Plant Nutrition and Transport Chapter 32 Plant Nutrition and Transport

Introduction Many plants can remove toxins such as heavy metals from soils by taking them up with their roots and storing them in their bodies. After Hurricane Katrina, sunflowers were used to remove toxins from soils in some parts of New Orleans. © 2012 Pearson Education, Inc. 2

The Uptake and Transport of Plant Nutrients Figure 32.0_1 Chapter 32: Big Ideas The Uptake and Transport of Plant Nutrients Plant Nutrients and the Soil Figure 32.0_1 Chapter 32: Big Ideas Plant Nutrition and Symbiosis 3

Figure 32.0_2 Figure 32.0_2 Sunflowers, a species of plant used to detoxify soil contaminated with heavy metals 4

THE UPTAKE AND TRANSPORT OF PLANT NUTRIENTS THE UPTAKE AND TRANSPORT OF PLANT NUTRIENTS © 2012 Pearson Education, Inc. 5

32.1 Plants acquire nutrients from air, water, and soil Plant growth uses air, water, and soil. Plants obtain water, minerals, and some oxygen from the soil. Student Misconceptions and Concerns The first five 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? 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, humans get most of our dietary carbohydrates from plants. © 2012 Pearson Education, Inc. 6

32.1 Plants acquire nutrients from air, water, and soil The sugars made by plants in photosynthesis use carbon and oxygen from the atmosphere and hydrogen from water. Plants use cellular respiration to break down some of these sugars obtaining energy and consuming oxygen. Student Misconceptions and Concerns The first five 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? 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, humans get most of our dietary carbohydrates from plants. © 2012 Pearson Education, Inc. 7

O2 CO2 Light H2O Sugar O2 CO2 H2O and minerals Figure 32.1A Figure 32.1A The uptake of nutrients by a plant O2 CO2 H2O and minerals 8

32.1 Plants acquire nutrients from air, water, and soil A plant must move water from its roots to its leaves and deliver sugars to specific areas of its body. Student Misconceptions and Concerns The first five 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? 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, humans get most of our dietary carbohydrates from plants. © 2012 Pearson Education, Inc. 9

Figure 32.1B Figure 32.1B A giant sequoia, a product of photosynthesis 10

32.2 The plasma membranes of root cells control solute uptake Root hairs greatly increase a root’s absorptive surface. Student Misconceptions and Concerns The first five 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? Teaching Tips 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. © 2012 Pearson Education, Inc. 11

Figure 32.2A Figure 32.2A Root hairs of a radish seedling 12

32.2 The plasma membranes of root cells control solute uptake Water and solutes can move through the root’s epidermis and cortex by going through cells, between cells, or through some combination of these routes. Student Misconceptions and Concerns The first five 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? Teaching Tips 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. © 2012 Pearson Education, Inc. 13

Figure 32.2B Root hair Epidermis Cortex Phloem Key Dermal tissue system Ground tissue system Vascular tissue system Casparian strip Xylem Endodermis Extracellular route, via cell walls and spaces between cells; stopped by Casparian strip Casparian strip Xylem Figure 32.2B Routes of water and solutes from soil to root xylem Root hair Intracellular route, via cell interiors, through plasmodesmata Plasmodesmata Epidermis Endodermis Cortex 14

32.2 The plasma membranes of root cells control solute uptake Once the water and solutes reach the endodermis, a continuous waxy barrier called the Casparian strip stops them from entering the xylem via cell walls and forces them to cross the selectively permeable plasma membrane of an endodermal cell to enter the xylem (water-conducting tissue) for transport upward. Student Misconceptions and Concerns The first five 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? Teaching Tips 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. Animation: Transport in Roots © 2012 Pearson Education, Inc. 15

Key Root hair Epidermis Cortex Phloem Casparian strip Xylem Endodermis Figure 32.2B_1 Root hair Epidermis Cortex Phloem Casparian strip Xylem Figure 32.2B_1 Routes of water and solutes from soil to root xylem (part 1) Endodermis Key Dermal tissue system Ground tissue system Vascular tissue system 16

