Growth and mitotic potential of multicelled fibers of cotton (Malvaceae).

We tested the hypothesis that the growth of multicelled cotton fibers of Gossypium hirsutum, cultivar MD51 ne, occurs exclusively within the tip cell. Direct cellular measurements proved the hypothesis incorrect. The results show that all cells within a fiber grow and that the relative growth of the tip cell is reduced as the number of cells per fiber increases. Also, measurements of two- and three-celled fibers show that the two daughter nuclei in two-celled fibers differ. The ability to divide resides primarily, if not exclusively, with the basal cell. Thus, the fate of the tip-cell nucleus is fixed while that of the base cell is not. This rule is unaltered by the presence of IAA (indoleacetic acid) and GA3 (gibberellic acid-3) in the culture medium.