title: Developing fruit direct post-floral morphogenesis in Helleborus niger L.
abstract: In fertilized flowers of Helleborus niger L., the sepals (the showy elements of the perianth at anthesis) grow, spread, and turn green, and the peduncles elongate. These processes did not proceed to completion when the pistils were removed at the bud stage, but could be restored by the application of plant growth regulators. Cytokinins and gibberellins stimulated the formation of well-developed chloroplasts in, and spreading of, the sepals; the gibberellin, GA3, and the auxin, 4-chloroindole-3-acetic acid, promoted peduncle elongation. In fruit-bearing flowers, on the other hand, paclobutrazol, an inhibitor of gibberellin biosynthesis, reduced chlorophyll formation in the sepals, reversed sepal spreading, and inhibited peduncle elongation. Of the endogenous growth regulators in developing fruit, the following cytokinins were identified: zeatin, dihydrozeatin, N6-(2-isopentenyl)adenine and their ribosides and 9-glucosides. Zeatin riboside drastically increased in abundance (about 200 times), shortly after fertilization, when chlorophyll accumulation in the sepals occurred at the fastest rate, and remained the most prominent identified cytokinin until seed ripening.
authors.affiliation: Ruether Bosković Institute, Bijenicka c. 54, PO Box 180, HR-10002 Zagreb, Croatia.
authors.forename: Branka
authors.initials: B
authors.lastname: Salopek-Sondi
authors.forename: Maja
authors.initials: M
authors.lastname: Kovac
authors.forename: Tatjana
authors.initials: T
authors.lastname: Prebeg
authors.forename: Volker
authors.initials: V
authors.lastname: Magnus
mesh_terms: D000465:Algorithms; D002734:Chlorophyll / Q000037:antagonists & inhibitors; D003583:Cytokinins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D005638:Fruit / Q000187:drug effects / Q000254:growth & development* / Q000648:ultrastructure; D005875:Gibberellins / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000494:pharmacology; D008854:Microscopy, Electron; D009024:Morphogenesis; D010937:Plant Growth Regulators / Q000494:pharmacology; D018547:Plant Stems / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D018087:Plastids / Q000187:drug effects / Q000648:ultrastructure; D029626:Ranunculaceae / Q000187:drug effects / Q000254:growth & development*; D012098:Reproduction / Q000502:physiology; D014230:Triazoles / Q000494:pharmacology
chemical_list: D003583:Cytokinins; D005875:Gibberellins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D014230:Triazoles; D002734:Chlorophyll; C096198:4-chloroindole-3-acetic acid; C053370:paclobutrazol; C007842:gibberellic acid