Gonzaga Maria Isidória Silva, Ma Lena Qying, Santos Jorge Antônio Gonzaga, Matias Maria Iraildes Silva
Universidade Federal de Sergipe, Aracaju, SE, 49 060-100, Brazil.
Sci Total Environ. 2009 Aug 1;407(16):4711-6. doi: 10.1016/j.scitotenv.2009.04.037. Epub 2009 May 24.
Better understanding of the processes controlling arsenic bioavailability in the rhizosphere is important to enhance plant arsenic accumulation by hyperaccumulators. This greenhouse experiment was conducted to evaluate the chemical characteristics of the rhizosphere of two arsenic hyperaccumulators Pterisvittata and Pterisbiaurita. They were grown for 8 weeks in rhizopots containing arsenic-contaminated soils (153 and 266 mg kg(-1) arsenic). Bulk and rhizosphere soil samples were analyzed for water-soluble As (WS-As) and P (WS-P), pH, and dissolved organic carbon (DOC). Comparing the two plants, P.vittata was more tolerant to arsenic and more efficient in arsenic accumulation than P.biaurita, with the highest frond arsenic being 3222 and 2397 mg kg(-1). Arsenic-induced root exudates reduced soil pH (by 0.74-0.92 units) and increased DOC concentrations (2-3 times) in the rhizosphere, resulting in higher WS-P (2.6-3.8 times higher) compared to the bulk soil. Where there was no difference in WS-As between the rhizosphere and bulk soil in soil-153 for both plants, WS-As in the rhizosphere was 20-40% higher than those in bulk soil in soil-266, indicating that the rate of As-solubilization was more rapid than that of plant uptake. The ability to solubilize arsenic via root exudation in the rhizosphere and the ability to accumulate more P under arsenic stress may have contributed to the efficiency of hyperaccumulator plants in arsenic accumulation.
更好地了解根际中控制砷生物有效性的过程对于提高超富集植物对砷的积累至关重要。本温室试验旨在评估两种砷超富集植物蜈蚣草和双齿蜈蚣草根际的化学特性。它们在含有砷污染土壤（砷含量为153和266 mg kg(-1)）的根际盆中生长8周。对根际和非根际土壤样品进行了水溶性砷（WS-As）、磷（WS-P）、pH值和溶解有机碳（DOC）的分析。比较这两种植物，蜈蚣草比双齿蜈蚣草对砷的耐受性更强，砷积累效率更高，其最高叶砷含量分别为3222和2397 mg kg(-1)。砷诱导的根系分泌物降低了根际土壤pH值（降低0.74 - 0.92个单位），提高了DOC浓度（提高2 - 3倍），导致根际水溶性磷比非根际土壤高（高2.6 - 3.8倍）。对于两种植物，在土壤砷含量为153时，根际和非根际土壤的水溶性砷没有差异，但在土壤砷含量为266时，根际水溶性砷比非根际土壤高20 - 40%，这表明砷的溶解速率比植物吸收速率更快。通过根际根系分泌物溶解砷的能力以及在砷胁迫下积累更多磷的能力可能有助于超富集植物积累砷的效率。
