chap 1 transport in plant

CHAPTER CHAPTER 1: 1:

TRANSPORTRANSPORTT

PlantPlant

Plants

Water & mineral

Food

xylem phloem

Vascular tissues

involves

stem root leaf

structure

translocation

need

Transported by

Relate toRelate

to

involvesRoot

pressure

Transpirational pull

Factors1. Air movement2. Temperature3. Light intensity4. Relative

humidity

Capillary action

affectingTranspiratio

n

Results in

Found in

The Transport of The Transport of Substances in PlantsSubstances in Plants

Necessity for Transport of Substances in Necessity for Transport of Substances in PlantsPlants

Plants absorb Plants absorb water water and and mineral ionsmineral ions from the soil to all parts of the body.from the soil to all parts of the body.

Water needed by plants to carry out Water needed by plants to carry out photosynthesisphotosynthesis, acts as a solvent and , acts as a solvent and reactantreactant in the cell metabolisms. in the cell metabolisms.

Mineral ions are required for healthy Mineral ions are required for healthy growth and growth and developmentdevelopment..

Small multicellular plants such as Small multicellular plants such as mossesmosses and and liverwortsliverworts have a large have a large TSA/V ratio and a short distance for TSA/V ratio and a short distance for diffusion of substances. Therefore, diffusion of substances. Therefore, they do not require transport system.they do not require transport system.

However, in large flowering plants, However, in large flowering plants, conifers and ferns, they have a conifers and ferns, they have a smallsmall TSA/V ratio and TSA/V ratio and greatergreater distance for a distance for a diffusion of substances. Hence, they diffusion of substances. Hence, they require an internal transport system require an internal transport system in their body.in their body.

Vascular Tissue in PlantVascular Tissue in Plant Transportation of substances in plant is Transportation of substances in plant is

carried out by carried out by vascular tissuevascular tissue.. There are two types of vascular tissue; There are two types of vascular tissue;

xylemxylem and and phloemphloem tissues. tissues. Xylem transport Xylem transport waterwater and and dissolved dissolved

mineral saltsmineral salts absorbed by roots to the absorbed by roots to the upper parts of the plants. It also gives upper parts of the plants. It also gives supportsupport to the plant. to the plant.

Phloem transports Phloem transports organic substancesorganic substances synthesized by the leaves during synthesized by the leaves during photosynthesis to other parts of the plant.photosynthesis to other parts of the plant.

Cross-section of a LeafCross-section of a Leaf

Cuticle

Xylem

Phloem

Stoma

CuticleCuticle Wax substances to reduce Wax substances to reduce

water losswater loss

Xylem and PhloemXylem and Phloem Vascular bundle or veinVascular bundle or vein

Cross-section of a StemCross-section of a Stem

EpidermisCortex

Pith

Vascular bundle

EpidermisEpidermis One-celled thick with One-celled thick with

cuticle layer outsidecuticle layer outside Has Has lenticels lenticels for for

respirationrespiration

CortexCortex Consists of Consists of collenchymacollenchyma cells cells

in outer region and in outer region and parenchymaparenchyma cells in inner cells in inner region.region.

Provides support to the stemProvides support to the stem

PithPith Consists of large Consists of large

parenchyma parenchyma cells.cells. FoodFood storage storage

Vascular bundleVascular bundle Arranged in the Arranged in the ringring around around

the pith.the pith. Xylem and phloem Xylem and phloem

separated by separated by cambiumcambium tissuetissue

Cross-section of a RootCross-section of a Root

EpidermisEndoder

misPericycl

e

Vascular

cylinder

Phloem

Root hair

Xylem

Root hairRoot hair A specialised A specialised epidermalepidermal

cellcell Increase the Increase the surface areasurface area

for water absorption.for water absorption.

EpidermisEpidermis Does not have Does not have cuticlecuticle Absorbs water and Absorbs water and ionsions

from soilfrom soil

EndodermisEndodermis Single layer of cellsSingle layer of cells

PericyclePericycle Consists of Consists of sclerenchymasclerenchyma

tissue which provide tissue which provide mechanical support to the mechanical support to the root.root.

Vascular cylinderVascular cylinder Consists of vascular tissue and Consists of vascular tissue and

pericyclepericycle Xylem radiates from the centre Xylem radiates from the centre

forming forming star star shapeshape Phloem fills the area between Phloem fills the area between

xylemxylem

Structure of Vascular Tissue Structure of Vascular Tissue Related to the TransportRelated to the Transport

XylemXylem Consists of four types of cells; vessel, Consists of four types of cells; vessel,

tracheid,tracheid, parenchyma and parenchyma and fibresfibres..1.1. Xylem vesselXylem vessel

Xylem vessel are long, hollow and Xylem vessel are long, hollow and continuouscontinuous tubes.tubes.

Dead cellsDead cells, no protoplasm to easier the flow of , no protoplasm to easier the flow of water.water.

The cell walls are strengthened by The cell walls are strengthened by ligninlignin, deposited , deposited in various patterns and gives in various patterns and gives mechanicalmechanical support. support.

The cell wall with numerous hole or The cell wall with numerous hole or pit pit to allow to allow waterwater and mineral pass side way between the and mineral pass side way between the cells.cells.

