The Effect of Auxin on Synthesis of Oat Coleoptile Cell Wall Constituents

Abstract

The auxin-induced promotion of cell wall synthesis in oat coleoptile segments whose elongation was inhibited by Ca++ was a general promotion of synthesis of matrix polysaccharides, including glucan, glucuronoarabinoxylan, and polysaccharides containing galacturonic acid. Synthesis of [alpha]-cellulose glucan was not promoted. By contrast, promotion by auxin of elongation of uninhibited segments was accompanied by large increases in synthesis of all polysaccharide fractions including a-cellulose. It is concluded that the direct effect of auxin was probably on metabolism of matrix polysaccharides and that the promotion of [alpha]-cellulose synthesis was induced by elongation. Fractionation of coleoptile tissue after 1-hour treatment with auxin did not show differences in incorporation as large as were observed after several hours of auxin treatment. However, the data also demonstrate features of internal compartmentation of the tissue that restrict the interpretation of radioisotope experiments of short duration.