CAN CARBON DIOXIDE SERVE AS OXIDANT IN HILL REACTION? 1531 



nature by suspending chloroplasts in an artificial medium of low rH. To simulate 

 natural conditions also in respect to pH and osmotic pressure, she followed the advice 

 of Kuzin, and used as medium a solution of a reducing sugar (glucose, fructose) in satu- 

 rated solution of basic magnesium acetate. 



What she called "chloroplasts" was a preparation obtained simply by shredding 

 leaves of clover with scissors, washing in a 0.5 mole/liter glucose or galactose solution, 

 and passing the suspension through a paper filter under suction. The filter paper 

 carrying the dark-green precipitate was cut into strips, and immersed into the above- 

 mentioned reducing medium, to which bicarbonate was added. The pH of the solution 

 was 7.5-8.5. Boichenko claimed that if the medium contained 0.1% reducing sugar, 

 giving rH <9.9 (estimated by means of redox indicator dyes), oxygen was evolved, and 

 carbon dioxide used up, upon illumination of the green strip. The results are sum- 

 marized in Table 35.IV. The table shows that with fructose and, to a lesser extent, 

 with glucose, the rH decreased and the pH increased upon exposure to light, and oxygen 

 was liberated. With hydrosulfite and glycolaldehyde, the pH and rH changes were in 

 the opposite direction, and no oxygen evolution was observed. 



Table 35.IV 



"Photosynthesis" with Chloroplast Films on Filter Paper 

 (after Boichenko 1943, 1944) 



The fact that the rH of hexose solutions did not increase upon illumination was taken 

 by Boichenko as proof that these sugars were not used up, and she concluded that they 

 must have served as catalysts for the oxidation of water by carbon dioxide — which was 

 also indicated by the increase in pH. She recalled in this connection the observation of 

 van Niel and Gaffron that purple bacteria and "adapted" green algae can use organic 

 hydrogen donors to reduce carbon dioxide. Inverting the reaction sequence suggested 

 by them (which involved water as the primary, and organic compound as ultimate hy- 

 drogen donor), she suggested that organic H donors (such as fructose) serve as primary 

 reductants (even in normal photosynthesis!), and that the oxidation of water (and libera- 

 tion of oxygen) are caused by a secondary reaction between the oxidized sugars and 

 water. It hardly needs pointing out that using carbohydrates as primary hydrogen 

 donors to reduce carbon dioxide in the photochemical stage of photosynthesis leaves to 

 dark stages a reaction which must require all the energy of photosynthesis, namely, the 

 oxidation of water to oxygen by the oxidation product of a carbohydrate (such as a 

 gluconic acid). The hypothesis is therefore utterly implausible. 



Later, Boichenko (1947, 1948) described the "chemosynthetic" activity of the same 



