REPRODUCTION OF FLOWERING PLANTS

REPRODUCTION OF FLOWERING PLANTS
REPRODUCTION OF FLOWERING PLANTS Copyright © 2009 Pearson Education, Inc.

31.9 The flower is the organ of sexual reproduction in angiosperms
Flowers typically contain four types of highly modified leaves called floral organs Sepals—enclose and protect flower bud Petals—showy; attract pollinators Stamens—male reproductive structures Carpels—female reproductive structures Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. Teaching Tips 1. The authors note in Module 31.9 that Modules 17.9 and provide important background information on the sexual life cycle of a flowering plant. If these modules have not been addressed previously, consider adding them to the Chapter 31 assignment. 2. More students will recall that stamens are the male organs if they emphasize the word’s last syllable: stamens. 3. The four main parts of a flower, which are modified leaves, represent additional examples of evolutionary remodeling. Copyright © 2009 Pearson Education, Inc.

A stamen has two parts Anther—produces pollen, which house cells which develop into sperm Filament—elevates anther A carpel has three parts Stigma—site of pollination Style—“neck” that leads to ovary Ovary—houses ovules, which contain developing egg Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. Teaching Tips 1. The authors note in Module 31.9 that Modules 17.9 and provide important background information on the sexual life cycle of a flowering plant. If these modules have not been addressed previously, consider adding them to the Chapter 31 assignment. 2. More students will recall that stamens are the male organs if they emphasize the word’s last syllable: stamens. 3. The four main parts of a flower, which are modified leaves, represent additional examples of evolutionary remodeling. For the BLAST Animation Flower Structure, go to Animation and Video Files. Video: Flower Blooming (time lapse) Copyright © 2009 Pearson Education, Inc.

Stigma Carpel Style Stamen Anther Ovary Filament Petal Ovule Sepal
Figure 31.9A The structure of a flower. Petal Ovule Sepal

Angiosperm life cycle overview Fertilization occurs in the ovule; the fertilized egg develops into an embryo encased in a seed The ovary develops into a fruit, which protects the seed and aids in dispersal The seed germinates under suitable conditions to produce a seedling, which grows into a mature plant Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. Teaching Tips 1. The authors note in Module 31.9 that Modules 17.9 and provide important background information on the sexual life cycle of a flowering plant. If these modules have not been addressed previously, consider adding them to the Chapter 31 assignment. 2. More students will recall that stamens are the male organs if they emphasize the word’s last syllable: stamens. 3. The four main parts of a flower, which are modified leaves, represent additional examples of evolutionary remodeling. Video: Flowering Plant Life (time lapse) Copyright © 2009 Pearson Education, Inc.

Ovary, containing ovule Embryo Seed Fruit (mature ovary),
containing seed Mature plant with flowers, where fertilization occurs Figure 31.9B Life cycle of a generalized angiosperm. Seedling Germinating seed

31.10 The development of pollen and ovules culminates in fertilization
Plant life cycles involve alternating diploid (2n) and haploid (n) generations The diploid generation is called the sporophyte Specialized diploid cells in anthers and ovules undergo meiosis to produce haploid spores The haploid spores undergo mitosis and produce the haploid generation The haploid generation is called the gametophyte Gametophytes produce gametes via mitosis Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. 2. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals. Teaching Tips 1. Plants that produce lightweight, windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains. Copyright © 2009 Pearson Education, Inc.

The male gametophyte is a pollen grain A cell in the anther undergoes meiosis to produce four haploid spores Each spore divides via mitosis to produce two cells called the tube cell and generative cell A tough wall forms around the cells to produce a pollen grain Pollen grains are released from the anther Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. 2. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals. Teaching Tips 1. Plants that produce lightweight, windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains. Copyright © 2009 Pearson Education, Inc.

The female gametophyte is an embryo sac A cell in the ovule undergoes meiosis to produce four haploid spores Three of the spores degenerate The surviving spore undergoes a series of mitotic divisions to produce the embryo sac One cell within the embryo sac is an egg ready for fertilization One central cell within the embryo sac has two nuclei and will produce endosperm Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. 2. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals. Teaching Tips 1. Plants that produce lightweight, windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains. Copyright © 2009 Pearson Education, Inc.

