Effects of temperature, light and plant growth regulators on fuel-efficient poinsettia production
Odula Francis, Faust James Brown, White Sarah, Adelberg Jeffrey and Bridges William.
Thesis, Master of Scince (Plant and Environmental Scince), Clemson University. 65pages. 2011
2011
บทคัดย่อ
Experiments were carried out to determine the effects of Fascination (a plant growth regulator), production temperature, light, and cold pre-harvest temperature on bract expansion, cyathia development, and retention for fuel-efficient poinsettia production.
The first experiment (Chapter 2) examined the effects of the plant growth regulator Fascination on bract expansion of poinsettias grown at relatively cool production temperatures. Fascination increased plant height at 15.5 and 18 °C for both cultivars. Therefore, Fascination has the potential to increase bract size of 'Freedom Early Red' poinsettias that have been grown at 15.5 °C; however, temperature will need to be increased to 18 °C to attain marketable bract size.
The second project (Chapter 3) included three experiments to determine the effect of temperature and light on poinsettia cyathia development. In the first experiment, 'Prestige Red' plants were grown at 18, 20, or 22 °C and three different shade levels (0, 50 or 75%) resulting in average daily light integrals (DLI) of 4.2, 2.1, or 1.1 mol . m-2 d-1 , respectively, from the start of short days. In the second experiment, 'Prestige Red' plants were grown from the start of short days at 20 °C and under one of three daily light integral (DLI) treatments (0, 50 or 75% shade). In the third experiment, five poinsettia cultivars ('Advent Red', 'Early Freedom Red', 'Jubilee Red', 'Prestige Red', and 'Prestige Early Red') were moved at the start of visible bud to different greenhouses that had average daily set point temperatures of 15.5, 18, 20, or 22 °C.
The third experiment (Chapter 4) examined the effect of pre-harvest temperatures on post-harvest longevity of flowering. Five poinsettia cultivars were grown at standard greenhouse production temperatures until anthesis of the primary cyathium. Assuming that 14 days of secondary cyathia retention in the postharvest environment is considered to be acceptable, 'Advent Red' and 'Polar Bear' met this criterion following four weeks of pre-harvest, cold temperatures. 'Polly's Pink' met this criterion following one week of cold pre-harvest temperature. 'Prestige Red' and 'Freedom Early Red' did not meet this criterion even when no cold pre-harvest environment was provided.
In conclusion, our first experiment, Fascination application rate of 10 ppm resulted in a significant increase in bract area for 'Freedom Early Red' if the application date was relatively late in bract development, e.g., 3 to 4 weeks after first color, and the air temperature was sufficiently warm, e.g., 18 °C. For 'Prestige Red', the trend was that bract area increased at 18 °C and 10 ppm Fascination; however these treatments were not statistically different from the control. Increases in 'Freedom Early Red' height were observed with the Fascination treatments that also positively increased bract area. Our results showed that Fascination can be used for fuel-efficient poinsettia production to increase plant height and bract expansion when the plants have experienced reduced bract size due to low temperature production.
In the second experiment, cyathia development increased as temperature or light increased. At 22 °C and 0% shade treatment, 70% of the shoots had cyathia that reached the nectar stage, while no shoots reached the nectar stage at 18 or 20 °C. No cyathia development occurred at 18 °C, regardless of light level. Similarly, no more than 10% of the shoots displayed cyathia development at 75% shade, regardless of temperature. The DLI treatments that had cumulative light levels of 42.9 to 56.1 mol . m-2. d-1 during the two weeks preceding data collection successfully developed to the nectary gland stage. In contrast, DLI treatments that had cumulative light levels from 14.0 to 28.1 mol m-2. d-1 during the two weeks preceding data collection did not develop to the nectary gland stage.