Continuous phytoextraction relies on the ability of plants to accumulate metals in their shoots over extended periods. To achieve this, plants must possess efficient mechanisms for the detoxification of the accumulating metal. Undestanding the mechanism of metal bioaccumulation, sequestration and assimilation by plant species may give a clue to the efficiency of phytoremediation technique (Salt et al., 1995). To know the mechanism behind the Ni accumulation by Ricinus communis (wild type and cultivar TMV 5, were identified as Ni hyper accumulators), one green house experiment has been carried out under different levels of Ni (0, 100, 250 & 500 mg / kg) contamination in Vertisols and Alfisols. The amino acid separation and quantification in the leaf sample was carried out using paper chromatography. The amino acid present in the sample are then identified by comparing the Rf values with that of the authentic amino acids, co - chromatographed. The results showed that among the 20 amino acids tested a total of 9 free amino acids were detected in the leaves of Ricinus communis added with Ni. They included histidine, arginine, phenylalanine, tryptophane, lysine, glutamic acid, methionine, serine and leucine. Ricinus communis grown with zero level of Ni revealed 7 free amino acids. Among the amino acids, histidine and arginine were present more under Ni contaminated condition. The quantification results showed that the histidine and arginine were prodeced in larger quantities (7 and 6 µg/g respectively in wild species) with 500 mg of Ni /kg of soil. The enhanced production of histidine and arginine may be responsible for the enhanced Ni accumulation by Ricinus communis. In Ni hyper accumulators, in the genus Alyssum, free histidine has been proposed as the metal chelator involved in Ni tolerance and translocation (Kramer et al., 1996).Smith et al. (1999) reported that at pH values above six, histidine forms Ni complexes of greater stability than those of any other organic or amino acids.