Classification of the Stem Elongation Pattern in Ornamental Plants under Different Day and Night Temperature Conditions

We investigated the pattern of stem elongation in response to temperatures in the light and dark periods in 6 bedding plants and 2 potted plants. The plants that responded well to different day and night conditions (DIF) could be classified into 2 groups. In the first group comprising plants Northpole and Verbena, the stem elongated mainly in the light period, and in the second group comprising plants chrysanthemum and Habotan, the stem elongated mainly in the dark period. Moreover, in the case of Zinnia, which exhibited an opposite reaction to DIF, stem elongation was observed in the dark period as the temperature increased. In the case of French marigold, Snapdragon, and Stock, which were not affected by DIF, stem elongation was not observed even when the temperature in the light and dark periods was varied.