Molecular weight distribution of hemicellulosic polysaccharides of the cell wall of tall and dwarf rice cultivars, and the effect of GA3

Growth rate, osmotic potential of the cell, cell wall mechanical properties, sugar composition and molecular weight (MW) distribution of water-soluble hemicellulosic polysaccharides of the second leaf sheath of one tall ( Oryza sativa L. cv. Nihonbare) and two dwarf ( Oryza sativa L. cvs. Tan-ginbozu and Waito C) cultivars of rice were compared. The effect of gibberellic acid (GA₃) on the above-mentioned parameters was also studied using the tall (Nihonbare) and one of the dwarf (Waito C) cultivar. The minimum stress-relaxation time (T₀) was higher in the cell wall from the two dwarfs than in the tall cultivar. Furthermore, in the water-soluble hemicellulosic polysaccharides the mass-average MW of β -glucan was higher and that of arabinoxylan was lower in the tall cultivar than in the dwarf ones. Thus, dwarfism of cvs Tan-ginbnozu and Waito C might be correlated with the different MW distributions of β -glucan and arabinoxylan. GA₃ induces growth in the dwarf Waito C cultivar, decreases the T₀ value of the cell wall, and also decreases the average MW of water-soluble hemicelluloses. Changes in β (1–3)(1–4)glucan or arabinoxylan or in both are proposed as part of the cell wall loosening mechanism induced by gibberellin.