Effects of Gibberellic Acid on Growth and Development of Plants of Various Genera and Species

• Published in: Botanical gazette (Chicago, Ill.) Ill.), 1956-12, Vol.118 (2), p.106-111
• Main Authors: Marth, Paul C., Audia, William V., Mitchell, John W.
• Format: Article
• Language: English
• Subjects: Chemical mixtures; Flower buds; Fungi; Genera; Gibberellins; Leaves; Petioles; Plant roots; Plants; Stem elongation
• ISSN: 0006-8071
• DOI: 10.1086/335932

1. Growth responses of forty-nine kinds of plants were studied when gibberellic acid, a naturally occurring plant regulator, was applied to them in various ways. The plants included representatives of various genera, species, varieties, and hybrids of agronomic, forestry, or horticultural interest. Gibberellic acid is a growth substance produced by the fungus Gibberella fujikuroi (Saw.) Wr. (conidial stage Fusarium moniliforme Sheld.), a pathogen of rice. The chemical was applied in lanolin or as an aqueous spray, dip, or soak. Treated parts of plants included stems, leaves, vegetative buds, flowers, fruits, and roots. 2. Most kinds of plants studied responded in several ways to gibberellic acid, the most obvious of these responses being stem elongation. Marked differences in the responsiveness of different genera, however, were noted. Pinto bean plants, for example, responded when sprayed with a mixture containing 0.01-p.p.m. concentration of the acid, while Virginia pine, white pine, and white spruce responded only slightly or not at all to much larger amounts of the chemical. No important differences were observed in responsiveness either among the different species of the genera studied or among the different varieties and hybrids. 3. Greatest stem elongation resulted when the chemical was applied to stems that had just begun to elongate. Treatment of 0.75-inch-long flower stems of Better Times roses (table 1) with a 1% gibberellic acid-lanolin paste mixture resulted in their average increase of 57% in length over the controls during a 3-week period following treatment. The longer, treated stems were thicker than the controls, and the flower buds produced on them were similar in quality to the controls. Non-dormant but unsprouted potato tubers failed to respond to the gibberellic acid. Treatment of young potato stems as they emerged from the soil, however, resulted in a very marked response. 4. The following responses by different parts of plants resulted from the application of gibberellic acid. Stems: Once stem elongation had been initiated, most of the treated plants developed longer internodes than in the controls, including internodes above the treated portion of the plant. Some treated plants developed very thin, threadlike stems; in others, these elongated stems thickened as the plant matured and finally reached a greater diameter than those of control plants (fig. 1). Leaves: Most treated plants developed leaves that were temporarily lighter gr