plant hormone

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Related to Plant growth substance: phytohormone

plant hormone

any of several chemical substances produced in very low concentrations in plants, that control growth and development. They are now usually called growth substances. Plant HORMONES are produced in active MERISTEMS (e.g. root and shoot apices) from where they diffuse to other parts of the plant. A distinct contrast with animal hormonal systems is the fact that plants do not possess specific tissues for hormone production, nor a well-defined distribution system equivalent to the blood system.

Plant hormones are classified generally into several groups, discussed under separate headings: ABSCISSIC ACID, AUXINS, CYTOKININS and GIBBERELLINS.

References in periodicals archive ?
In 1928, Went developed a method for the quantification of plant growth substances present in a sample, which was called the Avena curvature bioassay and is still commonly used today (Figure 10-9).