The role of the osmotic potential of the cell in auxin-induced cell elongation

IAA-induced elongation of light-grown cucumber hypocotyl sectionswas examined with respect to the osmotic relationship of thecell. Sucrose suppression of IAA-induced elongation in the lightoccurred at a lower sucrose concentration than in the dark,but there was no difference in the mannitol concentration whichsuppressed elongation. This differential sucrose suppressioncould be explained by the difference in the osmotic potentialof the cells between light and darkness. It was lower in thedark than in light, and the difference was more distinct inthe presence of sucrose. Treatment of sections with a photosyntheticinhibitor, CMU, also resulted in the maintenance of a low osmoticpotential. Under the experimental conditions where a largerIAA-induced elongation was obtained, a lower osmotic potentialwas also obtained. The results are discussed with respect tothe role of the osmotic potential of the cell in the enhancementof IAAinduced elongation. (Received April 3, 1978; )