INHIBITION OF CURVATURE RESPONSES BY SHUNTING THE INHERENT ELECTRICAL FIELD

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Abstract
Geotropic curvature (60 min. in the horizontal position), positive phototropism (200 meter-candle-seconds of unilateral illumination), and bending induced by transversely applied direct current (10 microamps. applied for 2 min. at a level 5 mm. below the apex) all are inhibited when the internal cylinder of the sheath is filled with an electrolyte such as Shive''s soln. The degree of inhibition is to a large extent dependent on the concn. of the soln. used. However, these curvature responses are not inhibited when the cylinders are filled with a non-conducting soln. of glycerol with the osmotic concn. adjusted to exceed the osmotic pressure of the lowest dilution of Shive''s soln. used. Since it is known that the longitudinal electrical polarity of the Avena coleoptile can be shunted by filling the sheath with an electrolyte, and that non-electrolytes have no shunting effect, these results apparently support the hypothesis that the existence of an inherent electrical field is an essential prerequisite for growth responses of this kind.