PHOTOSYNTHESIS BATE UNDER NATURAL CONDITIONS 1005 



that the average yields of Noddack and Komor are two to three times 

 smaller than the most reliable short-time averages in Table 28. VII. 



The measurements of Noddack and Komor represent the only available 

 parallel large-scale measurements of irradiation and production of organic 

 matter by plants. There is, however, no dearth of estimates, often on a 

 much larger scale, based on agricultural and meteorological statistics. They 

 have been mentioned in chapter 1, where we used them for the estimation 

 of the total yield or organic synthesis on earth. We will now consider 

 these estimates somewhat closer. Putter (1914) took the insolation data 

 from observations of the l^rightness of daylight carried out by Weber in 

 Kiel, Germany, over a period of several years, and used the relation 1 lux 

 = 6.3 erg/cm. =^ sec. to calculate the corresponding energy flux. He cal- 

 culated, for the total irradiation over a year, 35.3 kcal./cm.^, corresponding 

 to an average illumination intensity of about 7000 lux. 



For the calculation of the heat of combustion of the synthesized organic 

 matter Putter used estimates of "exceptionally high" crops from agricul- 

 tural yearbooks; he then added the (estimated) heat of combustion of the 

 roots and stubbles, and subtracted the heat of combustion of the seed. 

 Thus he obtained values for AHc] for the calculation of S Idt, he inte- 

 grated Weber's data over the periods of vegetation of the several crops, and 

 subtracted the energy of infrared radiations (above 1 m) • (It would be more 

 reasonable to subtract all radiations above 0.7 n, since light between 700 

 and 1000 niM probably is not used for photosynthesis at all, cf. chapter 30.) 

 Table 28.VHI shows some of Putter's results. In the last column, the 

 conversion yields are corrected for losses by respiration, estimated at 15% 

 of the weight increase due to photosynthesis during the vegetation period. 



Table 28.VIII 

 Energy Conversion by Field Plants (after Pi tter 1914) 



The average conversion jaeld in Table 28.VHI is 3.3%, referred to inci- 

 dent radiation below 1 /x. This corresponds to 2.3% referred to the total 

 incident radiation, or about 6% referred to the absorbed radiation below^ 

 700 my.. Tluis, Piittcr's average value is two to three times larger than the 