Pollination Transfer of pollen from anther to stigma Pollen is carried by wind, water, and animals Pollen grain germination Tube nucleus produces pollen tube, which grows down through the style to the ovary Generative nucleus divides to produce two sperm Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. 2. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals. Teaching Tips 1. Plants that produce lightweight, windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains. Copyright © 2009 Pearson Education, Inc.

Double fertilization One sperm fertilizes the egg to produce a zygote One sperm fuses with the central cell nuclei to produce 3n endosperm Endosperm nourishes the developing embryo Coconut “milk” is an example of liquid endosperm. Coconut “meat” is solid endosperm. Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. 2. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals. Teaching Tips 1. Plants that produce lightweight, windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains. For the Discovery Video Plant Pollination, go to Animation and Video Files. For the BLAST Animation Pollination and Fertilization, go to Animation and Video Files. Video: Bat Pollinating Agave Plant Video: Bee Pollinating Animation: Plant Fertilization Copyright © 2009 Pearson Education, Inc.

Wall forms Mitosis Egg cell
Development of male gametophyte (pollen grain) Development of female gametophyte (embryo sac) Anther Ovule Cell within anther Ovary Meiosis Meiosis Surviving cell (haploid spore) Four haploid spores Single spore Wall forms Mitosis Figure Gametophyte development and fertilization in an angiosperm. Mitosis (of each spore) Two cells Pollen grain released from anther Embryo sac Egg cell

Pollen Wall germinates forms Pollination Two cells Embryo Pollen grain
released from anther Embryo sac Egg cell Two sperm in pollen tube Figure Gametophyte development and fertilization in an angiosperm. Pollen tube enters embryo sac Triploid (3n) endosperm nucleus Two sperm discharged Diploid (2n) zygote (egg plus sperm) Double fertilization occurs

31.11 The ovule develops into a seed
The zygote divides many times via mitosis to produce the embryo The embryo consists of tiny root and shoot apical meristems and one or two cotyledons A tough seed coat develops Seed dormancy Embryo growth and development are suspended Allows delay of germination until conditions are favorable Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. Teaching Tips 1. Coconut milk is an example of liquid endosperm. Coconut meat is solid endosperm. Animation: Seed Development Copyright © 2009 Pearson Education, Inc.

Triploid cell Ovule Cotyledons Zygote Endosperm Seed Two cells coat
Shoot Figure 31.11A Development of a eudicot plant embryo. Embryo Root Seed

31.11 The ovule develops into a seed
Eudicot seeds Two cotyledons Apical meristems lack protective sheaths Endosperm absorbed by cotyledons Monocot seeds Single cotyledon Apical meristems have a protective sheaths Endosperm is present Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. Teaching Tips 1. Coconut milk is an example of liquid endosperm. Coconut meat is solid endosperm. Copyright © 2009 Pearson Education, Inc.

Embryonic leaves Embryonic shoot Embryonic root Cotyledons Seed coat
Common bean (eudicot) Fruit tissue Cotyledon Seed coat Figure 31.11B Seed structure. Endosperm Embryonic leaf Embryonic Shoot Sheath Embryonic root Corn (monocot)

31.12 The ovary develops into a fruit
Hormonal changes induced by fertilization trigger the ovary to develop into a fruit Fruits protect the seed and aid in dispersal Mature fruits may be fleshy or dry Fleshy fruits—oranges, tomatoes, grapes Dry fruits—beans, nuts, grains Student Misconceptions and Concerns 1. The development of the male and female gametophytes in flowers is rarely well understood by students who are more familiar with animals. A thorough review of the alternation of generations life cycle of plants is helpful before discussing the details of plant sexual reproduction. 2. The distinction between fruits and vegetables is a frequent, if trivial, point of contention. Module specifically notes the structures and functions of fruits; to further understanding, consider discussing what the term vegetable means as well. Teaching Tips 1. Seed dispersal mechanisms are diverse and reflect specific adaptive strategies. The inventor of Velcro was inspired by the seed dispersal mechanisms of the common burdock plant. Animation: Fruit Development Copyright © 2009 Pearson Education, Inc.

