SECRETARY'S REPORT 77 



The Director attended and contributed to the International Geo- 

 physical Year conference at Barcelona, Spain, September 1956, and the 

 International Federation of Astronautics Congress at Rome in Sep- 

 tember 1956. He was panel leader of and contributor to an Astronau- 

 tics Symposium, San Diego, January 1957, sponsored by U. S. Air 

 Force, Office of Scientific Research, and by the Convair Corp. 



In national science and defense, the Director contributed by serving 

 in the following capacities : Chairman of Technical Panel on Rocketry 

 of the International Geophysical Year; member Technical Panel on 

 the Earth Satellite Program of the International Geophysical Year; 

 member of the working group on Tracking Earth Satellites on above 

 panel; member Panel of the Atmosphere of the Scientific Advisory 

 Board to the Air Force ; member Committee on Cosmic and Terrestrial 

 Relationships of the American Geophysical Union ; Editor, Harvard 

 Announcement Cards ; and general editor, Smithsonian Contributions 

 to Astrophysics. 



DIVISION OF RADIATION AND ORGANISMS 

 (Prepared by R. B. Withrow, Chief of the Division) 



The major activities of this division have been concerned with fun- 

 damental physiological and biochemical research on the role of light 

 in regulating growth in higher plants. Seed germination, seedling 

 growth, flowering, and the development of what is commonly referred 

 to as a "normal plant" are controlled by light. Pigments within the 

 organism absorb the light and convert it into chemical bond energy 

 and thus initiate a chain of events that produces the observed growth 

 effects. In most instances, relatively little light is necessary. This 

 is in contrast to the photosynthesis of sugars where very high inten- 

 sities are required for optimal results. There is a similar group of 

 light-controlled reactions in animals which regulate many phases of 

 reproductive behavior. Plans are now being implemented to inves- 

 tigate this phase of animal physiology. 



The two general groups of photochemical reactions that regulate 

 plant growth are (1) those controlling photomorphogenesis, which 

 are activated chiefly by red and far-red light, and (2) those con- 

 cerned with phototropism, controlled principally by blue light. The 

 respective pigment systems channel the energy into different biochem- 

 ical pathways and therefore induce entirely different physiological 

 responses. 



Photomorphogenesis. — Seed germination, seedling development, 

 flowering, bud development of woody plants, and changes in stem 

 length are examples of formative processes controlled by light from 

 the red end of the spectrum. Collectively, these may be grouped un- 

 der the term "photomorphogenesis." 



