h arsenate uptake experiment under hydroponic growth conditions. During an 8-h arsenate uptake experiment, P-supplied (P+) P. vittata exhibited much greater arsenite efflux relative to arsenate uptake when compared with P-deprived (P-) P. vittata, indicating that arsenite efflux was not proportional to arsenate uptake. In the As efflux experiment following 24 h of arsenate uptake, arsenate efflux was also observed with arsenite efflux in the external solution. All the results showed relatively low rates of arsenate efflux, ranging from 5.4 to 16.1% of the previously absorbed As, indicating that a low rate of arsenate efflux to the external solution is also a characteristic of P. vittata, as was reported with arsenite efflux. In conclusion, after 24 h of arsenate uptake, both P+ and P- P. vittata loaded/effluxed similar amounts of arsenite to the fronds and the external solution, indicating a similar process of xylem loading and efflux for arsenite, with the order of the arsenite concentrations being solution ≪ roots ≪ fronds.
在一些植物物种中，已经报道了各种砷（As）物种从根部流出。然而，砷超积累植物凤尾蕨（Pteris vittata）的砷流出的细节仍不清楚。在这项研究中，在水培生长条件下进行 24 小时砷酸盐吸收实验期间或之后，研究了不同磷（P）供应条件下的根砷流出。在 8 小时的砷酸盐吸收实验中，与磷剥夺（P-）凤尾蕨相比，磷供应（P+）凤尾蕨表现出相对更大的亚砷酸盐流出相对于砷酸盐吸收，表明亚砷酸盐流出与砷酸盐吸收不成比例。在 24 小时的砷酸盐吸收后进行的砷流出实验中，在外部溶液中也观察到了砷酸盐流出和亚砷酸盐流出。所有结果均显示出相对较低的砷酸盐流出率，范围为先前吸收的 As 的 5.4%至 16.1%，表明向外部溶液的低砷酸盐流出率也是凤尾蕨的特征，正如亚砷酸盐流出所报道的那样。总之，在 24 小时的砷酸盐吸收后，P+和 P-凤尾蕨将相似量的亚砷酸盐加载/流出到叶片和外部溶液中，表明亚砷酸盐的木质部加载和流出过程相似，亚砷酸盐浓度的顺序为溶液<根部<叶片。