1 2 3 Figure 31.12A Development of a fruit, a pea pod.

Upper part of carpel Ovule Seed Pod (opened) Ovary wall Sepal
Figure 31.12A Development of a fruit, a pea pod. Sepal

31.13 Seed germination continues the life cycle
Germination breaks seed dormancy Germination begins when water is taken up Eudicot seedling shoots emerge from the soil with the apical meristem “hooked” downward to protect it Monocot seedling shoots are covered by a protective sheath and emerge straight from the soil Teaching Tips 1. Seed production in plants clearly illustrates the ability of organisms to produce more offspring than can survive, a premise of natural selection. While discussing seed production, consider reminding students of this important principle, which is well-illustrated in plants. Copyright © 2009 Pearson Education, Inc.

Foliage leaves Cotyledon Embryonic Cotyledon shoot Cotyledon Embryonic
Figure 31.13A Pea germination (a eudicot). Embryonic root Seed coat

Foliage leaves Protective sheath enclosing shoot Embryonic root
Figure 31.13B Corn germination (a monocot). Embryonic root Cotyledon

31.14 Asexual reproduction produces plant clones
Most plants are capable of asexual reproduction, producing genetically identical offspring (clones) Production of clones via bulbs, root sprouts, and runners is common Plants are often propagated by taking cuttings, which can produce roots Plants can be cultured on specialized media in tubes Asexual reproduction can be advantageous in very stable environments Teaching Tips 1. Depending upon your prior discussions of animal reproduction and diversity, you might challenge your students to identify natural examples of animal cloning. Cnidarians and flatworms are groups that are often mentioned as examples. Copyright © 2009 Pearson Education, Inc.

Figure 31.14A Cloves of a garlic bulb.

Figure 31.14E Test-tube cloning.

PLANT STRUCTURE AND FUNCTION
PLANT STRUCTURE AND FUNCTION Copyright © 2009 Pearson Education, Inc.

31.2 The two main groups of angiosperms are the monocots and the eudicots
Monocots and eudicots differ in Number of cotyledons (seed leaves) Pattern of leaf venation Arrangement of stem vascular tissue Number of flower parts Root structure Student Misconceptions and Concerns 1. Students often fail to see the specific applications of fundamental principles of biology. For example, many structural adaptations increase the surface-to-volume ratio in plants and animals. The divisions within the human lung, as well as microvilli, leaves, and root hairs, are 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 serve as a unifying review. Teaching Tips 1. Figure 31.2 provides a visually simple but important comparison of monocots and eudicots. By referring to this figure in class, students will be able to absorb more details during lecture that they can then review at their leisure. 2. Consider bringing living examples of monocots and eudicots to class or taking a short trip outside during a related lab to quickly compare examples. Copyright © 2009 Pearson Education, Inc.

Monocots One cotyledon Parallel leaf venation Scattered vascular bundles Flower parts in 3s or multiples of 3 Fibrous roots Student Misconceptions and Concerns 1. Students often fail to see the specific applications of fundamental principles of biology. For example, many structural adaptations increase the surface-to-volume ratio in plants and animals. The divisions within the human lung, as well as microvilli, leaves, and root hairs, are 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 serve as a unifying review. Teaching Tips 1. Figure 31.2 provides a visually simple but important comparison of monocots and eudicots. By referring to this figure in class, students will be able to absorb more details during lecture that they can then review at their leisure. 2. Consider bringing living examples of monocots and eudicots to class or taking a short trip outside during a related lab to quickly compare examples. Copyright © 2009 Pearson Education, Inc.

Eudicots—most plants are eudicots Two cotyledons Branched leaf venation Ring of vascular bundles Flower parts in 4s or 5s (or multiples) Taproot system Student Misconceptions and Concerns 1. Students often fail to see the specific applications of fundamental principles of biology. For example, many structural adaptations increase the surface-to-volume ratio in plants and animals. The divisions within the human lung, as well as microvilli, leaves, and root hairs, are 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 serve as a unifying review. Teaching Tips 1. Figure 31.2 provides a visually simple but important comparison of monocots and eudicots. By referring to this figure in class, students will be able to absorb more details during lecture that they can then review at their leisure. 2. Consider bringing living examples of monocots and eudicots to class or taking a short trip outside during a related lab to quickly compare examples. Copyright © 2009 Pearson Education, Inc.

