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Transport System in PlantsPrepared By: Faiz Abdullah

+Transport System in Flowering plants

Flowering plants have a system of vessels that runs up and down the plants carrying materials.

These vessels are called transport or vascular tissues.

YOU SHOULD KNOW TWO TYPES OF TRANSPORT TISSUES:

① Xylem

② Phloem

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O Level question:WHAT IS THE DIFFERENCE

BETWEEN XYLEM AND PHLOEM TISSUES?

+ XYLEM1) FUNCTION2) STRUCTURE3) ADAPTATION

+XYLEM -- Function

I. TRANSPORT WATER AND DISSOLVED MINERAL salts FROM roots to stems to leaves.

II. Provide MECHANICAL SUPPORT for the stem.

+XYLEM – STRUCTURE & ADAPTATION

Consists mainly of xylem vessels (long hollow tube)

Made up of many DEAD CELLS

Inner walls of the xylem vessels are STRENGTHENED by LIGNIN structural or mechanical support

Has empty lumen without protoplasm or cross walls.

Narrow lumen for capillary action (not the same as transpirational pull)

Structure ADAPTATION

+PHLOEM

FUNCTION:

Transports manufactured food (sucrose+amino acid) from leaves to other parts of plant.

STRUCTURE:

Consists of sieve tubes and companion cells.

Sieve tube consists of columns of elongated, thin walled living cells called sieve tube cells/elements.

They have cross walls with many holes or pores sieve plates

Each sieve tube has a companion cell

ADAPTATIONS:

Companion cells have many mitochondria provide energy needed to load sugars from mesophyll cells into sieve tubes by active transport.

Sieve pores allow rapid flow of manufactured food through sieve tubes

+ Phloem

Check out the:1. Sieve tubes2. Sieve pores3. Companion cell4. Sieve plates

+ROOT

The root is divided into several regions:

The root cap: located at the tip of the root. PROTECTS root during growth through the soil.

Zone of cell multiplication/division: growing zone

Zone of elongation: The region where newly divided cells elongate increase in length of root.

Zone of maturation: consists of root hairs, which increases surface area for rapid and efficient uptake of water and salts

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Transverse section of the root

Take note of the labels

+Vascular tissue in stem:USEFUL TERMS

In dicotyledonous stem:

- Xylem and Phloem grouped together vascular bundle

- Vascular bundles are arranged in a ring around a central region pith

- Phloem lies outside the xylem with a tissue in between cambium

- Region between vascular bundles and the epidermis cortex

- Stem is covered by a layer of cells epidermis

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Vascular tissues in a stem

• Cambium cells can divide and differentiate to form new xylem and phloem tissues thickening the stem

• Cortex and pith serve to store up food substances such as starch

• Epidermal cells are covered by a waxy, waterproof cuticle that greatly reduces evaporation of water from the stem

+ENTRY OF WATER INTO

PLANTFROM ROOT STEM LEAVES

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To understand the movement of water:

We need to know howWATER BEHAVES?

BEFORE THAT!!!!!

+PROPERTIES OF WATER

COHESION

Water molecules are attracted to one another by a force cohesion

ADHESION

Water tends to stick to the inner surface of the walls of xylem vessels adhesion

+ Analogy

+1) Movement of water into root hair cells

+1) Movement of water into root

hairs: Movement of substances

Water:

OSMOSIS water from the soil move into the root hairs via osmosis.

Mineral Ions:

Diffusion: Ions diffuse from a high concentration to a low concentration.

Active transport: minerals, such as Mg and N, which are in LOWER concentrations in SOIL, enter the root cell via active transport

OSMOSIS FOR WATER ONLYFOLLOWS CONCENTRATION GRADIENT

NO NEED ENERGY

DIFFUSION FOLLOWS CONCENTRATION GRADIENT

ACTIVE TRANSPORT NEEDS ENERGY (ATP)AGAINST CONCENTRATION GRADIENT

+1) Movement of water into root

hairs:Adaptations

a) Root hair is long and narrow increase surface area to absorb more water and mineral salts by root hair cell

b) Cell surface membrane prevents cell sap (vacuole) from leaking out. Also, Cell sap has lower water potential.

c) Root hair is living can provide energy for active transport

+1) Movement of water into root hairs

Once water has entered a root hair, it passes from one cell to another by Osmosis.

