COLLATERAL READING 613 



5. It is common nursery practice to cover the trunks of young trees with burlap 



or straw during the winter months. Can you see any benefits to the plants 

 from this practice? 



6. Peach trees often show winter injury on the side of the trunk with a southern 



exposure. The north sides of the trunk seldom show such injury. Explain. 



7. It is a common belief in some regions that frozen plant tissues may often 



be revived without permanent injury if they are sprinkled generously with 

 cold water. Is there any basis for such a belief? 



8. With most floricultural plants which is the more practical way of increasing 



flowering during the winter months — increasing the intensity of light or 

 its daily duration. Explain. 



9. The critical light period for Mandarin soy beam is 17 hours, but it is a short- 



day plant. How would its behavior at the latitude of Washington 

 (about 39° N.) and that of southern Canada (50-55° ^•) differ? 



10. W^hy do radishes rapidly "go to seed" if planted in late spring? 



11. Some of the largest yields per acre of hay have been obtained in Alaska. 



Why is the climate of Alaska favorable for such crops? 



12. In regrading lawns soil is often piled several feet deep over the roots of 



trees. Some species die following such treatment. Why? If a srnall 

 area around the tree trunk is kept free from soil the trees may survive. 

 Why? 



13. What type of low temperature injury is probably most effective m prevent- 



ing the natural spread of sub-tropical species into temperate regions? 



14. Suggest reasons why northern species of plants often fail to survive when 



transplanted to more southern latitudes. 



15. If a trench several feet deep is dug around an area of a few square rods 



in a forest and the trench then refilled with soil, herbaceous vegetation 

 within this area often shows a better development than in surrounding 

 untrenched areas, but sometimes does not. Suggest reasons for the dif- 

 ferences in results. 



16. List the important physiological processes occurring in a meristematic shoot 



of an herbaceous plant that will usually show a change in rate when a 

 cloud passes across the sun after a period of direct exposure to sunlight 

 on otherwise "standard day" conditions. Explain, for each process, whether 

 you would expect an increase or decrease in rate and why. 



Suggested for Collateral Reading 

 Belchradek, J. Temperature and living matter. Gebruder Borntrager. Ber- 



Duggar, B. M., Editor. Biological effects of radiation. McGraw-Hill Book 



Co. New York. 1936. 

 Harvey, R. B. An annotated bibliography of low temperature relations of 



plants. Rev. Ed. Burgess Publ. Co. Minneapolis. 1936. 

 Lundegardh, H. Environment arid plant development. Translated and 



edited bv E. Ashby. Edward Arnold and Co. London. 1931- 

 Maximov, N. A. The plant in relation to water. Edited by R. H. Yapp. 



George Allen and Unwin. London. 1929. 

 Weaver, J. E., and F. E. Clements. Plant ecology. 2nd Ed. McGraw-Hill 



Book Co. New York. 1938. 



