We compared between the plant root elongation and the damages observed in root tip surface using Scanning Electron Microscope (SEM) image analyzer, and also compared the absorption abilities between Ca and Mg in the root under 500μM Al stress with some Al tolerant plant species. Al, La or Ga stress inducible peptides in the root tips, which are assumed to be related with toxicity, were investigated by proteome analysis to clarify the Al tolerant mechanism of signalgrass (Brachiaria decumbens). 1. The prevention of the signalgrass root elongation was not so remarkable and decreased only 57.7% even under 200μM stress treatment. 2. The lateral shape and epidermis of Al-stressed signalgrass root tips was found to be stable as compared with that of oat. These results suggest that Al-resistance for epidermal cell wall may function the root elongation. 3. Ca and Mg contents increased in root tips of Al-resistant signalgrass. 4. The 11 peptide spots induced remarkably under Al stress, which were observed under La or Ga stressed root tip similarly. Single peptide spot was found under Al stress which was not appeared under La or Ga stress. We are analyzing amino acids of these peptides. In conclusion, the tolerance to Al toxicity of signalgrass is due to the absorption of more Ca and Mg and less Al in root tip cells under Al stress environment. Al specific inducible peptide, however, may function at least in part on Al tolerance under the Al specific stress.