Effect of GA3 on the Molecular Mass of Polyuronides in the Cell Walls of Alaska Pea Roots

The role of cell wall matrix polysaccharides in gib-berellin-regulated root growth is unknown. We examined pectic polysaccharides from pea roots treated with or with-out gibberellin A3 (GA3) in the presence of ancymidol, an inhibitor of gibberellin biosynthesis. Pectic polymers solubilized by CDTA (trans-l,2-cyclohexanediamine-Ar,iV,./V,W-tetraacetic acid) at 23°C and subjected to gel permeation analysis exhibited high polydispersity with a molecular mass in excess of 500 kDa. Subsequent extrac-tion of cell walls with CDTA at 100°C solubilized polymers with an average mol mass of 10 to 40 kDa. Subjecting the high molecular mass pectic polymers extracted at 23 °C to 70-100°C for 2h generated 10 to 40 kDa fragments, similar in size distribution to those solubilized directly from cell walls by CDTA solutions at 100°C. Pectic poly-mers from (GA3+Anc)-treated roots were of higher aver-age mol mass than those from Anc-treated roots in both the elongation zone and in the basal maturation zone. Since (GA3 + Anc)-treated roots elongate more quickly than Anc-treated roots [Tanimoto (1994) Plant Cell Physiol. 35:1019], the slender, GA3-treated roots may pro-duce and deposit highly integrated pectins more rapidly than the thicker, Anc-treated roots in the elongating or elongated cell walls. Key words: Cell wall — Gibberellin — Molecular mass dis-tribution — Pectin — Pisum sativum L. — Root growth. The role of matrix polysaccharides in growing cell walls has been extensively studied in stems and coleoptile