Physiology of the Cotton Plant

Abstract

A measure of distinction is attached to the physiology of the cotton plant by reason of the dimorphism of its branches, its indeterminate growth habit, and the shedding of small floral buds and young bolls. According to environ­ mental conditions, the branches produced by the cotton plant may be either vegetative or fruiting; the Upland cottons of the South produce variable proportions of the two. Customarily, one or more vegetative branches are developed from the lower sixth to ninth main-stalk nodes after which fruiting branches appear at the successively higher nodes. The interval between the appearance of new fruiting branches is about three days and between the successive nodes of the fruiting branches (each with a floral bud) there is an interval of about six days. Flowering is thus progressive and for a time it becomes more rapid as the plant grows. After flowering and boll setting have continued fot a number of weeks, however, both the growth of the plant and the production of flowers are checked and may stop. Also, many, if not most, of the floral buds abort before anthesis. The flowering and fruiting behavior of American Upland cotton, Gossypium hirsutum L., is day-length neutral; however, there are short-day cottons which develop only vegetative branches during long days. Without the advantage of suitably high temperatures, the day-length neutral cottons behave like short-day cottons under long days and produce only vegetative branches.