ISHS Acta Horticulturae 394: Plant Bioregulators in Horticulture
CONTROL OF PLANT HEIGHT IN CAMPANULA ISOPHYLLA BY TEMPERATURE ALTERNATIONS; INVOLVEMENT OF GAS |
| Authors: | H. Ihlebekk, S. Eilertsen, S. Junttila, G. Grindal, R. Moe |
| Keywords: | Campanula, DIF, Gibberellin, Growth control, Stem elongation, Temperature-drop |
| Abstract:
The difference between day and night temperature (DIF) regulates internode growth in the long day plant Campanula isophylla (Moe, 1990). Low temperature during the photoperiod (negative DIF) decreases the stem elongation compared to a high day/low night temperature (positive DIF) combination. This paper presents the effect of low temperature pulses (temperature-drop) of three, six, nine, or twelve hours applied from the beginning of the photoperiod. Stem and internode length decreased and dry weight per cm of the stem increased with the increasing duration of the temperature-drop which improved the plant quality. For practical purposes a temperature-drop of at least nine hours during the photoperiod is required for growth control in Campanula. DIF is suggested to influence stem elongation by affecting the gibberellin (GA) metabolism and/or the tissue responsiveness to GA1 (Erwin, 1989; Moe, 1990). In our study, gibberellin application stimulated stem elongation with an increasing activity from GA19 to GA20 under all DIF conditions. The stem elongation increased further from GA20 to GA1 under negative DIF, while the effect was similar for GA20 and GA1 applications under positive DIF. Therefore, we conclude that DIF does not influence the stem elongation in Campanula by blocking the conversion of GA19 to GA20, but negative DIF may inhibit the conversion of GA20 to GA1. | |
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