Articles
HIGH TEMPERATURE DELAY OF FLORAL INITIATION IN MODERN POINSETTIA CULTIVARS
Article number
711_36
Pages
273 – 278
Language
English
Abstract
The relative sensitivity of floral initiation to high temperatures in 16 modern poinsettia cultivars was investigated in a 2-year study. Night interruption lighting was used to prevent early initiation during a 4-week vegetative growth period.
Temperature treatments were applied for 4 weeks after the cessation of night interruption lighting and photoperiod treatments were maintained through the completion of the experiments.
After temperature treatments ended, all plants were grown to maturity with moderate temperatures (26°±2°/21°±2°C day/night average). Two photoperiod treatments were used: natural days at 29°40’N latitude and 13-hour dark period.
In conjunction, two day/night temperature regimes were imposed: 24°/21°C (low) and 28°/24°C (high). For most cultivars, the date of first bract color, visible bud and anthesis were significantly delayed in the high temperature treatment under natural days compared to the low temperature treatment.
Delay in anthesis between the low and high temperature treatments ranged from 0 to 19 days; 0 days in the cultivars Orion and Early Freedom Red, 6 days in Freedom Red, 14 days in Prestige Red and 19 days in Cortez Burgundy. In an additional study, Prestige Red and Freedom Red were exposed to elevated temperatures for 7, 14, or 21 days after the onset of short-days, and compared to the low temperature control, flowering in Prestige Red was delayed 3, 6, and 10 days, respectively.
Flowering in Freedom Red was delayed only 0, 2, and 4 days, respectively.
Temperature treatments were applied for 4 weeks after the cessation of night interruption lighting and photoperiod treatments were maintained through the completion of the experiments.
After temperature treatments ended, all plants were grown to maturity with moderate temperatures (26°±2°/21°±2°C day/night average). Two photoperiod treatments were used: natural days at 29°40’N latitude and 13-hour dark period.
In conjunction, two day/night temperature regimes were imposed: 24°/21°C (low) and 28°/24°C (high). For most cultivars, the date of first bract color, visible bud and anthesis were significantly delayed in the high temperature treatment under natural days compared to the low temperature treatment.
Delay in anthesis between the low and high temperature treatments ranged from 0 to 19 days; 0 days in the cultivars Orion and Early Freedom Red, 6 days in Freedom Red, 14 days in Prestige Red and 19 days in Cortez Burgundy. In an additional study, Prestige Red and Freedom Red were exposed to elevated temperatures for 7, 14, or 21 days after the onset of short-days, and compared to the low temperature control, flowering in Prestige Red was delayed 3, 6, and 10 days, respectively.
Flowering in Freedom Red was delayed only 0, 2, and 4 days, respectively.
Authors
R.A. Schnelle, J.E. Barett, D.G. Clark
Keywords
Euphorbia pulcherrima, flowering, photoperiod, heat delay
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