2.4 cell organisation in plants
TRANSCRIPT
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CELL ORGANISATION IN CELL ORGANISATION IN PLANTSPLANTS
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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ORGANS
Examples: leaf, stem, root & flowerLeaf – made up of ground tissues,
epidermal tissues and vascular tissues.
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SYSTEMSSYSTEMS
Not as specialised as in animal Have fewer organs2 main systems:
1. Root system2. Shoot system
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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
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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
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EXERCISE1. Complete the table below:
Organs Function
a.a. LeavesLeaves
b. Stems and b. Stems and
branchesbranches
c. Flowers c. Flowers
d. Rootsd. Roots
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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
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Things we have learnThings we have learn
PLANT CELL PLANT CELL ORGANISATION.docORGANISATION.doc