2.2 plant tissues

G.C.E. O/L Science

Sudarshana Elapatha Biology Grade 10

Photosynthetic autotrophsObtain inorganic materials from the external environment and process them into the organic compounds needed for lifeCells secrete a cell wall exterior to the plasma membrane

Tissue Tissue A group of similar structured cells which are specialized to certain function is known as a tissue



Responsible for increase in number of cellsMeristems do no t specializePlant tissues are derived from the meristems three types:

Apical meristems Lateral meristems Intercalary meristems

Apical Meristems Shoot tip meristems

Root tip meristems


Lateral Meristems


Plants without vascular cambium (grasses)

Growth regions that occur at the base of nodes

Primary growthIncreased length of plants

apical meristemSecondary growthIncreased plant girth or circumference of the plant

lateral meristemVascular cambium- between wood and barkCork cambium- found in the outer bark

Select plants only (woody plants such as dicot and gymnosperms)

Product: wood and cork




Root cap protects the delicate meristems as the root elongates through the abrasive soilsecretes mucous that lubricates the soil

3 Zones of cells at successive stationZone of cell divisionZone of cell elongationZone of cell differentiation

Have living cells A simple tissue composed of spherical-shaped cellsHave thin primary walls The cell wall is made up of cellulose Intercellular air spaces are present

Functions: Photosynthesis Storage (starch, oil droplets, air, water, and

salts) Wound healing & regeneration

most common type of tissue



Have living cells A simple tissue composed of polygonal -shaped cellsHave unevenly thickened cell walls especially in the corners The cell wall is made up of cellulose Intercellular air spaces are not presentA simple tissue found beneath the epidermis in young stemsProvides a flexible support (like our skeletal system).



Cells are often deadHave both primary and secondary cell walls.secondary cell wall is made up of lignin.No intercellular spaces A simple tissue specialized for structural support Two types:

Fibers Sclereids

Long, tapered cellsFound in leaves & stems.Primary function is support

Short, cells common in shells of nuts and pits of fruits (peaches, cherries)Found in all plant parts, usually clustered.Primary function is for protection


Vascular Tissue System

Functions: conduct water and solutes support and strength of the plantTypes of vascular tissues

Xylem- conducts water and mineralsPhloem- conducts solutes/foodContinues throughout the plant


Conduction of H2O from roots to leavesMade up the wood

Composed of:Composed of: Vessel Elements Tracheid Xylem fibers Xylem parenchyma

Vessel elements are typically

found in angiosperms

and aid in transporting

water.

Features Cells are not alive Cells are long and cylindricalCell walls are lignified The cell walls are thickened and impregnated with lignin

Lignin make the cell wall strong and impermeable


lignifications of xylem cellslignifications of xylem cells


Annular Annular

Spiral Spiral

ScalariformScalariform

ReticulateReticulate

Pitted Pitted

Tracheids are typically found in gymnosperms and

seedless vascular plants and aid in transporting water.

Features Cells are not alive

Elongated , narrow cells with secondary cell walls The cell walls are thickened and

impregnated with lignin

Simple pits appear in the cell walls



Moves solutes (especially carbs)

Composed of

Sieve tube cellsSieve tube cellsPhloem fibersPhloem parenchyma

Sieve tube cells Elongated cells forming

tubes End walls have pores

forming sieve plates Alive at functional maturity Carry food


Companion cellsParenchyma cells adjoining the sieve tube cells


Sieve tube members can secrete a protein called callose to plug sieve plates to stop the flow of food if the phloem is damaged


Dermal Tissues

ProtectionPrevents dessication

Epidermis ( Herbaceous plants )

Periderm or cork layer (woody plants)

Produced from cork cambium Secondary epidermis or periderm of woody plants

EpidermisOuter layer of the plant bodyCells are closely packed Most of cells have NO ChloroplastsHave a CuticlePoses stomata Composed of two types cells

Parenchyma cellsGuard cells


CuticleCuticle (protective waxy layer)prevents desiccation (remove water) and invasion of pathogens ,


StomataStomata Controls the gas exchange

Root hairs Root hairs

Controls the absorption of water

Guard cells form the tiny opening called the stomata

Woody plants initially produce an epidermis that splits as the plant grows.

These plants also have periderm, which is several cells thick and forms under the epidermis.Periderm composes the outer barkComposed of two types of cells

Cork cells- secrete suberinCork parenchyma

Epidermal modificationsEpidermal modificationsHairs of trichome

reduce transpiration Root hairs

absorption of waterGuard cells form stomata for gas exchange



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2.2 plant tissues