A. H. Sparrow and G. Fassuliotis, “Preliminary report of x-ray studies on the golden nematode,” Plant Disease Reporter 39, 7 (July 15, 1955): 572.
Note: This paper describes research carried out by Brookhaven researcher Arnold H. Sparrow and his collaborator G. Fassuliotis at the USDA Nematode Research Laboratory in Hicksville, NY, with support from the U.S. Atomic Energy Commission (AEC). Sparrow and Fassuliotis knew, based on work Sparrow had done at Brookhaven with Eric Christensen, that radiation could help preserve potatoes and prevent them from sprouting in storage. Sparrow and Fassuliotis’s work involved another problem that plagued potato growers, the golden nematode worm, an agricultural pest that had traveled the world from its point of origin in South America and had reached Long Island by the 1930s. It was difficult to detect when a potato field had become infested with these worms, and once there they were very hard to eradicate. They did not infest the potatoes themselves, but they damaged the root systems of plants and reduced the yield significantly. Sparrow and Fassuliotis subjected the cysts that contained the worm’s eggs to a bombardment of x-rays, and determined that radiation killed the eggs. “The lowest dose found to inhibit the development of embryonated eggs is the same as the dose found to inhibit completely the sprouting of potatoes.” In other words, there might be a single dose that would deal with both problems.
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A. H. Sparrow and E. Christensen, “Improved storage quality of potato tubers following exposure to gamma radiation from cobalt60,” Nucleonics 12, 8 (August 1954): 16-17.
Note: In this paper, Sparrow and Christensen describe how they subjected potatoes to varying amounts of radiation to see how this would affect the vegetables’ shelf life. They found that above a certain dose, radiation inhibited sprouting and the potatoes remained fresher when stored for long periods of time; there was also a point at which increasing the intensity of radiation brought no additional benefits. The work was based on previous research at Brookhaven that indicated that radiation might help preserve potatoes, and they authors planned to conduct further tests in collaboration with scientists at the Long Island Vegetable Research Farm in nearby Riverhead. Sparrow and Christensen’s research was “carried out,” as a note at the end of the article indicates, “under the auspices of the U. S. Atomic Energy Commission.” This was precisely the type of research that the AEC wanted to support in the 1950s, research that showed peaceful applications of nuclear technology that would be of interest to the general public. Nucleonics Magazine, in which this article was published, was a journal dedicated to nuclear research that ran from the late 1940s to the late 1960s. It was accessible to laypeople interested in atomic technology — as many were during the Cold War.
A. H. Sparrow and W. R. Singleton, “The use of radiocobalt as a source of gamma rays and some effects of chronic irradiation on growing plants,” The American Naturalist 87, 832 ( Jan-Feb. 1953): 29-48.
Note: In this paper, Sparrow and Singleton give a brief overview of the history of using radiation to induce mutations in plants. This work went back to the 1920s. The “advent of the atomic energy program” had changed things, however, making it possible to expose plants to more intense radiation for much longer periods of time (29). The paper goes on to describe the gamma field at Brookhaven and how the apparatus worked, offering several photographs and illustrations. The project had begun in 1949, and by 1953, preliminary results were available, including the kinds of anomalies produced by various doses of radiation over different periods of time. These were of interest to scientists interested in figuring out the genetic basis of heredity, but there was also a larger picture. As the authors noted, “one of the objectives of the cytological study was to find out what amount of radiation would give a significant increase in chromosome aberration” (36-37). In 1953, when this paper was published, tests of hydrogen bombs had raised concerns about the long term effects of exposure to nuclear fallout — it had not been immediately apparent to the designers of the first nuclear weapons that the radiation could harm or kill more living things than the explosion itself. Historians of science have noted that there was significant interest in the 1950s in the chromosomal effects of radiation exposure, for plants and animals but in particular for people. What sort of mutations were caused at what levels of exposure? Were the changes hereditary? The readers of Sparrow and Singleton’s paper would have had these concerns in mind as they read it, even though the experiment was carried out on plants.
DOI: https://doi.org/10.1086/281753
Singleton, “The effect of chronic gamma radiation on endosperm mutations in maize,” Genetics 39, 5 (Sept. 1954): 587-603.
