Use of Tomato Juice in the Asymbiotic Germination of Orchid Seeds

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Abstract
Germination and growth data indicate that tomato-juice-agar solns. are more effective than the synthetic culture media containing only sugar and salts (solns. B and C) used generally for the asymbiotic germination of orchid seeds. These tomato-juice solns. are more strongly buffered in the pH range, 4.5-5.5, for good growth, even when the concn. of KH2PO4 in the synthetic solns. is increased from 0.025% to 0.6%; likewise the pH values in the good growth range are not altered by auto-claving. Apparently the availability of the iron compounds in the tomato-juice solns. is not affected by either autoclaving or continued growth. Ashing of the tomato-juice solns. indicates that organic rather than inorganic compounds are responsible for the enhanced growth. A protein hydrolysate, rich in amino acids and vitamins, added to the inorganic solns., allowed even more rapid growth than the tomato-juice media. Concns. of protein hydrolysate greater than 1%, however, are toxic to Cymbidium embryos. In general, on organic culture media the protocorms fail to differentiate, only increasing in size. As the agar dries out, thus leaving a space between the agar and the flask, those protocorms not resting on the media but on the walls of the flask do differentiate, producing seedlings sturdier than those on solns. B and C, and hence lowering the mortality rate upon transplantation. When the enlarged undifferentiated protocorms are transplanted to osmunda fiber, differentiation occurs, and in 2 weeks sturdy seedlings begin to develop.

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