6533b822fe1ef96bd127d529

RESEARCH PRODUCT

Effect of auxin on the mitotic cell cycle in cultured leaf segments at different stages of development in wheat

subject

description

Young leaves of Triticum timopheevi Zukh. show a defined gradient of development. One-mm-long sections from such leaves were cultured in vitro. At a low concentration of exogenous auxin, cells in the most basal, highly meristematic explants divided readily in culture, but in the absence of auxin they soon ceased dividing and were arrested in G1 and G2 of the mitotic cell cycle. In the region adjoining the meristem, where most cells were arrested in G1, very high concentrations of auxin had to be applied to reinitiate cell division, i.e. stimulate transitions from G1 to S-phase and from G2 to mitosis. Above this potentially auxin-responsive region, which represented less than 50% of the total leaf length, there followed tissue, which, when excised, showed nuclear DNA replication in a number of cells in the absence of auxin. However, the cells did not complete the mitotic cycle, either in the absence or presence of exogenous auxin. We suggest this loss of responsiveness is correlated with an uncoupling of auxin from the control of the cell cycle.