APPARATUS FOR THE STUDY OF PHOTOSYNTHESIS 



AND RESPIRATION 



W. J. V. OSTERHOUT 



(with one figure) 



Two recent papers have dealt with methods of studying photo- 

 synthesis. The first of these^ discussed photosynthesis in land 

 plants, while the second^ dealt with aquatics. It seemed to the 

 writer that these methods might be combined, and some experi- 

 ments were made for this purpose. The outcome was a simple 

 method for the study of photosynthesis in t land plants. 



The apparatus consists of a large tube (a lamp chimney will 

 serve) closed at the bottom by a stopper through which passes 

 a tube {A, fig. i) of Pyrex glass. Through the stopper at the 

 upper end passes the neck of an atomizer bulb (B) with an 

 opening at C for the intake of air.^ To the neck of the bulb is 

 attached a tube of Pyrex glass which extends to within an inch of 

 the bottom of the tube A . 



Plants'* are placed in the chamber with their stems dipping 

 in water contained in a small beaker. By means of the tubes 

 D and E any desired amount of CO2 may be run into the chamber. 

 When this is finished the bulb is repeatedly squeezed so as to force 

 the gases in the chamber to bubble through the liquid contained 

 in the tube A. This liquid consists of distilled water, to which 

 has been added^ an indicator which is sensitive to CO2. As the 

 gas bubbles through the liquid^ the color of the indicator changes. 



' OsTERHOUT, W. J. v., Amer. Jour. Bot. 5: 105. 19 18. 



^ OsTERHOUT, W. J. v., and Haas, A. R. C, Science N.S. 47:420. 1918. 



3 This form of bulb can easily be obtained in the drug trade. 



4 Tradescantia may be recommended for this purpose, especially kinds without 

 stripes on the leaves. 



5 The choice of indicator depends on the amount of CO2 introduced into the 

 chamber; for most purposes phenolsulphonephthalein will prove useful. At the 

 start of the experiment the PH value should be such that a slight change in CO2 

 will alter the color of the indicator. 



^ The bulb does not permit the entrance of air from the outside; it merely causes 

 a circulation of the gas within the chamber. 



Botanical Gazette, vol. 68] [60 



