Master Thesis

Low Si accumulation in husk and flag leaf might result in higher dimethylarsenate translocation into grains of red rice from Camargue

Robin Heimes (11/2015-04/2017)

Support: Jörg Schaller, Britta Planer-Friedrich

Rice is the main crop plant in the world but has a tendency to accumulate arsenic (As). Under common flooded field conditions, As enters the rice plant as arsenite via the Si uptake system. A rice variety with high As contents is the red rice from Camargue, France (up to 421 μg kg-1). To unravel the underlying trait, we grew pigmented (TamTam) and non-pigmented rice (Arelate) from the Camargue under different silicon (Si) fertilization levels. Pigmented rice accumulated significantly more As in the grain compared to non-pigmented rice (19 %). With increasing Si availability during the reproductive phase, the As concentrations in the grain and the vegetative tissues decreased significantly for both varieties. However, we found a significantly higher accumulation of dimethylarsenate (DMA) in pigmented rice grains explaining the difference in the sum of As species between pigmented and non-pigmented grains. A principal component analysis (PCA) revealed a negative relationship between the husk and flag leaf Si and the grain total As and DMA concentration for brown rice, but not for red rice, with non-pigmented rice accumulating significantly more Si in the vegetative tissues than pigmented rice. Therefore, we propose that Si precipitations are capable of binding DMA at higher tissue Si concentrations inhibiting further translocation into the grain.