MORPHOLOGICAL RESPONSES OF BEDDING PLANTS TO 3 GREENHOUSE TEMPERATUREREGIMES

Seedling crops of gazania, geranium, marigold, mimulus, pansy, verbena and vinca were grown to 60% anthesis in three greenhouse temperature regimes: (a) 26 degrees C day/6+/-3 degrees C night (LT), with a 16.5 degrees C mean daily temperature (MDT), (b) 26 degrees C day/l7 +/- 4 degrees C night, with a 21 degrees C MDT, and (c) variable day/night t emperatures in response to heating and cooling by a phase change mater ial energy storage module (PCM) with an 8 +/- 2 degrees C night and a 16 degrees C MDT. Crops bloomed from 2 to 17 days earlier in the 26 de grees C/17 degrees C greenhouse. The morphological characteristics of ah cultivars of gazania, mimulus, pansy and verbena, geranium and vinc a were similar regardless of greenhouse temperature regime. Marigold d iploid and triploid cultivars and mimulus were morphologically more va riable than the other bedding plant species. Crops grown in the PCM an d LT greenhouses had virtually identical morphological characteristics and bloomed in about the same number of days. Plant height was not af fected by DIF environments in the greenhouses. The PCM and LT greenhou ses had a similar MDT, but the distribution of numbers of hours of mea n daily temperatures was different.