Plant Form and Function
©Gustavo Gilabert/Corbis SABA
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. �No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
22-1
Introduction: vegetative plant parts
Section 22.1
If asked to picture a plant, you probably wouldn’t think of unusual examples like a Venus flytrap or a barrel cactus.
Figure 22.3
Carnivory (Venus flytrap)
©Win Initiative/Getty Images RF
Water storage (cactus)
©G.C. Kelly/Science Source
22-2
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts
Section 22.1
But like other flowering plants, these have roots, stems, leaves, flowers, fruits, and seeds.
Figure 22.3
Carnivory (Venus flytrap)
©Win Initiative/Getty Images RF
Water storage (cactus)
©G.C. Kelly/Science Source
22-3
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: modified leaves
Section 22.1
Harsh environments have selected for adaptions in these plants, such as modified leaves.
Figure 22.3
Modified leaves
Pollinator attraction (poinsettia)
©Design Pics/Don Hammond RF
Carnivory (Venus flytrap)
©Win Initiative/Getty Images RF
22-4
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts = nonreproductive plant parts
Section 22.1
This chapter explores the anatomy and physiology of vegetative (nonreproductive) plant parts.
Figure 22.3
Carnivory (Venus flytrap)
©Win Initiative/Getty Images RF
Water storage (cactus)
©G.C.Kelly/Science Source
22-5
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Naming the vegetative plant parts
Section 22.1
Vegetative plant parts include stems, leaves, and roots. These organs work together.
Figure 22.1
22-6
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: the shoot
Section 22.1
The shoot is the aboveground part of the plant.
Figure 22.1
22-7
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: the stem
Section 22.1
The shoot’s stem supports the leaves, which produce carbohydrates by photosynthesis.
Figure 22.1
22-8
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: the roots
Section 22.1
Some of the sugar produced in the shoot system travels through the stem to the roots, which are usually below ground.
Figure 22.1
22-9
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: functions of roots
Section 22.1
Roots anchor the plant and absorb water and minerals that move via the stem to the leaves.
Later, we will explore how water, minerals, and sugars travel through plants.
Figure 22.1
22-10
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: nodes and internodes
Section 22.1
Leaves attach to stems at nodes. Spaces between nodes are internodes.
Figure 22.1
22-11
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: axillary buds
Section 22.1
Each node also features an axillary bud, an undeveloped shoot that could form
a new branch or flower.
Figure 22.1
22-12
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Two types of plants
Section 22.1
Biologists divide plants into two categories based on the characteristics of the stem.
Figures 22.1, 24.4
22-13
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Herbaceous and woody plants
Section 22.1
A herbaceous plant has a green, soft stem.
A woody plant is made of tough, bark-covered wood.
Figures 22.1, 24.4
22-14
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: specialized stems
Section 22.1
Natural selection produces stems, leaves, and roots with various forms.
Figure 22.3
Climbing (grape tendrils)
Underground nutrient storage (iris rhizomes)
Water storage (cactus)
Defense
(honey locust thorns)
(a, vine): ©Franz Krenn/Science Source; (a, iris): ©Dwight Kuhn; (a, cactus): ©G.C. Kelly/Science Source; (a, thorns): ©Kenneth W. Fink/Science Source
22-15
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: specialized leaves
Section 22.1
Natural selection produces stems, leaves, and roots with various forms.
Figure 22.3
Nutrient storage (onion)
Pollinator attraction (poinsettia)
Carnivory (Venus flytrap)
Asexual reproduction (kalanchöe)
(b, onion): ©YAY Media AS/Alamy RF; (b, poinsettia): ©Design Pics/Don Hammond RF; (b, flytrap): ©Win Initiative/Getty Images RF; (b, kalanchoe)
22-16
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vegetative plant parts: specialized roots
Section 22.1
Natural selection produces stems, leaves, and roots with various forms.
Figure 22.3
Nutrient storage (carrot)
Oxygen absorption (mangrove trees)
Photosynthesis (orchid aerial roots)
Support
(prop roots of screw pine)
(c, carrots): ©Huw Jones/Photolibrary/Getty Images; (c, mangrove): ©Tim Laman/Getty Images RF; (c, orchid): ©Settawut Visedbubpha/123R; (c, screw pine): ©Steven P. Lynch/McGraw-Hill Education
22-17
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Plant cells build tissues
Section 22.3
We’ve seen the organs and organ systems of plants. Now let’s zoom in and learn about the cells and tissues that make up these organs.
