Department of Biotechnologies for Food and Environmental Monitoring, Mediterranea University, Feo di Vito, 89124, Reggio Calabria, 89124, Italy.
Environ Sci Pollut Res Int. 2011 Aug;19(7):3046-53. doi: 10.1007/s11356-012-0820-5. Epub 2012 Feb 25.
This work focuses on the accumulation and mobility properties of arsenic (As) and the effects of phosphate (P) on its movement in Pennisetum clandestinum Hochst (kikuyu grass), grown hydroponically under increasing arsenate (As(V)) concentrations. The uptake of both ions and the relative kinetics show that phosphate is an efficient competitive inhibitor of As(V) uptake. The P/As uptake rate ratios in roots indicate that P is taken up preferentially by P/As transporters. An arsenite (As(III)) efflux from roots was also found, but this decreased when the arsenate concentration in the solution exceeded 5 μM.
Increases in both arsenite and arsenate concentrations in roots were observed when the arsenate concentration in the solution was increased, and the highest accumulation of As(III) in roots was found when plants were grown at 5 μM As(V). The low ratios of As accumulated in shoots compared to roots suggest limited mobility of the metalloid within Kikuyu plants.
The results indicate that arsenic resistance in kikuyu grass in conditions of moderate exposure is mainly dependent on the following factors: 1) phosphate nutrition: P is an efficient competitive inhibitor of As(V) uptake because of the higher selectivity of membrane transporters with respect to phosphate rather than arsenate; and 2) a detoxification mechanism including a reduction in both arsenate and arsenite root efflux.
The As tolerance strategy of Kikuyu limits arsenate uptake and As translocation from roots to shoots; therefore, this plant cannot be considered a viable candidate for use in the phytoextraction of arsenic from contaminated soils or water.
本研究专注于砷（As）的积累和迁移特性，以及磷酸盐（P）对其在水培条件下，随砷酸盐（As(V)）浓度增加，在香根草（Pennisetum clandestinum Hochst，俗称百慕大草）体内移动的影响。两种离子的吸收以及相对动力学表明，磷酸盐是砷酸盐吸收的有效竞争性抑制剂。根部的 P/As 吸收速率比表明，P 优先通过 P/As 转运蛋白被吸收。我们还发现根中有亚砷酸盐（As(III)）的外排，但当溶液中砷酸盐浓度超过 5μM 时，外排量会降低。
当溶液中砷酸盐浓度增加时，根中的砷酸盐和亚砷酸盐浓度均增加，当植物在 5μM As(V)条件下生长时，根中积累的 As(III)最多。与根相比，地上部分积累的砷比例较低，这表明该类金属在百慕大草体内的迁移性有限。
结果表明，在适度暴露条件下，百慕大草对砷的抗性主要取决于以下因素：1）磷营养：由于膜转运蛋白对 P 的选择性高于 As(V)，因此 P 是砷酸盐吸收的有效竞争性抑制剂；2）解毒机制，包括减少根中砷酸盐和亚砷酸盐的外排。
百慕大草对砷的耐受策略限制了砷酸盐的吸收和砷从根部向地上部分的转运；因此，该植物不能被认为是从受污染土壤或水中提取砷的可行候选植物。
