Impact of Temperature on Autumn- and Spring-initiated Inflorescence Systems within a Biennial Pruning System of Protea ‘Pink Ice’ Cut Flowers

in HortScience

The potential impact of increasing temperatures driven by climate change on cultivated Protea cut flower production systems is not known. This study used a biennial pruning system in Protea ‘Pink Ice’ to track the physiological and reproductive responses in comparable phenological stages, but exposed to different seasonally determined temperature conditions. Protea ‘Pink Ice’ generally initiates inflorescences terminally on the spring flush. A limited number of shoots can initiate inflorescences on the preceding autumn flush, leading to an advanced harvesting time compared with that of the spring-initiated inflorescences. In a commercial Protea orchard in Hopefield, South Africa, gas exchange, carbohydrate availability, and vegetative and reproductive growth were compared between the two shoot types in the context of seasonal temperature differences. Leaves of shoots, which initiated inflorescences on the autumn flush, generally had higher light-saturated net carbon dioxide (CO2) assimilation capacities in autumn (April–May) and spring (October–November). There is evidence of a requirement of minimum shoot diameter of 7.6 mm (four- or five-flush shoot), as measured directly above the intercalation between the terminal (uppermost mature flush) and subterminal flush, when the subsequent flush was at budbreak stage during April (autumn) and at least five flushes to be required for floral initiation in Protea ‘Pink Ice’. Spring-initiated inflorescences had a shorter developmental period (4 months) than that of autumn-initiated inflorescences (7 months) and developed into significantly smaller (width) inflorescences with a lower width and dry weight at harvest. These inflorescences were harvested on average a month later compared with autumn-initiated inflorescences. The ambient temperature during inflorescence development played a significant role in the inflorescence growth rate, affecting the time required from visible inflorescence detection to harvest. At the calculated optimum base temperature of 9 °C, autumn-initiated inflorescences required 41,010 growing degree hours (GDH), whereas spring-initiated inflorescences required 35,872 GDH from initiation to anthesis. Under future warmer growing conditions, anticipated decreased size and dry weight of inflorescences may reduce marketability and income for Protea producers.

Contributor Notes

This research was financially supported by Cape Flora SA (CFSA), the National Research Foundation (NRF), and Stellenbosch University.

Corresponding author. E-mail: eugenie@arnelia.co.za.

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    Monthly mean, maximum and minimum temperatures (°C) from July 2007 to May 2009, and mean temperatures of the days on which gas exchange measurements were performed on 6-year-old Protea ‘Pink Ice’ shoots. Data were obtained from the Agricultural Research Council weather station at Koperfontein, 10 km from the experimental site at Arnelia Farms. The maximum and minimum temperature value was recorded per month, whereas the mean temperature is the calculated mean monthly temperature using mean daily temperatures. The line inserted at 25 °C enables a temperature comparison between the respective years. The seasons of the Southern Hemisphere is indicated with Wtr = winter; Spr = spring; Sum = summer; Aut = autumn.

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    Maximum rate of light-saturated net CO2 assimilation (Amax) ±se recorded in 6-year-old Protea ‘Pink Ice’ shoots from Apr. 2008 to Feb. 2009. These shoots initiated inflorescences terminally on either the autumn (n = 7) or spring (n = 23) flush. *Significantly different at P < 0.05; **significantly different at P < 0.01; ***significantly different at P < 0.001.

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    Light- and CO2-saturated rate of net CO2 assimilation (Asat) ±se recorded on 6-year-old Protea ‘Pink Ice’ shoots from Apr. 2008 to Feb. 2009. These shoots initiated inflorescences terminally on either the autumn (n = 7) or spring (n = 23) flush. *Significantly different at P < 0.05; **significantly different at P < 0.01; ***significantly different at P < 0.001.

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    Dark respiration rate (Rd) ±se recorded on 6-year-old Protea ‘Pink Ice’ shoots from Apr. 2008 to Feb. 2009. These shoots initiated inflorescences terminally on either the autumn (n = 7) or spring (n = 23) flush. *Significantly different at P < 0.05; **significantly different at P < 0.01; ***significantly different at P < 0.001.

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    Stomatal conductance (gS) ±se recorded on 6-year-old Protea ‘Pink Ice’ shoots from Apr. 2008 to Feb. 2009. These shoots initiated inflorescences terminally on either the autumn (n = 7) or spring (n = 23) flush. *Significantly different at P < 0.05; **significantly different at P < 0.01; ***significantly different at P < 0.001.

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    Vegetative shoot elongation of 6-year-old Protea ‘Pink Ice’ shoots from Apr. 2008 to Jan. 2009. These shoots initiated inflorescences terminally on either the autumn (n = 7) or spring (n = 23) flush.

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    Inflorescence width ±se (A) and length ±se (B) of 6-year-old plants of Protea ‘Pink Ice’ initiated terminally on either the autumn (n = 7) or spring (n = 23) flush.

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    The total soluble sugar ±se (A) and starch ±se concentration (B) expressed in glucose equivalents per gram dry weight as determined for mature leaves of the terminal flush of shoots of 6-year-old Protea ‘Pink Ice’, sampled from Apr. 2008 to Jan. 2009. *Significantly different at P < 0.05; **significantly different at P < 0.01; ***significantly different at P < 0.001.

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    The scheduling of potential Protea ‘Pink Ice’ phenological events during the course of an entire season in an unpruned (annual harvesting cycle) system, either when subjected to the current climate or when exposed to predicted warming scenarios. From March to July the sequence of events is similar for all scenarios, but differences become evident with the onset of spring budbreak and onward.