Figure 32.2B_2 Extracellular route, via cell walls and spaces between cells; stopped by Casparian strip Casparian strip Xylem Root hair Intracellular route, via cell interiors, through plasmodesmata Plasmodesmata Epidermis Endodermis Figure 32.2B_2 Routes of water and solutes from soil to root xylem (part 2) Key Cortex Dermal tissue system Ground tissue system Vascular tissue system 17

32.3 Transpiration pulls water up xylem vessels Xylem sap consists of water and dissolved inorganic nutrients. Xylem tissues of angiosperms consist of very thin tubes composed of two types of cells that conduct xylem sap up a plant: tracheids and vessel elements. Student Misconceptions and Concerns The first five 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? Teaching Tips 1. The cohesive property of water allows some insects to walk or stand on a liquid water surface. The cohesion and adhesion of water is also the reason why we need to dry ourselves off after taking a shower, since water still clings to our skin and hair. 2. 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. © 2012 Pearson Education, Inc. 18

32.3 Transpiration pulls water up xylem vessels What force moves xylem sap up against the downward pull of gravity? Root pressure, the accumulation of water in roots by osmosis, can push xylem sap up a few meters. Transpiration, the loss of water by evaporation from leaves (and other aerial parts of a plant) is regulated by guard cells surrounding stomata and can move xylem sap to the top of the tallest tree. Student Misconceptions and Concerns The first five 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? Teaching Tips 1. The cohesive property of water allows some insects to walk or stand on a liquid water surface. The cohesion and adhesion of water is also the reason why we need to dry ourselves off after taking a shower, since water still clings to our skin and hair. 2. 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. © 2012 Pearson Education, Inc. 19

32.3 Transpiration pulls water up xylem vessels Transpiration can pull xylem sap up a tree because of two special properties of water: Cohesion is the sticking together of molecules of the same kind. Adhesion is the sticking together of molecules of different kinds. Student Misconceptions and Concerns The first five 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? Teaching Tips 1. The cohesive property of water allows some insects to walk or stand on a liquid water surface. The cohesion and adhesion of water is also the reason why we need to dry ourselves off after taking a shower, since water still clings to our skin and hair. 2. 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. Animation: Transpiration Animation: Water Transport © 2012 Pearson Education, Inc. 20

32.3 Transpiration pulls water up xylem vessels The overall process of this movement of xylem sap is called the transpiration-cohesion-tension mechanism. In this process, the air’s pull on water creates a tension and that tension pulls on an unbroken chain of water molecules in the xylem held together by cohesion and helped upward by adhesion. Therefore xylem sap moves up without any energy expenditure by the plant. Student Misconceptions and Concerns The first five 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? Teaching Tips 1. The cohesive property of water allows some insects to walk or stand on a liquid water surface. The cohesion and adhesion of water is also the reason why we need to dry ourselves off after taking a shower, since water still clings to our skin and hair. 2. 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. © 2012 Pearson Education, Inc. 21

Cohesion and adhesion in the xylem Figure 32.3 Leaf Xylem sap Mesophyll cells Air space within leaf Stoma 1 Water molecule Outside air Transpiration Adhesion 4 Stem Cell wall Water molecule 2 Flow of water Xylem cells Cohesion Cohesion and adhesion in the xylem Figure 32.3 The flow of water up a tree Root Xylem sap 3 Root hair Soil particle Water Water uptake from soil 22

Leaf Xylem sap Mesophyll cells Air space within leaf Stoma Figure 32.3_1 Leaf Xylem sap Mesophyll cells Air space within leaf Stoma 1 Water molecule Outside air Figure 32.3_1 The flow of water up a tree (part 1) Transpiration 23

Stem Water molecule Xylem cells Cohesion Cohesion in the xylem 2 Figure 32.3_2 Stem Water molecule 2 Xylem cells Cohesion Figure 32.3_2 The flow of water up a tree (part 2) Cohesion in the xylem 24

Root Xylem sap Root hair Soil particle Water Water uptake from soil 3 Figure 32.3_3 Root Xylem sap 3 Root hair Soil particle Water Figure 32.3_3 The flow of water up a tree (part 3) Water uptake from soil 25

