Effects of arbuscular mycorrhiza and phosphorus application on arsenic toxicity in sunflower (Helianthus annuus L.) and on the transformation of arsenic in the rhizosphere

• Published in: Plant and soil Vol. 290; no. 1-2; pp. 29 - 41
• Main Authors: Ultra, V. U. Jr, Tanaka, S, Sakurai, K, Iwasaki, K
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Kluwer Academic Publishers 2007; Springer; Springer Nature B.V
• Subjects: Acid phosphatase; Acid soils; Acidic soils; Agricultural soils; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Arbuscular mycorrhizas; Arsenates; Arsenic; Arsenite; Biological and medical sciences; Dimethylarsine; Fundamental and applied biological sciences. Psychology; Glomus; Helianthus; Helianthus annuus; Immunization; Inoculation; Nutrition; Phosphorus; Plant growth; Plant roots; Plants; Rhizosphere; Seedlings; Shoots; Soil contamination; Soil fungi; Soil pollution; Soil toxicity; Soils; Sunflowers; Toxicity; vesicular arbuscular mycorrhizae; Rhizosphere; Arbuscular mycorrhiza, Arsenic, Phosphorus; Soil plant relation; Sunflower
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-006-9087-2

Effects of arbuscular mycorrhiza (AM) and phosphorus (P) application on arsenic (As) toxicity were studied in a rhizobox system with As-contaminated soil collected from Shimane Prefecture, Japan. The treatments consisted of a combination of two levels of AM (Glomus aggregatum) inoculation (-AM and +AM) and two levels of P application (-P and +P at 30 mg P kg-¹). Sunflower (Helianthus annuus L.) seedlings were cultured in rhizoboxes for 6 weeks. Rates of root AM infection in +AM treatments were about 40% regardless of P application. AM inoculation as well as P application reduced As toxicity symptoms, most clearly so in the +AM-P treatment. Plant growth was highest in the +AM + P treatment. Shoot As concentrations were slightly reduced by AM inoculation but enhanced by P application. Shoot P concentration in the +AM-P treatment was similar to that of +P treatments and was higher than in -AM-P. Analyses of rhizosphere soils at the end of the cultivation period indicated that P application increased water-soluble As (WS-As) in all compartments while AM inoculation increased WS-As in the central compartment only. Both the WS-arsenite [WS-As⁽III⁾] and the dominant form, arsenate [WS-As⁽V⁾], showed gradients toward the root surface. Dimethylarsine (DMAA) was detected in the +AM treatments only. To our knowledge, this is the first report of the occurrence of DMAA in the mycorrhizosphere. AM inoculation increased WS-P similarly as +P treatments did and promoted acid phosphatase activity in the soil. In conclusion, AM inoculation alleviated the effects of As toxicity by improving P nutrition without increasing As concentrations in the shoots. Moreover, AM appeared to be involved in the transformation of soil inorganic As into less toxic organic forms.