0000000000515126
AUTHOR
Lydia Milkovits
Effect of auxin on the mitotic cell cycle in cultured leaf segments at different stages of development in wheat
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 tota…
The ambiguous role of 2,4-dichlorophenoxyacetic acid in wheat tissue culture
The very basal, highly immature regions of dissected young leaves of Triticum aestivum L. cv. Kite formed adventitious roots on a nutrient medium supplemented with comparatively low concentrations (0.16 to 0.63 μM) of 2,4-dichlorophenoxyacetic acid (2,4-D). Higher concentrations (up to 640 μM) had to be applied to stimulate growth from more mature regions higher up the leaf. Yet, already at 2.5 μM roots were less distinct and more callus-like, and eventually (at 10 to 640 μM) only a subculturable callus of apparently suppressed, slowly proliferating root primordia developed. Furthermore, at the most basal, highly immature regions growth was significantly retarded when the auxin concentratio…
Rates of uptake and metabolism of indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid by cultured leaf segments at different stages of development in wheat
Immature leaf tissue of Triticum timopheevi Zukh. responded to supplied auxin and showed cell division in culture. The rates of uptake and of metabolism of indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid by such tissues were measured and compared with those of mature auxin-unresponsive tissue. The purpose of these experiments was to determine whether or not the concentration of auxin in cultured mature tissue was a factor limiting the cell division response to auxin. The data indicate that neither alterations in rates of uptake nor alterations in rates of metabolism could explain the loss of responsiveness to auxin which apparently occurs during cell differentiation. The results are…