Abstract
THE Vol. BO T AN I C AL JANUARY-MARCH, REVIEW No. 1 FACTORS AFFECTING THE GERMINATION OF ORCH ID SEEDS 1 JOSEPH ARDITTI Department of Organismic Biology University of California Irvine, California 9266.f Introduction The orchid seed Orchid mycorrhiza and symbiosis Asymhiotic investigations Mineral nutrition _ .. _ Nitrogen nutrition .. The effects of sugars and other carbohydrates The effects of vitamins The effects of hormones . The effects of complex additives The effects of temperature The effects of light The effects of pH The effects of the atmosphere and its components The effects of moi sture The effects of miscellaneous factors . The nature of the factors required by germinating orchid seeds A note on the literature . Literature Cited ...... .. INTRODUCTION The Orchidaceae is one of che largest and most diverse of all plant families, consisting of 500- 800 genera and 20,000-30,000 species (Garay 1960, Schulces and Pease 1963). le is also among che masc widely distributed. Its representatives may be found from che Arctic to the Antarctic; in bogs, deserts, valleys, plains, hills, mountains, and even below ground (Hatch 195 3). Sizes of orchid planes vary from a few ( 3-4) mm. co several meters, whereas flowers may range from 2-3 mm. co 15-20 cm. or more in diameter. Some flowers are beauciful, e.g., Cattleya Lindi. and Phalaenop1i1 Blume, but 'Supported in pa rt by grants from the American Orchid Society, The Loeb Foundation, The Orchid Society of Southern California, and The Society of Sigma Xi.
Highlights
The Orchidaceae is one of che largest and most diverse of all plant families, consisting of 500- 800 genera and 20,000-30,000 species (Garay 1960, Schulces and Pease 1963). le is among che masc widely distributed
Proceeding on the assumption that orchid tubers contain all that is required by germinating orchid seeds, successful arrempts were made to germinate Cattleya X Laelia hybrid seeds on salep (Bernard 1909)
Inasmuch as hydrochloric acid is frequently employed to adjust pH of culture media (Scott and Arditti 1959) and several chlorides are used as culrure media components, it appears safe t0 assume that orchid seeds and seedlings are fairly resistant to this ion at least in the concentrations used (Table III)
Summary
The Orchidaceae is one of che largest and most diverse of all plant families, consisting of 500- 800 genera and 20,000-30,000 species (Garay 1960, Schulces and Pease 1963). le is among che masc widely distributed. THE BOTANICAL REVIEW others are grotesque, e.g., Gongora Ruiz & Pav. and Stanhopea Frost & Hooker They may be of almost any color from pure white to almost pitch black ( none are pure black ). 20 additional years had to pass before orchid seeds were germinated asymbiotically on a medium containing inorganic salts and sucrose (Knudson 1921, 1922). At least three distinct periods may be delineated in the investigations dealing with orchid seed germination. Investigations were at first limited to observation and later, following the discovery of orchid mycorrhiza, to srudies of symbiotic relationships (Bernard 1899, 1900, 1903, 1904a, b, 1905, 1906a, b, 1908, 1909, Ramsbottom 1922a, b, 1929, Wolff 1923a, Lami 1927a, Cordemoy 1904, Burgeff 1936, 1959). At present investigators are attempting the srudy of the physiology of orchid seed germination in the light of modern physiological, biochemical, and molecular biological concepts (Raghavan and Torrey 1963, 1964, Ardicci 1965a,c, In Press a, In Press c)
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