ISHS Acta Horticulturae 435: II Workshop on Environmental Regulation of Plant Morphogenesis
THE ROLE OF GIBBERELLIN AND PHYTOCHROME IN DIF MEDIATED STEM ELONGATION |
| Authors: | G. Grindal, R. Moe |
| Keywords: | DIF, endogenous gibberellins, internode elongation, mutants, phytochrome status |
| Abstract:
This paper summarizes current knowledge of the effects of day and night temperature fluctuations on processes controlling stem elongation, in particular gibberellin metabolism and phytochrome. An increase in the difference between day and night temperature increases stem and internode elongation. Campanula isophylla responds to increasing difference between day and night temperature by increasing the level of endogenous gibberellin in the tissue, including the level of bioactive gibberellin (GA1). Down regulation of GA1 may be caused by irreversible 2  -hydroxylations (viz., GA53 2-OH-GA53) of precursors to GA1. The responses to differences between day and night temperature is observed when the day is extended by red light, while there is no effect of the temperature treatments with far-red light.
The current hypothesis is that phytochrome in the Pfr form is necessary for the response to differences in day and night temperatures.
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