Promotion of leaf sheath growth by gibberellic acid in a dwarf mutant of rice

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 (GA 3 ) 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 GA 3 . 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 GA 3 -induced growth, starch granules completely disappeared from leaf sheath cells, whereas dense granules remained in control plants. These ®ndings indicate that GA enhances cell elongation by increasing wall extensibility, osmotic concentration being kept unchanged by starch degradation. Materials and methodsPlant materials. Seeds of rice (Oryza sativa L. cv. Tan-ginbozu), a dwarf mutant derived from the cultivar Ginbozu, were a gift from Abbreviations: ABA cis-abscisic acid; 2,4-D 2,4-dichlorophenoxyacetic acid; GA n gibberellin A n ; GA 3 gibberellic acid; PAS Periodic acid-Schi reaction; PCIB p-chlorophenoxy-isobutyric acid; TIBA 2,4,5-triiodobenzoic acid

Rice HOX12 Regulates Panicle Exsertion by Directly Modulating the Expression of ELONGATED UPPERMOST INTERNODE1

“…For GA sensitivity analysis, the effect of GA 3 on shoot elongation was quantified as previously described (Matsukura et al, 1998) with some modifications. Seeds of wild-type and mutant plants were dehusked and sterilized with 3% NaClO solution for 0.5 h, washed three times with sterile distilled water, and incubated in 6.9 mM uniconazole for 24 h to block endogenous GA biosynthesis, followed by sterile distilled water for an additional 24 h after washing out the uniconazole.…”

Mutation of RiceBC12/GDD1, Which Encodes a Kinesin-Like Protein That Binds to a GA Biosynthesis Gene Promoter, Leads to Dwarfism with Impaired Cell Elongation

“…Shoot elongation was quantified as described (Matsukura et al, 1998) with modification. Seeds of the wild type and gdd1 (n > 25) plants were surface sterilized for 30 min with a 3% NaClO solution, washed three times with sterile distilled water, then placed on a 1% agar plate by adding GA 3 of 10 212 ;10 24 M and grown under fluorescent light at 308C.…”

Cell Wall Extensibility and Effect of Cell-Wall-Loosening Proteins during Rose Flower Opening

“…Cell wall extensibility may be a growth-limiting factor for petal expansion. In stems and coleoptiles, mechanical properties of the walls have been investigated by stressrelaxation and load-extension analyses evaluating auxin-, gibberellin-, and acid-induced increases in extensibility (Adams et al, 1975;Carpita and Kanabus, 1988;Hohl and Schopfer, 1992;Matsukura et al, 1998;Nakamura et al, 1975;Tanimoto and Masuda, 1971;Yamamoto et al, 1970). Creep extension has been performed to determine the yield threshold load of cell walls (Kutschera and Kende, 1988;Nakahori et al, 1991;Okamoto and Okamoto, 1994;Pritchard et al, 1990;Tomos and Pritchard, 1994).…”