**2. The history of gamma radiation as applied to biological systems**

Most are familiar with the discovery of x-radiation by Roentgen in 1895 and the isolation of radium by the Curies in 1898 (Goodspeed and Uber 1939). Researchers soon learned that both x-rays and radioactive substances such as radium produced similar effects on biological materials. Koernicke (1905) noted that cell division was delayed on x-ray and radium treated cells. Both Koernicke (l905) and Gager (1907) described "striking chromosomal disruptions" after cells were dosed with x-rays or exposed to radium, a gamma emitter. Gamma irradiated cells were also broken or fragmented by radiation treatment (Gager 1907, 1908). For additional historical work on radiation and plant cytogenetics the reader is directed to a review article by Goodspeed and Uber (1939). Smith (1958) compiled a paper on the use of radiation in the production of useful mutations based on papers presented in three symposia in the United States from August 1956 to January 1957. A more recent review article on ionizing radiation damage to plants was prepared by Klein and Klein (1971).

There are numerous studies applying gamma radiation to biological systems. Several investigations involving botanicals follow. Nuttall et al (1961) found that yellow sweet Spanish onions exposed to 4000 or 8000 rad prevented sprouting in 97% of their experimental group suggesting that irradiation might be a viable method of prolonging storage life for onions. This study, while intriguing, has not been generally accepted by a public concerned with the problems of radiation. A second article by Heeney and Rutherford (1964) examined the effects of gamma radiation on the storage life of fresh strawberries. A dose of 330,000 rad prevented fungal development of the redcoat strawberry variety stored at 40 degrees F for 26 days. The fugal free period was sharply reduced at lower radiation doses and/or at higher temperatures. Pritchard et al (1962) studied the effect of gamma radiation on the utilization of wheat straw by rumen microorganisms. They concluded that, "high levels of gamma radiation were needed to release nutrients trapped in wheat straw needed by microbes. However, the levels of gamma irradiation necessary for nutrient release were well above what was practical for commercial purposes."

Baumhover et al (1955) investigated the use of gamma irradiation on male sterilization on the control of screw-worm flies in the southern United States while Bushland (l960) Cutcomp (l967) and Lawson (1967) discussed this practice as a general way of controlling certain insect pests. Gambino and Lindberg (1964) examined the response of the pocket

Gamma rays are external emitters that penetrate biological materials easily and produce their insidious effects without being taken internally. Alpha and beta particles are internal emitters; their damage to organisms is greatest when taken internally. Odum (1971) summarizes this concept best, "the alpha beta gamma series is one of increasing penetration but decreasing concentration of ionization and local damage." Alpha and beta radiation, unlike gamma radiation, are corpuscular in nature. While alpha particles travel but a few centimeters, and can be stopped by a layer of dead skin, they are dangerous because they produce a large amount of local ionization which can cause mutations disrupting cell processes. Beta particles are high speed electrons. While much smaller than alpha particles, they are able to travel up to a couple of centimeters in living tissue, giving up their energy over a large path. Beta particles, like alpha particles can damage tissue, and like alpha

particles, can cause mutations that affect the functioning of cells.

Klein and Klein (1971).

**2. The history of gamma radiation as applied to biological systems** 

Most are familiar with the discovery of x-radiation by Roentgen in 1895 and the isolation of radium by the Curies in 1898 (Goodspeed and Uber 1939). Researchers soon learned that both x-rays and radioactive substances such as radium produced similar effects on biological materials. Koernicke (1905) noted that cell division was delayed on x-ray and radium treated cells. Both Koernicke (l905) and Gager (1907) described "striking chromosomal disruptions" after cells were dosed with x-rays or exposed to radium, a gamma emitter. Gamma irradiated cells were also broken or fragmented by radiation treatment (Gager 1907, 1908). For additional historical work on radiation and plant cytogenetics the reader is directed to a review article by Goodspeed and Uber (1939). Smith (1958) compiled a paper on the use of radiation in the production of useful mutations based on papers presented in three symposia in the United States from August 1956 to January 1957. A more recent review article on ionizing radiation damage to plants was prepared by

There are numerous studies applying gamma radiation to biological systems. Several investigations involving botanicals follow. Nuttall et al (1961) found that yellow sweet Spanish onions exposed to 4000 or 8000 rad prevented sprouting in 97% of their experimental group suggesting that irradiation might be a viable method of prolonging storage life for onions. This study, while intriguing, has not been generally accepted by a public concerned with the problems of radiation. A second article by Heeney and Rutherford (1964) examined the effects of gamma radiation on the storage life of fresh strawberries. A dose of 330,000 rad prevented fungal development of the redcoat strawberry variety stored at 40 degrees F for 26 days. The fugal free period was sharply reduced at lower radiation doses and/or at higher temperatures. Pritchard et al (1962) studied the effect of gamma radiation on the utilization of wheat straw by rumen microorganisms. They concluded that, "high levels of gamma radiation were needed to release nutrients trapped in wheat straw needed by microbes. However, the levels of gamma irradiation necessary for

nutrient release were well above what was practical for commercial purposes."

Baumhover et al (1955) investigated the use of gamma irradiation on male sterilization on the control of screw-worm flies in the southern United States while Bushland (l960) Cutcomp (l967) and Lawson (1967) discussed this practice as a general way of controlling certain insect pests. Gambino and Lindberg (1964) examined the response of the pocket mouse to ionizing radiation. McCormick and Golley (1966) presented data on irradiation of natural vegetation in the southeastern United States while Monk (1966) published a similar study on the effects of short-term gamma radiation on an old field. Witherspoon (1965, 1969) examined radiation damage to a forest surrounding an unshielded fast reactor in l965, and followed this study with a report in 1969 on radiosensitivity of forest tree species to acute fast neutron radiation. Odum and Pigeon (1970) researched the effect of irradiation and ecology of a tropical rain forest in Puerto Rico.
