| The present study addresses the roles of auxin and gibberellin (GA) in controlling stem elongation through a genetic analysis of the auxin and GA responses in light-grown plants of Pisum sativum L. with differing endogenous contents of the two hormones.;The auxin indole-3-acetic acid (IAA), continuously delivered in aqueous solution to the elongating pea internodes, produced a sustainable growth stimulation in the intact plant with similar kinetics to the effect in the isolated stem segments. IAA was able to induce the growth of the subtending internodes, as it is basipetally transported within the stem from the apical regions. The magnitude of the IAA-inducible response was inversely correlated to the level of endogenous IAA in pea genotypes, where the growth rate was sustainably increased by about 30%, 6-fold and 10-fold respectively in the wild-type, dwarf le and lkb mutants. The effect of IAA in stem growth was confined to an increase in cell extension. Indole-3-butyric acid (IBA), another naturally occurring auxin, exhibited a stimulating effect on stem elongation comparable to that of IAA. While GA... |