Seed leaves Leaf veins Stems Flowers Roots MONOCOTS EUDICOTS
One cotyledon Vascular bundles in complex arrangement Floral parts usually in multiples of three Fibrous root system Veins usually parallel EUDICOTS Figure 31.2 A comparison of monocots and eudicots. Two cotyledons Vascular bundles arranged in ring Floral parts usually in multiples of four or five Taproot usually present Veins usually branched

31.3 A typical plant body contains three basic organs: roots, stems, and leaves
Plants absorb water and minerals from soil through roots Plants absorb the sun’s energy and carbon dioxide from the air through shoots (stems and leaves) Plant roots depend on shoots for carbohydrates produced via photosynthesis Plant shoots depend on roots for water and minerals Teaching Tips 1. Challenge your students to suggest circumstances when apical growth is more adaptive for a plant, and other situations in which branching would be more favorable. Copyright © 2009 Pearson Education, Inc.

Terminal bud Blade Leaf Flower Petiole Axillary bud Stem Shoot system
Node Internode Root hair Root hairs Figure 31.3 The body plan of a flowering plant (a eudicot). Taproot Root system Epidermal cell

31.3 A typical plant body contains three basic organs: roots, stems, and leaves
Plant roots Anchor plant Absorb water and nutrients Store food Plant shoots Stems, leaves, and reproductive structures Stems provide support Leaves carry out photosynthesis Teaching Tips 1. Challenge your students to suggest circumstances when apical growth is more adaptive for a plant, and other situations in which branching would be more favorable. Copyright © 2009 Pearson Education, Inc.

31.4 Many plants have modified roots, stems, and leaves
Modifications of plant parts are adaptations for various functions Food or water storage Asexual reproduction Protection Climbing Photosynthesis Teaching Tips 1. The modifications of the three plant organs described in Module 31.4 reveal the remodeling nature of evolution. As Francois Jacob noted, evolution works more like a tinkerer than an engineer. The common ancestry of eudicots is revealed by the diverse modifications of three basic plant organs derived from the shared ancestors. Your students’ appreciation of the enormous evidence in support of evolution will grow if you note such examples frequently throughout your course. Copyright © 2009 Pearson Education, Inc.

Root modifications Food storage Large taproots store starches Examples include carrots, turnips, sugar beets, sweet potatoes Teaching Tips 1. The modifications of the three plant organs described in Module 31.4 reveal the remodeling nature of evolution. As Francois Jacob noted, evolution works more like a tinkerer than an engineer. The common ancestry of eudicots is revealed by the diverse modifications of three basic plant organs derived from the shared ancestors. Your students’ appreciation of the enormous evidence in support of evolution will grow if you note such examples frequently throughout your course. Copyright © 2009 Pearson Education, Inc.

Figure 31.4A The modified root of a sugar beet plant.

Stem modifications Stolon—asexual reproduction Rhizomes—storage, asexual reproduction Tubers—storage, asexual reproduction Cactus stem—water storage and photosynthesis Teaching Tips 1. The modifications of the three plant organs described in Module 31.4 reveal the remodeling nature of evolution. As Francois Jacob noted, evolution works more like a tinkerer than an engineer. The common ancestry of eudicots is revealed by the diverse modifications of three basic plant organs derived from the shared ancestors. Your students’ appreciation of the enormous evidence in support of evolution will grow if you note such examples frequently throughout your course. Copyright © 2009 Pearson Education, Inc.

Strawberry plant Potato plant Ginger plant Stolon (runner) Taproot
Rhizome Figure 31.4B Three kinds of modified stems. Tuber Rhizome

Leaf modifications Protection Cactus spine Climbing Pea plant tendril Teaching Tips 1. The modifications of the three plant organs described in Module 31.4 reveal the remodeling nature of evolution. As Francois Jacob noted, evolution works more like a tinkerer than an engineer. The common ancestry of eudicots is revealed by the diverse modifications of three basic plant organs derived from the shared ancestors. Your students’ appreciation of the enormous evidence in support of evolution will grow if you note such examples frequently throughout your course. Copyright © 2009 Pearson Education, Inc.

