A Rice Variety is Able to Accumulate the Metal in its Grain
It is a rice variety with a silver touch, literally. Garib-sal, one of 505 types of rice plants tested by scientists, is capable of absorbing silver found naturally in soil and accumulating it in the grain to unusually high levels of 15 mg per kg.
The soil contained only about 0.15 mg per kg, but the rice was able to accumulate high quantities of silver. Researchers say that, the unusual accumulation of silver in the grain and other parts of the plant, throws open the possibility of commercial extraction of the metal through farming.
The maximum concentration of silver in the plant is in the grains. In the bran of the rice grain there is silver accumulation is largely and the silver in the grain is reduced significantly once polished.
Prof. T. Pradeep from the Department of Chemistry, Indian Institute of Technology Madras, who authored the research said, “We do not advocate consumption of the unpolished rice as staple food. If the rice is polished very well then it may not lead to silver toxicity.”
While screening for different metal ions in the 505 rice varieties, the researchers at IIT Madras stumbled upon the rice variety. With Garib-sal the highest, only nine showed high silver accumulation.
As part of rice variety conservation efforts, the rice varieties are maintained by Dr. Debal Deb, head, Centre of Interdisciplinary Studies, Kolkata. Farmers in Purulia, West Bengal grows the Garib-sal.
Even when Garib-sal is grown in soils with very low silver concentration, the researchers tested Garib-sal’s ability to accumulate silver. The rice plant was able to concentrate 0.20 mg of silver per kg in the grains, even when the soil contains only about 0.01 mg of silver per kg.
Prof. T. Pradeep said, “The rice variety has the ability to accumulate silver about 100 times more than any other rice.” Garib-sal accumulated 50 times more silver than another type in control tests. In soil containing about 0.15 mg per kg, the variety was cultivated in the farm for three successive years and the uptake and accumulation of the noble metal was nearly the same.