Light 



/ 



onnnaa 





nouM 



innnrPFx 





Water and 

 minerals 



Food 



(sugars, fats, 



proteins) 



Oxygen 



Carbon 

 dioxide 



Oxygen 



THE LEAF AS A MANUFACTURING PLANT 



The plant uses chemical engines, each consisting of a lump of protein with 

 some of the pigment that gives familiar plants their distinctive color. This 

 substance is called chlorophyl (from the Greek chloros^ ''green", and 

 phylloii, "leaf"). Chlorophyl is the actual transformer of energy in the 

 food-making process (see illustration above). 



The energy for doing this w^ork is the light from the sun. Although 

 the work cannot go on at too low a temperature, it is radiant energy, light, 

 that is active, not heat. 



The sugar formed by the action of sunlight upon chlorophyl consists of 

 the elements carbon, hydrogen and oxygen, which are derived from raw 

 material, water (H-O) and carbon dioxide (COl>). 



Sunlight and Life In the presence of light and chlorophyl the elements 

 of carbon dioxide and water recombine, forming sugar and liberating oxy- 

 gen. The action may be represented thus: 



6 COo + 6 H2O — > CeHisOe + 6 O2 



We may read this formula thus: six molecules of carbon dioxide plus six 

 molecules of water (under the action of sunlight) form one molecule of 

 sugar and six molecules of oxygen (see illustration, p. 139). Energy equiva- 

 lent to that absorbed from the sunlight is present as latent or "fuel" energy 

 in the carbohydrate. 



T38 