Note: This paper addresses the relationship between the amount of radiation a corn plant receives and the rate of endosperm mutations. (The endosperm is the starchy tissue on the inside of seeds that nourishes the developing plant embryo. Along with the germ and the bran, is the part of the plant that we eat.) The relationship between the two turned out not to be linear. Higher amounts of radiation produced disproportionately higher numbers of mutations. There also seemed to be a threshold dose required to produce more mutations than would occur naturally.
DOI: https://doi.org/10.1093/genetics/39.5.587
C. F. Konzak, “Stem rust resistance in oats induced by nuclear radiation,” Agronomy Journal 46, 12 (December, 1954): 538-540.
Note: In this paper, Konzak describes an experiment designed to determine whether irradiation of seeds could produce genes for disease resistance in agricultural plants. Specifically, he wanted to produce oats resistant to oat stem rust. The oat seeds were irradiated using the thermal column of Brookhaven’s reactor. (A thermal column is a part of research reactors containing large volume of graphite that slows and traps neutrons in order to irradiate samples placed inside the column.) These seeds were planted in Aberdeen, Idaho in 1952, and the seeds from this first generation were sown at Brookhaven in 1953. It appeared that mutations leading to rust-resistance had appeared in 48 irradiated seeds, as opposed to 1 in the non-irradiated control group. The resistance appeared to be heritable, as a single dominant “factor.” Konzak concluded that “the results favor the idea that radiations made be profitably used in plant breeding programs since disease reaction and other plant characteristics appear to be alterable toward greater agronomic usefulness” (540).
DOI: 10.2134/agronj1954.00021962004600120002x
C. F. Konzak, “Radiation-induced mutations for stem rust resistance in oats,” Agronomy Journal 51, 9 (Sept. 1959): 518-520.
Note: This paper is an example of something that happens frequently in science — promising initial results don’t pan out. Konzak had previously irradiated oat seeds and grown a few generations of plants from these seeds, separated from other oat plants. Among these plants were a number resistant to oat stem rust. Konzak had believed that the resistance originated in mutations caused by the irradiation of the initial set of seeds. However, further research revealed that the genes causing resistance to oat stem rust had come from oat plants growing in a nearby field unrelated to the experiment, which had pollinated some of the experimental plants. Konzak had thought that his experimental field was far enough away from other fields to prevent this, but this turned out not to be the case. Further experiments with seed irradiation — and stricter isolation of the resulting oat field — produced a few plants with resistance to rust, but far fewer.
DOI: https://doi.org/10.2134/agronj1959.00021962005100090003x
Y. Sagawa and G. A. L. Mehlquist, “The mechanism responsible for some x-ray induced changes in flower color of the carnation,” American Journal of Botany 44 (1957): 397-403.
Note: This paper has to do with the color of carnations, and the mechanism or mechanisms by which radiation might change them. It was known that irradiating carnations could cause color changes — but how could researchers be sure that the change was due to a genetic mutation? (In this case, it was assumed that it was a somatic genetic mutation, i.e. a mutation of non germline cells. If you were to take the seeds from a plant with a somatic mutation and plant them, the child plants would not have the mutation. But carnations can be propagated by cuttings — essentially, taking part of an existing plant and planting it — and in this case, the child plant has the same traits as the parent, or at least the part of the parent that formed the cutting.) The radiation might be affecting the plant in other ways and causing a change in color through other means. To test if this might be the case, these two researchers, one from Brookhaven and the other from the University of Connecticut, showed that not all color changes in carnations were created equal. They irradiated cuttings of red, pink and white carnations and recorded the color of the flowers that appeared months later when the cuttings had grown. Among the red carnations, a very small percentage of cuttings produced brick red or white flowers. Among the pink and white ones, a much larger percentage, nearly all, produced red flowers. The researchers determined that two different mechanisms were likely at work. In the case of the few red carnations that turned white through irradiation, the mechanism probably was a genetic change. But pink and white carnations were different. It was already known that these two particular types of pink and white carnation, Pink Sim and White Sim, were so-called “periclinal chimaeras,” that is, they were genotypically red carnations with a mutation of a specific layer of cells on the stem involved in forming the flower. Radiation destroyed this layer of cells, “which was followed by regeneration” of this layer “from the more deep-seated cells,” which had the gene for red flowers. Thus, the irradiated shoots produced red flowers (402-403). This was important for both geneticists and plant breeders because it indicated that not every change that occurred as a result of radiation exposure was necessarily genetic — radiation could affect plants in many different ways, and it was important to be sure of the mechanism if you wanted to study or commercialize the change.
DOI: 10.2307/2438508