Plant tissues

Plant OrganizationRoot system- growth toward gravity;

generally below ground; consists of rootsRoot – epidermis; cortex; stele (vascular

tissue); pith

Shoot systemGrowth away from gravity along the axisGenerally above the groundConsists of the stem and the leavesFlowers are modified shoot system

Plant TissuesMeristemsSurface or dermal tissuesVascular tissuesGround or fundamental tissues

Meristems Responsible for increase in number of cellsMeristems do not specializePlant tissues are derived from the meristemsThree types:

ApicalLateralIntercalary

MeristemsIntercalary Meristem- plants without vascular

cambium (grasses)Growth regions that occur at the base of nodes

Growth Primary growth

Inc in length of plants (apical meristem)Secondary growth

Inc in plant girth (lateral meristem)Select plants only (woody plants such as dicot

and gymnosperms)Product: wood and cork

Plant growth patterns and regionsPrimary growth- growth in length; primary

meristemsSecondary growth- growth which increases

the girth or circumference of the plantVascular cambium- bet wood and barkCork cambium-found in the outer bark

Primary meristemsAt tipsShoot tip meristems (shoot system)

Stem meristem; leaf primordia; bud primordiaRoot tip meristems

Primary meristems are permanent and self perpetuating

Derivative meristemsProduced when meristem cells divide; forms

the tissue systems of the plant Protoderm- develops into surface or dermal tissues Procambium- develops into vascular tissue Ground meristem- fundamental /ground tissues Secondary meristems Vascular cambium- produces wood (strength);

produces part of bark (protection) Cork cambium- produces protective layer of bark

called cork

Plant GrowthPrimary Growth

(roots and shoots)

Secondary Growth (roots and shoots)

Meristems from Cell DedifferentiationDedifferentiate-any plant cell has the ability

to dedifferentiate

Lateral root formation Adventitious growth Wound healing Secondary cork cambium

Primary Growth of RootsRoot cap

protects the delicate meristems as the root elongates through the abrasive soil

secretes mucous that lubricates the soil

3 Zones of cells at successive station Zone of cell division Zone of cell elongation Zone of cell differentiation

Simple Tissues

Ground or fundamental tissues

Fibers- for supportPhotosynthetic cellsStorage cellsFill in the spaces cells

Ground or Fundamental Tissues

Parenchyma basic tissue type

Collenchymasupports young plants

Sclerenchymasupports for mature plants

ParenchymaDefinition: a simple tissue composed of

spherical-shaped cells; most common type of tissue

Have thin primary wallsLiving, metabolizing tissueE.g. Chlorenchyma, AerenchymaFunctions:

Photosynthesis & RespirationStorage (starch, oil droplets, air, water, and

salts)Wound healing & regeneration

CollenchymaDefinition: a simple tissue found beneath

the epidermis in young stems and in large veins of leaves (“strings” in celery).

Provides a flexible support system (like our skeletal system).

Found uniformly throughout the plant.Elongated cells that have unevenly

thickened cell walls (especially in the corners)

Alive at maturity

SclerenchymaDefinition: a simple

tissue specialized for structural support; occurs in many areas

Two types:Fibers Sclereids

Have both primary and secondary cell walls.

At functional maturity cells are often dead

FibersLong, tapered cells

that often occur in groups or clumps (abundant in the wood and bark of flowering plants)

Found in leaves & stems.

Primary function is support

SclereidsShort, cuboidal

cells common in shells of nuts and pits of fruits (peaches, cherries)

Found in all plant parts, usually clustered.

Primary function is for protection

Complex tissuesVascular Tissue System

Vascular tissuesFunctions: conduct water and solutes support and strength of the

plantTypes of vascular tissues

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

XylemConduction of H2O from roots to leavesMade up the woodComposed of:

Vessel Elements- elongated cells with secondary walls Dead at functional maturity; perforated Large diameter

Tracheids – elongated, narrow cells with secondary walls; dead at functional maturity; pitted Xylem fibers Xylem parenchyma Xylem rays

Parenchyma cells and Fibers

TracheidsTracheids are

typically found in gymnosperms and seedless vascular plants and aid in transporting water.

Movement of water is only longitudinal

Vessel ElementsVessel elements are

typically found in angiosperms and aid in transporting water.

Movement of water can be transverse or longitudinal

Phloem Moves solutes (especially carbs)Composed of:

Sieve tube cells Elongated cells forming tubes End walls have pores forming sieve plates Alive at functional maturity Carry food

Companion cells Connected to the sieve tube through plasmodesmata Parenchyma cells adjoining the sieve tube cells Phloem fibers Phloem parenchyma(Sclerenchyma fibers and parenchyma cells)

Sieve tube membersSieve tube members

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

Complex tissuesDermal Tissues

Surface or dermal tissuesProtectionPrevents dessication

Dermal (surface) tissueEpidermis (herbaceous plants)

Cuticle (protective waxy layer)- prevents dessication (cuticle) and invasion of pathogens , absorption of water, control of gas exchange

Periderm or cork layer (woody plants) Produced from cork cambium Secondary epidermis or periderm of woody plants

DermisEpidermis: Two

typesParenchyma cellsGuard cells

NO Chloroplasts

CuticleA waxy layer

secreted by epidermal cells of stems and leaves

Prevents water loss and diffusion of gases

Cuticle Parenchyma cells

Guard cellsGuard cells form the tiny opening called the

stomata

PeridermisWoody 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

Dermal (surface) tissueEpidermal modifications

Hairs of trichomes Root hairs: absorption of water Guard cells: form stomata for gas exchange Glands: modified cells containing oils or other substances for secretion

Transport in PlantsCellular level transportLateral transportLong-distance transport

Plant NutritionChemical composition of plants

80%-85% of herbaceous plants is H2OPlants grow mainly by accumulating water in

the central vacuoles of their cellsCarbon, hydrogen, oxygen are the most

abundant elements in the dry weight of a plant

Essential NutrientsHydroponic structure- used to determine

which of the mineral elements are actually essential nutrients

Macronutrients- elements required by plants in relatively large amounts

Micronutrients- elements needed by plants in small amounts