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Title: GROWTH REGULATORS DO NOT INCREASE ONION BULB SIZE OR WEIGHT UNDER GREENHOUSE CONDITIONS

Author
item Russo, Vincent

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2002
Publication Date: 3/20/2003
Citation: RUSSO, V.M. GROWTH REGULATORS DO NOT INCREASE ONION BULB SIZE OR WEIGHT UNDER GREENHOUSE CONDITIONS. HORTSCIENCE. 2003. V. 38. P. 599-600.

Interpretive Summary: Individual or combinations of plant hormones have been placed on the market as aids to improve crop productivity. It is not clear if applications of plant hormones provide a benefit to vegetable production. An experiment was conducted under greenhouse conditions and the plant hormones abscisic acid, gibberellic acid, indole-acetic acid, and kinetin, and the plant growth regulators jasmonic acid and maleic acid hydrazide were applied at two concentrations each to onion plants at the 7- and 20-leaf stages. Total above ground plant weights and weights and diameters of bulbs were determined. The test substances did not appear to provide any benefit to plant development in general and bulb sizing in particular when compared to water only controls.

Technical Abstract: Abscisic acid, gibberellic acid, indole-acetic acid, jasmonic acid, kinetin, and maleic acid hydrazide were applied at the 7- and 20-leaf stages, at two concentrations for each substance and with water controls, to the middle of the leaf whorl in greenhouse grown onion plants. Effects on bulb and leaf fresh and dry weights, and bulb diameter, were determined. .Analysis was conducted to determine how bulb and leaf development were correlated. Bulbs from plants to which growth substances were applied at the 7-leaf stage were heavier and larger than those from plants treated at the 20-leaf stage. Leaf fresh weights at harvest from plants treated at the 7-leaf stage were greater than from plants treated at the 20-leaf stage. Dry weights of leaves from plants treated at the 20-leaf stage were heavier than from plants treated at the 7-leaf stage. Bulbs from plants treated with water controls had greater diameters and larger fresh weights than bulbs from plants treated with the growth substances. Leaf weights were not affected. Analysis indicated that patterns of correlations differed when application time, concentration of growth substances, and type of growth substance was considered individually. Plants treated at the 7-leaf stage had smaller, lighter, bulbs than those treated at the 20- leaf stage, and plants treated with growth substances produced bulbs that were the same size, or smaller, than those produced on plants treated with water. This data indicates that the use of growth substances to increase bulb size is not warranted.