The loss of electrolytes and amino acids from gamma-irradiated carrot tissues to an aqueous medium was found to be both dose and dose-rate dependent. Calcium was the cation most readily leached, followed by copper, zinc, sodium, phosphorus, boron, iron, aluminum, and manganese. The rate of amino acid loss was extensive at doses above 500 krads. Aspartic acid was the amino acid most readily leached.

A study of the effect of 60 Co γ-radiation on the metabolism of glucose and various organic acids by carrot tissue was conducted. Radiation resulted in the increased absorption of glucose and pyruvate and the decreased absorption of acetate and succinate. Only a slight effect on glucose and pyruvate catabolism was found, but there was an increase in acetate and a decrease in succinate catabolism. Radiation produced a reduction in the anabolic utilization of all substrates. This included a reduced lipid synthesis from acetate and a net accumulation of this substrate within the tissues. The evidence points to the tricarboxylic acid cycle as being the source of radiation-accelerated CO 2 evolution. It is postulated that a relatively radiation-resistant bypass system is present in carrots which is capable of circumventing the radiation-depressed succinate utilization. The high-level-radiation degradation products of glucose produced no toxic effects on glucose metabolism.

The possible indirect effect of radiation through radiolysis of sucrose on carbohydrate metabolism of carrot cells was investigated. This was accomplished by study of the utilization of specifically labeled substrates in the presence of γ-irradiated aqueous sucrose. It was found that the presence of irradiated sucrose did not cause abnormality in the utilization of labeled glucose, acetate, or succinate. An apparent effect of irradiated sucrose on utilization of labeled glucose proved to be an artifact, probably due to radiolytic formation of glucose from sucrose. It was concluded that the Embden-Meyerhof-Paranas pathway, the pentose phosphate pathway, and the citric acid cycle of carrot cells were not affected by the presence of irradiated sucrose.

Studies were conducted to determine the effect of 60 Co γ-radiation on the radiosensitivity of free amino acids in metabolizing carrot tissue and on the synthesis of free amino acids from specifically labeled acetate. At 100-krad doses, the concentration of some amino acids decreased; at 500 krads, all were depressed; and at 1000 krads, the concentration of all amino acids was severely reduced. With the exception of isoleucine, glycine, valine, and phenylalanine, synthesis from labeled acetate of all amino acids occurred, with glutamate, serine, and aspartate being synthesized in the greatest amounts. In general, γ-radiation reduced synthesis from labeled acetate at all doses above 100 krads and severely inhibited synthesis at 1000 krads. Incorporation of the carboxyl carbon of acetate was generally less extensive and more radiation-reduced than that of the methyl carbon.