Developmental Stages of the Cotton Plant as Related to the Effects of 2,4-D

Abstract

1. Stoneville 2B cotton plants were treated at the developmental stages of seedling, floral primordia, anthesis, and fruiting with acid equivalent amounts of 0.01 mg. or 0.04 mg. of the sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-D). 2. The earlier the developmental stage at the time of application, the more severely these amounts of 2,4-D affected the vegetative habit of the plants. At the seedling stage these quantities significantly inhibited main-stem height, number of main-stem nodes, and internodal length, but the number of vegetative laterals was greater. Application of 0.04 mg. at the floral-primordia stage also significantly inhibited main-stem height and stimulated the production of vegetative laterals. 3. The degree of malformation of leaves on the main stem and on vegetative lateral branches was dependent upon the developmental stage of the plants at the time of 2,4-D application and upon the quantity of this substance applied. The same was true for malformation of flowers and bolls.