Effect of Inorganic Ions and Their Conductances on Geotropic Curvature of the Avena Coleoptile

Experimental results of WILKs and LUND (4) show that filling isolated Avena coleoptiles taken from seedlings 34 to 36 mm. long with Shive's solution reduces the longitudinal electrical polarity from a maximum of 60 to less than 10 millivolts. When the solution is removed from the inside of the sheath, the original electrical polarity promptly reappears. These observations were presented as proof of internal shunting of some of the polar units which contribute to the longitudinal electrical polarity of the isolated coleoptile. Previously reported data also show that geotropic curvature of the Avena coleoptile is inhibited by filling the internal cylinder with an electrolyte such as Shive's solution (3). The degree of inhibition is directly dependent on the concentration and specific conductance of the solution used. If it could be demonstrated that such inhibition of curvature is due exclusively to the shunting effect of the electrolyte, then it would appear that an inherent electrical field is a prerequisite for growth curvature responses. In the present paper data are presented to show the effects of solutions of various monovalent cations (Li, Na, K) on geotropic curvature in an attempt to distinguish between the specific effects of concentration and conductance. These ions were selected because equal concentrations of LiCl, NaCl, and KCI should have different shunting effects depending on their equivalent conductances.