48 PHOTOSYNTHESIS 



tion regarding- the influence of the carbon dioxide-content of the atmosphere 

 on our economic plants. Many schemes have been advanced for increas- 

 ing the atmospheric carbon dioxide. These have included the setting 

 afire of the coal deposits of the polar regions. Nernst has suggested that 

 this coal, which is inaccessible for mining purposes, be ignited and kept 

 burning by means of shafts. It would thus become useful to man by 

 increasing the carbon dioxide-content of the atmosphere, resulting in 

 higher crop yields. It has also lieen suggested that powdered coal of low 

 grade be spread over the cultivated land. Through auto-oxidation the coal 

 would yield carbon dioxide which would be directly available for the 

 plant. ^^ 



The respiration of plants including fungi and bacteria yields very con- 

 siderable quantities of carbon dioxide. Fundamentally, of course, most 

 of the material which is thus burned is of photosynthetic origin, so that 

 these organisms are simply reconverting the products of photosynthesis 

 into carbon dioxide and water. The rate of respiration of most of the 

 lower organisms is relatively very high, so that even when the period of 

 their activity is short the amount of work accomplished is great. The 

 amount of carbon dioxide produced by micro-organisms per unit surface 

 or weight is many times that of man. 



The number of substances which bacteria can convert into carbon 

 dioxide is very great ; this assures the complete conversion of plants and 

 animals after death to the simplest substances. The complete process 

 of the degradation of carbon compounds by lower organisms presents in 

 detail an exceedingly complex and intricate picture of the interrelation 

 of these organisms. The chief product of photosynthesis is probably 

 cellulose. This is converted by various organisms into soluble carbo- 

 hydrates or in the absence of air into formic, acetic, butyric acids, carbon 

 dioxide, hydrogen and methane. The latter two gases are further oxidized 

 by special organisms to carbon dioxide and water, so that while there are 

 enormous quantities of hydrogen and methane produced in this manner 

 annually and have been for eons, only traces of these gases are found 

 in our atmosphere. The soluble carbohydrates may be fermented to 

 alcohols and fatty acids which in turn are converted by other bacteria and 

 some fungi to carbon dioxide and water. The anaerobic cellulose-destroy- 

 ing organisms ])lay an enormously important role in the carbon dioxide 

 cycle, as much of the cellulose is finally buried under water or soil. 

 Similarly other substances, such as proteins, which contain besides car- 

 bon, hydrogen and oxygen also nitrogen, phosphorus and sulphur are com- 

 pletely broken down to simple inorganic compounds. In these processes, 

 many of which are analogous to step-reactions, there often exists a close 

 interrelationship between aerobic and anaerobic organisms. Were it not 

 for the lower organisms such as bacteria and fungi which rapidly convert 

 the components of dead ])lants and animals to carbon dioxide and other 

 simple compounds, it is conceivable that large quantities of carbon dioxide 



"Reinau, E., Kohlcnsdure und Pnanzen. Halle, 1920, p. 125. 



