The control of flower initiation by gibberellin in Helianthus annuus L. (sunflower), a non-photoperiodic plant |
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Authors: | Julieta A S Almeida M Fátima D A Pereira |
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Institution: | (1) Departamento de Fisiologia Vegetal, IB, Universidade Estadual de Campinas, CP6109, CEP., 13083-970 Campinas, SP, Brazil |
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Abstract: | The involvement of gibberellins in the control of flowering of sunflower was studied by direct application of GA3 to the apex of the plants, analysis of the endogenous levels of gibberellin-like substances at different plant ages, and indirectly by the application of paclobutrazol, an inhibitor of gibberellin synthesis. GA3 speeded-up flower initiation and floral apex development. The time of GA3 application was more critical than the amount of GA3 applied. The endogenous levels of gibberellin-like compounds increased significantly by day 15 after sowing. The application of paclobutrazol markedly delayed floral initiation and this effect was also depedent on plant age. Both GA3 and paclobutrazol had their greatest effects between 10 and 20 days after sowing suggesting that an increase in gibberellins in that time period plays a role in floral initiation. |
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Keywords: | Helianthus annuus floral initiation gibberellins floral apex analysis |
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