Growth Patterns of Plants Developed from Immature Embryos in Artificial Culture

Abstract

1. Methods and results are given in culturing embryos of twelve varieties of sweet cherry (Prunus avium), five of sour cherry (P. cerasus), three of European plum (P. domestica), two of American plum (P. americana), thirty-two of peach (P. persica), one of apricot (P. armeniaca), five of apple (Malus domestica), and four of pear (P. communis and P. communis x P. serotina), during five growing seasons, 1932 to 1936 inclusive. More than 20,000 individual cultures have been made. Material has been cultured from Georgia and from three locations in New York State. 2. Embryos in culture do not pass through the embryonic stages characteristic of embryos on the mother plant. Instead they enter at once into an independent development characteristic of the age of the embryo when excised. 3. The growth pattern for peach embryos treated with a disinfectant and grown on 0.6 per cent agar media with 0.5 per cent glucose and salt mixture T may be summarized as follows: (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 to 4 mm. and roots 10 to 15 mm. in length, central axis of epicotyl 1 to 2 mm. in length terminated by rosette of six to ten small white stipule-like appendages; 80 days, roots 10 to 20 mm. in length, central axis of epicotyl 7 to 15 mm. in length surmounted by rosette of eight to twelve anomalous, white, stipule-like appendages; (D) 87 days, vigorous root development, central axis of epicotyl 20 to 22 mm. in length terminated by rosette of green stipule-like appendages; (E) 94 days, vigorous root development, central axis of epicotyl 25 to 30 mm. in length terminated by rosette of small, green stipule-like appendages, occasional peachlike but malformed leaves; (F) 105 days, vigorous root formation, stem 40 to 45 mm. in length terminated by rosette of small, green stipule-like leaves, with peachlike 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. 4. After 30 days in subdued light at 45⚬ F., dwarfish plants began normal development and showed no further abnormal behavior. 5. Embryos of sour cherry, sweet cherry, apricot, plum, apple, and pear behaved similarly with minor differences. 6. 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. 7. 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. 8. The data are discussed with reference to physiological changes in the embryo itself, juvenile and adult forms of plants, and general problems of morphogenesis.