The uptake rate of Hg and As of rice is greater than that of wheat. But the uptake rate of Cu, Pb, Zn and Cd of rice is lower than that of wheat, and their order is: Zn> Cd>Cu>As>Hg>Cr>Pb.The sequence of some heavy metals contained in various organs of rice and wheat is as follows: roots>stems leaves>grains. The amount in vegetables also varies with different kinds of vegetable. Pb is obstructed in roots, and is difficult to be transported into stems, leaves and grains. It is easy for Cd to be absorbed into...