Promotion of leaf sheath growth by gibberellic acid in a dwarf mutant of rice |
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Authors: | Chiaki Matsukura Shin-ichi Itoh Keisuke Nemoto Eiichi Tanimoto Junji Yamaguchi |
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Affiliation: | (1) Bioscience Center and School of Agricultural Sciences, Nagoya University, Chikusa-ku, Nagoya 464-01, Japan, JP;(2) Faculty of Agriculture, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan, JP;(3) Institute of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya 467, Japan, JP |
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Abstract: | The mechanism of gibberellin (GA)-induced leaf sheath growth was examined using a dwarf mutant of rice (Oryza sativa L. cv. Tan-ginbozu) treated in advance with an inhibitor of GA biosynthesis. Gibberellic acid (GA3) enhanced the growth of the second leaf sheath, but auxins did not. Measurement of the mitotic index and cell size revealed that cell elongation rather than cell division is promoted by GA3. Gibberellic acid increased the extensibility of cell walls in the elongation zone of the leaf sheath. It also increased the total amount of osmotic solutes including sugars in the leaf sheath, but did not increase the osmotic concentration of the cell sap, due to an accompanying increase in cell volume by water absorption. In the later stage of GA3-induced growth, starch granules completely disappeared from leaf sheath cells, whereas dense granules remained in control plants. These findings indicate that GA enhances cell elongation by increasing wall extensibility, osmotic concentration being kept unchanged by starch degradation. Received: 28 August 1997 / Accepted: 16 October 1997 |
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Keywords: | : Gibberellin Leaf sheath elongation Cell extension Cell wall extensibility Oryza (dwarf mutant) Starch degradation |
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