Figure 31.4C Modified leaves: the tendrils of a pea plant (top) and cactus spines (bottom).

31.5 Three tissue systems make up the plant body
Dermal tissue Outer protective covering Vascular tissue Support and long-distance transport Ground tissue Bulk of the plant body Food production, storage, support Teaching Tips 1. Module 31.5 can be particularly problematic for students with limited backgrounds in plant biology. The basic structures and functions of tissues and subtypes of plants are introduced, and monocots and eudicots are compared. The terminology is extensive. Students may benefit most by creating their own mini-glossary for quick reference and study before, during, and after related lectures. 2. The functions of human epidermis have some analogues in plants. As in plants, our epidermis serves as a defense against physical damage and infectious organisms. In addition, oils on our skin help us retain water (and keep the epidermis flexible). Copyright © 2009 Pearson Education, Inc.

Dermal tissue Layer of tightly packed cells called the epidermis First line of defense against damage and infection Waxy layer called cuticle reduces water loss Teaching Tips 1. Module 31.5 can be particularly problematic for students with limited backgrounds in plant biology. The basic structures and functions of tissues and subtypes of plants are introduced, and monocots and eudicots are compared. The terminology is extensive. Students may benefit most by creating their own mini-glossary for quick reference and study before, during, and after related lectures. 2. The functions of human epidermis have some analogues in plants. As in plants, our epidermis serves as a defense against physical damage and infectious organisms. In addition, oils on our skin help us retain water (and keep the epidermis flexible). Copyright © 2009 Pearson Education, Inc.

Vascular tissue Composed of xylem and phloem Arranged in bundles Ground tissue Lies between dermal and vascular tissue Eudicot stem ground tissue is divided into pith and cortex Leaf ground tissue is called mesophyll Teaching Tips 1. Module 31.5 can be particularly problematic for students with limited backgrounds in plant biology. The basic structures and functions of tissues and subtypes of plants are introduced, and monocots and eudicots are compared. The terminology is extensive. Students may benefit most by creating their own mini-glossary for quick reference and study before, during, and after related lectures. 2. The functions of human epidermis have some analogues in plants. As in plants, our epidermis serves as a defense against physical damage and infectious organisms. In addition, oils on our skin help us retain water (and keep the epidermis flexible). Copyright © 2009 Pearson Education, Inc.

Vascular tissue system
Eudicot leaf Cuticle Upper epidermis Xylem Vein Phloem Mesophyll Guard cells Lower epidermis Stoma Sheath Eudicot stem Monocot stem Vascular bundle Vascular bundle Cortex Pith Epidermis Epidermis Figure 31.5 The three tissue systems. Xylem Vascular cylinder Phloem Key Epidermis Dermal tissue system Ground tissue system Cortex Vascular tissue system Endodermis Eudicot root

Key Dermal tissue system Ground tissue system Vascular tissue system Eudicot leaf Cuticle Upper epidermis Xylem Vein Phloem Mesophyll Figure 31.5 The three tissue systems. Guard cells Lower epidermis Stoma Sheath

Key Dermal tissue system Ground tissue system Vascular tissue system Eudicot stem Monocot stem Vascular bundle Vascular bundle Cortex Figure 31.5 The three tissue systems. Pith Epidermis Epidermis

Xylem Vascular cylinder Phloem Epidermis Cortex Key Endodermis Figure 31.5 The three tissue systems. Dermal tissue system Ground tissue system Eudicot root Vascular tissue system

31.6 Plant cells and tissues are diverse in structure and function
Plants cells have three structures that distinguish them from animals cells Chloroplasts used in photosynthesis A large, fluid-filled vacuole A cell wall composed of cellulose Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. For the BioFlix Animation Tour of a Plant Cell, go to Animation and Video Files. Copyright © 2009 Pearson Education, Inc.