Figure 22.1
22-18
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Three main tissue types
Section 22.2
Plants have three main tissue types:
Figure 22.6
22-19
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Ground tissue
Section 22.2
Ground tissue consists of three main cell types: parenchyma, collenchyma, and sclerenchyma.
Figure 22.4
Cell Type
Description
Alive at Maturity
Functions
Parenchyma
Yes
Make up most nonwoody tissues; carry out photosynthesis, respiration, gas exchange, secretion, wound repair, and storage
Collenchyma
Yes
Elastic support for growing stems and leaves
Sclerenchyma:
Fiber
No
Inelastic support for nongrowing plant parts
Sclerenchyma:
Sclereid
No
Inelastic support for nongrowing plant parts
(parenchyma): ©Malcolm Park microimages/Alamy; (collenchyma): ©Biophoto Associates/Science Source; (fibers): ©Steven P. Lynch/McGraw-Hill Education; (sclereid): ©Garry Delong/Oxford Scientific/Getty Images
22-20
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Functions of ground tissue
Section 22.2
The cells that compose ground tissue are important sites of photosynthesis, respiration, storage, and support.
Figure 22.4
Cell Type
Description
Alive at Maturity
Functions
Parenchyma
Yes
Make up most nonwoody tissues; carry out photosynthesis, respiration, gas exchange, secretion, wound repair, and storage
Collenchyma
Yes
Elastic support for growing stems and leaves
Sclerenchyma:
Fiber
No
Inelastic support for nongrowing plant parts
Sclerenchyma:
Sclereid
No
Inelastic support for nongrowing plant parts
(parenchyma): ©Malcolm Park microimages/Alamy; (collenchyma): ©Biophoto Associates/Science Source; (fibers): ©Steven P. Lynch/McGraw-Hill Education; (sclereid): ©Garry Delong/Oxford Scientific/Getty Images
22-21
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vascular tissue
Section 22.2
Vascular tissues transport water, minerals, carbohydrates, and other dissolved compounds.
Figure 22.5
Cell Type
Functions
XYLEM
Tracheid
Conduct water and minerals through pits
Vessel element
Conduct water and minerals through pits and perforated end walls
PHLOEM
Sieve tube element
Conduct dissolved sucrose and other organic compounds through sieve plates
Companion cell
Transfer materials into and out of
sieve tube elements
©Biophoto Associates/Science Source
22-22
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vascular tissue: xylem
Section 22.2
Xylem tissue transports water and minerals from the roots to other plant parts. It consists of long, narrow cells called tracheids and wide, barrel-shaped cells called vessel elements.
Figure 22.5
Cell Type
Functions
XYLEM
Tracheid
Conduct water and minerals through pits
Vessel element
Conduct water and minerals through pits and perforated end walls
PHLOEM
Sieve tube element
Conduct dissolved sucrose and other organic compounds through sieve plates
Companion cell
Transfer materials into and out of
sieve tube elements
©Biophoto Associates/Science Source
22-23
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vascular tissue: phloem
Section 22.2
Phloem tissue transports dissolved organic compounds like sugars. Sieve tube elements are the conducting cells; they are separated by sieve plates.
Figure 22.5
Cell Type
Functions
XYLEM
Tracheid
Conduct water and minerals through pits
Vessel element
Conduct water and minerals through pits and perforated end walls
PHLOEM
Sieve tube element
Conduct dissolved sucrose and other organic compounds through sieve plates
Companion cell
Transfer materials into and out of
sieve tube elements
©Biophoto Associates/Science Source
22-24
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vascular tissue: phloem cells
Section 22.2
Companion cells transfer materials in and out of sieve tubes.
