CHAPTER VI 



RESPIRATION AND THE LIBERATION OF ENERGY IN 

 PLANTS 



I. THE STORAGE AND LIBERATION OF ENERGY 



74. Examples of energy in plants. By energy we mean 

 the capacity to do work. In the preceding chapters we 

 have considered to some extent the structure of various parts 

 of plants and some of the functions which they are fitted to 

 perform. Now to carry on most of these functions requires 

 the expenditure of energy on the part of the plant. Thus, 

 for example, roots in growing expend considerable energy, 

 pushing their way through the soil. Stems in like manner 

 exert energy in lifting to the light and air their weight of 

 branches and leaves. We know, too, that soil-water is 

 carried up through plants to considerable heights (several 

 hundred feet in very large trees), that substances obtained 

 from the soil and air are transported from one part of a plant 

 to another. Still another form of energy exhibited to a cer- 

 tain degree by plants is heat, as the following experiment 

 will show. 



75. To prove that heat energy is liberated in growing seed- 

 lings. Laboratory Study No. 38. 



Secure two wide-mouthed bottles of the same size (light- 

 ning fruit jars will answer) and put some wet blotting paper 

 in the bottom of each. Fill one of the jars half full of sprout- 

 ing peas. Fill the other jar half full of peas that have been 

 killed by being soaked in a 5 per cent solution of formalin for 



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