Plant Anatomy

Quiz 12B

Two important characteristics of plant cells

• cell walls

• plastids

Cell Walls

• outer boundary, provide support, made mostly of cellulose

• Most plants are supported by two related systems: cell walls & turgor pressure.

Turgor Pressure

water pressure inside a plant cell’s central vacuole;

causes the stiffness of the plant cells

Plastids

storage center in plant cells

•Stores pigments, starch or oil.

•Examples are chloroplasts

Chloroplasts

contain the green pigment chlorophyll which is used

in photosynthesis to capture light energy

Plant Pigments

Chlorophyll: green

Xanthophyll: yellowish colors

Carotene: yellowish-orange colors

Anthocyanin: red, blue, and purple

tissuea group of similar cells

working together to perform a particular function

Our bodies have four basic kinds of tissues

• epithelial (skin)

• muscle

• connective

• nerve

A typical plant has 3 distinct kinds of tissue

• Structural tissue

• Meristematic tissue

• Vascular tissue

Structural Tissue

Most of the body, or structure, of the plant is structural tissue.

Produce food, store food, cover, support, and protect plant

Examples: epidermis, parenchyma, mesophyll, collenchyma, cork, sclerenchyma

Structural Tissue

Meristematic Tissue

Found in growing areas (buds, tips of roots and stems)

Purpose: the growth and repair of plants and plant parts (where mitosis is occurring)

Examples: apical & lateral meristems; vascular cambium, cork cambium, pericycle

Meristematic Tissue

Vascular Tissue

The plant’s sap-conducting tissues

Two types: xylem & phloem

Xylem: transports water and dissolved minerals (one kind of sap) upward (long, thick-walled cells)

Phloem: transports food manufactured in the leaves (the other kind of sap) downward

Vascular Tissue

Xylem: long, thick-walled hollow cells (like staws)

Phloem: slightly thinner than xylem and not completely hollow tubes

Vascular Tissue

In leaves and in non-woody plants, the xylem and phloem are usually arranged in vascular bundles (veins). Vascular bundles are often supported by thick-walled cells called fibers.

Fibrovasular bundles: xylem and phloem surrounded by supporting tissues

Vascular Tissue

Vascular Tissue

XylemPhloem

Vascular Tissue

Vascular Tissue

Vascular Tissue

SunflowerStem

Vascular Tissue

Epidermis

The outer most tissue of most leaves, young roots, and young stems is the epidermis. Top and Bottom layer - epidermis (one cell thick) lack chlorophyll and serves as protection. Often epidermal cells secrete a waxy substances that form a cuticle (a noncellular protective covering of leaves) give a leaf a shiny appearance

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

Cross Section of a Leaf

wooda collection of layers of xylem that have built up over several years

The oldest layer of xylem is at the center of the

woody plant part newest layer is the

outermost layer

Kinds of Wood

• Heartwood - dead xylem cells that are often darker

• Sapwood - xylem that conduct water and minerals

Heartwood & Sapwood

Kinds of Wood

• Springwood - xylem cells that develop early in the growing season

• Summerwood - small, thick-walled xylem cells that develop later in the growing season

Springwood & Summerwood

Kinds of Wood

• Hardwood - comes primarily from angiosperms (oaks, maples, walnut, cherries)

• Softwood - comes primarily from gymnosperms (firs, pine, cedars, spruce)

Hardwood

Softwood

Heartwood & Sapwood

bark

the outer covering of woody plant parts(makes new xylem and phloem cells)

cork (the outer layer of bark) tough, thick-walled cells forming the outer layer of bark in woody plant stems; made of dead, thick-cell walls

cork

forms a tough, water proof coating that keeps harmful organisms out and moisture

heartwood

sapwood(xylem)

phloem

cork

vascular cambium

Annual growth ring

cork cambium

a layer of living cells just

under the dead cork

(produces new cork cells)