Figure 22.5
Cell Type
Functions
XYLEM
Tracheid
Conduct water and minerals through pits
Vessel element
Conduct water and minerals through pits and perforated end walls
PHLOEM
Sieve tube element
Conduct dissolved sucrose and other organic compounds through sieve plates
Companion cell
Transfer materials into and out of
sieve tube elements
©Biophoto Associates/Science Source
22-25
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Dermal tissues
Section 22.2
Dermal tissue covers the plant; it consists of the epidermis, which is coated with a waxy cuticle.
Figure 22.7
©Steven P. Lynch/McGraw-Hill Education
22-26
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Cuticle and stomata
Section 22.2
The cuticle conserves water and protects the plant. Pores in the cuticle, called stomata, allow leaves to exchange gases with the atmosphere.
Figure 22.7
©Steven P. Lynch/McGraw-Hill Education
22-27
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Guard cells
Section 22.2
Guard cells surround each stoma and control its opening and closing.
Figure 22.8
©Steven P. Lynch/McGraw-Hill Education
22-28
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Tissues build stems, leaves, and roots
Section 22.3
The three tissue types make up the stems, leaves, and roots of the plant.
Let’s look at each of these organs, starting with the stem.
Figure 22.6
22-29
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Tissue types found in a stem
Section 22.3
Ground tissue occupies most of the stem of a herbaceous plant.
Vascular bundles are embedded in the ground tissue.
Dermal tissue covers the stem.
Figure 22.6
22-30
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Arrangement of tissues differs in monocots and eudicots
Section 22.3
Monocots and eudicots have different arrangements of vascular tissue and ground tissue in their stems.
Figure 22.9
(a, stem): ©Steven P. Lynch/RF; (a, corn close up; b, both): ©Steven P. Lynch/McGraw-Hill Education
22-31
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vascular bundles in monocot and eudicot stems
Section 22.3
In monocots, vascular bundles are scattered throughout the stem.
In eudicots, vascular bundles are arranged in a ring near the epidermis.
The cortex is ground tissue that fills the space between the epidermis and vascular bundles. The pith occupies the center of the stem.
Figure 22.9
(a, stem): ©Steven P. Lynch/RF; (a, corn close up; b, both): ©Steven P. Lynch/McGraw-Hill Education
22-32
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Tissues found in leaves
Section 22.3
Ground tissue occupies most of a leaf.
Vascular bundles are embedded in the ground tissue.
Dermal tissue covers the leaf.
Figure 22.6
22-33
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
The structure of leaves
Section 22.3
Leaves are flattened blades supported with a stalklike petiole.
Figure 22.10
Simple leaf
Compound leaves
22-34
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Simple vs. compound leaves
Section 22.3
Simple leaves have undivided blades.
Compound leaves are divided into leaflets attached to one petiole.
Figure 22.10
Simple leaf
Compound leaves
22-35
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vein patterns on monocot and eudicot leaves
Section 22.3
Veins are vascular bundles inside leaves. Many monocots have parallel veins; most eudicots have netted veins.
Figure 22.11
Veins on typical monocot leaf
Veins on typical eudicot leaf
(both): ©Dwight Kuhn
22-36
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Mesophyll: the middle of a leaf
Section 22.3
Leaf anatomy shown here is that of a eudicot plant.
The ground tissue inside a leaf is called mesophyll, which consists of cells with abundant chloroplasts that produce sugars by photosynthesis.
Figure 22.12
©M. I. Walker/Science Source
22-37
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Stomata: locations of gas exchange
Section 22.3
When stomata are open, mesophyll cells exchange gases with the atmosphere.
Figure 22.12
©M. I. Walker/Science Source
22-38
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Mesophyll cells interact with vascular tissue
Section 22.3
Mesophyll cells also exchange materials with vascular tissues.
Figure 22.12
©M. I. Walker/Science Source
22-39
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Monocot leaf structures
Section 22.3
Monocots have similar leaf anatomy to dicots. Note the prominent bundle sheath cells in this monocot leaf, surrounded by a layer of mesophyll.
Figure 22.12
©Steven P. Lynch/McGraw-Hill Education
22-40
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Tissues of the root
Section 22.3
In a root, ground tissue surrounds a central core of vascular tissue.
Dermal tissue forms the root epidermis.
Figure 22.6
22-41
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Fibrous roots vs. taproots
Section 22.3
Roots might form a fibrous root system or a taproot system.
