Plant Nutrition and Transport Chapter 32 Plant Nutrition and Transport

32.1 Plants acquire nutrients from air, water, and soil What is needed for photosynthesis? Plant cells use the sugars made by photosynthesis in constructing all the other organic materials they need, but primarily for carbohydrates. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Teaching Tips 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. (32.1) With the exception of small amounts of glycogen obtained from meat and lactose obtained from dairy products, humans get most of our dietary carbohydrates from plants. (32.1)

32.1 Plants acquire nutrients from air, water, and soil Plants use cellular respiration to break down some of these sugars, obtaining energy and consuming oxygen. A plant must move water from its roots to its leaves and deliver sugars to specific areas of its body. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Teaching Tips 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. (32.1) With the exception of small amounts of glycogen obtained from meat and lactose obtained from dairy products, humans get most of our dietary carbohydrates from plants. (32.1)

32.1 Plants acquire nutrients from air, water, and soil What inorganic substance is obtained in the greatest quantities from the soil? What other nutrients are absorbed from the soil? Checkpoint Question Response Water Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Teaching Tips 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. (32.1) With the exception of small amounts of glycogen obtained from meat and lactose obtained from dairy products, humans get most of our dietary carbohydrates from plants. (32.1)

32.2 The plasma membranes of root cells control solute uptake Root hairs greatly increase a root’s absorptive surface. Water and solutes can move in two ways. Water and solutes must pass through the selectively permeable plasma membranes of cells in the endodermis to enter the xylem (water-conducting tissue) for transport upward. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Active Lecture Tips Root hairs are yet another example of an adaptation to increase the surface area of an organism. Challenge your students to identify at least two other examples of adaptations that increase surface area. Then create a class list drawing on these examples. Some students might be very creative. Other examples include (1) the divisions within the human lung, (2) microvilli, (3) plant leaves, (4) highly branched gills in fish, (5) highly branched air passageways leading to alveoli in the lungs, and (6) the tiny, microscopic bristles of a gecko’s feet! 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. But in gecko feet, the increased surface area promotes adhesion. 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. (32.2)

Water and nutrients enter in several ways but ultimately are controlled by the Casparian strip

Animation: Transport in Roots

32.3 Transpiration pulls water up xylem vessels Transpiration can move xylem sap, consisting of water and dissolved inorganic nutrients, to the top of the tallest tree. Xylem sap flows through very thin tubes within xylem tissue, pulled by transpiration. Sap movement is aided by the unique properties of water ( ___________ and _________) and requires no energy expenditure by the plant. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Teaching Tips Demonstrate or ask students to recall what happens when a soda straw is lifted out of a beverage: some of the beverage still sticks to the straw. This is an example of adhesion. (32.3)

(regulated by guard cells surrounding stomata) Transpiration H2O (regulated by guard cells surrounding stomata) Tension Flow of water (pulls continuous string of water molecules upward) Cohesion and adhesion in xylem (cohesion of H2O molecules to each other and adhesion of H2O molecules to cell walls) Figure 32.UN01 Reviewing the concepts, 32.3 Water uptake H2O (via root hairs)

Animation: Transpiration What are the two reasons that the stomata can’t remain closed even though being closed reduces transpiration?

32.4 Guard cells control transpiration Adaptations that increase photosynthesis—such as large leaf surface areas—have the serious drawback of increasing water loss by transpiration. By changing shape, guard cells generally keep stomata open during the day (allowing transpiration) but closed at night (preventing excess water loss). Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Teaching Tips The change in shape of guard cells is due to internal fluid pressure, or turgor—important in many other organisms. Turgor helps maintain the shape of plant cells, gives structure to the hydrostatic skeletons of sea anemones and earthworms, and causes a penis and nipples to become firm upon erection. Before addressing guard cells, you may challenge your class to explain what leaves, earthworms, and an erect penis have in common. The answer is turgor. (32.4)

32.4 Guard cells control transpiration Some leaf molds secrete a chemical that causes guard cells to accumulate K+. How does this help the mold infect the plant? Checkpoint Question Response Accumulation of K+ by guard cells causes the stomata to stay open. The mold can then grow into the leaf interior via the stomata. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Teaching Tips The change in shape of guard cells is due to internal fluid pressure, or turgor—important in many other organisms. Turgor helps maintain the shape of plant cells, gives structure to the hydrostatic skeletons of sea anemones and earthworms, and causes a penis and nipples to become firm upon erection. Before addressing guard cells, you may challenge your class to explain what leaves, earthworms, and an erect penis have in common. The answer is turgor. (32.4)