This goes on and on and on……..and on….until the water reaches the xylem

At the same time, ions diffuse inwards through the cells of the root until they reach the xylem

+2) Movement of water UP the stem

+2) Movement of water up the stem

1) Transpiration pull

Other forces involved:

2) Root pressure (Guttation)

3) Capillarity

4) Adhesion and cohesion of water molecules

+Transpiration

The loss of water from the aerial parts of a plant (esp. through the stomata of leaves)

- Diffusion of water vapor through stomata lowers water potential in the leaves.

- This DRAW in water from the xylem

- Pulling force results in water entering the roots known as transpiration pull

This results in a column of water moving up, which are held together by strong cohesive bonds

+2) Root pressure (Guttation)

At night, mineral ions are actively transported into the xylem vessel.

This lowers the water potential in the xylem vessel.

Therefore, water passes from the living cells into the xylem by osmosis and flows upwards root pressure

Guttation stops when transpiration begins

+ 3) Capillary action

When water reaches the xylem vessel,Its NARROW LUMEN allows water to move up the stem process known as capillarity

+3) MOVEMENT OF WATER THROUGH THE LEAVES

+3) Movement of water through

the leaves

Mesophyll cells evaporate large quantities of water into the intercellular air spaces

Water vapor diffuses out of the leaves through the

STOMATA Small amount of water is lost through the waxy

CUTICLE

+What is happening inside leaves..

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TRANSPIRATIONIMPORTANCE AND ITS FACTORS

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TRANSPIRATION IS INEVITABLE/UNAVOIDABLE

+IMPORTANCE OF TRANSPIRATION

Enables water to move up the stem to the plants:

water can be used for photosynthesis and keep the cells turgid (help leaves spread out widely to trap more light)

Evaporation of water cools the plant.

Enables plant to obtain mineral salts.

Why do you think transpiration can help the plant?

+ Transpiration- features that

facilitate water loss

(a) Mesophyll cells with wet surfaces and large total surface area

(b) Large intercellular spaces in the leaf

Other factors:

a) Greater number in stomata

b) Stomata exposed directly to sunlight or remain open

These features ALSO HELP THE RATE OF PHOTOSYNTHESIS!!

+Environmental factors that

affect transpiration

① Temperature

② Air Humidity

③ Wind

④ Light intensity

⑤ Carbon dioxide concentration

Guess!!!

Guess!!!

Guess!!!

Guess!!!

Guess!!!

+Pictures for transpiration factors

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WILTING

+ Wilting

+WHEN? And WHY?

Wilting occurs when:

RATE OF TRANSPIRATION EXCEEDS RATE OF ABSORBTION OF WATER

Cells lose their turgidity

Cells become flaccid

Plant wilts

+WHY wilting?

Water becomes a limiting factor.

Wilting causes a decrease in the rate of photosynthesis Water is getting less

Wilting makes the leaves fold less area exposed to sunlight

The greater the size of stomatal opening, the greater the water loss

+ The transport or movement of food

substances in the phloemTRANSLOCATION

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LET’S STUDY THE PATHWAY OF WATER IN A PLANT

+EXPERIMENTInvestigation: to show water travels up the stem in the xylem

Procedure:

1. Set up the apparatus as shown.

2. Allow the plant to stand immersed in the red food dye for 3-4 hours

3. Observe the color change in the stem

4. Cut thin transverse section of the stem

5. Observe under a microscope

+ Observation

The red dye will appear in the stem and leaves.

Xylem tissue has been stained red

CONCLUSION:

Water is transported by

The Xylem Vessel