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The Influence of Gibberellic Acid and Indoleacetic Acid on Cotton Embryos Cultured In vitro

1957; University of Chicago Press; Volume: 118; Issue: 4 Linguagem: Inglês

10.1086/335951

1940-1205

Leon Dure, William A. Jensen,

Research in Cotton Cultivation

1. Embryos of upland cotton (Gossypium hirsutum) at two ages, having fresh weights of 37 and 64 mg., were cultured for 10 days in four different media: (a) Cultured control, complete medium containing inorganic salts and sucrose. (b) IAA, complete medium plus indoleacetic acid 10-5 M. (c) IAA/GA, complete medium plus indoleacetic acid 10-5 M and gibberellic acid 10-5 M. (d) GA, complete medium plus gibberellic acid 10-5 M. 2. Fresh and dry weights of the embryos and cell numbers of the cotyledons and axes individually were obtained for the various groups of each culture. After freeze-drying, biochemical determinations for total nitrogen and total carbohydrate were found and calculated on a per embryo and per cell basis. Starch and aleurone protein were identified by microscopic examination of sectioned material. These determinations were made on samples both of the initial embryos and after 10 days of culturing. 3. The embryos of the 37-mg. culture showed no capacity for cell division or elongation, nor could this be induced by IAA or GA. Expansion of cotyledon cells and accompanying large water uptake were encountered; both responses were intensified by GA and IAA/GA. Sucrose was taken up and stored as starch. Little nitrogen appeared to be taken up, and the degradation of aleurone grains in the cotyledons seemed to supply any protein needed in cell expansion of those organs. 4. The 64-mg. embryos demonstrated a capability for cell division and elongation in the axis. There was evidence for the synthesis of protein and cell-wall material in the cultured controls. If this growth was inhibited (IAA), the sucrose taken up was stored as starch, giving high values for dry weight and for carbohydrate per embryo and per cell. If there was very rapid cell division and elongation (cultured control and GA groups), there was no starch formed, and there was less dry weight and less carbohydrate per embryo and per cell, presumably as a result of the expenditure of energy. Carbohydrate per cell was so low in the GA cultures that a dilution of cell-wall material is believed to have occurred in the accelerated cell division and elongation of this group. A dilution of protoplasm is also suggested in this group as a result of the apparent inhibition by GA of nitrate uptake or of protein synthesis. Embryos grown without GA exceeded the initial values for nitrogen per embryo, suggesting a capacity for protein synthesis. 5. The only synergistic effect found in the IAA/GA culture was in water uptake. 6. There was no cell division in the cotyledons of any group.