the transport of substances in plant

8/3/2019 The Transport of Substances in Plant

1/23

THE TRANSPORT OF

SUBSTANCES IN PLANT


2/23

The vascular tissues

The vascular tissues transport substances inplant.

There are two types of vascular tissues

Xylem: transport water and dissolve mineralsalts absorbed by the roots up to the stem andthe leaves. Provide mechanical support to

woody plants. Phloem: transport organic substances (sucrose)

from leaves to the other part of plants.


3/23

The stem of dicotyledonous

plant.1) Epidermis layer1) help maintain the shape of the stem.

2) Have waxy cuticle

2) Cortex layer1) From collenchyma cells.

2) Provide support and flexibility to the stem.

3) Pith1) Ass food storage in young plants.

2) May absent in older plants.

4) Vascular bundle (xylem and phloem)1) Arrange in a ring around the pith.


4/23

1) Epidermis layer1) No waxy cuticle

2) Root hairs (specialised epidermal cells)

2) Cortex1) Parenchyma tissue: store starch and grains

3) Endodermis

4) Pericycle1) Sclerenchyma tissue for mechanical support.

5) Vascular cylinder1) Vascular tissues and pericycle

The root of dicotyledonous

plant.


5/23

Wheat seed

Root hairsFragile parts of cellsthat grow from themain root

They massivelyincrease the surfacearea for absorption


6/23

Root hair cells (x150)


7/23

1) Leaf blade (lamina)

2) Leaf stalk (petiole)

1) Connect lamina to the stem2) Contain vascular tissues (xylem and phloem) that

are continuous with those in the stem and root.

3) Leaf veins

1) Contain vascular tissues.

The leaf of dicotyledonous

plant.


8/23

Xylem

4 types of cells1) Xylem vessels

2) Tracheids

3) Fibres(sclerenchyma)

4) Parenchyma


9/23

Xylem vessels and tracheids

water conducting cells

Elongated cells arranged endto end

Walls thickened with lignin,become woody, strong andimpermeable.

Dead and hollow when

mature.Walls perforated by pits,allow water and mineral saltsto past sideways between thecells.


10/23

Xylem vessels Tracheids

Shorter cell Longer cell

Large diameter Small diameter

Pointed end wallsand have pits

Open end walls

xylem can only transport substances upward fromthe roots to the leaves.


11/23

Phloem

4 types of cells

1) Sieves tubes

2) companion cells

3) parenchyma

4) Fibres

Sieve tubes transportorganic substanceslike sucrose andamino acids


12/23

Sieve tube

cylindrical column of long cells living cells

has no nucleus when matureand cytoplasm pushed aside

each cells has pores end wallsto form sieve plates

companion cell normal cell with lot ofmitochondria

provide proteins, ATP and

nutrients to the sieve tube cells.

Sievetube cell

Companioncell

Longitudinal strands

of cytoplasm


13/23

The transport of organic

substances and water in plants

Transpiration is the loss ofwater vapourthrough evaporation from the surface f

plants Water is absorbs by plant from soil

1% is used for photosynthesis and keeps thecell turgid.

99% evaporated from plants surface throughtranspiration.


14/23

Transpiration mostly occur through thestomata of the leaves surface. It also occursthrough the lenticels of woody stems.

Transpiration is important to

Helps in absorption and transport of water andmineral ions in roots

Produce cooling effect in plant

Helps to supply water to all plant cells formetabolic process

Maintain cell turgidity

The transport of organic

substances and water in plants


15/23

Factor that affect the rate

of transpiration

a) Light intensity

a) Higher the light intensity, higher the rate or

transpirationb) Light stimulate the opening of stomata,

hence more water vapour evaporatesthrough it

b) Temperature of surroundinga) Higher the temperature, higher the rate of

transpiration


16/23

c) Air movementa) Higher air movement, higher the rate of

transpiration

b) A faster air movement helps to remove watervapour that accumulate near the leaf surface

c) It increase the concentration gradient betweenthe water vapour inside the leaf and that outside

the leafd) Humidity

a) Higher the relative humidity, lower the rate oftranspiration.

Factor that affect the rate

of transpiration


17/23

Movement of water from soil

to the leaves

Root pressure Occur due to concentration gradient

of solutes that exist across the cortex

that result the pushing force andinflow of water into xylem vessel

Guttation


18/23

Movement of water through

the roots


19/23

Endodermalcell


20/23

Capillary action

Occur in narrowvessel (xylem)

Due to hydrogenbonding that createcohesive force (watermolecules adhere to

one another) andadhesive force (watermolecule adhere toxylem wall

Movement of water through

the stem

Capillary action is limited bygravity and the size of the straw.The thinner the straw or tube thehigher up capillary action will pull

the water


21/23

Cohesioncauses waterto form drops,surface tensioncauses them tobe nearlyspherical and

adhesion keepsthe drops inplace


22/23

Transpiration pull

Act as the main driving force for water absorptionfrom soil

Water evaporates through stomata in leaves. Theloss of water creates the tension or pulling forceand draw water from xylem in leaves, stem andeventually the roots of plants.

Movement of water from the

leaves to the atmosphere


23/23

the transport of substances in plant

Documents