EFFECTS OF EXOGENOUS AUXIN ON THE REGULATION OF ELONGATION GROWTH OF EXCISED SEGMENTS OF VIGNA HYPOCOTYLS UNDER OSMOTIC-STRESS

IAA applied simultaneously with osmotica greatly enhanced the adaptive recovery of the elongation growth of segments of Vigna hypocotyls during osmotic stress irrespective of whether or not absorbable solutes were present. IAA stimulated both the surface pump and the xylem pump, which have been shown to be stimulated by osmotic stress and to control the yielding of the cell wall and the absorption of solutes. Thus, wall extensibility and the effective turgor were further enhanced under osmotic stress in the presence of IAA. These results indicate that the simultaneous presence of IAA can reduce the inhibition of growth by osmotic stress, and they support numerical predictions based on the apoplast canal model. The mechanism involved in the rapid recovery of growth is discussed.