PLANT STRUCTURE AND COMPOSITION 



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FIGURE 8-1. Cross section of a portion of a leaf, showing the pahsade parenchyma 

 (PP) and spongy parenchyma (SP) containing the chloroplasts (C). The stoma (S) 

 permit the exchange of gases with the surrounding atmosphere. 



ash. Chloroplasts perform an important role in the photosynthetic 

 process (Chapter 9). 



Another group of very small bodies, mitochondria, is found to be 

 almost universally present in the cytoplasm of plant and animal cells. 

 The mitochondria are small granules about 1 fi in diameter. They are 

 particularly rich in enzyme activity associated with the aerobic oxida- 

 tion of metabolic intermediates and with oxidative phosphorylation 

 (Chapter 9). The biological activity of the mitochondrial fraction 



