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UBC Theses and Dissertations

Effects of plant growth regulators and temperature on floral induction and development of Exacum Styer Group Sand, Laura Marie


Plants of Exacum Styer Group, interspecific hybrids from five Sri Lankan taxa from the Gentian family, have significant horticultural potential as flowering potted plants, bedding plants and cut flowers. However, a better understanding of the requirements for floral induction and flower development is needed before commercialization. Experiments examining the impact of plant growth regulators (PGRs) on floral induction and subsequent plant development consisted of seven treatments: ethephon (500 and 1000 PPM), daminozide (2500 and 3500 PPM), gibberellin (GA₄₊₇ at 10 and 15 PPM), and a control of water plus surfactant. Analysis of data collected on weeks to anthesis resulted in a significant interaction between treatment and genotype indicating that genotypes did not behave uniformly across treatments. Overall, the effect of PGR treatments on flowering of E. Styer Group is impacted more by genotype than by chemical with late flowering genotypes less affected by chemical than earlier flowering genotypes. Nonetheless, daminozide effectively reduced stem length without dramatic negative impact on flowering and can be considered safe for commercial production. Experiments to evaluate the effect of temperature on floral induction and subsequent plant development consisted of four temperature treatments over two seasons (one treatment repeated in both seasons). The two most extreme treatments prevented flowering for some or all genotypes (35° C DT/31° C NT and 16° C DT/12° C NT, respectively). Intermediate treatments (23° C DT/19° C NT and 30° C/26° C NT) were optimal for fastest flowering depending on genotype. As with the response to PGR treatments, significant genotypic variation was observed in response to temperature indicating production schemes must be developed empirically for each individual genotype. However, the optimal temperature for fast flowering and attractive plant conformation is likely between 21° and 28° C average daily temperature for most E. Styer Group genotypes and should be used as a starting point for future studies. In addition, a cultivar series of E. Styer Group should be selected based on common production responses, not based on genetic relationships.

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