Abstract
Rice is known to be tolerant to aluminum (Al). To elucidate Al tolerant mechanism in rice at cellular level, Al responses were examined in a cultured rice cell line established from a variety Nipponbare, together with a cultured tobacco cell line (SL) for a comparison. Rice cells were much more tolerant to Al than tobacco cells, although both cells exhibited a similar sensitivity to NaCl. Rice cells accumulated less Al than tobacco cells. NMR analyses indicated that most Al ion species in rice culture medium were monomeric, suggesting that rice cells do not secrete any Al chelating substances. Comparative studies of medium pH and the plasma membrane H+-ATPase activity of rice and tobacco cells suggest that the activation of the plasma membrane H+pump by Al in rice cells increases H+ concentration in the apoplast, which prevents the binding of cationic Al in the rice apoplast.
