| Arbuscular mycorrhiza (AM) is a symbiotic structure formed by arbuscular mycorrihizal fungi (AMF) and plants, and plays a significant role in terrestrial ecological system, especially in plants’uptake of mineral nutrients, mainly phosphorus, and antioxidant response. Arsenic (As), a dead heavy metal pollutant, is an analogus of phosphorus, and it may be interesting to know its absorption and speciation, and distribution as well as the detoxisity influenced by AM systems. Thus, this study was designed to understand the effects of AMF inoculation on plant growth, As uptake, As speciation, root exudation, antioxidant response, and detoxicity in plant under As stress, by using Glomus. Mosseae and two kinds of mycorhizal plants (Pteris vittata, an arsenic hyperaccumulator, and Astragalus sinicus Linn, an arsenic senstive plant). The results are summarized as follows:1. The effects of AMF and As stress on the growth and antioxidatant systems of A. sinicus and P. vittata’s showed that the fresh biomass of A. sinicus and P. vittata were decreased, while the activity of SOD, POD and CAT, and the contents of GSH and MDA all increased significantly under As stress. Inoculation of AMF increased the biomass of the plant, but had no influences on enzymes activity.2. Determination of organic acids in root exudates of A. sunicus and P. vittata under arsenic stress and inoculation of AMF. showed that the main components of organic acids were oxalate, formic acid, and malic acid in root exudates of A. sinicus, and were oxalate, acetic acid, malic acid and succinic acid in root exudates of P. vittata. The secretion of oxalate in A. sinicus increased by4times under As stress, formic acid and malic acid increased after As (Ⅲ) added, but declined after the addition As (V). Acetic acid, malic acid and succinic acid all increased under As stress in P. vittata, while only oxalate raised under As (V) treated plants. AMF application released more oxalate in A. sinicus, but less oxalate, malic acid and acetic acid in P. vittata treated by As (V), and less acetic acid and succinic acid in As (Ⅲ) treated ferns.3. The absorption and transportation of As in P. vittata and A. sinicus under the effect of AMF were also determined. The results showed that P. vittata can absorp As (Ⅲ) more than As (V), the P. vittata accumulated more As (III) moreover, the leaves accumulate more than rachis and roots, but under As (V) stress, rachis exhibited the highest concentration of As. A. sinicus could also absorb As (Ⅲ) efficiently, but the maximum As (Ⅲ) was transported to shoots while As (V) remained nearly equal in shoots and roots. The findings also show that the P. vittata has the ability to transport As more efficiently with the help of AMF, but the final concentration of As in leaves, cauloids and roots were not significantly different. At the same time, the rate of As transportation and its concentration in A. sinicus showed non-significant difference after AMF inoculation.4. The distribution and concentration of As (Ⅲ) and As (V) in cell wall, cell sap and organelle of A. sinicus and P. vittata have also compared. The results showed that cell sap had the highest concentration of As in these three sub-cellular fractions, while organelle had the lowest. The cell wall and cell organelle in shoots of A. sinicus accumulated more As when exposed to As (Ⅲ) and As (V) while only cell organelle in roots accumulated more As when treated with As (Ⅲ). The cell wall and cell sap of P. vittata showed variation for As uptake, the concentration of As in cell wall of pinnae was raised dramatically but the organelle showed variation for As (Ⅲ) and As (V) solutions however, As contents in cell wall and organelle of rachis were increased and decreased respectively; the proportion of As in organelle of roots reduced under the effect of As (Ⅲ) while it was totally opposite for roots treated with As (V). Moreover, the AMF significantly reduced the percentage in cell wall and cell sap in roots of P. villata but there was non-significant difference for A. sinicus.Secondly, the concentration of As (Ⅲ) in cell wall of A. sinicus shoots was increased while it was decreased in sub-cellular fractions in roots. In pinnae of P. vittata, the distribution of As (Ⅲ) and As (Ⅴ) were significantly different, As (Ⅲ) contents were reduced step by step in cell sap and organelle as well as in cell wall of pinnae when exposed to As (Ⅲ); similar results were found for cell wall and organelle of rachis after the application of As (Ⅲ) however, organelle in roots contained lowest As (Ⅲ) and highest As (Ⅴ) when treated with As (Ⅲ) and As (Ⅴ), respectively. But the addition of AMF showed non-significant difference for As (Ⅲ) and As (Ⅴ) in sub-cellular fractions of A. sinicus and P. vittata.5.The results about degradation of DNA in As treated P. vittata leaves show that DNA of P. vittata leaves was not broken after As treatment, so it can be said that P. vittata has the potential to keep safe DNA from damage under As stress. |
PDF Full Text Request