Fisiologia da germinação das cipselas heteromórficas em Bidens L

• Autor(a) principal: Souza Filho, Paulo Roberto de Moura [UNESP]
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/123306; http://www.athena.biblioteca.unesp.br/exlibris/bd/cathedra/06-05-2015/000828559.pdf
• topic: Plant physiology; Fisiologia vegetal; Germinação; Plantas - Reprodução; Pericarpo (Botânica)

Bidens is an Asteraceae genus that presents heteromorphic cypsela which differ in the germination behavior. For the genus, the pattern is that the peripheral cypselae have lower germination rate than the central ones. The objectives were to investigate which are the intrinsic diaspora factors that are related to different germination behaviors, and how that strategy varies in the nature. We initially focused in the fruit (or pericarp) from eight Bidens species to verify if there is a pattern in it structure and chemical composition on the different morphotypes and relate to its germination processes (Chapter 1). We verified that the type pericarps differ anatomically, but it are not related to germination difference. On the other hand, the secondary compounds composition of the fruits showed difference between the types, thus it was related to the physiological difference. Then, to verify by which way the hormonal control and pericarp constraints differ in the dicarpic species germination, we used Bidens pilosa as dicarpic model species (Chapter 2). As results, the types did not differ in the response to abscisic acid (ABA), hormone that induces dormancy: both types showed similar sensitivity and did not catabolize ABA. When the cypselae were treated with exogenous gibberellic acid (GA3), germination promoter hormone, the central type answer to low concentration. However, when endogenous GA synthesis was blocked, both types presented similar sensitivity to added GA3. Also were tested the physical and chemical influence from the fruit. When fruits were removed, the isolated peripheral seeds germinated faster than intact cypsela, but the final germination percentage difference were kept between the types. When the intact cypsela were treated with fruit extracts, just the central types suffered inhibition from peripheral fruit extract. We discuss the possible nature and inhibition mechanisms of the compound, that still unknown...