Effects of Some Growth Regulating Substances on the Transpiration of Zea Mays, L. and Ricinus Communis, L.

In 1943 AMLONG (1) reported an increase in the transpiration of Cooper's Ernite tomato plants grown from seeds that had been soaked for 24 hours in a solution containing 100 mg. of potassium naphalene acetate, 100 mg. of ascorbic acid and 2000 mng. of thiourea per liter of water. Three years later, BROWN (2) investigating the effect of 2,4-Dichlorophenoxyacetic acid (1000 p.p.m.) on the water relations of Phaseolus vulgaris found: "the total amount of water absorbed and transpired bysprayed plants during the five days immediately following treatment was 34% less than that for comparable untreated ones". FERRI and AUREA LEX (3) added to the soil of potted plants of Tropacolitni majus 75 ml. of an aqueous solution of B-Napthoxyacetic acid (300 mg./l.). Twenty-four hours after treatment the transpiration rates of leaves, detached from control and treated plants, were determined. Water losses from the latter were decreased. FERRI an1d MERCEDES RACHID (4) report that 2,4-Dichlorophenoxyacetic acid (100 and 200 mg./1.) and BN\apthoxyacetic acid (various concentrations) generally caused a decrease in the transpiration rates of leaves detached from potted plants. The authors studied both monocotyledonous and dicotyledonous plants. The increasing order of effectiveness of treatment on the former was: Coix lacrymna jobl, Zea Mays and Stenotaphrtrn antericanrtm; of the latter: Tauaxacutm officinale, Verbascicin blattarioides and Nicotiana tabaccenn. The results of this study, carried on during the spring (Expt. I; corn) and summer of 1947, indicate that application of the growtth regulating sprays tested had a negligible effect on the water loss of corn. Contrarily. most of the sprays affected the trainspiration of castor bean plants. Also, the results tend to sugg,est a possible correlation between the toxicity of the acid employed and the magnitude of its effeet on the transpiration of the castor bean planits. Materials and methods Corn seeds (a single cross obtained through the generosity of Funk Bros. Seed Company) and castor bean seeds, Conner variety, (obtained through the courtesy of the United States Department of Agrriculture) were used in this study. The seeds, sown in soil (three parts loam, two parts peat-moss and one part sand) in three inch pots, were allowed to grow outdoors' until two leaves, not cotyledons, of the plant were "mature."