Plant cell wall Some plant cell walls have two layers Primary cell wall—outermost layer Secondary cell wall—tough layer inside primary wall A sticky layer called the middle lamella lies between adjacent plant cells Openings in cell walls called plasmodesmata allow cells to communicate and exchange materials easily Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Chloroplast Central Nucleus vacuole Cell walls Endoplasmic reticulum
Primary cell wall Secondary cell wall Middle lamella Mitochondrion Golgi apparatus Cell walls of adjoining cells Ribosomes Figure 31.6A The structure of a plant cell. Plasma membrane Microtubules Plasmodesmata Pit Plasma membrane

Plant cell structure is related to function There are five major types of plant cells Parenchyma cells Collenchyma cells Sclerenchyma cells Water-conducting cells Food-conducting cells Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Parenchyma cells Most abundant cell type Thin primary cell wall Lack secondary cell wall Alive at maturity Function in photosynthesis, food and water storage Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Starch-storing vesicles
Primary cell wall (thin) Pit Figure 31.6B Parenchyma cell. Starch-storing vesicles

Collenchyma cells Unevenly thickened primary cell wall Lack secondary cell wall Alive at maturity Provide flexible support Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Primary cell wall (thick) Figure 31.6C Collenchyma cell.

Sclerenchyma cells Thick secondary cell wall containing lignin Lignin is a main component of wood Dead at maturity Rigid support Two types of sclerenchyma cells are fibers and sclereids Fibers—long and thin, arranged in bundles Sclereids—shorter than fibers, present in nut shells and pear tissue Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Pits Secondary cell wall Fiber cells Primary cell wall Fiber
Figure 31.6D Sclerenchyma cells: fiber. Primary cell wall Fiber

Secondary Sclereid cell wall cells Primary Pits cell wall Sclereid
Figure 31.6D Sclerenchyma cells sclereid . Primary cell wall Pits Sclereid

Water conducting cells—tracheids and vessel elements Both have thick secondary cell walls Both are dead at maturity Chains of tracheids and vessel elements form tubes that make up the vascular tissue called xylem Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Pits Tracheids Vessel element Pits Openings in end wall
Figure 31.6E Water-conducting cells.

Food-conducting cells—sieve tube members No secondary cell wall Alive at maturity but lack most organelles Companion cells Contain organelles Control operations of sieve tube members Chains of sieve tube members, separated by porous sieve plates, form the vascular tissue called phloem Student Misconceptions and Concerns 1. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor. Teaching Tips 1. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering. 2. Students will remember the function of phloem more easily if you remind them that both phloem and food start with an “F” sound. Copyright © 2009 Pearson Education, Inc.

Sieve plate Companion cell Primary cell wall Cytoplasm
Figure 31.6F Food-conducting cell (sieve-tube member). Cytoplasm

31.7 Primary growth lengthens roots and shoots
Plant growth is indeterminate Growth occurs throughout a plant’s life Plants are categorized based on how long they live Annuals complete their life cycle in one year Biennials complete their life cycle in two years Perennials live for many years Animal growth is determinate Growth stops after a certain size is reached Student Misconceptions and Concerns 1. Students often expect determinate growth in plants, because it is characteristic of humans. However, most plant species show indeterminate growth and are capable of growing as long as they can live. Teaching Tips 1. Lobsters are one of the few animals that show indeterminate growth. Copyright © 2009 Pearson Education, Inc.

Plant growth occurs in specialized tissues called meristems Meristems are regions of active cell division Apical meristems are found at the tips of roots and shoots Primary growth occurs at apical meristems Primary growth allows roots to push downward through the soil and shoots to grow upward toward the sun Student Misconceptions and Concerns 1. Students often expect determinate growth in plants, because it is characteristic of humans. However, most plant species show indeterminate growth and are capable of growing as long as they can live. Teaching Tips 1. Lobsters are one of the few animals that show indeterminate growth. Video: Root Growth in a Radish Seed (time lapse) Copyright © 2009 Pearson Education, Inc.

