Uptake of fluoride by two paddy (Oryza sativa L.) varieties treated with fluoride-contaminated water

Abstract

The use of fluoride enriched groundwater for irrigating the paddy crops is prevalent in many parts of the world. The fluoride in the irrigated water not only affects the growth and productivity of the crops, but is also accumulated in the plant tissues. We studied the accumulation of fluoride in roots, leaves and seeds two paddy varieties (i.e. Oryza sativa L. var. IR-36 and Oryza sativa L. var. Swarno) when treated with different concentrations of fluoridated water. The translocation pattern of fluoride was also observed. The water soluble fluoride (${\text{F}}_{{{\text{H}}_{ 2} {\text{O}}}}$) in the soil and plant parts increased substantially with increasing fluoride concentration in treated water. The Swarno variety showed a slight but consistent higher uptake of fluoride than the IR-36 variety. Fluoride uptake by the germinated seedlings was many folds higher than the uptake by mature plants. At 30 mg l⁻¹ fluoride exposure, the mean ${\text{F}}_{{{\text{H}}_{ 2} {\text{O}}}}$ accumulation (mg kg⁻¹ dry weight) in root, leaves, and seeds of Swarno was 54.1, 51.4 and 42.3, whereas the corresponding values in IR-36 were 50.9, 48.5 and 39.2. For the same exposure, the fluoride accumulation in root and shoot of Swarno and IR-36 seedlings were 3,480, 3,463 and 3,386, 3,360 mg kg⁻¹, respectively. Normally, the fluoride accumulation follows the order of soil > root > shoot > grain. However, at early stage of fluoride contamination (5 mg l⁻¹ NaF) roots tended to hyper accumulate fluoride from the soil.