Cohesion and adhesion in the xylem Figure 32.3_4 Adhesion 4 Stem Cell wall Water molecule 2 Xylem cells Figure 32.3_4 The flow of water up a tree (part 4) Cohesion Cohesion and adhesion in the xylem 26

32.4 Guard cells control transpiration A plant must make a trade-off between its need for water and to make food by photosynthesis. Stomata can open and close and help plants adjust their transpiration rates to changing environmental conditions. Guard cells control the opening of a stoma by changing shape. Student Misconceptions and Concerns The first five 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? 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 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. © 2012 Pearson Education, Inc. 27

32.4 Guard cells control transpiration Stomata open when guard cells take up water in the following process: Potassium is actively taken up by guard cells from nearby cells. This creates an osmotic gradient and water follows. Uneven cell walls of guard cells cause them to bow when water is taken up. The bowing of the guard cells causes the pore of the stoma to open. When guard cells lose K+ ions, the guard cells become flaccid and the stoma closes. Student Misconceptions and Concerns The first five 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? 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 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. © 2012 Pearson Education, Inc. 28

Figure 32.4 How guard cells control stomata K Vacuole H2O H2O H2O Figure 32.4 How guard cells control stomata H2O Stoma Stoma opening Stoma closing 29

Guard cells H2O H2O H2O H2O H2O H2O K Vacuole H2O H2O H2O H2O Stoma Figure 32.4_1 Guard cells H2O H2O H2O H2O H2O H2O K Vacuole H2O H2O H2O Figure 32.4_1 How guard cells control stomata (part 1) H2O Stoma Stoma opening Stoma closing 30

Figure 32.4_2 Stoma opening Figure 32.4_2 How guard cells control stomata (part 2) 31

Figure 32.4_3 Stoma closing Figure 32.4_3 How guard cells control stomata (part 3) 32

32.4 Guard cells control transpiration Several factors influence guard cell activity. In general, stomata are open during the day and closed at night. Sunlight signals guard cells to accumulate K+ and open stomata. Low CO2 concentration in leaves also signals guard cells to open stomata. Plants have natural rhythms that help them close stomata at night to conserve water. Plants may also close stomata during the day to conserve water when necessary. Student Misconceptions and Concerns The first five 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? 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 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. © 2012 Pearson Education, Inc. 33

32.5 Phloem transports sugars Phloem sap transports sugars made by photosynthesis and using a pressure flow mechanism. At a sugar source sugar is loaded into the phloem tube, sugar raises the solute concentration in the tube, and water follows, raising the pressure in the tube. Student Misconceptions and Concerns 1. The first five 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? 2. Although analogies are often useful, some of their particulars 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. 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. © 2012 Pearson Education, Inc. 34

32.5 Phloem transports sugars At a sugar sink sugar is removed, water follows, and phloem sap flows from source to sink in a process called the pressure flow mechanism. Student Misconceptions and Concerns 1. The first five 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? 2. Although analogies are often useful, some of their particulars 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. 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. Animation: Translocation of Phloem Sap in Spring Animation: Translocation of Phloem Sap in Summer © 2012 Pearson Education, Inc. 35

Sieve- tube element Sieve plate Sieve- tube element Figure 32.5A Sieve- tube element Sieve plate Figure 32.5A Food-conducting cells of phloem Sieve- tube element 36

Sieve- tube element Sieve plate Sieve- tube element Figure 32.5A_1 Figure 32.5A_1 Food-conducting cells of phloem (micrograph) Sieve- tube element 37

Phloem Sugar source Sugar sink Figure 32.5B Phloem Xylem High sugar concentration 1 High water pressure Sugar 2 Water Sugar source Source cell (in leaf) Sieve plate 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 38

High sugar concentration Figure 32.5B_1 Phloem Xylem High sugar concentration 1 High water pressure Sugar 2 Water Source cell (in leaf) Sieve plate Figure 32.5B_1 Pressure flow in plant phloem from a sugar source to a sugar sink (and the return of water to the source via xylem) (part 1) 39

