Effect of Indoleacetic Acid on Growth and Chemical Composition of Etiolated Bean Plants

Abstract

3% indoleacetic acid lanolin paste was applied to the 1st intemodes of kidney bean plants grown in the dark and its effect upon their subsequent growth and composition was studied. Histological observations, physical measurements, and chemical analyses of various portions of the plants were made at the beginning and end of a 4-day period of treatment. Indoleacetic acid caused a marked retardation of elongation of the epicotyls, and at the point of treatment caused the formation of galls. Roots developed in these galls and in many cases dense rows of roots developed the entire length of the hypocotyl. Histological studies showed that responses by plants grown in complete darkness were similar to those observed by other investigators in plants grown under natural conditions of alternating periods of light and darkness. Data from approximately 3800 plants showed that the use of indoleacetic acid retarded transport of materials from the cotyledons, and also inhibited the uptake of water. Analyses of treated and untreated plants showed that indoleacetic acid affected the direction of transport of materials from the cotyledons. Materials were conducted upwards only as far a? the 1st internode (point of treatment) in the case of treated plants. Transverse sections through the treated portions, however, showed no evidence of mechanical blockage of the conductive tissues. No significant difference was noted between the respiration rate of treated as compared to that of control plants.