The Duration of Differentiation in Excised Anthers

Abstract

THE ADVANTAGES, as well as the difficulties, of cultivating excised anthers or isolated microspore mother cells for the study of meiosis are well recognized by those who have attacked such problems. One of the earliest successful steps in this direction was that of Shimakura (1934), who was able to get Tradescantia microspore mother cells to proceed from metaphase I through both divisions of meiosis in a solution containing 7.93 per cent sucrose, with the pH adjusted to 7.2-7.3. In an attempt to determine the causes of the initiation of meiosis, Gregory (1940) reported the successful culture of anthers of Lilium longiflorum. However, when these were excised earlier than diplotene, meiosis failed. In those excised previous to the initiation of meiosis the sporogenous tissue failed to advance into meiotic divisions. Mitosis continued for several days, after which the cells of the sporogenous tissue changed into vacuolated and elongated, parenchymatous cells. Cultures of Datura and tomato anthers were unsuccessful. La Rue (1938) was able to maintain stamens of Tradescantia paludosa alive, but not actively growing, in cultures for a year. With these experiments in mind, an attempt has been made to analyze the development of the sporogenous tissue of anthers of Tradescantia paludosa (Karl Sax's Clone 5) in various media and to evaluate the usefulness of the technique in solving problems of meiosis and differentiation in general. TEcHNIQUE.-Inflorescences were surface-sterilized by rinsing for 2-3 min. in a 2.5 per cent solution of sodium hypochlorite (half-strength Clorox) with a trace of some detergent such as Glim. This was followed by a rinse in sterile distilled water. Buds of the desired size were removed to steri1a filter paper and dissected under a widefield binocular microscope over which was mounted a dustproof transparent leucite hood. A 15-watt G. E. germicidal lamp was fixed inside the hood and allowed to burn 15-20 min. before the dissections were to be made. Such precautions effectively prevent contamination while the anthers are removed and transferred to culture media by means of small dissecting knives. The first medium tried was that suggested by White (1943) for tissue culture. However, for most of the cultures a basic medium similar to that used by Bonner (1943) for isolated roots and by Loo (1945) for excised stem tips was used. This is prepared by dissolving in sufficient triple distilled water to make 1 liter: 40 g. sucrose; 236 mg. Ca(NOs:)2 4H2O; 36 mg. MgSO4 7H20; 81 mg. KN03; 65 mg. KCI; 20 mg. KH2PO4 and 1 ml. of a solution of 1 g. FeCl3 and 1 g. tartaric acid