PLANT CELLS AND TISSUES

LEARNING OBJECTIVES 1.  Describe plant tissues, their function and organization 2.  Distinguish between different types of plant cells based

on their properties and function 3.  Analyze the cell composition of various plant parts and

how this contributes to plant function

Campbell, Ch. 35.1 and 35.2

PLANT PARTS AND TISSUES

C H A P T E R 3 5 Plant Structure, Growth, and Development 757

needed—usually roots and sites of growth, such as develop-ing leaves and fruits. The vascular tissue of a root or stem is collectively called the stele (the Greek word for “pillar”). The arrangement of the stele varies, depending on the spe-cies and organ. In angiosperms, for example, the root stele is a solid central vascular cylinder of xylem and phloem, whereas the stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem (see Figure 35.8). Both xylem and phloem are composed of a va-riety of cell types, including cells that are highly specialized for transport or support.

Tissues that are neither dermal nor vascular are part of the ground tissue system. Ground tissue that is internal to the vascular tissue is known as pith, and ground tissue that is external to the vascular tissue is called cortex. The ground tissue system is not just filler: It includes cells specialized for functions such as storage, photosynthesis, support, and short-distance transport.

Common Types of Plant CellsIn a plant, as in any multicellular organism, cells undergo cell differentiation; that is, they become specialized in struc-ture and function during the course of development. Cell differentiation may involve changes both in the cytoplasm and its organelles and in the cell wall. Figure 35.10, on the next two pages, focuses on the major types of plant cells. Notice the structural adaptations that make specific func-tions possible. You may also wish to review basic plant cell structure (see Figures 6.8 and 6.28).

layer of tightly packed cells. In leaves and most stems, the cuticle, a waxy epidermal coating, helps prevent water loss. In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots. In ad-dition to protecting the plant from water loss and disease, the epidermis has specialized characteristics in each organ. In roots, water and minerals absorbed from the soil enter through the epidermis, especially in root hairs. In shoots, specialized epidermal cells called guard cells are involved in gaseous exchange. Trichomes are another class of highly specialized epidermal cells found in shoots. In some desert species, hairlike trichomes reduce water loss and reflect ex-cess light. Some trichomes defend against insects through shapes that hinder movement or glands that secrete sticky fluids or toxic compounds (Figure 35.9).

The chief functions of the vascular tissue system are to facilitate the transport of materials through the plant and to provide mechanical support. The two types of vascular tis-sues are xylem and phloem. Xylem conducts water and dis-solved minerals upward from roots into the shoots. Phloem transports sugars, the products of photosynthesis, from where they are made (usually the leaves) to where they are

Dermaltissue

Vascular tissue

Ground tissue

▲ Figure 35.8 The three tissue systems. The dermal tissue system (blue) provides a protective cover for the entire body of a plant. The vascular tissue system (purple), which transports materials between the root and shoot systems, is also continuous throughout the plant but is arranged differently in each organ. The ground tissue system (yellow), which is responsible for most of the metabolic functions, is located between the dermal tissue and the vascular tissue in each organ.

Trichomes

300

μm

▲ Figure 35.9 Trichome diversity on the surface of a leaf. Three types of trichomes are found on the surface of marjoram (Origa-num majorana). Spear-like trichomes help hinder the movement of crawling insects, while the other two types of trichomes secrete oils and other chemicals involved in defense (colorized SEM).

C O N C E P T C H E C K 3 5 . 1

1. How does the vascular tissue system enable leaves and roots to function together in supporting growth and development of the whole plant?

2. W H AT I F ? If humans were photoautotrophs, making food by capturing light energy for photosynthesis, how might our anatomy be different?

3. M A K E C O N N E C T I O N S Explain how central vacuoles and cellulose cell walls contribute to plant growth (see Concepts 6.4 and 6.7).

For suggested answers, see Appendix A.

Meristematic tissue

MERISTEM CELLS

DERMIS CELLS epidermis

periderm

herbaceous woody

root hair

C H A P T E R 3 5 Plant Structure, Growth, and Development 757

needed—usually roots and sites of growth, such as develop-ing leaves and fruits. The vascular tissue of a root or stem is collectively called the stele (the Greek word for “pillar”). The arrangement of the stele varies, depending on the spe-cies and organ. In angiosperms, for example, the root stele is a solid central vascular cylinder of xylem and phloem, whereas the stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem (see Figure 35.8). Both xylem and phloem are composed of a va-riety of cell types, including cells that are highly specialized for transport or support.

Tissues that are neither dermal nor vascular are part of the ground tissue system. Ground tissue that is internal to the vascular tissue is known as pith, and ground tissue that is external to the vascular tissue is called cortex. The ground tissue system is not just filler: It includes cells specialized for functions such as storage, photosynthesis, support, and short-distance transport.

