Absorption and Translocation of Plant Regulators

Naturally-occurring auxins, of which indoleacetic acid is the best known example, have a striking apex-to-base polar transport. This may have led to the belief that all plant regulators have a rather specific mode of absorption and of transport. However, since plant regulators now (5) include a wide variety of organic compounds this seems most unlikely.

Many of the phenomena which are involved in the absorption and translocation of regulators in plants are well known. However, a unified picture seems lacking. It is a rather new field, which one will not find discussed in standard texts of plant physiology. The significance of this subject is more than academic. In recent years sprays have been applied to plants for a multitude of practical purposes (106a).

New techniques have helped in the understanding of the principles of absorption and translocation. Enzymatic digestion is used for the isolation of the plant cuticle, a principal barrier through which materials must pass. Electron microscopy is showing its detailed structure. Radioactive tracers and chromatography have been useful in the microanalysis of materials, revealing their distribution on and in the plant. The author has attempted to outline the broad principles involved.