Roots, Stems and Leaves Roots, Stems and Leaves Chapter 23Chapter 23

BiologyBiology – Miller – Miller • Levine• Levine

Specialized Tissue in PlantsSpecialized Tissue in Plants

The three organs of a plant are the roots, stems The three organs of a plant are the roots, stems and leavesand leaves

The three tissue systems of a plant are dermal The three tissue systems of a plant are dermal tissue, vascular tissue, and ground tissuetissue, vascular tissue, and ground tissue

A special type of tissue called A special type of tissue called meristematicmeristematic tissue is the only plant tissue that can produce tissue is the only plant tissue that can produce new cells by mitosisnew cells by mitosis Found in the tips of shoots and rootsFound in the tips of shoots and roots

Dermal TissueDermal Tissue

The outer covering of a plantThe outer covering of a plant Consists of a single layer of epidermal cellsConsists of a single layer of epidermal cells CuticleCuticle – a waxy layer that often covers the – a waxy layer that often covers the

epidermisepidermis Provides protection against water loss & injuryProvides protection against water loss & injury

May include specialized structures such as root May include specialized structures such as root hairs and guard cellshairs and guard cells

Vascular TissueVascular Tissue

Transports water and Transports water and nutrients throughout the nutrients throughout the plantplant

XylemXylem – transports – transports water; composed of water; composed of dead cellsdead cells

PhloemPhloem – transports – transports nutrients; composed of nutrients; composed of living cells called sieve living cells called sieve tube elementstube elements

Ground TissueGround Tissue Lies between the dermal and Lies between the dermal and

vascular tissuesvascular tissues Parenchyma – has thin cell walls Parenchyma – has thin cell walls

and large central vacuolesand large central vacuoles Collenchyma – has strong, flexible Collenchyma – has strong, flexible

cell walls and is found in larger cell walls and is found in larger plantsplants

Sclerenchyma – has extremely Sclerenchyma – has extremely thick, rigid cells wallsthick, rigid cells walls

RootsRoots

Types of roots:Types of roots: Taproot - A thick primary root that grows long and Taproot - A thick primary root that grows long and

is found mainly in dicotsis found mainly in dicots Fibrous roots – branch extensively and are found Fibrous roots – branch extensively and are found

mainly in monocotsmainly in monocots

Root Structure & GrowthRoot Structure & Growth

Root hairsRoot hairs – tiny projections from the – tiny projections from the epidermis that increases the surface area for epidermis that increases the surface area for absorption of waterabsorption of water

CortexCortex – layer of ground tissue – layer of ground tissue EndodermisEndodermis – layer of tissue that encloses the – layer of tissue that encloses the

vascular tissuevascular tissue Root capRoot cap – protects the root as it forces its – protects the root as it forces its

way through the soilway through the soil

Root Structure & FunctionRoot Structure & Function

Root FunctionRoot Function

Anchor a plant in Anchor a plant in the groundthe ground

Absorb water and Absorb water and dissolved nutrients dissolved nutrients from the soilfrom the soil

Stem Function & TypesStem Function & Types

Three important functions:Three important functions: Produce leaves, branches and flowersProduce leaves, branches and flowers Hold leaves up in the sunlightHold leaves up in the sunlight Transport substances between roots and leavesTransport substances between roots and leaves

Two types:Two types: Monocot – has vascular bundles that contain the Monocot – has vascular bundles that contain the

xylem & phloem scattered randomlyxylem & phloem scattered randomly Dicot – have vascular bundles organized in a Dicot – have vascular bundles organized in a

ringlike patternringlike pattern

Monocots and DicotsMonocots and Dicots

Stem StructuresStem Structures

NodesNodes – where – where leaves are attachedleaves are attached

Internodes Internodes – regions – regions between the nodesbetween the nodes

BudsBuds – contain – contain undeveloped tissue undeveloped tissue that can produce new that can produce new stems and leavesstems and leaves

Leaf StructureLeaf Structure

BladeBlade – thin, – thin, flattened sectionflattened section

PetiolePetiole – thin stalk – thin stalk that attaches the leaf that attaches the leaf to the stemto the stem

VeinsVeins – contain the – contain the xylem and phloemxylem and phloem

Leaf StructureLeaf Structure

Palisade mesophyllPalisade mesophyll – tightly packed cells that – tightly packed cells that absorb lightabsorb light

Spongy mesophyllSpongy mesophyll – loosely packed cells with – loosely packed cells with air spacesair spaces

StomataStomata – pore-like openings for taking in – pore-like openings for taking in COCO22 and releasing O and releasing O22

Guard cellsGuard cells – cells that open and close the – cells that open and close the stomatastomata

Leaf StructureLeaf Structure

Leaf FunctionsLeaf Functions

Photosynthesis – takes place in the mesophyll Photosynthesis – takes place in the mesophyll cells of the leafcells of the leaf

Transpiration – the loss of water from a plant Transpiration – the loss of water from a plant through its leaves (helps to pull water up from through its leaves (helps to pull water up from the roots)the roots)

Gas exchange – taking in carbon dioxide and Gas exchange – taking in carbon dioxide and releasing oxygenreleasing oxygen