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 (GA 3 ) 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 (T 0 ) 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. GA 3 induces growth in the dwarf Waito C cultivar, decreases the T 0 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.