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ISHS Acta Horticulturae 1104: XXIX International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (IHC2014): International Symposium on Ornamental Horticulture in the Global Greenhouse

Temperature affects seed germination of native Australian Gomphrena and Ptilotus species differently

Authors:   C.J. Currey, R.G. Lopez, R.L. Cave, D.K. Harrison, M.E. Johnston
Keywords:   dormancy, base temperature, optimum temperature, degree days
DOI:   10.17660/ActaHortic.2015.1104.71
Seed germination is influenced by several environmental factors, including light and temperature. Several native Australian taxa in the Amaranth family (Amaranthaceae) have ornamental qualities that are prerequisites for commercialization of a new crop. Our objective was to quantify the effect of temperature on seed germination of native Australian forbs with desirable ornamental qualities. We germinated seeds of Gomphrena flaccida, Ptilotus exaltatus, P. spicatus, and P. macrocephalus across temperatures ranging from ≈8 to 30C on a thermal gradient table. Seeds were monitored daily for germination. After 28 d, germination of P. macrocephalus and all three P. spicatus seed lots was 0 to 5 or 8%, respectively, across all temperatures. Alternatively, up to 85 and 90% of G. flaccida and P. exaltatus seeds germinated, respectively. The time to initial germination (t1) of G. flaccida was delayed by ≈5-11 d for temperatures below 17C, whereas t1 of P. exaltatus was delayed by ≈5-9 d at 11C compared to warmer temperatures. Although the metabolic rate of G. flaccida and P. exaltatus is similar, as indicated by reciprocal time to median germination (1/t50), the range of base (Tb) and optimum temperatures (Topt) for germination benchmarks varied between species. Our data indicate that G. flaccida requires higher temperatures during germination for maximizing cumulative germination and minimizing germination time compared to P. exaltatus.

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