High temperature affects flowering time and flowering shoot morphology differently in poinsettia
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Six cultivars of poinsettia (Euphorbia pulcherrima Willd. Ex Klotzsch) were grown in greenhouses in Overton, Texas, USA to determine the effects of elevated temperature on flowering time and morphology. Plants were potted in late August and pinched to 4 nodes three weeks later for natural season flowering. Half of the plants were exposed to a high temperature treatment consisting of a daily average temperature of 27C from early September until the end of October. For the rest of the forcing period and for the other half of the plants, an average daily temperature of 22C was maintained. Dates of first bract color, visible bud, and anthesis were recorded for each plant. Plants of 'Advent Red', 'Premier Red', 'Jubilee', and 'Tikal Red' reached first bract color, visible bud, and anthesis at similar times regardless of temperature treatment. However, 'Prestige Early Red' and 'Prestige Red' were delayed in all aspects by the high temperature treatment. At anthesis, number of leaves, transitional bracts, and fully expanded and pigmented bracts were recorded for each of the two distal flowering shoots on each plant. Effects of high temperature on plant morphology were not related to timing of floral developmental events. High temperature resulted in more transitional bracts and greater total number of nodes per shoot regardless of cultivar. However, high temperature resulted in more leaves and fewer fully expanded bracts per shoot for 'Jubilee', 'Prestige Early Red', and 'Prestige Red' while leaf and bract count increased for 'Advent Red', but were similar for 'Premier Red' and 'Tikal Red'.
XXIX INTERNATIONAL HORTICULTURAL CONGRESS ON HORTICULTURE: SUSTAINING LIVES, LIVELIHOODS AND LANDSCAPES (IHC2014): INTERNATIONAL SYMPOSIUM ON ORNAMENTAL HORTICULTURE IN THE GLOBAL GREENHOUSE
