sheryl searcy ninth grade center 2012 roots, leaves & stems specialized tissue in plants...

Sheryl Searcy Ninth Grade Center 2012

ROOTS, LEAVES &

STEMSSpecialized Tissue in Plants

Chapter 23

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Basic Parts of a Plant Roots Stem Leaves Flower

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ROOTSSection 23-2

Sheryl Searcy Ninth Grade Center 2012Sheryl Searcy Ninth Grade Center 2012

Types of Root Systems Taproot System

– Primary roots grow down from the stem with some secondary roots forming.

Fibrous Root System– Small lateral roots that

spread out just below the soil surface.

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Four Root Functions1. Absorption of water and nutrients.2. Transportation of water and nutrients to

stem.3. Anchor plant to maintain stability.4. Store food and wate.r

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Parts of a Root

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Parts of a Root Epidermis

– Outermost layer of cells, like the skin of the root.

Cortex– Tissue inside epidermis that stores starch and

other substances for the growth of the root.

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Parts of a Root Root Cap

– Provides protection for the root tip.

Root Hairs– Site of absorption.

Vascular Tissue– Within cortex, contains cells that transport water,

nutrients, and minerals to all parts of the plant.

Image found at: www.bio.psu.edu

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Parts of a Root

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STEMSSection 23.3

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Function of Stems Transport water and nutrients from roots

to leaves. Supports/produces

leaves, branches, and fruit/flowers.

Food storage.

Image found at: www.karencarr.com

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Types of Stems Woody:

– Thick cell walls that support the plant.– Trees, shrubs, and vines.

Herbaceous:– Stems are smooth, supported by hydrostatic

pressure (turgor).– Dandelions, zinnias, petunias.

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Types of StemsWoody Stem Herbaceous Stem

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Parts of a Stem Node

– Areas where side branches and leaves develop.

Internode– Area between nodes.

Xylem– Carries water up.

Phloem– Carries nutrients throughout plant.

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Monocot & Dicot Stems

Monocot: vascular bundles scattered throughout the stem.

Dicot (and most gymnosperms): vascular bundles are arranged in a cylinder.

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Cross-Section of Stems

Woody Stem Dicot Stem Monocot Stem

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Growth of Stems Primary growth of stems is

produced by cell divisions in the apical meristem.– It takes place in all seed plants.

In conifers and dicots, secondary growth takes place in the lateral meristematic tissues called the vascular cambium and cork cambium.

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Woody Stems Actual wood part of the stem is xylem

tissue. Heartwood (pith): stores food. Sapwood: active in fluid transport; xylem

and phloem. Cambium:

producing new tissue, vascular.

Cork: bark

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Formation of Bark

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LEAVESSection 23.4

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Function of Leaves The structure of a leaf is optimized for absorbing

light and carrying out photosynthesis. Photosynthesis

– Process that plants use to produce their food.– 6CO2 + 6H2O C6H12O6 + 6O2

Transpiration– Loss of water and

exchange of carbon dioxide.

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Parts of a Leaf Cuticle

– Waxy outer surface; retains moisture.

Mesophyll – Middle layer of leaf

where photosynthesis occurs.

– Palisade layer (upper)– Spongy layer

(underside)

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Parts of a Leaf Epidermis

– “Skin” of leaf - responsible for gas exchange– Upper and lower

Stomata– Outside layer of leaf opening

in epidermis where gas and water exchange (controlled by guard cells)

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Leaves

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LeavesLetter Structure Color Function

A Cuticle Yellow Waxy outer surface; retains moisture.

B Epidermis Orange “Skin” of leaf - responsible for gas exchange.

C Vein (Xylem) Blue Pumps water up from soil through roots.

D Vein (Phloem) Red Moves nutrients and carbohydrates throughout the plant.

E Mesophyll Green Middle layer of leaf where photosynthesis occurs.

F Stomata Pink Outside layer of leaf opening in epidermis where gas and water exchange.

G Guard Cells Brown Control stomata; trigger when water is scarce causing stomata to become flaccid and pores close.

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LeavesDicot Leaf

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Turgor Pressure Turgor pressure (water pressure)

– Stomata close automatically when supplies of water from roots start to dry up

– Guard cells trigger when water is scarce causing stomata to become flaccid and pores close

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Leaf Venation

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Leaf Adaptations

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TRANSPORT IN PLANTS

Section 23.5

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Capillary Action The tendency of water

to rise in a thin tube.– The result of the water

molecules’ ability to stick to one another (cohesion) and to the walls of the tube (adhesion); contributes to the movement of water up the cells of the xylem tissue.