Chapter 37
Plant Nutrition
Teaching Objectives
Nutritional Requirements of Plants
1. Describe the ecological role of plants in transforming inorganic molecules into organic compounds.
2. Define the term essential nutrient.
3. Explain how hydroponic culture is used to determine which minerals are essential nutrients.
4. Distinguish between macronutrient and micronutrient.
5. Name the nine macronutrients required by plants.
6. List the eight micronutrients required by plants and explain why plants need only minute quantities of these elements.
7. Explain how a nutrient’s role and mobility determine the symptoms of a mineral deficiency.
The Role of Soil in Plant Nutrition
8. Define soil texture and soil composition.
9. Explain how soil is formed.
10. Name the components of topsoil.
11. Describe the composition of loams and explain why they are the most fertile soils.
12. Explain how humus contributes to the texture and composition of soils.
13. Explain why plants cannot extract all of the water in soil.
14. Explain how the presence of clay in soil helps prevent the leaching of mineral cations.
15. Define cation exchange, explain why it is necessary for plant nutrition, and describe how plants can stimulate the process.
16. Explain why soil management is necessary in agricultural systems but not in natural ecosystems such as forests and grasslands. Describe an example of human mismanagement of soil.
17. List the three mineral elements that are most commonly deficient in agricultural soils.
18. Explain how soil pH determines the effectiveness of fertilizers and a plant’s ability to absorb specific mineral nutrients.
19. Describe problems resulting from farm irrigation in arid regions.
20. Describe actions that can reduce loss of topsoil due to erosion.
21. Explain how phytoremediation can help detoxify polluted soil.
The Special Case of Nitrogen as a Plant Nutrient
22. Define nitrogen fixation and write an overall equation representing the conversion of gaseous nitrogen to ammonia.
23. Explain the importance of nitrogen-fixing bacteria to life on Earth.
24. Summarize the ecological role of each of the following groups of bacteria.
a. ammonifying bacteria
b. denitrifying bacteria
c. nitrogen-fixing bacteria
d. nitrifying bacteria
25. Explain why improving the protein yield of crops is a major goal of agricultural research.
Nutritional Adaptations: Symbiosis of Plants and Soil Microbes
26. Describe the development of a root nodule in a legume.
27. Explain how a legume protects its nitrogen-fixing bacteria from free oxygen, and explain why this protection is necessary.
28. Describe the basis for crop rotation.
29. Explain why a symbiosis between a legume and its nitrogen-fixing bacteria is considered to be mutualistic.
30. Explain why a symbiosis between a plant and a mycorrhizal fungus is considered to be mutualistic.
31. Distinguish between ectomycorrhizae and endomycorrhizae.
Nutritional Adaptations: Parasitism and Predation by Plants
32. Name one modification for nutrition in each of the following groups of plants:
a. epiphytes
b. parasitic plants
c. carnivorous plants
Student Misconceptions
1. Some students have the mistaken idea that plants obtain “food” from their environment. Although these students understand that plants are photosynthetic, they consider a plant’s uptake of water, minerals, and carbon dioxide as analogous to the feeding of animals. It is important to emphasize that the key ecological role of plants and other photoautotrophs is the synthesis of organic matter from inorganic precursors, using the energy from light. Clarify to students that, although plants take in raw materials from the air and soil, these inorganic nutrients are not energy sources and are not analogous to animal food.
2. This chapter provides an excellent opportunity to challenge student views of prokaryotes as important only because of their roles in “cheese and disease.” The crucial role of bacteria in the nitrogen cycle, especially in nitrogen fixation, can be used to reinforce the fact that all life on Earth depends on prokaryotic metabolism.
3. Mycorrhizal associations may be considered as plant oddities and not recognized as ubiquitous and essential to the majority of plants. Point out to your students that mycorrhizal associations are as old as plants themselves, that the great majority of plants have mycorrhizal associations, and that many plants, such as conifers, cannot survive without their fungal companions.
Chapter Guide to Teaching Resources
Overview: A nutritional network
Concept 37.1Plants require certain chemical elements to complete their life cycle
Transparencies
Figure 37.2 The uptake of nutrients by a plant: A review
Figure 37.3 Hydroponic culture
Table 37.1 Essential elements in plants
Figure 37.6 The availability of soil water and minerals
Concept 37.2Soil quality is a major determinant of plant distribution and growth
Student Media Resources
Activity: How plants obtain minerals from soil
Investigation: How does acid precipitation affect mineral deficiency?
Graph It: Global soil degradation
Concept 37.3Nitrogen is often the mineral that has the greatest effect on plant growth
Transparencies
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants (layer 1)
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants (layer 2)
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants (layer 3)
Student Media Resource
Activity: The nitrogen cycle
Concept 37.4Plant nutritional adaptations often involve relationships with other organisms
Transparencies
Figure 37.11 Development of a soybean root nodule
Figure 37.12 Mycorrhizae
Instructor and Student Media Resource
Video: Sun dew trapping prey
For additional resources such as digital images and lecture outlines, goto the Campbell Media Manager or the Instructor Resources section of www.campbellbiology.com.
Key Terms
bacteroids
cation exchange
crop rotation
ectomycorrhizae
endomycorrhizae
epiphyte
essential element
horizon
humus
hydroponic culture
inflorescence
loam
macronutrient
micronutrient
mineral nutrient
mycorrhizae
nitrogen fixation
nitrogenase
nitrogen-fixing bacteria
nodule
phytoremediation
sustainable agriculture
topsoil
Word Roots
ecto- 5 outside; myco- 5 a fungus; -rhizo 5 a root (ectomycorrhizae: a type of mycorrhizae in which the mycelium forms a dense sheath, or mantle, over the surface of the root; hyphae extend from the mantle into the soil, greatly increasing the surface area for water and mineral absorption)
endo- 5 inside (endomycorrhizae: a type of mycorrhizae that unlike ectomycorrhizae, do not have a dense mantle ensheathing the root; instead, microscopic fungal hyphae extend from the root into the soil)
macro- 5 large (macronutrient: elements required by plants and animals in relatively large amounts)
micro- 5 small (micronutrient: elements required by plants and animals in very small amounts)
-phyto 5 a plant (phytoremediation: an emerging, non-destructive technology that seeks to cheaply reclaim contaminated areas by taking advantage of the remarkable ability of some plant species to extract heavy metals and other pollutants from the soil and to concentrate them in easily harvested portions of the plant)Instructor’s Guide for Campbell/Reece Biology, Seventh EditionChapter 37Plant NutritionInstructor’s Guide for Campbell/Reece Biology, Seventh EditionChapter 36Transport in Vascular Plants