RESUMO
In flowering plants, guidance of the pollen tube to the embryo sac (the haploid female gametophyte) is critical for successful fertilization. The target embryo sac may attract the pollen tube as the final step of guidance in the pistil. We show by laser cell ablation that two synergid cells adjacent to the egg cell attract the pollen tube. A single synergid cell was sufficient to generate an attraction signal, and two cells enhanced it. After fertilization, the embryo sac no longer attracts the pollen tube, despite the persistence of one synergid cell. This cessation of attraction might be involved in blocking polyspermy.
Assuntos
Magnoliopsida/fisiologia , Estruturas Vegetais/citologia , Estruturas Vegetais/fisiologia , Pólen/fisiologia , Técnicas de Cultura , Células Germinativas/citologia , Células Germinativas/fisiologia , Lasers , Magnoliopsida/citologia , Reprodução , Sementes/fisiologia , Raios UltravioletaRESUMO
From the aerial parts of Verbascum (V.) sinaiticum, V. thapsiforme, V. fruticulosum and Celsia roripifolia, seven new saikosaponin homologues, called mulleinsaponins I-VII, having 13,28-epoxy-olean-11-ene skelton were isolated together with eight known saikosaponin homologues, 3-O-beta-D-fucopyranosyl saikogenin F, saikosaponin a, desrhamnosylverbascosaponin, songarosaponins C, D, mimengoside A and buddlejasaponins I, IV. The structures of mulleinsaponins I-VII were characterized as 3-O-beta-D-glucopyronosyl-(1-->3)-beta-D-fucopyranosyl-6-deoxy- saikogenin F, 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->3)-beta-D - fucopyranosyl-16-deoxysaikogenin F, 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->3)-beta-D - fucopyranosyl-saikogenin F, 3-O-alpha-L-rhamnopyranosyl- (1-->4)-beta-D-glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->2)]-be ta -D-fucopyranosyl-21 beta-hydroxysaikogenin F, 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->3)-[beta- D- glucopyranosyl-(1-->2)]-beta-D-fucopyranosyl-21 beta-acetoxysaikogenin F, 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D- glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->2)]-beta-D- fucopyranosyl-16 beta-acetoxysaikogenin F and 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl- (1-->3)-[beta-D-glucopyranosyl-(1-->2)]-beta-D-fucopyranosylsaikogeni n F 16-O-beta-D-glucopyranoside, respectively, from chemical and spectroscopic evidence.