Cell

Organisation in

Plants

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Tissues Two main types of

tissues :

MERISTEMATIC

TISSUE S and

PERMANENT

TISSUES

Meristematic

tissues are divided

into two

meristems; Apical

meristems and

Lateral meristems

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Meristematic Tissues Small cells with large nucleus, no vacuoles

and thin walls

Actively dividing to produce new cells for

growth

Apical meristems : located at the tips of

roots and shoots; produces new cells for

growth

Lateral meristems (cambium): found

between the xylem and phloem tissues;

responsible for secondary growth

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Shoot apex Root apex

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Permanent Tissues

Mature tissues that are undergoing

differentiation

Mature tissues which are already

differentiated

Can be categorised into epidermal tissue,

ground tissue and vascular tissue

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Epidermal Tissue

Covers the

surfaces of leaves,

stems, roots,

flowers, fruits and

seeds

Made up of one

layer of flat cells

which have large

vacuoles

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Upper epidermis : secretes waxy layer

called cuticle ; reduces loss of water

through transpiration

Guard cells : modified from epidermal

cells; control the opening and closing of

stoma

Root hairs : modified from epidermal cells;

help in the absorption of water and

minerals

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Ground tissues Fills up the spaces

between the

epidermal and

vascular tissues

Three types :

parenchyma,

collenchyma,

sclerenchyma tissues

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Collenchyma : polygonal cells with

uneven cellulose cell walls thickened by

pectin; provides support for young plants

and herbaceous or non-woody plants

Sclerenchyma : uneven cells walls

thickened by lignin and die when

matured; provides support and

mechanical strength to the plant

Parenchyma : thin-walled cells with large

vacuoles and loosely arranged with

spaces between them; photosynthesis

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Vascular tissues Involved in the transport of water and other

substances in the plant

Continuous vessels or tubes in all parts of a

plant

Two types : xylem tissue and phloem tissue

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Xylem tissue : long, hollow tube from the roots to

the leaves and shoots, has lignified walls and

consists of xylem vessels and tracheids

Function: Transports water and minerals salts from

the roots to the leaves

Phloem tissue : consists of elongated living cells

connect end to end to form a tube with sieve

plates

Function: Transport organic nutrients such as

carbohydrates from the leaves to other parts and

storage organs of plant

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Organs

Plant organs

include roots, stems,

flowers and leaves

which consists of

tissues

There are less

organs in plants as

compared to

animals.

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Systems Plants have two main systems: Root

system and shoot system

Root system : consists of all roots of a

plant; forms the absorptive system as roots

absorb water and mineral salts from the

soil

Shoot system: consists of leaves, flowers,

stems and fruits for flowering plants; stem

act as a support system and flowers form

the reproductive system

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Organism

The root system

and shoot system

work together for

the plant to

survive.

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Label parts of tissues shown in the diagram

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Regulating the internal

environment

The internal environment of multicellular

organism

Internal environment is the environment within

the body of an organism

The intercellular space between cells is filled

with a fluid = the interstitial fluid

The cells obtain the substances required for

biochemical reactions from the interstitial fluid.

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The necessity for maintaining an

optimal internal environment

Internal environment is affected by

physical and chemical factors.

Physical factors : temperature, blood

pressure, osmotic pressure.

Chemical factors : pH, blood glucose

level, salt level

Both factors are regulated by a process

called HOMEOSTASIS

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Homeostasis

A process in which the chemical and

physical factors of the internal

environment are regulated so that the

conditions are maintained at a relatively

constant level for the optimal functions of

cells

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Homeostasis is carried out by means of

ve feedback mechanism

In the ve feedback mechanism, the stimulus will trigger a response by the effector to reverse the change back to its normal level.

Receptor detects change in stimulus and sends message to control centre.

Control centre processes message and sends response message to effector.

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The involvement of various systems in

maintaining an optimal internal

environment

Regulations of chemical and physical

factors involve various systems such as

respiratory system, circulatory system,

nervous system, excretory system,

muscular system and endocrine system.

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Example :

Factor : Body Temperature

System Involved : Nervous system,

integumentary system, circulatory system,

endocrine system and muscular system

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Regulatory system in Plant Less important in plants because :

Most plant cells are dead cells = no biochemical

reactions

Water and minerals salts are transported by xylem tissues

and aided by natural factors = capillary action and

transpiration pull

The internal environment of a plant is air and not fluid.

Plant cells have vacuoles to store waste substances

before they are transformed into non-toxic substances to

be excreted.

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Appreciating the uniqueness

of the cell

The cellular components are dependent

on each other and work together

systematically to ensure the cell functions

optimally on its own.

Organisms cannot survive if cells fail to

function. The absence of certain cellular

components affects the activities of the

cell.

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Predict each effect on a cell if the

following cellular components are

absent

Mitochondrion

Chloroplast

Nucleus

lysosome

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