Changes in the structure of xyloglucan during cell elongation

Xyloglucans were isolated by sequential extraction of the cell walls of pea (Pisum sativum L. cv. Alaska) with a xyloglucan-specific endoglucanase and KOH. The xyloglucan content and xyloglucan-oligosaccharide composition wer e determined for fractions obtained from the elongating and non-elongating segments of pea stems grown in the light and in darkness. The results were consistent with the hypothesis that regulated growth of the cell wall depen ds on xyloglucan metabolism. Furthermore, the characterization of xylogluca n extracted from leaves of light-grown pea plants indicates that xyloglucan metabolism is tissue specific. Changes in xyloglucan subunit structure obs erved in elongating stems are consistent with the in muro realization of a metabolic pathway that was previously proposed solely on the basis of the i n vitro activities Of plant glycosyl hydrolases.