Figure 22.13
(a): ©AI Telser/McGraw-Hill Education; (b): ©Ed Reschke/Photolibrary/Getty Images
22-42
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Root hairs
Section 22.3
Near each root’s tip, root hairs are extensions of the epidermis that
absorb water and minerals.
Figure 22.14
©Dr. Jeremy Burgess/Science Source
22-43
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Plants have flexible growth patterns
Section 22.4
Some plants never stop growing. These plants have indeterminate growth.
Plants that stop growing when they reach their mature size have determinate growth.
Table 22.3
TABLE 22.3 Meristem Types: A Summary
Type | Locations | Function |
Apical | Terminal and axillary buds of shoots; root tips | Produces tissues that lengthen the tips of shoots and roots |
Lateral | Internal cylinder along the length of roots and stems of woody plants | Thickens roots and stems |
Intercalary | Between nodes of mature stems in grasses and other monocots | Regrowth of tissue if tip of stem is removed |
22-44
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Meristems
Section 22.4
Plants grow by adding units, or modules, consisting of repeated nodes and internodes. Growth occurs at meristems, regions of active cell division.
Table 22.3
22-45
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Apical meristems
Section 22.4
Apical meristems produce tissues that lengthen the tips of shoots and roots.
Table 22.3
22-46
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Primary growth
Section 22.4
Primary growth occurs at the apical meristems. New cells can differentiate into any tissue type.
Figs. 22.15, 22.16
©Steven P.Lynch/McGraw-Hill Education
Apical meristems
©Steven P.Lynch/McGraw-Hill Education
22-47
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Intercalary meristems
Section 22.4
Intercalary meristems occur at the base of a leaf blade. �Grasses tolerate grazing because they have intercalary meristems that regrow a leaf from its base when the tip is munched off.
Table 22.3
22-48
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Secondary growth
Section 22.4
Secondary growth thickens roots and stems; this growth occurs at lateral meristems.
Table 22.3
22-49
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Secondary growth in woody plants
Section 22.4
Secondary growth occurs in woody plants. Two types of lateral meristems produce wood and bark:
Figure 22.17
22-50
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Vascular cambium
Section 22.4
The vascular cambium (highlighted green) produces secondary xylem toward the inside of the stem and secondary phloem toward the outside.
Figure 22.17
22-51
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Wood
Section 22.4
Secondary xylem is more commonly called wood.
Figure 22.18
(b): ©Siede Preis/Getty Images RF; (c): ©Herve Conge/Phototake
22-52
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Rays
Section 22.4
The vascular cambium also produces rays (highlighted with yellow), bands of parenchyma that extend from the center of the stem or root and transport nutrients laterally.
Figure 22.17
22-53
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Bark
Section 22.4
Secondary growth produces bark, a collective term for all tissues outside of the vascular cambium.
Figure 22.18
(b): ©Siede Preis/Getty Images RF; (c): ©Herve Conge/Phototake
22-54
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Cork cambium
Section 22.4
The cork cambium (highlighted white) produces parenchyma cells toward the inside and dense, waxy cells called cork toward the outside.
Cork is the outer protective layer of bark.
Figure 22.17
22-55
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Periderm
Section 22.4
Together, the cork cambium, parenchyma cells, and nonliving cork make up the periderm, a protective layer that covers a woody stem or root.
Figure 22.18
(b): ©Siede Preis/Getty Images RF; (c): ©Herve Conge/Phototake
22-56
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Heartwood
Section 22.4
Secondary xylem eventually becomes unable to conduct water, forming heartwood.
Figure 22.18
(b): ©Siede Preis/Getty Images RF; (c): ©Herve Conge/Phototake
22-57
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Sapwood
Section 22.4
The lighter sapwood transports water and dissolved minerals.
Figure 22.18
(b): ©Siede Preis/Getty Images RF; (c): ©Herve Conge/Phototake
22-58
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
Tree rings
Section 22.4
Tree rings arise from alternating moist and dry seasons. Wood that forms in the spring has larger cells than wood that forms in the summer.
Figure 22.18
(b): ©Siede Preis/Getty Images RF; (c): ©Herve Conge/Phototake
22-59
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.