QUESTIONS for FURTHER THOUGHT
and STUDY:
PLANT NUTRITION AND SOILS

1. Compare and contrast legume root nodules and mycorrhizae as two symbiotic relationships of roots that enhance plant nutrition.

2. How do mycorrhizae assist a plant in the uptake of nutrient elements?

3. How does the size of soil particles affect their ability to retain water?

4. What is cation exchange, and why is it important for plant nutrition?

5. What are the consequences of acid rain on nutrient availability to plants?

6. Chlorophyll contains nitrogen, but carotenoids do not. Therefore, could a nitrogen deficient plant still have color? Why or why not?

7. What is the difference between macronutrients and micronutrients? Will the consequences of depriving a plant of a micronutrient be less severe than those of depriving the pant of a macronutrient?

8. Trace the pathway taken by a potassium ion from the point where it enters the root to a leaf epidermal cell.

9. Summarize the processes that add nitrogen to soils and the processes that deplete nitrogen from soils.

10. If you were shown cross sections of a young root and a young stem from the same dicot plant, how could you tell them apart?

11. What is soil parent material? How does it become soil?

12. What types of soil water are recognized? What is available soil water?

13. List the 16 elements that are essential for the growth of all higher plants. Be able to identify one or more principal structural or metabolic roles for each essential element.

14. Deficiencies of iron, magnesium, and nitrogen all cause chlorosis. Iron chlorosis develops only between the veins of young leaves while chlorosis due to both magnesium and nitrogen deficiencies develop more generally in older leaves. Explain these differences. Why does each deficiency lead to chlorosis?

15. For what reason(s) might a soil rich in calcium supply too little phosphorous for plant growth?

16. What are ammonification, nitrification, and denitrification? What are their respective contributions to the nitrogen cycle?

17. What is meant by the statement that biological nitrogen fixation is exclusively a prokaryote domain?

18. Describe the process of rhizobial infection and nodule development in a legume root.

19. How does a bacteroid differ from a bacterium?

20. What is the function of leghemoglobin in symbiotic nitrogen fixation?

21. The product of nitrogen fixation is ammonia (or an ammonium ion). Trace the path of nitrogen as the ammonium ion is converted to organic nitrogen and translocated to a leaf cell.

22. What form of nitrogen is absorbed from the soil by most plants?

23. Soils are dynamic systems. What changes might result when land is subjected to heavy irrigation for agriculture, after being relatively dry for many years? What changes in the soil might result when a virgin, deciduous forest is replaced by crops that are harvested each year?

24. What is the function of each of the following enzymes:
        -- nitrogenase
        -- leghemoglobin
        -- alanine deaminase
        -- nitrate reductase
        -- nitrite reductase
        -- glutamine synthetase (GS)
        -- glutamate synthase (GOGAT)
        -- transaminases (= aminotransferases)

25. What is the difference between a mobile and an immobile element? Where are the first deficiency symptoms for each? List some example of mobile and immobile elements.

26. If roots of a plant are exposed continuously to an inhibitor which prevents the roots cells from making ATP. Several days later you notice some leaves exhibiting chlorosis, dieback and beginning to drop. What is the most likely explanation of these observations?

27. Describe two ways soil pH can be lowered (become more acidic) if the soil is to alkaline.

28. Explain how "liming" the soil causes the pH to become more alkaline.

29. What is loam soil? Why is loam soil so agriculturally advantageous?

30. What is the main nutritional benefit for plants of being carnivorous? Why are such plants principally found growing in acid bogs and volcanic clays?

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