Sink cell (in storage root) Figure 32.5B_2 Phloem Xylem Sink cell (in storage root) 3 Sugar 4 Water Figure 32.5B_2 Pressure flow in plant phloem from a sugar source to a sugar sink (and the return of water to the source via xylem) (part 2) Low sugar concentration Low water pressure 40

32.5 Phloem transports sugars Plant biologists use aphids to study phloem sap. Pressure in the phloem sap force-feeds an aphid. If an aphid is severed at the stylet (sucking mouthpart) and only the stylet remains, phloem sap continues to flow into the stylet. Student Misconceptions and Concerns 1. The first five 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? 2. Although analogies are often useful, some of their particulars 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. 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. © 2012 Pearson Education, Inc. 41

Figure 32.5C Aphids feeding on a branch Aphid with phloem droplet Stylet of aphid Figure 32.5C Aphids feeding, a process used to study the flow of phloem sap Aphid’s stylet inserted into a phloem cell Severed stylet dripping phloem sap 42

Aphids feeding on a branch Figure 32.5C_1 Figure 32.5C_1 Aphids feeding, a process used to study the flow of phloem sap (part 1) Aphids feeding on a branch 43

Aphid’s stylet inserted into a phloem cell Figure 32.5C_2 Figure 32.5C_2 Aphids feeding, a process used to study the flow of phloem sap (part 2) Stylet of aphid Aphid’s stylet inserted into a phloem cell 44

Aphid with phloem droplet Figure 32.5C_3 Figure 32.5C_3 Aphids feeding, a process used to study the flow of phloem sap (part 3) Aphid with phloem droplet 45

Severed stylet dripping phloem sap Figure 32.5C_4 Figure 32.5C_4 Aphids feeding, a process used to study the flow of phloem sap (part 4) Severed stylet dripping phloem sap 46

PLANT NUTRIENTS AND THE SOIL PLANT NUTRIENTS AND THE SOIL © 2012 Pearson Education, Inc. 47

32.6 Plant health depends on a complete diet of essential inorganic nutrients A plant must obtain inorganic substances to survive and grow. Essential elements are those that a plant must obtain to complete its life cycle of growth and have reproductive success. 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. 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. © 2012 Pearson Education, Inc. 48

32.6 Plant health depends on a complete diet of essential inorganic nutrients There are 17 elements essential to plant growth and reproduction. There are nine macronutrients that plants require in relatively large amounts. There are eight micronutrients that plants require in relatively small amounts. Both types of nutrients have vital functions. 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. 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. © 2012 Pearson Education, Inc. 49

32.6 Plant health depends on a complete diet of essential inorganic nutrients Macronutrients are components of organic molecules and include carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, potassium, calcium, and magnesium. These six make up 98% of a plant’s dry weight. 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. 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. © 2012 Pearson Education, Inc. 50

32.6 Plant health depends on a complete diet of essential inorganic nutrients Micronutrients often act as cofactors and include chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum. 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. 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. © 2012 Pearson Education, Inc. 51

Complete solution containing all minerals (control) Figure 32.6 Figure 32.6 A hydroponic culture experiment Complete solution containing all minerals (control) Solution lacking potassium (experimental) 52

32.7 CONNECTION: 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. Nitrogen shortage is the most common nutritional problem for plants. 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. 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 32.7 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. © 2012 Pearson Education, Inc. 53

32.7 CONNECTION: Fertilizers can help prevent nutrient deficiencies Fertilizers are compounds given to plants to promote growth. Nutrient deficiencies can be alleviated by adding to soil inorganic chemical fertilizers or compost, a soil-like mixture of decomposed organic matter. 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. 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 32.7 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. © 2012 Pearson Education, Inc. 54

Phosphorus-deficient Figure 32.7A Healthy Nitrogen-deficient Phosphorus-deficient Figure 32.7A The most common mineral deficiencies as seen in corn leaves Potassium-deficient 55

Figure 32.7B Figure 32.7B Steam produced by the metabolic activity of organisms within a compost pile 56

