animals and such plants as mushrooms, which have no chlorophyl, must 

 get their organic food from the bodies of other living things. 



Ce^i206 +60 



PHOTOSYNTHESIS AND RESPIRATION 



When photosynthesis takes place, light energy is absorbed and stored. When sugar 

 is oxidized, the stored energy is liberated as heat. The waste products of respiration 

 are the raw materials of photosynthesis 



In the end, all food comes from green plants. It is as if the carbon and 

 the oxygen in CO2 were pulled asunder by the action of sunlight through 

 chlorophyl. They are then able to combine again and so liberate energy. 

 It is thus that carbohydrates yield energy in becoming oxidized, whether 

 in the body of a living thing or in a flame. All the energy which plants and 

 animals get from the oxidation of carbohydrates, fats, or proteins is thus 

 derived from the sun's energy. There is more than poetry in the statement 

 that every human act is a transformed sunbeam. 



How Do Minerals Reach the Leaves? 



The Work of the Root^ Roots are familiar to us as plant anchors. 

 They are also special organs through which plants absorb water and dis- 

 solved minerals, and through which they get rid of wastes. The actual 

 exchange of material between the plant and the soil takes place through 

 the thin walls of the delicate root hair (see illustration, p. 144). As the 

 plant grows larger, its absorbing area increases by the branching of the 

 roots. But it is always in the regions near the growing tips of rootlets that 

 root hairs are formed — and that absorption takes place. 



iSee No. 7, p. 158. 

 142 



