Plant Growth Regulators That Are Less Toxic to Humans
Plant growth regulators that are expected to be less toxic to humans were produced by a Purdue University scientist and researchers in Japan. Angus Murphy, a professor of horticulture, said the growth inhibitors block the transport of auxin, a plant hormone that, when transported throughout the plant, controls growth processes. Current growth regulators that inhibit auxin transport are inefficient because they also have hormone-like activity or affect other important plant processes. Current growth inhibitors also are often toxic.
Growth regulators are important in ornamental plants and horticultural crops that would require labor-intensive manipulation and pruning. The inhibitors are used to keep plants a desired size and shape and control fruit formation.
The toxicity of growth regulators can be an environmental concern and add safety and monitoring costs to commercial growing operations. They are generally not applied to edible portions of plants or are applied early enough that there is little or no residue on edible portions of plants.
The new plant growth inhibitors are derived from natural and artificial auxins but have a bulky benzoyl group - a chemical conjugate derived from benzoic acid - attached that prevents movement of the inhibitor out of the cell. "Since it looks like auxin, it will open the door, but it can't get through," Murphy said. "However, these new growth regulators have no hormonal activity themselves."
Murphy worked with scientists from several universities in Japan, including Okayama University of Science, Tokyo Metropolitan University, Niigata University and the Nara Institute of Science and Technology.
Tsuda E. et al.: Alkoxy-auxins Are Selective Inhibitors of Auxin Transport Mediated by PIN, ABCB, and AUX1 Transporters. The Journal of Biological Chemistry, 286, 2354-2364. Jan. 21, 2011