102 PHOTOSYNTHESIS AND RESPIRATION. 



6. What is a stornate, and how does it work ? Why do people often 

 syringe or sponge the leaves of plants grown indoors or beside a dusty 

 road? 



7. To what substance do the green parts of plants owe their colour ? 

 State and explain the nature of the work which only the green parts of 

 plants are able to perform. 



8. Explain how it is that a green plant cannot carry on its nutrition 

 in darkness. 



9. What constituent of plant-food is obtained from the atmosphere? 

 What changes do plants affect in it ? Describe an experiment to demon- 

 strate this. 



10. What is meant by the term Photosynthesis ? What is the first 

 visible (solid) result of this process, and how would you detect it in a 

 leaf? 



11. What gases would you expect to find in the air of a closed glass 

 vessel exposed to light before and after leaving a green plant within 

 it? State the relative quantity of the various gases, and how the 

 presence of each can be detected. How could you measure the quantity 

 of each gas ? 



12. Two leaves, while still attached to the plant, are kept in the 

 dark for twenty-four hours ; then one is exposed to sunlight for some 

 hours, while the other still remains in the dark. By what after- treat- 

 ment would you distinguish between the two? Explain your exact 

 procedure and the reasoning on which you base your conclusions. 



13. Explain as fully as you can how it is that the guard-cells of a 

 stoma are enabled to alter the size of the aperture between them. 



14. What is the importance of carbon to a plant ? From what source 

 does a green plant get its carbon, and how is it assimilated ? 



15. What do you consider the essential characters of the foliage- 

 leaves of a green plant i.e. the characters in which all or nearly all 

 leaves you know agree ? How are these features of leaves of service to 

 the plant ? 



16. On what law does the intensity of light depend? How does 

 light-intensity affect Photosynthesis ? 



17. What is meant by Refraction ? What is a prism, and how 

 could you prove by its use that white light consists of rays having 

 different colours ? 



18. Describe the continuous Spectrum. How is the appearance of 

 the spectrum affected by an extract of chlorophyll being placed 

 between the prism and the screen on which the spectrum is received ? 



19. What is the function of Chlorophyll ? Under what conditions is 

 it formed, and how does it occur in the plant ? 



20. Explain the term Photosynthesis. What gases would you 

 expect to find in the air of a closed glass chamber exposed to the sun 



