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Chapter 26

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Chapter 26:  Plant Structure and Function


Using your vocabulary words, make notecards/flashcards that you can use outside of class to study. 


Work on your Directed Reading in class every chance you get.  Remember that I will assist you on the harder questions.  This assignment is due the day we take the test on this chapter.  Use the information in this assignment as a study guide for your test.

This study guide is to help you study for your test.  It should not be the only item you use to study w hen preparing for the test.  Remember to complete your Directed Reading for every chapter along with writing your vocabulary words on notecards to help you remember them.  And always remember to listen carefully in lecture because all of the information in this study guide will be covered.



I. Vascular plants have three types of tissues 

A. Dermal Tissue

1.    Covers the outside of the plant body, provides protection

2.    Functions in gas exchange and mineral absorption

3.    Epidermis - “skin” of non-woody plants; made of a single layer of flat cells covered with a waxy cuticle; may have hair-like extension on leaves to prevent water loss or on the roots to help with water absorption

4.    Cork - dermal tissue of woody plants made of many layers of dead cells, contain a waterproof chemical and do not have a cuticle

B. Ground Tissue

1.    Makes up must of the inside of most plants

2.    Most is made of thin-walled live cells that contain a nucleus

3.    Specialized functions vary depending on the location of the tissue;

a)   Leaves - photosynthesis,

b)  Stems and roots - storage of water & nutrients,

c)   All other areas - surrounds and supports the vascular tissue



C. Vascular Tissue

1.  Xylem - composed of thick walled cells that form a hollow tube which carries water and minerals upward through the plant; there are two types of xylem

a)   tracheid (narrow, elongated, and tapered at each end; water flows from one to the next through “pits” or thin areas in the cell wall), and

b)  vessels (wider cells with large holes called “perforations” that allow for a faster flow of water)

2.  Phloem - composed of thinner walled cells that carry organic materials produced within the plant downward through the plant body

a)   Phloem cells are organized into stands called sieve tubes

b)  Pores between the neighboring cells connect them and allow organic material to floe freely through the tube 


II.     Roots

A. Functions

1.  Anchor the plant to the ground

2.  Absorb water and minerals

3.  Store organic nutrients

B. Types of root systems

1.  Taproots - large central root from which smaller roots branch, found mostly in dicots (ex. carrot, radish)

2.  Fibrous roots - highly branched root system (ex. grass), found mostly in monocots

3.  Adventurous roots - roots that grow from above ground leaves or stems (ex. aerial roots, see figure 26-5, pg 573)


C. Root Parts (see figure 26-6, pg 573)

1.  Cortex - ground tissue found between the epidermis and central core of vascular tissue in the root

2.  Root cap - mass of cells at the end of the root, covers and protects the actively growing tip of the root

3.  Root Hairs - slender projections extending from the epidermis just above the root cap, allow for greater absorption of water and minerals from the soil



III.   Stems & Leaves

A. Stems are the part of the shoot that supports the leaves and contains the vascular tissues

1.  Leaves attach to the stems at locations called “nodes”

2.  The distance between two nodes is called the “internode”


B. Types of stems

1.  Non-Woody Stems (see figure 26-7, pg 574)

a)  Flexible and usually green stems found on what are called “herbaceous” (aka non-woody) plants like violets or grass

b)  Vascular bundle - bundles of xylem and phloem surrounded by ground tissue

(1) In monocots these bundles are scattered throughout the ground tissue

(2) In dicots the bundles are arranged in a ring, the ground tissue outside the ring is called the “ cortex”, and the ground tissue inside the ring is called the “pith”



2.  Woody Stems (see figure 26-8, pg 575)

a)  Stiff and usually non-green stems found on trees and shrubs

b)  Buds - found at the tips and nodes, produce new growth and exchange gasses through pores in their bark

c)  Mature woody stems have many layers

(1) Heartwood - found in the center, contains xylem that can no longer move water but can provide strength to the plant

(2) Sapwood - layer outside the heartwood that contains active xylem tissues

(3) Bark -outer layer, made of cork and phloem tissues



C. Leaves are the primary location for photosynthesis (using light energy to produce organic compounds such as sugar)

1.  Leaf parts

a)  Blade - flattened part of the leaf

b)  Petiole - stalk that attaches the blade to the stem

c)  Cuticle & epidermis - outer layer of leaf tissue

d)  Vascular tissue - found in “veins” throughout the leaf

e)  Mesophyll - ground tissue found in the middle of the leaf, contains the chlorophyll where photosynthesis occurs

f)  Stomata & guard cells - pores in the cuticle that regulate gas and water exchange with the environment



2.  Types of leaves

a)  Simple - leaves with a single undivided leaf

b)  Compound - leaves with multiple segments called “leaflets”

c)  Modified Leaves - leaves with special purposes, (ex. cactus spines for water conservation, pea tendrils for climbing)




A.  Transpiration is the loss of water from a plant through the stomata

B.  Three steps (see figure 26-11, pg 578)

1.    Wind carries away water vapor that exits leaves through the stomata

2.    This loss of water creates a pull that draws more water up through the xylem

3.    Roots absorb new water by osmosis to replace the water lost through the leaves and stems



C.  Process is driven by water cohesion, or the attraction between molecules of water that causes it to “stick” together

D.  Guard cells regulate this process

1.    Guard cells open and close in response to changes in water pressure within the cells

2.    When water pressure increases the cells swell and draw away from each other allowing water to exit by transpiration

3.    As water exits, pressure decreases, and the cells close together again stopping the water loss



V.   Translocation

A.  Source - any part of the plant that produces or provides organic compounds to the plant

B.  Sink - any part of the plant that receives or stores organic compounds for the plant

C.  Translocation - the process by which organic compounds move from the source to the sink

D.  More complex that water movement for three reasons

1.    Water flows freely thorough empty xylem cells, sugars must pass through the cytoplasm (cell guts) of the phloem

2.    Water moves only upward, while sugars are moved in all directions through the plant

3.    Water can move by diffusion through the membranes where sugars can not

E.  Four steps in translocation                                                                        (aka The Pressure-Flow Model, see figure 26-13, pg 582)

1.    Sugar from source is actively moved into to phloem

2.    As sugar concentration increases, water moves into the sieve tube by osmosis

3.    Pressure in the sieve tube caused by the increased amounts of water and sugar pushes the mixture through the phloem

4.    At the sink, sugar is actively moved from the phloem to the sink area



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