Toxic heavy metal stress in paddy: Metalaccumulation profile and development of a novel stress protein in seed

Impact of toxic heavy metals lead, mercury and cadmium have been studied in paddy with respect to their impact on harvest index, metal accumulation in grain and plant body and seed protein profile. All the three metals brought about significant decline in harvest index. Lead treatment resulted in 8.85 to 14.06% decline in harvest index compared to control. Mercury also showed similar effect, but cadmium treatment caused 14.29 to 25.0% decline in harvest index. For all the three metals accumulation was highest in roots, ranging from 53.0 to 56.0% for lead, 47.0 to 54.0% for mercury and 66.0 to 69.0% for cadmium. Following roots, accumulation was in descending order in stem, leaf sheath, grain and leaf. In grains, accumulation was 7.0 to 8.0% for lead, 10.0 to 11.0% for mercury and 6.0 to 8.0% for cadmium, clearly indicating the possible health hazard. Seed protein profile analysed through SDS-PAGE revealed elimination of a high molecular weight protein (≥120) for mercury and cadmium treatment generated a novel 66.5 kDa stress protein.