Control of hemicellulose and pectin synthesis during differentiation of vascular tissue in bean (Phaseolus vulgaris) callus and in bean hypocotyl.

Membrane fractions from bean hypocotyl or callus incorporate arabinose from UDP-β-L-arabinose into arabinan and xylose from UDP-α-D-xylose into xylan. The control of these syntheses has been studied during xylogenesis in stele and in xylogenesis induced in callus tissue. Induction of arabinan synthetase activity occurs during division and extension growth while that of xylan synthetase occurs subsequently during the period of secondary thickening of the cell wall. The xylan synthetase induction is correlated with the induction of phenylalanine ammonia-lyase and with lignin synthesis.