THERMOMORPHOGENESIS IN POT PLANTS

Authors:	R. Moe, L.M. Mortensen
Keywords:	Thermomorphogenesis, pot plants, endogenous rhythm, DIF, flowering
Abstract: Plant morphogenesis was influenced more by the difference (DIF) between day temperature (DT) and night temperature (NT) than absolute temperature in a wide range of pot plants, including Campanula isophylla, Euphorbia pulcherrima and Begonia x hiemalis. Plant height and plant diameter increased as DIF increased. In Campanula DIF interacted with light quality in the following manner: Day-extension with light from incandescent lamps (low R/FR ratio) eliminated the negative DIF response, Day-extension with light from fluorescent lamps (high R/FR ratio) enhanced the negative DIF response. Stem elongation in plants is sensitive to temperature fluctuations during the daily 24-hour cycle. Euphorbia and Begonia internode lengths (plant heights) were significantly reduced when plants received a cool temperature pulse during the first 2 hours of the day. In Begonia the strongest response to cool temperature pulse was obtained during the last 2 hours of the night. A possible involvement of an endogenous rhythm in temperature sensitivity during the photoperiod is suggested.
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