CELL ORGANISATION IN CELL ORGANISATION IN PLANTSPLANTS

TissuesTissues

- two main types:- two main types:

1. Meristematic tissues1. Meristematic tissues

2. Permanent tissues2. Permanent tissues

PLANT PLANT TISSUES.docTISSUES.doc

Cell organisation in plantsCell organisation in plants

1. Meristematic tissues 1. Meristematic tissues Consist of small cells – thin Consist of small cells – thin walls, large nuclei, dense walls, large nuclei, dense cytoplasm and no vacuolescytoplasm and no vacuolesComprise young & active Comprise young & active dividing cells and not dividing cells and not undergone differentiationundergone differentiationEpical meristemsEpical meristems – – tip of tip of root and buds of shootsroot and buds of shoots which undergo miotic which undergo miotic cell cell divisiondivision (increase number of (increase number of cell)cell)Lateral meristems/cambiaLateral meristems/cambia – – peripheral areas of stems peripheral areas of stems and rootand root which responsible for which responsible for secondary secondary growthgrowth (add girth) (add girth)

2. Permanent tissues2. Permanent tissues

consist of more mature cells which have consist of more mature cells which have undergoing differentiation or undergone undergoing differentiation or undergone differentiationdifferentiation

3 main types:3 main types:

a) Epidermal tissuesa) Epidermal tissues

b) Ground tissuesb) Ground tissues

c) Vascular tissuesc) Vascular tissues

a) Epidermal tissuesa) Epidermal tissuesCharacteristics:Characteristics:

- forms epidermis- forms epidermis- parts that exposed to air are covered - parts that exposed to air are covered

with cuticlewith cuticle- flat & have large vacuoles- flat & have large vacuolesFunctionsFunctions::- the cuticle - the cuticle prevent the loss of prevent the loss of

excessive water, give protection & excessive water, give protection & prevent invasionprevent invasion

- - root hairroot hair in roots increase the surface in roots increase the surface area for area for absorption of water & mineralsabsorption of water & minerals

- - guard cellsguard cells surround the stomata surround the stomata control the opening and closing the control the opening and closing the stomatastomata

Root hair

Guard cells and stomata

b. Ground tissuesb. Ground tissues

Form the bulk of a plantForm the bulk of a plant

Consist ofConsist of

i)i) Parenchyma tissuesParenchyma tissues

- thin-walled cell, loosely- thin-walled cell, loosely

arrange, have large vacuole arrange, have large vacuole

- store starch & sugar

- turgid and give support & shape to

herbaceous plants

ii) ii) Collenchyma tissuesCollenchyma tissues

- unevenly thickened cell wall - unevenly thickened cell wall

(thickened by cellulose & pectin), (thickened by cellulose & pectin),

strong & flexiblestrong & flexible

- support non-woody- support non-woody plants plants (herbaceous plant), (herbaceous plant), young stems & young stems & petiolespetioles

iii) iii) Sclerenchyma tissuesSclerenchyma tissues

- much more rigid, have uniformly- much more rigid, have uniformly

thickened cell walls by lignin & may be thickened cell walls by lignin & may be

deaddead

- - support & strengthens the plant bodysupport & strengthens the plant body

- provides protection- provides protection

c. Vascular tissuesc. Vascular tissuesInvolve in the transport of substances between the Involve in the transport of substances between the root & the shootsroot & the shoots2 types2 types::

i) i) XylemXylem- consist of xylem vessel extending - consist of xylem vessel extending

from the roots to the leavesfrom the roots to the leaves- cell wall thickened with lignin- cell wall thickened with lignin- - transport water & minerals from the root to transport water & minerals from the root to

thethe leavesleaves

ii) ii) PhloemPhloem

- consists mainly of sieve tubes- consists mainly of sieve tubes

which obtain nutrient from the adjacentwhich obtain nutrient from the adjacent

companion cellcompanion cell

- - Transport organic nutrient from the leaves Transport organic nutrient from the leaves to all parts of the plantsto all parts of the plants

ExerciseExercise1.1. What are the main types of plant tissues?What are the main types of plant tissues?

2.2. Give the location of these tissues:Give the location of these tissues:

a) meristematic tissuesa) meristematic tissues

b) epidermal tissuesb) epidermal tissues

3.3. Give the function of these tissuesGive the function of these tissues

a) parenchyma tissuesa) parenchyma tissues

b) xylem b) xylem

AnswersAnswers1. Meristematic tissues1. Meristematic tissues

2. Permanent tissues2. Permanent tissues

a) Meristematic tissues – tips of the a) Meristematic tissues – tips of the

root/buds of shoot/peripheral area of stemroot/buds of shoot/peripheral area of stem

b) Epidermal tissues – outermost layers thatb) Epidermal tissues – outermost layers that

covers the leaves, stems & roots of youngcovers the leaves, stems & roots of young

plant, the flowers, fruits & seedplant, the flowers, fruits & seed

a) Parenchyma tissues - a) Parenchyma tissues - store starch & sugar/

give support to herbaceous plants

b) Xylem -conducts water & minerals from the rootb) Xylem -conducts water & minerals from the root

to the leavesto the leaves

ORGANS

Examples: leaf, stem, root & flowerLeaf – made up of ground tissues,

epidermal tissues and vascular tissues.

SYSTEMSSYSTEMS

Not as specialised as in animal Have fewer organs2 main systems:

1. Root system2. Shoot system

1. Root system– main organs are the roots– absorptive system– highly branched to absorb water &

minerals from the soil & transport them to the main vascular system (xylem)

– anchor the plant to the ground

2. Shoot system- main organs are the stems, leaves, buds,

flowers & fruits- stems and branches act as support

system, holding the leaves in a position that facilitate maximum absorption of sunlight & position flower for pollination

- leaves are main photosynthesis system, the product transported via phloem to other parts of plants

- flowers are the reproductive system of the plant which produce fruits and seeds

EXERCISE1. Complete the table below:

Organs Function

a.a. LeavesLeaves

b. Stems and b. Stems and

branchesbranches

c. Flowers c. Flowers

d. Rootsd. Roots

AnswersAnswersOrgans Function

a.a. LeavesLeaves • The site of

photosynthesis

b. Stems and b. Stems and

branchesbranches

• act as support system

c. Flowers c. Flowers • involved in pollinationinvolved in pollination

d. Rootsd. Roots • absorptive system• anchor the plant to the ground

Things we have learnThings we have learn

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