Asymbiotic seed germination and in vitro seedling development of Habenaria macroceratitis (Orchidaceae), a rare Florida terrestrial orchid

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Continuing loss of native orchid habitat has lead to an increased emphasis on orchid conservation. Major obstacles in the production of native orchid seedlings for use in conservation have been: (1) development of efficient and reliable seed germination protocols and (2) an understanding of early seedling growth and development. Effects of six asymbiotic media (Modified Lucke, Murashige & Skoog, Lindemann, Vacin & Went, Malmgren Modified, Knudson C), four exogenous cytokinins (BA, Zea, Kin, 2-iP), and three photoperiods (0/24, 16/8, 24/0 h L/D) were examined on seed germination and early protocorm development of Habenaria macroceratitis, a rare native Florida terrestrial orchid. Finally, the effects of three photoperiods (8/16, 12/12, 16/8 h L/D) on in vitro seedling development were examined. Percent seed germination was highest on both LM and KC after seven weeks culture (LM = 89.1%, KC = 89.2%); however, protocorm development was enhanced on MM after both seven and 16 weeks. Both zeatin and kinetin at 1 μM enhanced seed germination (Zea = 58.1%, Kin = 47.2%). Final percent seed germination (91.7%) and protocorm development (Stage 4) was increased in the absence of light (0/24 h L/D). In vitro seedlings cultured under 8/16 h L/D conditions produced the highest number of tubers per seedling (1.06) with the greatest tuber (42.7 μg) and shoot (fwt = 69.5 μg) biomass and tuber diameter (3.1 mm).

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