EFFECTS OF SOME GROWTH REGULATING SUBSTANCES ON THE TRANSPIRATION OF ZEA MAYS, L. AND RICINUS COMMUNIS, L

Abstract

Indole-3-acetic acid (IAA), beta-naphthoxyacetic acid (B-NAA), P-chlorophenoxy-acetic acid (P-CAA), 2,4-dichlorophenoxyacetic acid (2,4-D), beta-(indole-3)-propionic acid (beta-IPA) and gamma-(indole-3)-butyric acid (gamma-IBA) were applied, as aqueous sprays, to the stems and blades of potted plants of Z. mays, and R. communis. The pots, containing the soil and roots of the exptl. plants, had previously been sealed as described by Meyer and Anderson (Laboratory Plant Physiology, 1940) to make possible the measurement of transpiration. P-CAA and 2,4-D were used at 0.01 or 0.02%; the other compounds at 0.01 or 0.1% concn. The avg. total transpiration of treated corn plants (g./dm.2) was not considered to be affected by treatment with the growth-regulating sprays, but all of the sprays, with the exception of beta-IPA, decreased the avg. total transpiration of castor bean plants. Also, an increase in the concn. of each of the effective sprays resulted in a greater decrease in the avg. total water loss of the treated plants. The order of effectiveness of the sprays in decreasing transpiration of castor bean plants was consistently; 2,4-D, P-CAA, IAA, gamma-IBA and beta-NAA. Moreover, increase in the avg. total transpiration of treated castor bean plants during the hrs. of the night, in comparison with the avg. total transpiration of comparable untreated plants was repeatedly observed. A possible explanation of this phenomena might be the increased surface area exposed by splitting of the stems of plants sprayed with 2,4-D, P-CAA and sometimes IAA.