Rice Coleoptile Growth under Water and in Air - Possible Effect of Buoyancy on Growth and Cell Walls

Abstract

Rice seedlings were grown under water, under water with air bubbling, and in air. Maximum growth was achieved in coleoptiles grown under water. Differences in coleoptile growth were detected between air bubbling and air conditions, which could be due to buoyancy effect under water. Promoted growth under water was due to an increase in the cell wall extensibility. The increase in the cell wall extensibility correlated with a decrease in the amount of diferulic acids bound to cell walls, suggesting that the enhancement of the formation of diferulic acid bridges in hemicelluloses in air or under water with air bubbling makes cell walls mechanically rigid, thereby inhibiting cell elongation in rice coleoptiles. Differences in the cell wall extensibility and the amount of diferulic acid in cell walls existed between air bubbling and air conditions. These differences seem to be due to buoyancy effect.