. Auxins and plant growth. Auxin; Plant growth promoting substances. Rooting 203 the control of differentiation is the physiological basis for the rooting of cuttings as we understand it today. While it is not clear what the exact action of auxin in this process is, there are several established facts concerning the auxin function. The stiniidation of root formation is not restricted to auxins alone, as similar responses can be obtained with compounds which increase auxin activity and with (ompounds which are epinastic agents. It is known that where roots are formed there is a pronounced incre
. Auxins and plant growth. Auxin; Plant growth promoting substances. Rooting 203 the control of differentiation is the physiological basis for the rooting of cuttings as we understand it today. While it is not clear what the exact action of auxin in this process is, there are several established facts concerning the auxin function. The stiniidation of root formation is not restricted to auxins alone, as similar responses can be obtained with compounds which increase auxin activity and with (ompounds which are epinastic agents. It is known that where roots are formed there is a pronounced increase in the auxin content. This increase occurs in each of the auxin frac- tions: the free auxin, bound auxin, and the neutral auxin (figure 86). Some evidence about the nature of the substances which interact with auxin to control root formation has been brought to light through the observation that leaves strongly promote rooting of cuttings. Van Overbeek et nl (1946) have analyzed the nature of the promotive materials which leaves provide for the cutting, and found that they could entirely replace the effect of leaves by supplying the or. < a UJ I- 2 O O X < 600 400 200 o.^^ ^N Neutral Auxin. o-o ^•>- 8 DAYS TIME AFTER CUTTING Fig. 86. The changes in content of neutral, bound, and free auxin in the basal ends of chicory root cuttings during root formation (Warmke and Warmke, 1950).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Leopold, A. Carl (Aldo Carl), 1919-. Berkeley, University of California Press
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