Ultrastructural alterations in response to zinc and nickel stress in the root cells of pigeonpea

Ultrastructure of root cortical cells of two genotypes of pigeonpea ( Cajanus cajan), namely LRG30 and ICPL87, were grown under different concentrations of zinc and nickel. Growth reduction was found in roots. Electron micrographs of the root cortex cells of the two pigeonpea genotypes exposed to zinc and nickel showed alterations both at the cellular and the organelle level. At the lower concentrations, appearance of unusual deposition of electron dense globules in the vacuoles of the root cortical cells suggests that they may be involved in metal detoxification. Some of the cortical cells showed two nucleoli. The ultrastructural alterations are discussed in relation to the tolerance indices of the two genotypes.