Design and Operation of a Carbon-fl4 Biosynthesis Chamber 



By J. H. Smith and F. E. Allison, soil scientists, and J. F. Mullins, design, engineer, Soil and Water Conservation 



Research Division, Agricultural Research Service 



Carbon-14 labeled plant material can be used 

 to advantage in many types of research. Two of 

 these uses — for studies of soil organic matter and 

 for plant physiological investigations — are being 

 employed at Beltsville, Md. Preparation of 

 labeled plant material requires a special growth 

 chamber in which plants can be grown for con- 

 siderable periods of time in an atmosphere con- 

 taining carbon dioxide labeled with carbon-14 at 

 constant specific activity. 



Several such facilities have been constructed. 

 Some are located at the Argonne National Labora- 

 tories, Chicago, 111. (7) ; x at the University of 

 Bonn, Germany (6) ; at Rothamsted Experiment 



Station, Harpenden, England (J.) ; at the Radio- 

 logical Nutriculture Laboratory, Medical College 

 of Virginia, Richmond ; and at the Danish Atomic 

 Energy Commission, Research Establishment, 

 Riso, Denmark (1). The above-mentioned cham- 

 bers are all used for long-term labeling of 

 plants grown in an atmosphere containing carbon- 

 14 dioxide. A chamber for short-term labeling of 

 plants was designed by Brown (2) and was also 

 reported by Fisher (3). 



This publication describes an improved growth 

 chamber for growing plants in an atmosphere con- 

 taining carbon-14 dioxide to produce labeled plant 

 material. 



DESIGN AND CONSTRUCTION OF CHAMBER 



The biosynthesis chamber resembles a small 

 greenhouse with flat top, 9 feet long by 6.75 feet 

 wide by 6.75 feet high. The chamber is located 

 in a room 23 by 13.5 feet. One corner, 6 feet by 

 7.5 feet, has been partitioned off to contain most 

 of the machinery required for operation. 



The air in the room in which the chamber is 

 located is constantly changed by a positive pres- 

 sure blower ducted to circulate fresh air from out- 

 side. A large exhaust fan located in the ceiling 

 of the room provides for rapid air removal. 



Framework 



The framework of the chamber was assembled 

 in four sections, as shown in figure 1, brought into 

 the room where it was to be installed, and the 

 sections arc-welded together. The top was made 

 from 2 x 2 x 14 -inch angle iron welded together 

 to form T-shaped members in which the glass was 

 supported. The vertical corner members were 



1 Italic numbers in parentheses refer to Literature Cited, 

 p. 15. 



made from 2.5 x 2.5 x 14-inch angle iron. The 

 vertical window frames were made from 2 x 2 x 

 14-inch angle iron. A channel iron was welded 

 into the horizontal framework to be used as a 

 service entrance area for all electrical, water, and 

 thermostat lines. The bottom section of the cham- 

 ber was supported on the top, bottom, and corners 

 by 2 x 2 x ^-inch angle iron. The bottom and 

 sides, 18 inches high, were covered with % 6 -inch 

 sheet metal, which was welded to the supporting 

 members to form a gastight base; the sides were 

 reinforced with 2 x 14-inch iron strap. 



Glazing 



For maximum light transmission, large windows 

 of 14-inch thick plate glass were used. The size 

 of the largest pane was calculated from the manu- 

 facturer's formula to stand a pressure variation 

 of ±20 inches of water. 2 Each pane of glass was 



I" 



2 Glass for Modern Needs. Engineering Data, Pitts- 

 burgh Plate Glass Co., One Gateway Center, Pittsburgh 

 22, Pa. June 1956. 



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