摘要：

Irradiation of white fluorescent light (5 W m-2) inhibited the growth of Oryza coleoptiles. Light irradiation increased stress-relaxation parameters of coleoptile cell walls, minimum stressrelaxationtime and relaxation rate, and decreased cell wall extensibility (strain/load). Under light conditions, the contents of ferulic and diferulic acids ester-linked to the hemicellulosic arabinose residue in cell walls increased and correlated with the modification of the cell wall mechanical properties. These results suggest that light irradiation enhances the formation of diferulic acid bridges in hemicelluloses, making cell walls mechanically rigid and thus inhibits cell elongation in rice coleoptiles. Also, irrespective of coleoptile age or the presence of light, the ratio of diferulic acid to ferulic acid was almost constant, suggesting that the rate limiting step in the formation of diferulic acid bridges in Oryza cell walls is in the step of feruloylation.

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