BIOLOGY FOR BEGINNERS 



pBocesses 



8t Proci. 

 Prd tran.fr,(duct.) 

 cunward trar.ifer, (bait} 

 upport I expour of 



The Energy for Photosynthesis. The chemical energy of the 

 sun's light, which causes these two substances to unite, is some- 

 thing that we know very little about, but is, nevertheless, a very 

 real and a very great force. We realize that the sun gives us light 

 to see by, and heat is evident enough, but when we think of how 

 it tans our skin, bleaches our clothes, and makes our photographs, 



we have some evidences 

 of the chemical action 

 of light, though none of 

 these can compare with 

 the work done by these 

 same rays in the leaf 

 laboratory, during the 

 making of starch in the 

 plant. 



This word photo- 

 synthesis can now be 

 better understood, mean- 

 ing as it does " union by 

 means of light," since it 

 is by the chemical power 

 of the light rays that 

 the water and carbon 

 dioxide are united. 



The leaf is sometimes 

 compared to a mill in 

 which the power is the 

 sunlight; the machinery 

 is the chlorophyll; the 



raw materials are the carbon dioxide and water; the product is 

 starch; and the waste material is oxygen. 



The Waste Product. A benefit arising from photosynthesis 

 almost as important as the production of starch itself, is the libera- 

 tion of oxygen as a by-product. We have learned that every living 

 tissue breathes in oxygen. The resulting oxidation produces the 

 energy without which we could not live. 



Absorbed by root 



lotlc* th connsctlon 

 btwtn root hair* and duett 

 thence to I.T ( . 



FIG. 26. Diagram of Plant Processes. 



