164 ^11 Food Is Made by Green Plants unit hi 



water can be lost only through the leaves (and branches). Keep an accu- 

 rate record of weights. Discuss your method with the class before pro- 

 ceeding. Can you calculate the amount of water lost per square inch of 

 leaf surface per hour? Weigh the whole set-up at intervals of two or 

 more hours. 



16. Is transpiration more rapid through one side of the leaf than the 

 other? Prepare a set-up like the one in Exercise 15. Use a plant with few 

 and large leaves. Be sure to state which kind of plant was used. Prevent 

 transpiration from one surface of the leaves by coating them with a thick 

 layer of petroleum jelly. Measure the amount of transpiration by weigh- 

 ing. Now coat the other side. Explain your results. 



17. To test your understanding answer the following questions, (a) Do 

 you think the following statement is true? Why or why not? "Transpira- 

 tion increases with a larger amount of moisture in the soil, and the 

 amount of moisture in the soil in time increases with transpiration." 

 (b) What else besides the amount of moisture in the soil determines the 

 amount of transpiration? (c) After watering it thoroughly, what else 

 might you do to help revive a wilted house plant? 



Further Activities in Biology 



1. How does the lack of minerals affect the plant? Plant pea seeds in 

 moist clean sand. When the seedlings are three inches high, transplant 

 them into the following solutions. (Only the roots should be under 

 water.) 



Solution 1. (all minerals present) 



Water (distilled) i liter 



Calcium nitrate i gram 



Magnesium sulphate 0.25 gram 



Potassium acid phosphate 0.25 gram 



Potassium chloride o.io gram 



Ferric chloride 2 drops 



Soh/tion 2. (no nitrogen) Use calcium sulphate instead of calcium 



nitrate. 

 Solution 5. (no potassium) Use sodium chloride instead of potassium 

 chloride and monosodium acid phosphate instead of potassium acid 

 phosphate. 

 Solution 4. (no magnesium) Use calcium sulphate instead of magne- 

 sium sulphate. 

 Solution 5. (no calcium) Use sodium nitrate instead of calcium nitrate. 

 Solution 6. (no iron) Omit the ferric chloride. 



How is the rate of growth affected by the lack of the various minerals? 

 Are all parts of the plant similarly affected? Make a chart showing your 

 results. 



2. Using wax or any plastic substance make a model of a small root. 



