HANDLING OF RADIOISOTOPES WITH ANIMALS AND PLANTS 



149 



attached to the generating tube which will show when the CO2 supply has 

 been exhausted. Carbon dioxide is produced in the system by the injec- 

 tion of 30 per cent perchloric acid through the serum-vial stopper with a 

 hypodermic needle. The HaCOs should l)e moistened before acid treat- 

 ment to avoid particles being blown from the generating tube into the 

 chamber. If several additions of CO2 are required, 

 the generating tube can be removed and replaced 

 with a charged tube. It may be convenient to seal 

 into the jar a ground-glass joint to accommodate a 

 vessel that mixes acid and BaC^^Os upon rotation. 

 Quantitative COo generation can be obtained, if 

 desired, by the use of known amounts of carbonate 

 or acid. 



The jars should be opened in a well-ventilated 

 hood. However, if the plant is allowed to photo- 

 synthesize for some time after completion of the 

 C^^02 generation, the radioactivity will be almost 

 entirely removed from the gas phase of the system. 

 The use of small systems to produce compounds of 

 relatively high specific activity seems to offer some 

 advantage in the control of radioactivity over facili- 

 ties for the production of large quantities of plants 

 wdth low specific activities. 



A single leaf of the intact plant may be enclosed in 

 a glass photosynthetic chamber for exposure toC^^Oa. 

 Chen (37) has described a 9.5-liter chamber into 

 which the leaf blade of a geranium plant was inserted 

 through a hole and sealed. The BaC^^Os was placed 

 in a beaker at the bottom of the chamber, and the 

 acid introduced through a separatory funnel at the 

 top of the chamber. 



In short-term studies of photosynthesis the excised 

 leaf may be used to synthesize C^^ carbohydrates 

 from C'H)2- The leaf is simply removed from the 

 plant and the petiole is immersed in a solution containing C'*- labeled 

 bicarbonate. Dubbs (38) has described a simplified photosynthesis 

 apparatus by means of which a detached leaf can be exposed to an atmos- 

 phere of C'^02 to carry on photosynthesis for as long as 24 hr. 



A typical procedure for the tagging of aquatic algae with C^^ has been 

 reported by Clendeiniing and (Jorham (39). The plant material, 2 to 

 5 g, was distributed in 150 ml of distilled water that had been aerated with 

 5 per cent CO2 in air. A Waring Blendor jar was used for the tagging 

 vessel. Under the desired conditions of illumination a dilute XaHC'^Os 



Fig. 4-22. Closed 

 plant-culture cham- 

 ber for the internal 

 generation of CO2. 

 [From R. H. Biirris, 

 P. W. Wilson, and 

 R. E. Stiitz, Incor- 

 poration of Isolopic 

 Carbon into Com- 

 pounds by Biosyn- 

 thesis, Botan. Gaz., 

 Ill: 63-69 (1949).] 



