Unravelling the role of temperature and photoperiod on Poinsettia heat delay

The effects of day temperature ( DT ) , night temperature ( NT ) , and night length ( NL ) were appraise on the flowering responses of heat - kind and heat - sensitive poinsettia ( Euphorbia pulcherrima Willd . ex Klotzsch ) cultivars Orion Red and Prestige Red , severally . Plants were placed under 60 DT × NT × NL treatments that consisted of three DT ( 20 , 24 , 28 ° C ) , four NT ( 16 , 20 , 24 , 28 ° C ) , and five NL for the first 17 Clarence Shepard Day Jr. of the experiment . After 17 days , all plant were consolidated to one nursery with an inductive environment and the timing of the first vividness , seeable bud , and flowering were recorded . ‘ Orion Red ’ reached anthesis 8 to 10 days faster than ‘ Prestige Red ’ across all NLs ; however , in both cultivars , days to flowering fall in a sigmoidal pattern as NL increased .

The relative charge per unit of progress to anthesis ( 1 / days to flowering ) under a 12 - hour NL was approximately half that of plant grow at a 13- or 14 - hour NL . At a 12 - time of day NL , the proportional charge per unit of progress to anthesis decreased linearly as DT increased for both cultivar . At 13- to 14 - hour NL , DT had relatively little upshot on the relative rate of progress to flowering . Thus , in high spirits DT stay flowering of both heat - kind and heat - sensible cultivars when flower founding occurred under NL , typical of naturally go on NLs in September and other October ( i.e. , 12 - hour NL ) , whereas high DT did not delay bloom for either cultivar under a 14 - time of day NL , which is typically supply under black cloth systems . In dividing line , the efflorescence responses to NT were quite different for the two cultivar . The heat - liberal cultivar designate comparatively petty variety in the proportional rate of progression to anthesis as NT increased from 16 to 28 ° coulomb within each NL treatment ; however , the heat - sore cultivar displayed a large decrease in the comparative rate progression to anthesis as NT increased from 20 to 28 ° C within each NL discourse .

Although the delayed unfolding that occurred at 28 ° C and 14 - minute NL was significant , the relative charge per unit of progress to blossoming at this discourse was significantly high than the 28 ° snow and 12 - hour NL treatment . This suggests that artificially expurgate NL to 14 hour with a black cloth organization does not foreclose heat energy hold of poinsettia , but it allows for more rapid flowering than if efflorescence installation occupy place under natural NL ( ≈12 minute ) . To summarize , high DT impact efflorescence when heyday initiation took position at 12 - hour NL for heat - tolerant and heating - sensitive poinsettia cultivars , whereas high NT uniquely stay flowering of the heat - sensitive cultivar at NL from 12 to 14 hour .

Alden , Michael & Faust , James . ( 2021 ) . ravel out the Role of Temperature and Photoperiod on Poinsettia Heat Delay . HortScience . 1 - 7 . 10.21273 / HORTSCI15874 - 21 .