Common Types of Plant CellsIn a plant, as in any multicellular organism, cells undergo cell differentiation; that is, they become specialized in struc-ture and function during the course of development. Cell differentiation may involve changes both in the cytoplasm and its organelles and in the cell wall. Figure 35.10, on the next two pages, focuses on the major types of plant cells. Notice the structural adaptations that make specific func-tions possible. You may also wish to review basic plant cell structure (see Figures 6.8 and 6.28).

layer of tightly packed cells. In leaves and most stems, the cuticle, a waxy epidermal coating, helps prevent water loss. In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots. In ad-dition to protecting the plant from water loss and disease, the epidermis has specialized characteristics in each organ. In roots, water and minerals absorbed from the soil enter through the epidermis, especially in root hairs. In shoots, specialized epidermal cells called guard cells are involved in gaseous exchange. Trichomes are another class of highly specialized epidermal cells found in shoots. In some desert species, hairlike trichomes reduce water loss and reflect ex-cess light. Some trichomes defend against insects through shapes that hinder movement or glands that secrete sticky fluids or toxic compounds (Figure 35.9).

The chief functions of the vascular tissue system are to facilitate the transport of materials through the plant and to provide mechanical support. The two types of vascular tis-sues are xylem and phloem. Xylem conducts water and dis-solved minerals upward from roots into the shoots. Phloem transports sugars, the products of photosynthesis, from where they are made (usually the leaves) to where they are

Dermaltissue

Vascular tissue

Ground tissue

▲ Figure 35.8 The three tissue systems. The dermal tissue system (blue) provides a protective cover for the entire body of a plant. The vascular tissue system (purple), which transports materials between the root and shoot systems, is also continuous throughout the plant but is arranged differently in each organ. The ground tissue system (yellow), which is responsible for most of the metabolic functions, is located between the dermal tissue and the vascular tissue in each organ.

Trichomes

300

μm

▲ Figure 35.9 Trichome diversity on the surface of a leaf. Three types of trichomes are found on the surface of marjoram (Origa-num majorana). Spear-like trichomes help hinder the movement of crawling insects, while the other two types of trichomes secrete oils and other chemicals involved in defense (colorized SEM).

C O N C E P T C H E C K 3 5 . 1

1. How does the vascular tissue system enable leaves and roots to function together in supporting growth and development of the whole plant?

2. W H AT I F ? If humans were photoautotrophs, making food by capturing light energy for photosynthesis, how might our anatomy be different?

3. M A K E C O N N E C T I O N S Explain how central vacuoles and cellulose cell walls contribute to plant growth (see Concepts 6.4 and 6.7).

For suggested answers, see Appendix A.

DERMIS MODIFIED CELLS

trichome guard cells

C H A P T E R 3 5 Plant Structure, Growth, and Development 757

needed—usually roots and sites of growth, such as develop-ing leaves and fruits. The vascular tissue of a root or stem is collectively called the stele (the Greek word for “pillar”). The arrangement of the stele varies, depending on the spe-cies and organ. In angiosperms, for example, the root stele is a solid central vascular cylinder of xylem and phloem, whereas the stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem (see Figure 35.8). Both xylem and phloem are composed of a va-riety of cell types, including cells that are highly specialized for transport or support.

Tissues that are neither dermal nor vascular are part of the ground tissue system. Ground tissue that is internal to the vascular tissue is known as pith, and ground tissue that is external to the vascular tissue is called cortex. The ground tissue system is not just filler: It includes cells specialized for functions such as storage, photosynthesis, support, and short-distance transport.

Common Types of Plant CellsIn a plant, as in any multicellular organism, cells undergo cell differentiation; that is, they become specialized in struc-ture and function during the course of development. Cell differentiation may involve changes both in the cytoplasm and its organelles and in the cell wall. Figure 35.10, on the next two pages, focuses on the major types of plant cells. Notice the structural adaptations that make specific func-tions possible. You may also wish to review basic plant cell structure (see Figures 6.8 and 6.28).

layer of tightly packed cells. In leaves and most stems, the cuticle, a waxy epidermal coating, helps prevent water loss. In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots. In ad-dition to protecting the plant from water loss and disease, the epidermis has specialized characteristics in each organ. In roots, water and minerals absorbed from the soil enter through the epidermis, especially in root hairs. In shoots, specialized epidermal cells called guard cells are involved in gaseous exchange. Trichomes are another class of highly specialized epidermal cells found in shoots. In some desert species, hairlike trichomes reduce water loss and reflect ex-cess light. Some trichomes defend against insects through shapes that hinder movement or glands that secrete sticky fluids or toxic compounds (Figure 35.9).

