Roles of auxin and gibberellic acid in growth and maturation of epicotyls of Vigna angularis: Cell wall changes
Nishitani K, Masuda Y
Physiologia Plantarum 56: 38-45
The effects of auxin and gibberellic acid on cell wall composition on various regions of epicotyls of azuki bean (Vigna angularis Ohwi and Ohashi cv. Takara) were investigated with the following results. (1)Young segments excised from apical regions of the epicotyl elongated in response to added 10-4 M indole-3-acetic acid (IAA). When the segments were supplied with 50 mM sucrose, the IAA-induced segment growth was accompanied by enhanced overall synthesis of cell wall polysaccharides, such as xyloglucans, polyuronides and cellulose. This IAA effect on the cell wall synthesis is a consequence of extension growth induced by IAA. Gibberellic acid (GA) at 10-4 M synergistically enhanced the IAA-induced cell wall systhesis as well as IAA-indeced extension growth, although GA by itself neither stimulated the cell wall synthesis nor extension growth. In the absence of sucrose, cell wall systhesis wasnot indeced by IAA or GA. (2) In mature segments excised from basal regions of the epicotyl, no extension growth was induced by IAA or GA. GA enhanced the synthesis of xylans and cellulose when the segments were supplied with 50 mM sucrose. IAA had no effect on the cell wall systhesis. These findings indicate that synthesis of polyuronides, xyloglucans and cellulose, which occurs during extension growth of the apical region of the epicotyl, is regulated chiefly by auxin whereas synthesis of xylans and cellulose during cell maturation in the basal region of the epicotyl is regulated by GA.