Terminal bud Axillary buds Arrows = direction of growth Root tips
Figure 31.7A Locations of apical meristems, which are responsible for primary growth. Arrows = direction of growth Root tips

The apical meristems of root tips are covered by a root cap Root growth occurs behind the root cap in 3 zones Zone of cell division—the apical meristem Zone of cell elongation—cells lengthen by as much as 10 times Zone of maturation—cells differentiate into dermal, vascular, and ground tissues Student Misconceptions and Concerns 1. Students often expect determinate growth in plants, because it is characteristic of humans. However, most plant species show indeterminate growth and are capable of growing as long as they can live. Teaching Tips 1. Lobsters are one of the few animals that show indeterminate growth. Copyright © 2009 Pearson Education, Inc.

Vascular cylinder Cortex Root hair Epidermis Zone of maturation Zone of elongation Cellulose fibers Figure 31.7B Primary growth of a root. Zone of cell division Apical meristem region Key Root cap Dermal tissue system Ground tissue system Vascular tissue system

The apical meristems of shoot tips occur as buds at the stem tip and at the base of leaves Cells produced in the shoot apical meristem differentiate into dermal, vascular, and ground tissues Vascular tissue produced from the apical meristem is called primary vascular tissue Primary xylem Primary phloem Student Misconceptions and Concerns 1. Students often expect determinate growth in plants, because it is characteristic of humans. However, most plant species show indeterminate growth and are capable of growing as long as they can live. Teaching Tips 1. Lobsters are one of the few animals that show indeterminate growth. Copyright © 2009 Pearson Education, Inc.

Leaves Axillary bud meristems Apical meristem
Figure 31.7C Primary growth of a shoot. 1 2

31.8 Secondary growth increases the girth of woody plants
Secondary growth occurs at lateral meristems Lateral meristems are areas of active cell division that exist in two cylinders that extend along the length of roots and shoots Vascular cambium is a lateral meristem that lies between primary xylem and phloem Cork cambium is a lateral meristem that lies at the outer edge of the stem cortex Student Misconceptions and Concerns 1. Students typically expect that as a tree grows taller, the trunk will “stretch” upward along its entire length. This expectation arises naturally from the experience of our own growth as humans. However, as a tree grows, the entire trunk does not increase in size. Instead, growth occurs at the upper ends and through expansion of the trunk. Therefore, initials carved into the trunk of a tree will remain at that height as long as the tree is upright and healthy. Teaching Tips 1. Students may not realize that the cork used to seal a wine bottle is the same cork that is discussed in Module 31.8. 2. Students may not appreciate the many important functions of tree bark. Carving into bark, or peeling it away from a trunk, exposes the inner tissues to pathogens. In many ways, the functions of human skin and bark are similar. Copyright © 2009 Pearson Education, Inc.

Vascular cambium produces cells in two directions Secondary xylem produces wood toward the interior of the stem Secondary phloem produces the inner bark toward the exterior of the stem Cork cambium produces cells in one direction Cork cambium produces the outer bark, which is composed of cork cells Student Misconceptions and Concerns 1. Students typically expect that as a tree grows taller, the trunk will “stretch” upward along its entire length. This expectation arises naturally from the experience of our own growth as humans. However, as a tree grows, the entire trunk does not increase in size. Instead, growth occurs at the upper ends and through expansion of the trunk. Therefore, initials carved into the trunk of a tree will remain at that height as long as the tree is upright and healthy. Teaching Tips 1. Students may not realize that the cork used to seal a wine bottle is the same cork that is discussed in Module 31.8. 2. Students may not appreciate the many important functions of tree bark. Carving into bark, or peeling it away from a trunk, exposes the inner tissues to pathogens. In many ways, the functions of human skin and bark are similar. Copyright © 2009 Pearson Education, Inc.

Year 1 Early Spring Year 1 Late Summer Year 2 Late Summer Key Dermal tissue system Ground tissue system Vascular tissue system Shed epidermis Growth Growth Growth Primary xylem Epidermis Secondary xylem (wood) Cork Vascular cambium Figure 31.8A Secondary growth of a woody eudicot stem. Cortex Secondary xylem (2 years’ growth) Cork cambium Bark Primary phloem Secondary phloem

