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Any of a group of synthetic compounds, all derivatives of fluorene-carboxylic acid, that affect many aspects of plant growth and differentiation. Morphactins have little effect on mature tissues but in seedlings and growing shoots apical dominance is removed and internode elongation inhibited, giving a dwarfed bushy appearance. Expansion of the leaf lamina is also prevented and flowers, if produced, may be deformed. Seeds from morphactintreated plants may contain abnormal embryos. Morphactins applied to seeds slow down germination and inhibit lateral root formation from the radicle. In legumes, root nodule formation is prevented. Other diverse effects of morphactins include the inhibition of phototropism and geotropism, the induction of parthenocarpy, and an alteration in sex expression in dioecious plants. Morphactin is thought to induce dwarfism by affecting the orientation of the spindle in dividing cells. It also disrupts the formation of a middle lamella between daughter cells. Although morphactins superficially resemble gibberellins in structure their effects are not thought to be brought about by interaction wth gibberellin or any of the other natural growth substances. Morphactins may be used commercially to slow growth of, for example, mixed plant populations at roadsides.
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