The chief functions of the vascular tissue system are to facilitate the transport of materials through the plant and to provide mechanical support. The two types of vascular tis-sues are xylem and phloem. Xylem conducts water and dis-solved minerals upward from roots into the shoots. Phloem transports sugars, the products of photosynthesis, from where they are made (usually the leaves) to where they are

Dermaltissue

Vascular tissue

Ground tissue

▲ Figure 35.8 The three tissue systems. The dermal tissue system (blue) provides a protective cover for the entire body of a plant. The vascular tissue system (purple), which transports materials between the root and shoot systems, is also continuous throughout the plant but is arranged differently in each organ. The ground tissue system (yellow), which is responsible for most of the metabolic functions, is located between the dermal tissue and the vascular tissue in each organ.

Trichomes

300

μm

▲ Figure 35.9 Trichome diversity on the surface of a leaf. Three types of trichomes are found on the surface of marjoram (Origa-num majorana). Spear-like trichomes help hinder the movement of crawling insects, while the other two types of trichomes secrete oils and other chemicals involved in defense (colorized SEM).

C O N C E P T C H E C K 3 5 . 1

1. How does the vascular tissue system enable leaves and roots to function together in supporting growth and development of the whole plant?

2. W H AT I F ? If humans were photoautotrophs, making food by capturing light energy for photosynthesis, how might our anatomy be different?

3. M A K E C O N N E C T I O N S Explain how central vacuoles and cellulose cell walls contribute to plant growth (see Concepts 6.4 and 6.7).

For suggested answers, see Appendix A.

GROUND TISSUE CELLS

•  metabolic activities, storage

•  located everywhere

•  flexible support •  soft stem, leaf

•  rigid support •  wood, hard stem, leaves,

fruits, seeds

C H A P T E R 3 5 Plant Structure, Growth, and Development 757

needed—usually roots and sites of growth, such as develop-ing leaves and fruits. The vascular tissue of a root or stem is collectively called the stele (the Greek word for “pillar”). The arrangement of the stele varies, depending on the spe-cies and organ. In angiosperms, for example, the root stele is a solid central vascular cylinder of xylem and phloem, whereas the stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem (see Figure 35.8). Both xylem and phloem are composed of a va-riety of cell types, including cells that are highly specialized for transport or support.

Tissues that are neither dermal nor vascular are part of the ground tissue system. Ground tissue that is internal to the vascular tissue is known as pith, and ground tissue that is external to the vascular tissue is called cortex. The ground tissue system is not just filler: It includes cells specialized for functions such as storage, photosynthesis, support, and short-distance transport.

Common Types of Plant CellsIn a plant, as in any multicellular organism, cells undergo cell differentiation; that is, they become specialized in struc-ture and function during the course of development. Cell differentiation may involve changes both in the cytoplasm and its organelles and in the cell wall. Figure 35.10, on the next two pages, focuses on the major types of plant cells. Notice the structural adaptations that make specific func-tions possible. You may also wish to review basic plant cell structure (see Figures 6.8 and 6.28).

layer of tightly packed cells. In leaves and most stems, the cuticle, a waxy epidermal coating, helps prevent water loss. In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots. In ad-dition to protecting the plant from water loss and disease, the epidermis has specialized characteristics in each organ. In roots, water and minerals absorbed from the soil enter through the epidermis, especially in root hairs. In shoots, specialized epidermal cells called guard cells are involved in gaseous exchange. Trichomes are another class of highly specialized epidermal cells found in shoots. In some desert species, hairlike trichomes reduce water loss and reflect ex-cess light. Some trichomes defend against insects through shapes that hinder movement or glands that secrete sticky fluids or toxic compounds (Figure 35.9).

The chief functions of the vascular tissue system are to facilitate the transport of materials through the plant and to provide mechanical support. The two types of vascular tis-sues are xylem and phloem. Xylem conducts water and dis-solved minerals upward from roots into the shoots. Phloem transports sugars, the products of photosynthesis, from where they are made (usually the leaves) to where they are

Dermaltissue

Vascular tissue

Ground tissue

▲ Figure 35.8 The three tissue systems. The dermal tissue system (blue) provides a protective cover for the entire body of a plant. The vascular tissue system (purple), which transports materials between the root and shoot systems, is also continuous throughout the plant but is arranged differently in each organ. The ground tissue system (yellow), which is responsible for most of the metabolic functions, is located between the dermal tissue and the vascular tissue in each organ.

Trichomes

300

μm

▲ Figure 35.9 Trichome diversity on the surface of a leaf. Three types of trichomes are found on the surface of marjoram (Origa-num majorana). Spear-like trichomes help hinder the movement of crawling insects, while the other two types of trichomes secrete oils and other chemicals involved in defense (colorized SEM).