Article References

  • AllenS.E.GrimshawH.M.ParkinsonJ.A.QuarmbyC.1974Chemical analysis of ecological materials. Blackwell Scientific PublicationsOxford, UK

    • Search Google Scholar
    • Export Citation
  • ArnoldC.Y.1959The determination and significance of the base temperature in a linear heat unit systemJ. Amer. Soc. Hort. Sci.74430445

  • CaustonD.R.DaleM.P.1990The monomolecular and rectangular hyperbola as empirical models of the response of photosynthetic rate to photon flux density, with applications to three Veronica speciesAnn. Bot.380389394

    • Search Google Scholar
    • Export Citation
  • CoetzeeJ.H.LittlejohnG.M.2001Protea: A floricultural crop from the Cape Floristic KingdomHort. Rev.26148

  • CrileyR.A.ParvinP.E.LekawatanaS.1990Flower development in Leucospermum cordifolium ‘Vlam’Acta Hort.2646170

  • DischeZ.1962Color reactions of carbohydratesp. 475514R.L.WhistlerM.L.WolfromMethods in carbohydrate chemistryAcademic PressNew York, NY

    • Search Google Scholar
    • Export Citation
  • GerberA.I.2000Flower initiation and development in selected cultivars of the genus Protea. Stellenbosch University South Africa PhD Thesis

  • GerberA.I.GreenfieldE.J.TheronK.I.JacobsG.1995Pruning of Protea cv. Carnival to optimise economic biomass productionActa Hort.38799106

    • Search Google Scholar
    • Export Citation
  • GerberA.I.TheronK.I.JacobsG.2001aManipulation of flowering time by pruning of Protea cv. Sylvia (P. eximia × P. susannae)HortScience.36909912

    • Search Google Scholar
    • Export Citation
  • GerberA.I.TheronK.I.JacobsG.2001bThe role of leaves and carbohydrates in flowering of Protea cv. Lady DiHortScience.36905908

  • GreenfieldE.J.TheronK.I.JacobsG.1994The effect of pruning on growth and flowering response of Protea cv. CarnivalJ. S. Afr. Soc. Hort. Sci.44246

    • Search Google Scholar
    • Export Citation
  • HamidG.A.Van GundyS.D.LovattC.J.1985Citrus nematode alters carbohydrate partitioning in the ‘Washington’ navel orangeJ. Amer. Soc. Hort. Sci.110642646

    • Search Google Scholar
    • Export Citation
  • HettaschH.B.GerberA.I.TheronK.I.1997Pruning Protea cv. Carnival for biennial crops of improved yield and qualityActa Hort.453127133

  • HettaschH.B.JacobsG.2006Leucadendron are short-day plants: A preliminary reportActa Hort.716113116

  • HoffmanE.W.2006Flower initiation and development of Protea cv. Carnival. Stellenbosch University South Africa PhD Diss. (Agric.)

  • HoffmanE.W.BellstedtD.U.JacobsG.2009Exogenous cytokinin induces “out of season” flowering in Protea cv. CarnivalJ. Amer. Soc. Hort. Sci.134308313

    • Search Google Scholar
    • Export Citation
  • HoffmanE.W.JacobsG.2010Phenology of and heat unit requirements for growth in Protea ‘Carnival’ induced by benzyladenine-containing growth regulatorsActa Hort.8697180

    • Search Google Scholar
    • Export Citation
  • LiangS.WuX.ByrneD.2017Flower-size heritability and floral heat-shock tolerance in diploid rosesHortScience.52682685

  • LouwE-L.HoffmanE.W.TheronK.I.MidgleyS.J.E.2015Physiological and phenological responses of Protea ‘Pink Ice’ to elevated temperaturesS. Afr. J. Bot.9993102

    • Search Google Scholar
    • Export Citation
  • MalanD.G.JacobsG.1990Effect of photoperiod and shoot decapitation on flowering of Leucospermum ‘Red Sunset’J. Amer. Soc. Hort. Sci.115131135

    • Search Google Scholar
    • Export Citation
  • MidgleyS.J.E.NewM.MethnerN.ColeM.CullisJ.DrimieS.DzamaK.GuillotB.HarperJ.JackC.JohnstonP.KnowlesT.LouwD.MapiyeC.OosthuizenH.SmitJ.van den BroeckD.2016A status quo review of climate change and the agriculture sector of the Western Cape Province. Report submitted to the Western Cape Department of Agriculture and the Western Cape Department of Environmental Affairs & Development Planning. African Climate & Development Initiative University of Cape Town Cape Town South Africa

  • NieuwoudtG.JacobsG.2010Time of pruning affects yield, flowering time and flower quality of Protea ‘Pink Ice’Acta Hort.8696370

  • ReedA.B.O’ConnorC.J.MeltonL.D.SmithB.G.2004Determination of sugar composition in grapevine rootstock cuttings used for propagationAmer. J. Enol. Viticult.55181186

    • Search Google Scholar
    • Export Citation
  • RiegerM.A.SedgleyM.1996Effect of daylength and temperature on flowering of the cut flower species Banksia coccinea and Banksia hookerianaAust. J. Expt. Agr.36747753

    • Search Google Scholar
    • Export Citation
  • SAS Institute Inc2003SAS 9.1.3 service pack 4. Cary NC

  • SedgleyM.FussA.M.1992Correct pruning lifts Banksia yieldsAustral. Hort.905053

  • SmithA.SteynW.J.HoffmanE.W.2015Involucral bract browning in Proteas—The what, how and what now?Acta Hort.1097125132

  • WebsterA.D.2005Shoot growthJ.TrompA.D.WebsterS.J.WertheimFundamentals of temperate zone tree fruit productionBackhuys PublishersKerkwerve, The Netherlands

    • Search Google Scholar
    • Export Citation

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