| Abstract: | Solutions of mannitol and carbowax 1540 reduced the geotropicresponse of Avena sativa coleoptiles to at least the same extentas a potassium chloride solution of equal osmotic potential.Similar results were obtained with the phototropic response.The magnitude of these decreases increased almost linearly withthe osmotic concentration of the solutions over the range 0.025–0.45J cm–3. In contrast, the geotropic and phototropic responseswere scarcely affected by exposing the coleoptiles to solutionsof glycerol. The absence of an effect with glycerol is probably due to thepenetration of the coleoptile cells by this solute. The similaror greater reduction in tropic curvature brought about by mannitoland carbowax 1540 solutions, as compared with a potassium chloridesolution of equal osmotic potential, makes untenable a previoussuggestion attributing the inhibitory effects of electrolytesolutions to a shunting of the electro-potential differenceson the plant surface. |
