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TEXTBOOK OF BOTANY 



Table 7. A Comparative Summary of Energy Transformations in an Annual 

 Herb and in a Woody Perennial 



Acre of Corn 

 (Illinois) 



Acre of 

 Apple Trees 

 (New York) 



Length of growing season 



Number of plants per acre 



Average leaf area is attained in 



Total radiant energy available 



Total energy bound in sugar 



Percentage of light energy bound in 

 photosynthesis 



Photosynthetic efficiency based on part 

 of spectrum that is effective in photo- 

 synthesis 



Average amount of sugar made per day 



Total sugar made per season 



Chemically bound energy released by 

 respiration in the plant 



Percentage of energy bound by photo- 

 synthesis released within the plants 

 by respiration 



Of the sugar made each season there is 

 oxidized by respiration in the plant 



The average rate of photosynthesis (l!2 

 hrs.) compared with respiration (24 

 hrs.) 



Bound energy in the structures and ac- 

 cumulated food in the plants 



Percentage of total energy of photo- 

 synthesis in accumulated foods 



Percentage of total energy of photo- 

 synthesis accumulated in structures 



100 days 

 10,000 



50 days 

 2,043 million Cal. 

 33 million Cal. 



1.6% 



188 days 

 400 



28 days 

 2,718 million Cal. 



30 million Cal. 



1% 



Sources and amounts of energy. Several investigators have analyzed 

 plants and calculated the amount of carbon and bound energy in them 

 per acre. From all these data it seems that an average acre of corn 

 accumulated a little more than 8 million Calories of energy, or about 

 one-third as much as the acre of corn described above; and that in all 

 kinds of crops the average annual accumulation of energy per acre is 

 about 6 million Calories. In an acre of forest it is about 10 million 



