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The phytochromes, a family of photoreceptors that maximally absorb red (R) and far-red (FR) light, play an important role in defining the architecture of the plant and consequently its value in the market. In this work, we evaluated the manipulation of light quality as an alternative to the use of plant growth regulators (PGRs) to produce poinsettia plants (Euphorbia pulcherrima Willd. ex Klotzsch) without affecting commercial quality parameters. ‘Freedom Red’ poinsettia plants were cultivated in two light environments characterized by different R/FR ratios in combination with or without one application of PGR. We used a photoselective film that significantly reduced the FR component of the light and a transparent film to obtain high and low R/FR ratios (5.7 and 1.1, respectively). Plants cultivated under a high R/FR ratio were shorter and more compact than those grown under transparent film. Other quality characters like bract and leaf area, dry weight, stem diameter, number of lateral branches, and plant width did not differ significantly between light treatments. Flowering time was slightly delayed in plants grown under a high R/FR ratio compared with those cultivated under the control treatment. Additive effects were detected between light quality and PGR factors indicating that light quality manipulation is an alternative strategy to reduce or to replace the use of PGRs in commercial production systems that usually require several PGR applications.
In vitro germination of immature seeds of Jacaranda mimosifolia treated with gibberellic acid (GA3) was studied. Immature seeds were collected monthly after crossings and sown on Murashige and Skoog (1962) medium with 3.0% sucrose and 0.6% agar after soaked 24 hours with 0, 10, 100, and 500 mg·L–1 GA3 solutions. Though germination was observed in the immature seeds harvested 2 months after crossing (2 MAC), the rate was quite low. When immature seeds of 3 MAC treated with 100 or 500 mg·L–1 GA3 solution were cultured, >60% germination were obtained within 2 weeks after culturing. These results indicate that immature seeds of 3 MAC treated with adequate GA3 solutions, seedlings can be obtained precociously and the period from crossing to the seedling stage was shorter than for mature seeds.