32.8 Fertile soil supports plant growth Soil horizons are layers of soil with different characteristics. The A horizon, or topsoil, is subject to weathering and contains humus (decayed organic matter) and many soil organisms. The B horizon primarily consists of clay and dissolved elements. The C horizon consists of rocks of the “parent material” from which soil is formed. 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. Teaching Tips 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. Animation: How Plants Obtain Minerals from Soil © 2012 Pearson Education, Inc. 57

Figure 32.8A A B Figure 32.8A Three soil horizons visible beneath grass C 58

32.8 Fertile soil supports plant growth A soil’s physical and chemical characteristics affect plant growth. Small rock and clay particles hold water and ions and allow oxygen to diffuse into plant roots. Humus provides nutrients and supports the growth of organisms that enhance soil fertility. 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. Teaching Tips 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. © 2012 Pearson Education, Inc. 59

32.8 Fertile soil supports plant growth Anions such as nitrate are readily available to plants because they are not bound to soil particles. Cations such as K+ adhere to soil particles. In cation exchange, root hairs release H+ ions, which displace cations from soil particles, and then absorb the free cations. 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. Teaching Tips 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. © 2012 Pearson Education, Inc. 60

Soil particle surrounded by film of water Root hair Figure 32.8B–C Soil particle surrounded by film of water Root hair Air space Water Figure 32.8B–C A close-up view of roots K K K H K Clay particle K K K K K K Root hair 61

Soil particle surrounded by film of water Root hair Figure 32.8B Soil particle surrounded by film of water Root hair Air space Water Figure 32.8B A close-up view of root hairs in soil 62

Clay particle Root hair K K K H K K K K K K K Figure 32.8C Figure 32.8C Cation exchange 63

32.9 CONNECTION: Soil conservation is essential to human life Human practices in agriculture have degraded soils. Irrigation can gradually make soil salty. Plowed lands are subject to erosion by wind and rain, which removes topsoil. Chemical fertilizers are costly and may contaminate groundwater. 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. Teaching Tips The U.S. Department of Agriculture’s Natural Resources Conservation Service provides numerous links and abundant information on soil conservation at www.nrcs.usda.gov/feature/. © 2012 Pearson Education, Inc. 64

Figure 32.9A Figure 32.9A A sinkhole caused by overuse of groundwater for irrigation 65

Figure 32.9B Figure 32.9B A dust storm in the American Great Plains during the 1930s 66

32.9 CONNECTION: Soil conservation is essential to human life Good soil management includes water-conserving irrigation, erosion control, and the prudent use of herbicides and fertilizers. 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. Teaching Tips The U.S. Department of Agriculture’s Natural Resources Conservation Service provides numerous links and abundant information on soil conservation at www.nrcs.usda.gov/feature/. © 2012 Pearson Education, Inc. 67

Figure 32.9C Figure 32.9C Planting to prevent soil erosion in a hilly area 68

32.10 CONNECTION: Organic farmers follow principles of sustainable agriculture Organic farming promotes sustainable agriculture, a system embracing farming methods that are conservation-minded, environmentally safe, and profitable. The USDA has established guidelines for foods labeled “organic.” 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. Teaching Tips 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. © 2012 Pearson Education, Inc. 69

32.10 CONNECTION: Organic farmers follow principles of sustainable agriculture Organic farming guidelines are intended to sustain biological diversity, maintain soil quality, reduce or eliminate the use of chemical pesticides, avoid use of genetically modified plants, and reduce or eliminate the use of chemical fertilizers. 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. Teaching Tips 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. © 2012 Pearson Education, Inc. 70

Figure 32.10 Figure 32.10 An organic farmer harvesting sweet corn 71

32.11 CONNECTION: Agricultural research is improving the yields and nutritional values of crops Advances in genetic engineering have led to many improvements in crops that are more resistant to disease and insects, reducing the need to use pesticides, are resistant to weed-killing herbicides, reducing the need to till the soil, which promotes erosion, and have improved nutritional quality, allowing less land to feed more people. 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. Teaching Tips 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. © 2012 Pearson Education, Inc. 72

