THE CONTROL OF GROWTH AND DEVELOPMENT IN RED CLOVER (TRIFOLIUM PRATENSE L.): III. ENDOGENOUS DIFFUSIBLE AUXIN

Abstract

Significant amounts of endogenous diffusible auxin have been obtained from apices and leaves of red clover plants and differences in endogenous diffusible auxin level have been related to characteristic differences in morphogenesis.Less diffusible auxin was obtained from the apices and leaves of autotetraploid than diploid plants of the same clone; a slower rate of growth was observed in the tetraploids.Changes in the diffusible auxin level can be brought about by variations in light that occur in a normal growth situation. Greater amounts of diffusible auxin were obtained under longer daylengths. Lesser amounts of diffusible auxin were obtained from plants that were shaded. A greater amount of diffusible auxin was obtained from apices when in light than in darkness.Application of 2,3,5-triiodobenzoic acid lowered the diffusible auxin level within the plant and interfered with normal polarity.An interaction between application of 3-indoleacetic acid, light intensity, and diffusible auxin level has been observed. This interaction is most readily explicable on the postulation, based on indirect evidence, that a mechanism for the regulation of endogenous free auxin level may exist in red clover whereby an auxin production system can be linked with some adaptive system, possibly IAA oxidase, that decreases the amount of endogenous free auxin.