Cytokinin Effects on Leaf Architecture inPhaseolus vulgarisL.

Treatment of expanding primary leaves of bean plants (Phaseolns vulgaris L. cv. Limburgse vroege) with benzyladenine (BA) or kinetin at 0.5 mM for five consecutive days resulted in thicker leaves showing a significant decrease in intercellular air space volume. Compared with control plants, exposed mesophyll cell surface area was lower per unit tissue volume, but unchanged when expressed per unit leaf surface area. Stomata of treated plants were not fully closed in the dark and they did not open as wide as controls in the middle of the light period, suggesting that the treatment resulted in impaired stomatal action. All the effects mentioned were more pronounced after treatment with BA, compared to kinetin. In spite of their magnitude, the observed changes in leaf structure and function did not seem to have an important effect on total leaf diffusion resistance to carbon dioxide during the course of the light period.