1060 BIOLOGICAL EFFECTS OF RADIATION 



reviewed by Maximow (12) who took notice of representative papers 

 published previous to his time. Those of which he did not write give 

 the same contradictory results based on inadequate experiments. For 

 example, he omitted reference to numerous experiments by Day (4) with 

 germinating seeds of barley and wheat. Barley was reported to show 

 3 to 4 per cent more respiration in diffuse daylight than in darkness, 

 as measured by O2 consumption and CO2 production. The variations 

 in measurements were great and the differences in favor of light were 

 not significant. 



Maximow contributed the first complete analysis of the problem 

 with proper regard for experimental methods and justifiable conclusions. 

 He used the lower fungi (such as Aspergillus) for plant material, an 

 electric light with and without a reflector as a source of light, and con- 

 trolled the temperature of his cultures by means of a water bath and 

 thermostat. He was careful to provide sufficient organic food for the 

 life of the mold and to eliminate the variables due to changing growth 

 rates of cultures at different ages. 



Maximow concluded that the response to light depends on the age 

 of the fungus, with young cultures unaffected by visible rays from an 

 electric light. Older cultures show a small but short-lived acceleration 

 of respiration which is more pronounced if the mycelium is under- 

 nourished. The failure of this initial acceleration to continue for more 

 than a few minutes led Maximow to the conclusion that light has little 

 or no direct effect upon respiration. 



A few years later Lowschin (9) performed numerous experiments 

 with the same type of plants and with due consideration of temperature 

 and nutritive relations. He used diffuse daylight and reported that he 

 never found a real increase in rate of respiration which was not caused 

 by rise in temperature of the culture. 



Finally, we have the recent work of de Boer (3) with fungi, using 

 modern apparatus, which led him to conclude that there is no direct 

 influence of the visible spectrum on the respiration of these plants. His 

 methods and precautions are beyond criticism. He measured both 

 O2 and CO2 as well as the intensity of illumination. When he found no 

 response to light by Phycomyces blakesleeanus, he turned to other fungi. 

 He used small fruiting bodies of mushrooms, pure cultures of their 

 mycelia, and a growth of Polyporus destructor on carrot slices. In all 

 cases his measurements showed a complete lack of response to light. 

 The table, top of page 1061, is typical of his data and of the accuracy 

 of his analyses. 



It must be mentioned that there is a still more recent report of an 

 increase in rate of respiration in a nongreen leaf of Croton as the result 

 of exposure to artificial light. This effect is described by Ranjan (15) 

 on the basis of two experiments with excised leaves contained in a glass 