Figure 32.11 Figure 32.11 Researchers with high-protein rice 73

PLANT NUTRITION AND SYMBIOSIS PLANT NUTRITION AND SYMBIOSIS © 2012 Pearson Education, Inc. 74

32.12 Most plants depend on bacteria to supply nitrogen The Earth’s atmosphere consists of about 80% nitrogen. However, nitrogen deficiency is the most common nutritional problem in plants. Why is that? Plants cannot absorb nitrogen directly from the air. Instead, to be used by plants, nitrogen must be converted to ammonium (NH4+) or nitrate (NO3–). 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. Teaching 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 explain why planting seeds in sterilized soil could be problematic. © 2012 Pearson Education, Inc. 75

32.12 Most plants depend on bacteria to supply nitrogen Soil bacteria can convert N2 gas from the air into forms usable by plants via several processes. Nitrogen-fixing bacteria convert atmospheric N2 to ammonia (NH3) in a process called nitrogen fixation. Ammonifying bacteria add to the supply of ammonium by decomposing organic matter. Nitrifying bacteria convert ammonium to nitrates, the form most often taken up by plants. 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. Teaching 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 explain why planting seeds in sterilized soil could be problematic. © 2012 Pearson Education, Inc. 76

Nitrogen-fixing bacteria Figure 32.12 N2 ATMOSPHERE ATMOSPHERE SOIL Amino acids, etc. N2 Nitrogen-fixing bacteria NH4 H NH3 NH4 NO3 SOIL (ammonium) (nitrate) Nitrifying bacteria Ammonifying bacteria Figure 32.12 The roles of bacteria in supplying nitrogen to plants Organic material Root 77

Nitrogen-fixing bacteria Figure 32.12_1 N2 ATMOSPHERE SOIL Nitrogen-fixing bacteria H NH3 NH4 (ammonium) Figure 32.12_1 The roles of bacteria in supplying nitrogen to plants (part 1) Ammonifying bacteria Organic material 78

Amino acids, etc. Nitrifying bacteria Root Figure 32.12_2 Amino acids, etc. NH4 NH4 NO3 (ammonium) (nitrate) Nitrifying bacteria Figure 32.12_2 The roles of bacteria in supplying nitrogen to plants (part 2) Root 79

32.13 EVOLUTION CONNECTION: Plants have evolved symbiotic relationships that are mutually beneficial Most plants form mutually beneficial symbioses with fungi called mycorrhizae, which act like extensions of plant roots, increasing the area for absorption of water and minerals from soil, selectively absorb phosphate and other minerals from the soil, release growth factors and antibiotics into the soil, and have evolved with plants and were important to plants successfully invading land. 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. Teaching Tips 1. For additional specific details on mycorrhizal relationships, see the literature exchange website for mycorrhiza at http://mycorrhiza.ag.utk.edu/. 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 32.13–32.14. © 2012 Pearson Education, Inc. 80

Fungal filament Root Figure 32.13A Figure 32.13A Part of a eucalyptus mycorrhiza Root 81

32.13 EVOLUTION CONNECTION: Plants have evolved symbiotic relationships that are mutually beneficial Some plants form symbioses with nitrogen-fixing bacteria. Legumes (peas, beans, alfalfa, and others) form root nodules to house nitrogen-fixing symbionts in the genus Rhizobium. Other plants, such as alders, form symbioses with other kinds of nitrogen-fixing bacteria. Plants that form these associations are rich in nitrogen. Mycorrhizae and nitrogen-fixing bacteria benefit by receiving sugars from the plants they colonize. 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. Teaching Tips 1. For additional specific details on mycorrhizal relationships, see the literature exchange website for mycorrhiza at http://mycorrhiza.ag.utk.edu/. 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 32.13–32.14. © 2012 Pearson Education, Inc. 82

Figure 32.13B Root nodules on a soybean plant Shoot Bacteria within vesicle in an infected cell Nodules Roots Figure 32.13B Root nodules on a soybean plant 83

Bacteria within vesicle in an infected cell Figure 32.13B_1 Bacteria within vesicle in an infected cell Figure 32.13B_1 Root nodules on a soybean plant (part 1) 84

