Identifying the Temporal Sensitivity of Poinsettia Flowering to High Temperatures

The objective of this study was to identify the specific weeks and night lengths when poinsettia ( Euphorbia pulcherrima Willd. ex Klotzsch) flowering is most sensitive high temperatures. One experiment conducted in greenhouses under natural daylength (ND) conditions at lat. 34.7°N starting on 4 Sep, a second growth chambers with an initial length (NL) 11 hours 01 minutes that increased by 2 min/d simulate ND through September October. Each week, one group plants moved from moderate-temperature environment [22 °C average daily temperature (ADT)] high-temperature 28 ADT. spent 1 week before returning environment. treatments lasted for 7 or 8 chamber greenhouse studies, respectively. Additional groups were kept either moderate- entire treatment period as controls. Four cultivars used study: Advent Red, Freedom Prestige Tikal Red; only Red study. identified heat-tolerant cultivar followed Red. ‘Advent Red’s’ sensitivity temperatures ranged Sep Oct. ‘Tikal ‘Freedom Red’ had longer sensitivity: 22 ‘Prestige longest encompassing 29 Oct, minute 12 37 NL Within periods temperatures, time visible bud anthesis affected earlier weeks, final bract color development first more during latter weeks. As varied their duration duration, well magnitude response temperature, should be considered future breeding projects.