DIFFERENTIAL ROOT RESPONSES TO ALUMINUM STRESS AMONG BRAZILIAN RICE GENOTYPES

Abstract

Reports on aluminum (Al) tolerance of local rice varieties (Oryza sativa L.) in Brazil are few. In this paper, we investigate the effects of Al toxicity on root elongation of a local rice variety and three improved rice genotypes in simple and complete growth solutions. Seedlings (4–5 days) were exposed to Al levels of 0 to 640 μM for two days in simple solutions, while seedlings of 12 days were grown for 9 days in solution with levels of Al ranging from 0 to 320 μM. We found that differences in Al tolerance were more distinct in simple growth solution tests than in complete growth solution tests. The local variety Comum Branco, cropped on acid soils, showed higher Al tolerance than the new improved genotypes. Relative root elongation of the local variety seemed to depend on the Al concentration of the growth medium, displaying a reduction in root elongation at low Al levels and a recovery of root growth at moderate Al levels. Further investigation is needed to elucidate if this particular pattern of Al tolerance in primary roots is also expressed in lateral root growth.

ACKNOWLEDGMENTS

This work was supported by a grant from FAPERJ, Rio de Janeiro, Brazil (to ROPR). The authors thank CNPq of Brazil, for research fellowships, Dr. M.S. Freire (CNPAF-EMBRAPA) for the supply of seeds, and J.M. Tucker (University of Florida) for English revision of the text.