ISHS Acta Horticulturae 272: Symposium on Bedding and Pot Plant Culture
TEMPERATURE CONTROLLED LEAF UNFOLDING RATE IN HIBISCUS |
| Authors: | Meriam G. Karlsson, M. E. Hackmann, Royal D. Heins |
| Abstract:
Leaf unfolding rate of Hibiscus rosa-sinensis 'Brilliant Red' and 'Pink Versicolor' was determined in the temperature range of 5° to 35°C. Plants grown at 5° and 11°C developed chilling injury. At 5°C, plants did not survive and at 11°C, plants grew very slowly. The two cultivars unfolded leaves at similar rates over the 11° to 35° temperature range. Daily leaf unfolding rate was described as a cubic polynomial function of temperature (T) where leaves day-1 = 0.0628876 – 0.0202625 * T + 0.0017497 * T2 - 0.00002983 * T3. Based on this function, predicted leaf unfolding varied from 0.012 leaves day-1 at 11° to a maximum of 0.229 leaves day-1 at 32°C. A linear function (leaves day-1 = -0.113 + 0.01148 * temperature) could approximate the curvilinear leaf unfolding relationship in the range from 11° to 29°C. Using the linear function, a degree-day relationship was calculated to 0.0115 leaves day-1 using a base of 9.8°C. Alternatively, 87 degree-days were required to unfold one leaf. Both the linear model and the cubic model predicted leaf unfolding within 0.5 leaves in a commercial Florida greenhouse over a seven week period. | |
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