C O N C E P T C H E C K 3 5 . 1

1. How does the vascular tissue system enable leaves and roots to function together in supporting growth and development of the whole plant?

2. W H AT I F ? If humans were photoautotrophs, making food by capturing light energy for photosynthesis, how might our anatomy be different?

3. M A K E C O N N E C T I O N S Explain how central vacuoles and cellulose cell walls contribute to plant growth (see Concepts 6.4 and 6.7).

For suggested answers, see Appendix A.

VASCULAR TISSUE CELLS

water and mineral transport nutrient transport

xylem phloem

vessel elements

tracheids

sieve tubes

companion cells

pits

(no nucleus)

C H A P T E R 3 5 Plant Structure, Growth, and Development 757

needed—usually roots and sites of growth, such as develop-ing leaves and fruits. The vascular tissue of a root or stem is collectively called the stele (the Greek word for “pillar”). The arrangement of the stele varies, depending on the spe-cies and organ. In angiosperms, for example, the root stele is a solid central vascular cylinder of xylem and phloem, whereas the stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem (see Figure 35.8). Both xylem and phloem are composed of a va-riety of cell types, including cells that are highly specialized for transport or support.

Tissues that are neither dermal nor vascular are part of the ground tissue system. Ground tissue that is internal to the vascular tissue is known as pith, and ground tissue that is external to the vascular tissue is called cortex. The ground tissue system is not just filler: It includes cells specialized for functions such as storage, photosynthesis, support, and short-distance transport.

Common Types of Plant CellsIn a plant, as in any multicellular organism, cells undergo cell differentiation; that is, they become specialized in struc-ture and function during the course of development. Cell differentiation may involve changes both in the cytoplasm and its organelles and in the cell wall. Figure 35.10, on the next two pages, focuses on the major types of plant cells. Notice the structural adaptations that make specific func-tions possible. You may also wish to review basic plant cell structure (see Figures 6.8 and 6.28).

layer of tightly packed cells. In leaves and most stems, the cuticle, a waxy epidermal coating, helps prevent water loss. In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots. In ad-dition to protecting the plant from water loss and disease, the epidermis has specialized characteristics in each organ. In roots, water and minerals absorbed from the soil enter through the epidermis, especially in root hairs. In shoots, specialized epidermal cells called guard cells are involved in gaseous exchange. Trichomes are another class of highly specialized epidermal cells found in shoots. In some desert species, hairlike trichomes reduce water loss and reflect ex-cess light. Some trichomes defend against insects through shapes that hinder movement or glands that secrete sticky fluids or toxic compounds (Figure 35.9).

The chief functions of the vascular tissue system are to facilitate the transport of materials through the plant and to provide mechanical support. The two types of vascular tis-sues are xylem and phloem. Xylem conducts water and dis-solved minerals upward from roots into the shoots. Phloem transports sugars, the products of photosynthesis, from where they are made (usually the leaves) to where they are

Dermaltissue

Vascular tissue

Ground tissue

▲ Figure 35.8 The three tissue systems. The dermal tissue system (blue) provides a protective cover for the entire body of a plant. The vascular tissue system (purple), which transports materials between the root and shoot systems, is also continuous throughout the plant but is arranged differently in each organ. The ground tissue system (yellow), which is responsible for most of the metabolic functions, is located between the dermal tissue and the vascular tissue in each organ.

Trichomes

300

μm

▲ Figure 35.9 Trichome diversity on the surface of a leaf. Three types of trichomes are found on the surface of marjoram (Origa-num majorana). Spear-like trichomes help hinder the movement of crawling insects, while the other two types of trichomes secrete oils and other chemicals involved in defense (colorized SEM).

C O N C E P T C H E C K 3 5 . 1

1. How does the vascular tissue system enable leaves and roots to function together in supporting growth and development of the whole plant?

2. W H AT I F ? If humans were photoautotrophs, making food by capturing light energy for photosynthesis, how might our anatomy be different?

3. M A K E C O N N E C T I O N S Explain how central vacuoles and cellulose cell walls contribute to plant growth (see Concepts 6.4 and 6.7).

For suggested answers, see Appendix A.

VASCULAR BUNDLE

SELF-STUDY Construct an organizational chart for the following terms:

1.  collenchyma 2.  companion cell 3.  dermis 4.  differentiated 5.  epidermis 6.  ground 7.  meristem 10. parenchyma

10. periderm 11. sclerenchyma 12. sieve tube 13. tracheid 14. undifferentiated 15. vascular 16. vessel elements 17. xylem 18. phloem

plant cell

??? ???

? ?

GROUP HOMEWORK Bring the ff items to class: •  leaf with “ribs”

•  shoot tip of any plant

•  spiny cactus plant

•  coconut husk

•  apple cut in cross-section