The metal gobblers
AS A result of industrial and mining operations, extensive acres of agricultural land are poisoned worldwide due to toxic effluents. Scientists at Oxford Universitv LJK, have found a possible solution to this growing menace by producing genetically engineered cabbages, cauliflowers arid Brussels sprouts, that would soak up toxic metals and consequently cleanse polluted soils at a much lower cost than that engendered by chemical treatment. Then, these nictal-rich crops can be harvested arid burnt to reclaim metals for recycling (Spectrum, No 254).
Alyssum, a small common plant with white flowers widely grown along garden borders, was investigated by Andrew Smith of the department of plant sciences at Oxford and was found to be a hyper-accumulator of metals. The absorbed metals acted as a protective shield, too, on the plant as this gave the plant a bad taste, thus preventing birds and insects from feeding on it.
The mechanism by which plants are able to accumulate these metals without letting them interfere in their biochemistry is still unknown. The potentiality of plants in being able to do this is making them important in transforming wastelands into agricultural land. Scientists have been able to discover a particular molecule - histicline - that does this metal binding. Histidine accumulates in large quantities in plants that are able to store nickel.
To experiment on this, Smith sprayed histidine solution around Alyssum species which cannot tolerate toxic metals. As histidine was absorbed, the plants were temporarily able to tolerate metals effectively, but this lasted until histiclinc broke down and disappeared. However, such a wav of spraying histiclinc is not practically possible on a large scale. Therefore, an alternative and effective way was to alter the genetic constitution of the plants, so that they can themselves produce large quantities of histiclinc. For doing this the genes which produce histicline need to be identified and isolated. This will then make it possible to modify a large number of plants genetically so that they can - in situ - produce histidine and consequently, get transformed into metal accumulators.
Smith hopes to be doing all this on his selected brassicas (a family of plants which includes Brussels sprouts, cauliflowers and broccoli) which have extensive root systems. After transformation into metal-accumulating plants, they will prove to be very effective in decontaminating polluted soils.
Unfortunately, such vegetable grown on industrial wasteland will surely not be edible in the first few years. But they will help in cleaning Lip the soil at a much lower cost.