Large amounts of phytosiderophore are detected from both the solution and the rhizosphere soil when cereal crops are under Fe deficiency stress. The extension of phytosiderophore in the rhizosphere soil is found only ...Large amounts of phytosiderophore are detected from both the solution and the rhizosphere soil when cereal crops are under Fe deficiency stress. The extension of phytosiderophore in the rhizosphere soil is found only within 1 mm apart from the root surface. The rate of phytosiderophore secretion is negatively related to chlorophyll content in young leaves and positively related to the Fe-solubilizing capacity. Results from in vitro experiments show 10 μmoles mugineic acid can dissolve 501 μg Fe from iron hydroxide and 146 ug from strengite. Thus, phytosiderophore can considerably enhance the soil iron availability by increasing the solubility of amorphous iron hydroxide and iron phosphate, and active Fe is consequently accumulated in the plant rhizosphere , 43% higher than in the bulk soils. There is evidence to support that mugineic acid chelates with Fe3+at a rate of 1:1 in the acid condition. In addition ,we observe mugineic acid has certain effects on mobilization of P as well as Fe by dissolving the insoluble iron phosphate. And phytosiderophore seems to be an effective remedy for the chlorosis of dicotyledonous plants.展开更多
As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic spec...As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors（p H, relative humidity（RH）, humic acid（HA）, trisodium citrate, and additional iron ions） and the contributions of reactive oxygen species（ROS, mainly HO^- and HO2^-/O2^-） to photooxidation of As（Ⅲ） to As（Ⅴ） on kaolinite surfaces under UV irradiation（λ = 365 nm）were investigated. Results showed that lower p H facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate.Promotion or inhibition of As（Ⅲ） photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe^2＋competed with As（Ⅲ） for oxidation by ROS. Experiments on scavengers indicated that the HOUradical was the predominant oxidant in this system.Experiments on actual soil surfaces proved the occurrence of As（Ⅲ） photooxidation in real topsoil. This work demonstrates that the photooxidation process of As（Ⅲ） on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As（Ⅲ）.展开更多
文摘Large amounts of phytosiderophore are detected from both the solution and the rhizosphere soil when cereal crops are under Fe deficiency stress. The extension of phytosiderophore in the rhizosphere soil is found only within 1 mm apart from the root surface. The rate of phytosiderophore secretion is negatively related to chlorophyll content in young leaves and positively related to the Fe-solubilizing capacity. Results from in vitro experiments show 10 μmoles mugineic acid can dissolve 501 μg Fe from iron hydroxide and 146 ug from strengite. Thus, phytosiderophore can considerably enhance the soil iron availability by increasing the solubility of amorphous iron hydroxide and iron phosphate, and active Fe is consequently accumulated in the plant rhizosphere , 43% higher than in the bulk soils. There is evidence to support that mugineic acid chelates with Fe3+at a rate of 1:1 in the acid condition. In addition ,we observe mugineic acid has certain effects on mobilization of P as well as Fe by dissolving the insoluble iron phosphate. And phytosiderophore seems to be an effective remedy for the chlorosis of dicotyledonous plants.
基金supported by the National Natural Science Foundation of China(Nos.21077080,21477090)
文摘As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors（p H, relative humidity（RH）, humic acid（HA）, trisodium citrate, and additional iron ions） and the contributions of reactive oxygen species（ROS, mainly HO^- and HO2^-/O2^-） to photooxidation of As（Ⅲ） to As（Ⅴ） on kaolinite surfaces under UV irradiation（λ = 365 nm）were investigated. Results showed that lower p H facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate.Promotion or inhibition of As（Ⅲ） photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe^2＋competed with As（Ⅲ） for oxidation by ROS. Experiments on scavengers indicated that the HOUradical was the predominant oxidant in this system.Experiments on actual soil surfaces proved the occurrence of As（Ⅲ） photooxidation in real topsoil. This work demonstrates that the photooxidation process of As（Ⅲ） on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As（Ⅲ）.
