Factors affecting the aseptic culture of Lovell peach seedlings

THIS PAPER PRESENTS investigation of factors affecting the germination and growth of Lovell peach embryos. Presence of the cotyledons, length of after-ripening, sucrose, light, and a number of accessory substances are considered. The technique used consisted of aseptic stratification of Lovell peach seeds followed by the aseptic culture of the embryos on nutrient agar. The studies showed that reduction in the amount of cotyledons reduced over-all growth, and their complete removal prevented germination. With limiting amounts of the cotyledons the additional specific effect of inhibiting internode elongation appeared. Root length was not reduced until about 90 per cent of the cotyledons were removed. Injury resulted in initial stimulation to shoot growth. Addition of sucrose to the medium tended to be inhibiting when large amounts of cotyledons were present but became stimulating as they were reduced, and with ecotyledonized embryos allowed germination, though growth was maintained for only 10 to 14 days, a rosettelike shoot developed, and root tips became blackened. Increasing the length of after-ripening tended to increase growth. In darkness, internode inhibition was not present, but inhibition in root elongation was evident and the cotyledons did not overcome root-tip blackening. The function of the cotyledons seemed to be twofold: (1) to produce growth of shoots, leaves, and roots; and (2) to provide a stimulus for growth after germination had started. As little as 1/16 of the cotyledons could carry out both functions. The effect of the cotyledons could not be replaced by any of the accessory substances tested, though some of them had a slight stimulating effect on shoot or root growth or both. A similarity between growth from ecotyledonized embryos (embryos with cotyledons removed), growth of excised immature embryos, and growth from non-after-ripened embryos is pointed out and the significance discussed.