Manipulation of flowering in cineraria. II. Juvenility

Abstract

SummaryCompetence to perceive florally inductive stimuli was examined in cineraria cvs Cindy Blue and Cindy Dark Red. Juvenility was observed in imbibed, but not germinated, seeds and persisted until the initiation of a critical number of leaves which defined transition to the senisitive, competent form at 6–7 leaves initiated in cv. Cindy Blue and 7–8 leaves initiated in cv. Cindy Dark Red. During this juvenile phase, plants were incompetent to perceive either chilling at 3°C and 6°C as a vernalization stimulus or short days as a photoperiodic stimulus. After phase transition, the level of competence was not affected by plant age or size. Chilling imbibed seeds at 4°C for four weeks reduced the leaf number below the flower in both cultivars. The competent stage for vernalization during germination appeared between radicle emergence and cotyledon unfolding. The seed vernalization effect was only apparent when plants from chilled germinated seeds were grown subsequently at a non-vernalizing temperature (ca...