Ameliorative effect of silicon an aluminum injury in the rice plant

Rice (cv: Koshihikari) plants were subjected to water-culture during 3 or 4 d with Al (0.2 and 0.8 mM) and low molecular Si (3.0 mM) or high molecular Si (3.0 mM low molecular Si + 21.7 mM high molecular Si) in a 0.5 mM Ca(NO 3)(2) solution in order to evaluate the ameliorative effect of silicon (Si) on Al injury. The concentration of monomer Al in the culture solution with out plants decreased with time and was 65-75% of its original value at 54 h after low or high molecular Si was added. Root and plant growth was inhibi ted by the single Al treatment, but improved by the addition of silicon, es pecially high molecular Si. The total Al content in the roots and shoots wa s highest when low molecular Si was added in the presence of Al, followed b y a single Al treatment and the addition of high molecular Si. The total Si content in the roots increased by the addition of high rather than low mol ecular Si irrespective of the Al treatment. The content of water-sellable p olymer Al in the roots and leaves increased by the addition of low molecula r Si, and the content of water-soluble monomer Al in the leaves decreased. These results suggest that the ameliorative effect of Si on Al injury is at tributable not only to the decrease of Al concentration by Si in the cultur e solution but also to the changes of the Al chemical forms in the solution and plant by Si.