Wood annual rings show layers of secondary xylem In temperate regions, periods of dormancy stop growth of secondary xylem Rings occur in areas when new growth starts each year The bark (secondary phloem and cork) is sloughed off over time Student Misconceptions and Concerns 1. Students typically expect that as a tree grows taller, the trunk will “stretch” upward along its entire length. This expectation arises naturally from the experience of our own growth as humans. However, as a tree grows, the entire trunk does not increase in size. Instead, growth occurs at the upper ends and through expansion of the trunk. Therefore, initials carved into the trunk of a tree will remain at that height as long as the tree is upright and healthy. Teaching Tips 1. Students may not realize that the cork used to seal a wine bottle is the same cork that is discussed in Module 31.8. 2. Students may not appreciate the many important functions of tree bark. Carving into bark, or peeling it away from a trunk, exposes the inner tissues to pathogens. In many ways, the functions of human skin and bark are similar. Copyright © 2009 Pearson Education, Inc.

Wood rays are parenchyma tissue that radiate from the stem’s center Wood rays function in lateral transport and storage Most transport occurs near the vascular cambium Sapwood near the vascular cambium transports water Heartwood stores resins and wastes Transport of sugars occurs in the secondary phloem near the vascular cambium Student Misconceptions and Concerns 1. Students typically expect that as a tree grows taller, the trunk will “stretch” upward along its entire length. This expectation arises naturally from the experience of our own growth as humans. However, as a tree grows, the entire trunk does not increase in size. Instead, growth occurs at the upper ends and through expansion of the trunk. Therefore, initials carved into the trunk of a tree will remain at that height as long as the tree is upright and healthy. Teaching Tips 1. Students may not realize that the cork used to seal a wine bottle is the same cork that is discussed in Module 31.8. 2. Students may not appreciate the many important functions of tree bark. Carving into bark, or peeling it away from a trunk, exposes the inner tissues to pathogens. In many ways, the functions of human skin and bark are similar. Copyright © 2009 Pearson Education, Inc.

Sapwood Rings Wood rays Heartwood Sapwood Vascular cambium
Figure 31.8B Anatomy of a locust log. Secondary phloem Bark Cork cambium Cork Heartwood

31.15 EVOLUTION CONNECTION: Evolutionary adaptations allow some trees to live very long lives
The oldest organism on earth is thought to be a 4,600 year old bristlecone pine (Pinus longaeva) named Methuselah Several adaptations allow some plants to live much longer than animals Constant cell division in meristems can repair damage Plants produce defensive compounds that protect them Teaching Tips 1. Consider challenging your class to compare the biology of animals and plants and the respective adaptations that lengthen their lifespans. As discussed in Module 31.15, the regenerative capacity of plants promotes longevity. Do animals generally have the capacity to repair and replace organs? Stem cell research has recently revealed additional details about the ability to repair damaged or diseased tissues. Metabolic rates in animals have been generally correlated with longevity. How might the cellular metabolic rate of a mouse, which lives only a few years, compare with that found in a long-lived plant such as a redwood, which can live for centuries? Copyright © 2009 Pearson Education, Inc.

Figure 31.15 A bristlecone pine tree growing in California.

Terminal bud (grows stem)
Flower (reproductive organ) Stem (supports leaves and flowers) Shoot system (photosynthetic center) Axillary bud (produces a branch) Node Internode Blade Leaf (main photosynthetic organ) Petiole Root system (anchors, absorbs nutrients, and stores food) Root hairs (microscopic; increase surface area for absorption)

You should now be able to
Describe two main kinds of flowering plants and how they differ in number of seed leaves and in structures such as stems, roots, leaves, and flowers Name the three tissue systems that make up the plant body and the functions of each Describe the structure and function of five types of cells found in the plant body Give the name and location of the specialized areas where most plant growth occurs Copyright © 2009 Pearson Education, Inc.

Explain the difference between primary and secondary growth Describe the source and pattern of secondary plant growth Describe the structure of an angiosperm flower and the function of each part Explain the difference between the angiosperm sporophyte and gametophyte Copyright © 2009 Pearson Education, Inc.

Describe the series of events that occur in the angiosperm life cycle from spore production to seed germination Describe some modes of plant asexual reproduction and conditions that favor asexual reproduction Identify evolutionary adaptations that allow plants to live very long lives Copyright © 2009 Pearson Education, Inc.

REPRODUCTION OF FLOWERING PLANTS

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