The influence of chemical form and concentration of arsenic on rice growth and tissue arsenic concentration

Abstract

Arsenic absorption by rice (Oryza sativa, L.) in relation to the chemical form and concentration of arsenic added in nutrient solution was examined. A 4 x 3 x 2 factorial experiment was conducted with treatments consisting of four arsenic chemical forms [arsenite, As(Ill); arsenate, As(V); monomethyl arsenic acid, MMAA; and dimethyl arsenic acid, DMAA], three arsenic concentrations [0.05, 0.2, and 0.8 mg As L-J], and two cultivars [Lemont and Mercury] with a different degree of susceptibility to straighthead, a physiological disease attributed to arsenic toxicity. Two controls, one for each cultivar, were also included. Arsenic phytoavailability and phytotoxicity are determined primarily by the arsenic chemical form present. Application of DMAA increased total dry matter production. While application of As(V) did not affect plant growth, both As(Ill) and MMAA were phytotoxic to rice. Availability of arsenic to rice followed the trend: DMAA < As(V) < MMAA < As(III). Upon absorption, DMAA was readily translocated to the shoot. Arsenic(Ill), As(V), and MMAA accumulated in the roots. With increased arsenic application rates the arsenic shoot/root concentration decreased for the As(Ill) and As(V) treatments. Monomethyl arsenic acid (MMAA), however, was translocated to the shoot upon increased application. The observed differential absorption and translocation of arsenic chemical forms by rice is possibly responsible for the straighthead disorder attributed to arsenic.

Arsenic Speciation in Phloem and Xylem Exudates of Castor Bean

“…Previous studies have shown that methylated As species are generally taken up more slowly than inorganic As, but translocated more efficiently from roots to shoots (Marin et al, 1992;Abedin et al, 2002;Raab et al, 2007;Li et al, 2009). Similar results were obtained with castor bean, with As uptake following the order of As(V) .…”

“…When rice plants were exposed to MMA(V) or DMA(V), both As species were found in the xylem sap (Li et al, 2009). Generally, methylated As species are taken up by roots at slower rates than inorganic As, but they are more mobile during the xylem transport from roots to shoots (Marin et al, 1992;Raab et al, 2007;Li et al, 2009).…”

Phytotoxicity of Arsenate and Salinity on Early Seedling Growth of Rice (Oryza sativa L.): A Threat to Sustainable Rice Cultivation in South and South-East Asia

“…The results reveal that the individual phytotoxicity of As(V) in seed germination depends on rice varieties. Varietal differences of As phytotoxicity to rice seed germination have been reported in other studies (Abedin and Meharg 2002;Marin et al 1992). The present study also shows that saline-tolerant rice varieties are more susceptible to As(V) phytotoxicity than the saline non-tolerant varieties.…”

Arsenate (As) uptake by and distribution in two cultivars of winter wheat (Triticum aestivum L.)

“…Other workers have also found similar shoot-to-root ratios of As concentrations, e.g. <0.02 in tomato (Lycopersicum esculentum), <0.1 in Brassica juncea, and <0.2 in rice when arsenate was supplied (Marin et al, 1992;Burló et al, 1999;Pickering et al, 2000;Geng et al, in press). Arsenic allocation to the above ground portion of cereal crops is generally undesirable, as it will reduce the quality of the grains.…”