The effect of 3-indoleacetic acid on the response of Lactobacillus arabinosus 17-5 to nicotinamide

Lactobacillus arabinosus 17-5 has been widely used as an assay organism for nicotinic acid (NA) since the development of the method by Snell and Wright (1). Although it has been realized that other substances present in tissue extracts may interfere with the bioassay, the nature of such substances has not been elucidated. During an investigation of tryptophan metabolism in the pea plant, we studied the possible conversion of this compound to nicotinic acid, since such a transformation has been demonstrated to occur in numerous organisms (2-4). The method involved infiltration of tissue with large quantities of tryptophan and subsequent bioassay for nicotinic acid with Lactobacillus arabinosus 17-5. Certain anomalous results led us to believe that other metabolites of tryptophan were interfering with the assay. Because 3-indoleacetic acid (IAA) is a known plant metabolite of tryptophan (5), we tested it for possible interference with the assay, and, as described below, found that such interference may occur under certain circumstances

Cultivation of Tomato Tissues Capable of Forming Flowers and Fruits in Vitro

The final phase of this research project was designed to develop a practical method for producing a steady supply of fresh cherry tomato fruits over a period of several months, for possible use as a fresh vegetable supplement to a standard diet of astronauts on extended missions. This effort was successful. We were able to excise immature flowers from Pixie tomato plants grown in a controlled condition room, implant them on artificial media under aseptic conditions, and get them to develop into edible fruits in a little over a month. The medium (Murashige-Skoog) was purchased from Sigma, supplemented with sugar plus a synthetic analog of the plant hormone cytokinin, and adjusted to pH 5.8. A temperature of at least 25 C and visible light helped to produce ripe red fruits within 7 weeks. To ensure a steady supply of such tomatoes, we found it possible to store the explanted flower buds in MS medium at 5 C for at least 6 weeks without significant loss of ability to develop into fruits. This means that many containers could be prepared before launch and put into a refrigerator; a convenient number could then be removed periodically to guarantee a succession of harvests during the life of an extended mission. Details are found in the attached reprints. Subsequent applications for funds for flight or continued research were denied, and the project was terminated

An Uncolored View of Chlorophyll

A plant physiologist casts a critical eye on the current chlorophyll craze