Springer Online Journal Archives 1860-2000
Summary The increment of Og in the guard cells in response to light as reported by previous investigators was found to be true qualitatively but not quantitatively. A special device was constructed, which permitted the elimination of the heat factor when the leaves were irradiated. In experiments 1 and 2 the relative values of the bell and the device were determined. In experiments 3 and 4 the relative effects of light were studied on younger and older leaves. In experiments 5 and 6 the effects were studied on old and young leaves ofHedera helix. This plant serves as a standard for comparisons of results obtained by subjecting plants to various factors of the environment. In experiments 7 and 8 the effect of light on young, middle-aged and old leaves ofHedera helix, when water was supplied, in one case but not in the other were studied. In experiment 8 the same leaf was treated in the device and then in the dark chamber, and once more in the light. The results are particularly enlightening. In the supplementary experiments, it was verified that the phenomenon of an increment of the guard cells and a decrement of the spongy parenchyma in Og, when irradiated, is probably general.
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