Growth Patterns of Plants Developed from Immature Embryos in Artificial Culture

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Abstract
Methods and results are given in culturing embryos of 12 vars. of sweet cherry (Prunus avium), 5 of sour cherry (P. cerasus), 3 of European plum (P. domestica), 2 of American plum (P. ameri-cana), 32 of peach (P. persica), 1 of apricot (P. armeniaca), 5 of apple (Malus domestica), and 4 of pear (P. communis and P. communis X P. serotina), during 5 growing seasons, 1932-1936 inclusive. Over 20,000 individual cultures were made. Material was cultured from Georgia and from 3 locations in New York State. Embryos in culture do not pass through the embryonic stages characteristic of embryos on the mother plant; they enter at once into an independent development characteristic of the age of the embryo when excised. The growth pattern for peach embryos treated with a disinfectant and grown on 0.6% agar media with 0.5% glucose and salt mixture T is described. (a) no development earlier than 51 days of age after full bloom; (b) 51 days, spreading and greening of the cotyledons and small white epicotyledonary leaves; (c) 73 days, cotyledons green, hypocotyl 2-4 mm. and roots 10-15 mm. in length, central axis of epicotyl 1-2 mm. in length terminated by rosette of 6-10 small white stipule-like appendages; 80 days, roots 10 to 20 mm. long, central axis of epicotyl 7-15 mm. long surmounted by rosette of 8-12 anomalous, white, stipule-like appendages; (d) 87 days, vigorous root development, central axis of epicotyl 20-22 mm. long, terminated by rosette of green stipule-like appendages; (e) 94 days, vigorous root development, central axis of epicotyl 25-30 mm. long, terminated by rosette of small, green stipule-like appendages, occasional peachlike but malformed leaves; (f) 105 days, vigorous root formation, stem 40-45 mm. long terminated by rosette of small, green stipule-like leaves, with peach-like leaves along the stem; (g) 108 days, vigorous root and shoot development but leaves often broad and crinkled and plants dwarfish; (h) 118 days, vigorous root and shoot growth but dwarfish plants. After 30 days in subdued light at 45[degree]F., dwarfish plants began normal development and showed no further abnormal behavior. Embryos of sour cherry, sweet cherry, apricot, plum, apple, and pear behaved similarly with minor differences. Aseptic methods resulted in earlier response than when a disinfecting agent was used, but growth patterns were similar. Very young embryos were injured by a disinfectant. Growth patterns were modified by altering the medium, especially glucose, in which at early stages of development glucose was beneficial and at later stages inhibiting. The data are discussed with reference to physiological changes in the embryo itself, juvenile and adult forms of plants, and general problems of morphogenesis.

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