EFFECTS OF ALPHA–NAPHTHALENEACETIC ACID AND ALPHA–NAPHTHALENEACETAMIDE ON THE DEVELOPMENT OF THE COTTON PLANT

DESPITE THE extensive literature on the effects of growth substances on the development of plants, there are very few reports on the influences of growth substances on the cotton plant. While there have been a number of attempts to reduce boll abscission by the use of growth substances, these have not been successful and few of them have been reported in the literature. Dunlap (1945) reported negative results when he used several growth substances including naphthaleneacetic acid, and Eaton and Rigler (1945) stated that "the present information does not permit any well-defined application of observation or theory to relations between hormone activity and the shedding of cotton bolls, but some of the marked differences between cottons in the extent to which shedding occurs would seem to preclude the possibility that in all cases this shedding can be attributed solely to nutritional relations." Except for the limited amount of work on growth substances in relation to boll shedding, there has apparently been no work done on the influences of growth substances on cotton. Any adequate review of the influence of growth substances on plant development in general would be unwieldy and unnecessary here, so further citations of the literature will be restricted to the papers pertinent to the discussion which appears later in this paper. The present study was initiated primarily to investigate the possible influence of the growth substances on boll abscission, but other effects were also observed and measured. As the experiment progressed it became apparent that a general study of the effects of the growth substances would be more valuable than a specific studv of abscission, especially since so little has been reported on the effects of growth substances on the development of the cotton plant. The results show that a-naphthaleneacetic acid, and to a lesser degree a-naphthaleneacetamide, have definite effects on the growth and development of the cotton plant. In general, growth was inhibited rather than stimulated by the treatments, and it is unlikely that any of the effects are of interest from the standpoint of agronomic application, either as regards boll abscission or otherwise. 1 Received for publication April 23, 1949. This paper is a complete revision and condensation by the junior author of a thesis submitted by the senior author (1948) in partial fulfillment of the requirements for the degree of master of science at the A. and M. College of Texas. The authors wish to acknowledge with thanks the suggestions made by Dr. A. A. Dunlap, the checking of the statistical analyses by Prof. C. B. Godbey, the critical reading of this manuscript by Dr. Frank M. Eaton, and the testing of the cotton fibers by Mr. J. L. Watson. METHODS.-Several seeds of the Stoneville 2B variety of cotton (Gossypium hirsutum L.) were planted in each of a number of 2-gal. glazed jars on February 28, 1948, and by March 6 the plants had been thinned to one per jar. The plants were maintained in fertile soil under good greenhouse cultural conditions throughout the experiment, and