32.5 Phloem transports sugars A plant has two separate transport systems: xylem and phloem. Xylem transports xylem sap (water and dissolved minerals). Phloem transports the products of photosynthesis from where they are made or stored to where they are needed. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Although analogies are often useful, some aspects can be misleading. In many ways, the vascular tissues and movement of fluid through plants are unlike the circulatory system of vertebrates. Whereas vertebrates have a one-way flow of fluid propelled by a contracting heart through a contained tubular system, phloem sap, propelled instead by a pressure flow mechanism, can move in either direction. (32.5) Teaching Tips Many phloem saps other than maple syrup are used commercially. For example, phloem sap from rubber trees native to the Brazilian Amazon was once the major source of rubber. (Most rubber is now synthetically produced.) Pine oil, derived from pine tree resin, is the active ingredient in Pine-Sol cleaner. (32.5-32.6)

32.5 Phloem transports sugars In angiosperms, phloem tissues contains food-conducting cells called sieve-tube elements arranged end to end into long tubes. Perforations in sieve plates connect the cytoplasm of these living cells into one continuous solution. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Although analogies are often useful, some aspects can be misleading. In many ways, the vascular tissues and movement of fluid through plants are unlike the circulatory system of vertebrates. Whereas vertebrates have a one-way flow of fluid propelled by a contracting heart through a contained tubular system, phloem sap, propelled instead by a pressure flow mechanism, can move in either direction. (32.5) Teaching Tips Many phloem saps other than maple syrup are used commercially. For example, phloem sap from rubber trees native to the Brazilian Amazon was once the major source of rubber. (Most rubber is now synthetically produced.) Pine oil, derived from pine tree resin, is the active ingredient in Pine-Sol cleaner. (32.5-32.6)

32.5 Phloem transports sugars What causes phloem sap to flow from a sugar source to a sugar sink? This movement is best explained by the pressure flow mechanism. Student Misconceptions and Concerns These first six modules of Chapter 32 help to answer questions that students may never have asked. Often, answers are more significant if we first spend time pondering the questions. Consider starting these discussions by raising some of the basic questions noted by the authors, including: (a) What is the source of the raw materials that make up a plant’s body? (b) Do plant roots act like a sponge, absorbing just about anything? (c) What makes plant saps move up a plant, especially the really tall ones? (32.1–32.6) Although analogies are often useful, some aspects can be misleading. In many ways, the vascular tissues and movement of fluid through plants are unlike the circulatory system of vertebrates. Whereas vertebrates have a one-way flow of fluid propelled by a contracting heart through a contained tubular system, phloem sap, propelled instead by a pressure flow mechanism, can move in either direction. (32.5) Teaching Tips Many phloem saps other than maple syrup are used commercially. For example, phloem sap from rubber trees native to the Brazilian Amazon was once the major source of rubber. (Most rubber is now synthetically produced.) Pine oil, derived from pine tree resin, is the active ingredient in Pine-Sol cleaner. (32.5-32.6) Active transport moves sugar into the phloem tissues. Water follows due to osmosis.

As sugar is removed at a sugar sink, water follows. High sugar concentration Phloem Xylem At a sugar source, sugar is loaded into a phloem tube and water follows, raising the pressure in the tube. As sugar is removed at a sugar sink, water follows. The increase in pressure at the sugar source and decrease at the sugar sink cause phloem sap to flow from source to sink. 1 High water pressure Sugar 2 Water Sugar source Source cell (in leaf) Sugar sink Sink cell (in storage root) Figure 32.5b Pressure flow in plant phloem from a sugar source to a sugar sink (and the return of water to the source via xylem) 3 Sugar 4 Water Low sugar concentration Low water pressure

Animation: Translocation of Phloem Sap in Spring © 2018 Pearson Education, Inc.

Animation: Translocation of Phloem Sap in Summer © 2018 Pearson Education, Inc.