Shoot Nodules Roots Figure 32.13B_2 Figure 32.13B_2 Root nodules on a soybean plant (part 2) 85

32.14 The plant kingdom includes epiphytes, parasites, and carnivores Some plants have nutritional adaptations that take advantage of other organisms. Epiphytes, including many orchids, grow anchored on other plants and absorb water and minerals from rain. Parasitic plants, such as dodder and mistletoe, may not use photosynthesis, use their roots to tap into the host plant’s vascular system, and absorb sugars and minerals from the host plant. 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. Teaching Tips 1. The International Carnivorous Plant Society maintains a website at www.carnivorousplants.org. The site contains many beautiful photographs of carnivorous plants, answers to FAQs, and numerous related resources. 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 32.13–32.14. © 2012 Pearson Education, Inc. 86

Figure 32.14A Figure 32.14A An orchid plant, a type of epiphyte, growing on the trunk of a tree 87

Figure 32.14B Figure 32.14B Dodder growing on a pickleweed 88

Figure 32.14C Figure 32.14C Mistletoe growing on an oak tree 89

32.14 The plant kingdom includes epiphytes, parasites, and carnivores Carnivores, such as a sundew plant or Venus flytrap, capture and digest small animals such as insects, absorb inorganic elements from prey, and are found in nutrient-poor environments. 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. Teaching Tips 1. The International Carnivorous Plant Society maintains a website at www.carnivorousplants.org. The site contains many beautiful photographs of carnivorous plants, answers to FAQs, and numerous related resources. 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 32.13–32.14. Video: Sun Dew Trapping Prey © 2012 Pearson Education, Inc. 90

Figure 32.14D Figure 32.14D A sundew plant trapping a winged ant 91

Figure 32.14E Figure 32.14E A Venus flytrap capturing a fly 92

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. Describe the function of the Casparian strip. Explain how root pressure is generated. Explain how the transpiration-cohesion-tension mechanism causes the ascent of xylem sap in a plant. © 2012 Pearson Education, Inc. 93

You should now be able to Explain how guard cells control transpiration. Explain how, when, and where phloem conducts sap. Explain how hydroponics helps to determine which plant nutrients are essential. Distinguish between micronutrients and macronutrients and note examples of each. Explain how fertilizers can prevent nutrient deficiencies in plants. © 2012 Pearson Education, Inc. 94

You should now be able to Describe the properties of different soil layers. Explain how irrigation and the use of fertilizers affect agriculture. Compare the processes and products of organic and conventional agriculture. Describe new strategies to improve the protein content of crops. Explain how and why most plants depend upon bacteria to supply nitrogen. © 2012 Pearson Education, Inc. 95

You should now be able to Explain how fungi help most plants absorb nutrients from the soil. Describe examples of parasitic and carnivorous plants. © 2012 Pearson Education, Inc. 96

(regulated by guard cells surrounding stomata) H2O Figure 32.UN01 Transpiration (regulated by guard cells surrounding stomata) H2O Flow of water 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) 97

Low sugar concentration High sugar concentration Figure 32.UN02 Source cell Sink cell Sugar Sugar s s u r e o e f l P h l e o m pr w s a p v ia Figure 32.UN02 Reviewing the Concepts, 32.5 Low sugar concentration High sugar concentration 98

Nitrogen-fixing bacteria Figure 32.UN03 N2 ATMOSPHERE Amino acids, etc. SOIL Nitrogen-fixing bacteria NH4 H NH3 NH4 NO3 (ammonium) Nitrifying bacteria (nitrate) Ammonifying bacteria Figure 32.UN03 Reviewing the Concepts, 32.12 Organic material Root 99

(a) (b) (c) (d) (e) (f) Transport in plants involves movement of Figure 32.UN04 Transport in plants involves movement of water and minerals sugar from through from through (a) (b) (c) (d) Figure 32.UN04 Connecting the Concepts, question 1 to driven by to driven by pressure flow leaves (e) (f) 100

Figure 32.UN05 Figure 32.UN05 Applying the Concepts, question 9 101