M LAN AND KONZAK: MUTATION INDUCTION EFFICIENCY 455 



is known and unless oxygen, temperature, and after-effects have 

 been adequately controlled. Certainly, information is now avail- 

 able that will provide greater precision, repetition, and prediction 

 in seed radiation experiments. A discussion of the techniques and 

 methods that should be followed in all seed radiation experiments 

 will be summarized by the authors in an early issue of Radiation 

 Botany. 



As we consider the needs of future plant breeders in terms of 

 genetic variability and of techniques for manipulating this vari- 

 ability, it is imperative that we keep abreast of modern advances in 

 genetics and biochemistry. Many of these advances may well pro- 

 vide means of inducing mutations in plants with greater efficiency 

 than ever before possible with physical or chemical mutagens. The 

 oene mutation controlling elements of McClintock and Brink, and 

 gene transduction through plant viruses may well be a future means 

 for inducing high frequencies of directed mutations in crop plants. 

 These and other similar possibilities, however, may be completely 

 overshadowed when we consider that deoxyribonucleic acid (DNA), 

 the basic genetic material, may soon be synthesized artificially. When 

 this is accomplished and when methods for its incorporation into 

 reduplicating chromosomes are found, man may have his most 

 powerful means for controlling and directing the heredity of the 

 plants and animals upon which he depends for his survival. 



References 



1. Bowen, H. J. M. 1961. Effects of seed extracts on radiosensitivity. 



In Effects of Ionizing Radiations on Seeds and Their Significance 

 for Crop Improvement. Proc. Sci. Symp. Sponsored by I.A.E.A. 

 and F.A.O., Karlsruhe, Germany, Aug. 8-12, 1960. 



2. and Thick, J. 1960. Factors from seed extracts that mod- 

 ify radiosensitivity. Radiation Res., 13: 23-1-241. 



3. Caldecott, R. S. 1959. Post-irradiation modification of injury in 



barley — its basic and applied significance. Proc. 2nd Geneva 



Conf. on Peaceful Uses of Atomic Energy, 27: 260-269. 

 4. . 1959. Irradiation and plant improvement. In Germ Plasm 



Resources in Agriculture. Symp. Sponsored by Amer. Assoc. Adv. 



Sci. Dec. 1959, 1-12. 

 5. . 1961. Seedling height, oxygen availability, storage, and 



temperature: Their relation to radiation-induced genetic and 



