38. (regulated by guard cells surrounding stomata) Flow of water H 2 O H 2 O Cohesion and adhesion in xylem Transpiration Water uptake (cohesion of H 2 O molecules to each other and adhesion of H 2 O molecules to cell walls) (via root hairs)
39. Nitrogen-fixing bacteria N 2 H + NH 3 NH 4 + (ammonium) NO 3 – (nitrate) NH 4 + Amino acids, etc. Nitrifying bacteria Ammonifying bacteria Organic material Root Air Soil
40.
41.
Hinweis der Redaktion
Large sunflower.
Woman in a garden.
Sunflowers after flooding.
Teaching Tips 1. Module 32.1 references the discussion of photosynthesis in Chapter 7. If you have not already addressed the content of Chapter 7, consider discussing the sources of carbon, hydrogen, and oxygen that are used in the construction of carbohydrates resulting from photosynthesis. 2. With the exception of small amounts of glycogen obtained from meat and lactose obtained from dairy products, we humans get all of our dietary carbohydrates from plants.
Teaching Tips 1. Module 32.1 references the discussion of photosynthesis in Chapter 7. If you have not already addressed the content of Chapter 7, consider discussing the sources of carbon, hydrogen, and oxygen that are used in the construction of carbohydrates resulting from photosynthesis. 2. With the exception of small amounts of glycogen obtained from meat and lactose obtained from dairy products, we humans get all of our dietary carbohydrates from plants.
Teaching Tips 1. Module 32.1 references the discussion of photosynthesis in Chapter 7. If you have not already addressed the content of Chapter 7, consider discussing the sources of carbon, hydrogen, and oxygen that are used in the construction of carbohydrates resulting from photosynthesis. 2. With the exception of small amounts of glycogen obtained from meat and lactose obtained from dairy products, we humans get all of our dietary carbohydrates from plants.
Figure 32.1A The uptake of nutrients by a plant.
Figure 32.1B Redwood trees, giant products of photosynthesis.
Teaching Tips 1. Root hairs are yet another example of an adaptation to increase the surface area of an organism. The divisions within the human lung, as well as microvilli, and plant leaves, are other examples. Increased surface areas are typically found where something is exchanged: gases exchanged at respiratory surfaces, nutrients absorbed by microvilli, light absorbed by leaves, and water and minerals absorbed by root hairs. If this chapter is one of the final topics addressed in your course, illustrating these broad principles with examples from a variety of subjects can provide a unifying review.
Teaching Tips 1. Root hairs are yet another example of an adaptation to increase the surface area of an organism. The divisions within the human lung, as well as microvilli, and plant leaves, are other examples. Increased surface areas are typically found where something is exchanged: gases exchanged at respiratory surfaces, nutrients absorbed by microvilli, light absorbed by leaves, and water and minerals absorbed by root hairs. If this chapter is one of the final topics addressed in your course, illustrating these broad principles with examples from a variety of subjects can provide a unifying review.
It is important to distinguish between the acquisition of nutrients and the acquisition of food. Plants do not obtain their food from the environment, like animals. Instead, plants are autotrophs that generate their own food. The essential elements required by plants are not sources of calories. Students might suspect that macronutrients are large and micronutrients are small. Instead, the word roots macro- and micro- refer to the quantities of nutrients required in each category. Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. With abundant antibacterial products now on the market, students may believe that all bacteria are harmful. Before addressing the mutualistic roles of soil bacteria and plants, challenge your students to explain why planting seeds in sterilized soil could be problematic.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. With abundant antibacterial products now on the market, students may believe that all bacteria are harmful. Before addressing the mutualistic roles of soil bacteria and plants, challenge your students to explain why planting seeds in sterilized soil could be problematic.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. With abundant antibacterial products now on the market, students may believe that all bacteria are harmful. Before addressing the mutualistic roles of soil bacteria and plants, challenge your students to explain why planting seeds in sterilized soil could be problematic.
Figure 32.6 A hydroponic culture experiment.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. Students who know that most (78%) of Earth’s atmosphere consists of nitrogen may be confused to learn that nitrogen shortage is the most common nutritional problem for plants. As Modules 32.7 and 32.12 indicate, plants cannot use nitrogen in its most common form, which is found in the atmosphere. However, they can use dissolved nitrate ions and ammonium ions.
Figure 32.7A The effect of nitrogen availability on corn growth: corn grown in nitrogen-rich soil (left) and nitrogen-poor soil (right).
Figure 32.7B Nitrogen deficiency in a tomato leaf.
Figure 32.7C Steam produced by the metabolic activity of organisms within a compost pile.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. Students with limited backgrounds in botany might be surprised to learn that roots need oxygen. Aeration of the soil by burrowing worms and other animals helps create small spaces for air. Highly compacted soils limit the movement of air and can interfere with plant survival.
Figure 32.8A Three soil horizons visible beneath grass.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. Students with limited backgrounds in botany might be surprised to learn that roots need oxygen. Aeration of the soil by burrowing worms and other animals helps create small spaces for air. Highly compacted soils limit the movement of air and can interfere with plant survival.
Figure 32.8B A close-up view of root hairs in soil.
Figure 32.8C Cation exchange.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. The U.S. Department of Agriculture’s Natural Resources Conservation Service provides numerous links and information on soil conservation at www.nrcs.usda.gov/feature/.
Figure 32.9A Flood irrigation.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. The U.S. Department of Agriculture’s Natural Resources Conservation Service provides numerous links and information on soil conservation at www.nrcs.usda.gov/feature/.
Figure 32.9B Planting to prevent soil erosion in a hilly area.
Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. At http://attra.ncat.org/organic.html, the National Sustainable Agriculture Information Service provides extensive online publications describing the USDA rules and requirements for certified organic farming.
Figure 32.10 An organic farmer harvesting sweet corn.
For the Discovery Video Colored Cotton, go to Animation and Video Files. Student Misconceptions and Concerns 1. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the win/win nature of mutualism. Teaching Tips 1. The acronym GMO stands for “genetically modified organisms.” 2. Roundup Ready corn, a product manufactured by Monsanto, is resistant to the commercial herbicide Roundup. Thus, farmers can spray fields of Roundup Ready corn directly with Roundup, killing weeds but not the corn. An Internet search will quickly reveal the controversy over this and other genetically modified organisms (GMOs), which can encourage interesting discussions and promote critical thinking skills. Module 12.9 discusses some of the issues related to the use of GM organisms.
Figure 32.11 Plant researchers with high-protein rice.
Teaching Tips 1. With abundant antibacterial products now on the market, students may believe that all bacteria are harmful. Before addressing the mutualistic roles of soil bacteria and plants, challenge your students to explain why planting seeds in sterilized soil could be problematic. 2. Mycorrhizae provide an excellent example of a mutualistic relationship. Unless the various types of symbiotic relationships have already been discussed, consider illustrating mutualism and parasitism with the relationships in Modules 32.12–32.14.