CHAPTER VII 



THE STORAGE AND DIGESTION OF FOODS 

 IN PLANTS 



Storage. — We have seen that the foods made in green 

 leaves and in other parts of the plant may be used at 

 once for the construction and operation of the plant 

 body, or they may be stored. This storage may occur 

 where they are made, or it may take place in other parts 

 of the plant body. In the latter case, the foods must be 

 removed from the places of manufacture, and this 

 movement, like the absorption of raw material and the 

 secretion and excretion of elaborated compounds, can 

 take place only in solution in water. 



The Common Places of Storage. — If photosynthesis 

 is more rapid than the diffusion of sugar from the cells 

 in which it is made in the green leaf, the sugar will accu- 

 mulate in the cells in which it is formed. It will gener- 

 ally be converted into starch, which is insoluble in water 

 and occurs in the form of granules formed in the green 

 chromatophores. Observation shows that, during the 

 hours of daylight, such accumulation ordinarily occurs 

 in mild or warm weather, and that during the night the 

 cells are emptied again. Thus, while the leaves of orange 

 trees may be very full of starch at sunset they are, gener- 

 ally speaking, completely emptied of it by sunrise, and 

 the sugar which has been removed from the leaves may 

 be stored elsewhere as starch or in other forms, or it may 

 be used in the manufacture of more complex compounds 

 in other parts of the plant. 



The Places of More Permanent Storage vary with 

 the length of life of the plant. Thus, we find in plants 



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