ISHS Acta Horticulturae 305: First European Workshop on Thermogenesis and Photomorphogenesis in the Cultivation of Ornamentals
THE DYNAMICS OF CHRYSANTHEMUM STEM ELONGATION IN RELATION TO DAY AND NIGHT TEMPERATURES |
| Authors: | Jason R. Tutty, Peter R. Hicklenton, David N. Kristie |
| Abstract:
High resolution studies of Chrysanthemum revealed distinctive patterns of internode elongation rate. These patterns were apparently the result of the temperature and photoperiodic conditions under which the plants were grown. Internode elongation was sensitive to the relationship between day and night temperatures with maximum elongation resulting from exposure to high day and low night temperatures (27.7 °C day/12 °C night). Records of stem growth over 24 hour periods revealed no difference in elongation rate between plants grown in constant temperature (18.3 °C), or in low day/high night (11.4 °C day/24 °C night) temperature regimes. These findings did not, however, correspond with observations on plants grown to harvest under similar conditions where internodes were significantly shorter in the low day/high night temperature plants. It appears, therefore, that the duration of growth of an individual internode may also be affected by the temperature regime under which the plant is grown. Applying low temperature pulses (8.3 °C) at the start of the photoperiod changed the daily pattern of internode elongation. In plants grown to harvest, early photoperiod, low temperature pulses applied for as little as two hours significantly decreased plant height. In comparison with plants grown at constant 18.3 °C, flowering was slightly delayed when plants were grown at 25.7/12 °C and when a low temperature (8.3 °C) pulse was applied for two hours at the start of the photoperiod. The greatest delay in flowering occurred when plants were grown under 11.5/24 °C conditions. | |
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