32.7 Plant health depends on obtaining all of the essential inorganic nutrients A plant must obtain the chemical elements—inorganic nutrients—it requires from its surroundings. Macronutrients, such as carbon and nitrogen, are needed in large amounts, mostly to build organic molecules. Micronutrients, including iron and zinc, act mainly as cofactors of enzymes. Student Misconceptions and Concerns It is important to distinguish between the acquisition of nutrients and the acquisition of food. Plants, unlike animals, do not obtain their food from the environment. Instead, plants are autotrophs that generate their own food. The essential elements required by plants are not sources of calories. (32.7–32.12) Teaching Tips Students might assume that macronutrients are large in size and micronutrients are small. Instead, the word roots “macro” and “micro” refer to the quantities of nutrients required in each category. (32.7)

(needed in relatively large amounts) (needed in only tiny quantities) 9 Macronutrients 99.7% of plant weight (needed in relatively large amounts) 9 Micronutrients 0.3% of plant weight (needed in only tiny quantities) Found in all organic compounds Carbon (C) 45.0% Molybdenum (Mo) Oxygen (O) 45.0% Iron (Fe) Hydrogen (H) 6.0% Component of proteins in electron transport chains Nitrogen (N) 1.5% Manganese (Mn) Component of nucleic acids, proteins, and chlorophyll Boron (B) Potassium (K) 1.0% Zinc (Zn) Helps regulate opening and closing of stomata Copper (Cu) The only element not also required by humans Chlorine (Cl) Calcium (Ca) 0.5% Nickel (Ni) Important to formation of cell walls; helps maintain membranes Sodium (Na) Only required by some plants Magnesium (Mg) 0.2% Figure 32.7 A summary of plant nutrients Component of chlorophyll Phosphorus (P) 0.2% Component of nucleic acids, phospholipids, and ATP Sulfur (S) 0.1% Component of proteins

32.8 Fertilizers can help prevent nutrient deficiencies The availability of nutrients in soil affects plant growth and health. Growers can often determine which nutrients are missing from soil by looking at plant symptoms. ________ shortage is the most common nutritional problem for plants. Nutrient deficiencies can often be fixed by using appropriate fertilizers, compounds given to plants via the soil to promote the plant’s growth. Student Misconceptions and Concerns It is important to distinguish between the acquisition of nutrients and the acquisition of food. Plants, unlike animals, do not obtain their food from the environment. Instead, plants are autotrophs that generate their own food. The essential elements required by plants are not sources of calories. (32.7–32.12) Teaching Tips 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 32.8 and 32.13 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. (32.8)

32.13 Most plants depend on bacteria to supply nitrogen Bacteria in the soil convert atmospheric N2 to forms that can be used by plants. Nitrogen-fixing bacteria convert atmospheric N2 to ammonia (NH3), a metabolic process called nitrogen fixation. Ammonifying bacteria add to the soil’s supply of ammonium by decomposing organic matter. Student Misconceptions and Concerns 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 more general meaning of symbiosis and the win/win nature of mutualism, a type of symbiosis. (32.13–32.15) Active Lecture Tips 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 work in small groups to explain why planting seeds in sterilized soil could be problematic. (32.13–32.14)

32.14 Mutually beneficial relationships have evolved between plants and other kinds of organisms Mycorrhizae, mutually beneficial associations between roots and fungi. fungal threads increases a plant’s absorption fungus receives some nutrients from the plant. Legumes and certain other plants have nodules in their roots that house nitrogen-fixing bacteria. Student Misconceptions and Concerns 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 more general meaning of symbiosis and the win/win nature of mutualism, a type of symbiosis. (32.13–32.15) Teaching Tips 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 32.14–32.15. (32.14–32.15) Active Lecture Tips 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 work in small groups to explain why planting seeds in sterilized soil could be problematic. (32.13–32.14)

You should now be able to Explain what happens to the materials that plants take up from the air and soil. Compare the intracellular and extracellular movements of material into root xylem. Explain why/how water moves upward in plant. Explain how guard cells control transpiration. Explain how phloem conducts sap. Discuss nutrients that plants acquire from their surroundings (mostly from the soil).

You should now be able to Explain how and why most plants depend upon bacteria to supply nitrogen. Explain how fungi help most plants absorb nutrients from the soil.