No abstract

No abstract

Radioactive sulphur (S35) with its weak beta radiation of 0.120 M.E.V. and its long half-life of 87 to 88 days (6, 8) has desirable characteristics as a biological tracer, particularly since its activity can be readily measured after recovery as barium sulphate (6). Further, as will be shown in the following paper (5), excellent autographs of thin sections of plant material can be made on photographic film. SEABORG (9) anld HA-MILTON (3, 4) lhave reviewed the literature up to 1941 on the use of radioactive elements as tracers in chemical and biological work. Radiosulphur in synthetic eystine, methionine, and thiamin as well as inorganic compounds, has been used in nutritional studies of animals (1, 10), but so far as is known, nutritional studies of plants using radiosulphur have not been reported. This paper describes experiments carried out in 1942 with radiosulphur furnished as barium sulphate*2 by Dr. J. G. HAMILTON of the Radiation Laboratory, University of California. The sulphur* was added to vegetation growing in the large sand cultures (13) both as a soluble sulphate* in the nutrient solution and as sulphur* dioxide in the air. No radiosulphur was available during the 1943 season. Methods and results DESCRIPTION OF THE PLOTS Six plots of mixed wheat and barley were treated between June 6, and June 30, 1942, three with sodium sulphate*, and three with sulphur* dioxide. A similar treatment was applied to a pair of Bancross corn plots on Sept. 16 to 18. The principal agronomic details of these plots are summarized in table I. Each of the wheat and barley plots had two rows of Federation spring wheat, one row of Velvon barley, and two rows of no. 54A-40 winter wheat supplied by the Utah Experiment Station. The winter wheat remained in the vegetative state until harvest, tillering continuously. The barley andl spring wheat plants began to head out during the first week of June. They began to flower about the middle of June, and their lower leaves and beards began to dry up at the end of June. The barley was a few days ahead of the wheat in all these processes. Ripeniing was well advanced, particularly of the primary heads, by the middle of July and the plots were harvested 1 This is the sixth of a series of papers on "The Effect of Prolonged Low Concentrations of Sulphur Dioxide Upon Plants." 2 The asterisk following sulplhur refers to active preparations containing sulphur of atomic weight 35.

No abstract

This investigation is essentially a collaboration between two laboratories bringing together problems in which each is interested.The Department of Agricultural Research of the American Smelting and Refining Company has long been interested in the problems of sulphur toxicity and sulphur metabolism in plants which are economically important. In the course of this work investigations have been made by the use of S35. These have shown the general distribution of the isotope in the plant body. To some extent chemical procedures have been employed to identify in the protein hydrolysate specific sulphur-containing compounds, notably cystine and probably methionine (8, 9, and 10). It remained, however, necessary to obtain unequivocable evidence on the sulphur compounds into which the isotope had entered.In the Department of Botany at Rochester, investigations have been in progress since 1946 utilizing the techniques of paper chromatography to identify the free and combined amino acids in plants (2, 6, and 7). The sulphur-containing amino acids present rather special problems. Due to the small quantities commonly present and the poor reactivity of these substances with ninhydrin, they tend to be less easily detectable by the methods of paper chromatography than many of the other amino acids (1). Furthermore, as two-directional paper chromatograms are commonly carried out (i.e., using phenol: collidine-lutidine), the sulphur-containing amino acids tend to be obscured by others which are commonly present. Methionine sulphoxide occupies the same area as y-amino butyric acid, a newly discovered free amino acid which is widely distributed (4, 6, and 7). Methionine itself is close to the leucines, and cystine can best be recognized if it is first converted to cysteic acid which occupies a posit-ion on the chromatograms well apart from other amino acids (1). In these circumstances the use of S35 combined with autoradiographs of paper chromatograms is an obvious device to aid in the identification of the sulphur-containing amino acids.In the laboratories of the American Smelting and Refining Company alfalfa plants were treated with S35 in the form of sulphate. The alfalfa