2.2. TracheidTracheid Also dead cells and Also dead cells and

hollow but more hollow but more longer and smaller longer and smaller than xylem vessel.than xylem vessel.

Pointed end and Pointed end and pitted.pitted.

3.3. Parenchyma and Parenchyma and fibresfibres

Parenchyma stores Parenchyma stores food.food.

Fibres provide Fibres provide supportsupport

LS of tracheid

LS of xylem vessel

PhloemPhloem Also consists of four types of cells; sieve Also consists of four types of cells; sieve

tube, tube, companion cell,companion cell, fibre and parenchyma. fibre and parenchyma.1.1. Sieve tubeSieve tube

Cylindrical in shape, consisting of elongated Cylindrical in shape, consisting of elongated sievesieve cellcell, arranged end to end., arranged end to end.

The end wall of each cell are perforated to form The end wall of each cell are perforated to form sieve platesieve plate and allow food substances such as and allow food substances such as sucrosesucrose and and amino acidamino acid to pass from one cell to to pass from one cell to another. another.

The sieve tube is a living cell but during The sieve tube is a living cell but during maturation, many organelle including nucleus maturation, many organelle including nucleus disintegrates.disintegrates.

There is a thin layer of There is a thin layer of cytoplasmcytoplasm lining the lining the cellulose wall of sieve tube.cellulose wall of sieve tube.

2.2. Companion cellCompanion cell Normal cell with nucleus, cytoplasm and Normal cell with nucleus, cytoplasm and

many mitochondria.many mitochondria. They are adjacent and closely related to the They are adjacent and closely related to the

sieve cell.sieve cell. It provides ATP to help the food transport on It provides ATP to help the food transport on

the sieve tube.the sieve tube.

3.3. Parenchyma and fibreParenchyma and fibre Parenchyma cells store food.Parenchyma cells store food. Fibres provide support.Fibres provide support.

cytoplasmCompanion cellnucleus

Sieve plate

Thin cytoplasm

Sieve tube

LS of the phloem

Transport of Substances in Transport of Substances in PlantsPlants

Transport of Organic Substances Transport of Organic Substances (Translocation)(Translocation)

1.1. Definition: Translocation is a transport of Definition: Translocation is a transport of soluble soluble organic substancesorganic substances such as such as sucrose and sucrose and aminoamino acidacid from the leaves from the leaves to other parts of the plants.to other parts of the plants.

Translocation is a two directional Translocation is a two directional

transport, transport, upwardupward and and downwarddownward and and occurs in the occurs in the sieve tubesieve tube of phloem tissue. of phloem tissue.

2.2. The importance of translocation The importance of translocation : to enable the product of : to enable the product of photosynthesis moves from the photosynthesis moves from the leaves to the:leaves to the:

a)a) GrowthGrowth region such as shoots, region such as shoots, roots, and young fruits.roots, and young fruits.

b)b) Storage organs like Storage organs like tubertuber..c)c) Other parts of the plants to be a Other parts of the plants to be a

raw material for cell raw material for cell respirationrespiration..

3.3. To show the role of phloem: Bark Ringing ExperimentTo show the role of phloem: Bark Ringing Experiment

MethodMethod ResultResulta)a) Choose a Choose a

healthy small healthy small branch of a branch of a tree.tree.

b)b) By using a By using a knife, remove knife, remove a complete a complete ring or bark, ring or bark, about 2 cm about 2 cm length.length.

c)c) Leave it for Leave it for one month.one month.

The tissue above the ring The tissue above the ring swell up, whereas the one swell up, whereas the one below the ring withers.below the ring withers.

ExplanationExplanationa)a) The tissue removed together with the The tissue removed together with the

bark is bark is phloemphloem..b)b) This disrupts the flow of organic This disrupts the flow of organic

substances from the leaves down to substances from the leaves down to the root.the root.

c)c) Accumulation of these substances Accumulation of these substances causes a causes a swellingswelling above the ring. above the ring.

d)d) The leaves of small branch do not wilt The leaves of small branch do not wilt because the because the xylemxylem has not been has not been removed. So, upward flow of water is removed. So, upward flow of water is not disrupted.not disrupted.


Transport of Water and Mineral IonsTransport of Water and Mineral Ions1.1. From the soil, water enters the root by From the soil, water enters the root by

osmosis osmosis whereas mineral ions by whereas mineral ions by active transportactive transport..

2.2. The presence of root hairs increase the The presence of root hairs increase the surface areasurface area for absorption. for absorption.

3.3. The movement of water from the root The movement of water from the root to the leaves is aided by three factors:to the leaves is aided by three factors:

Root pressureRoot pressure Capillary (capillary action)Capillary (capillary action) Transpirational pullTranspirational pull


Root PressureRoot Pressure The surrounding soil water is The surrounding soil water is hypotonichypotonic to to

the cell sap of root hair because it contains the cell sap of root hair because it contains salt, sugar and amino acid.salt, sugar and amino acid.

Therefore, water diffuses into root hair by Therefore, water diffuses into root hair by osmosisosmosis..

The entry of water into root hair dilutes its The entry of water into root hair dilutes its cell sap to become hypotonic to the cell sap to become hypotonic to the adjacent cells.adjacent cells.

The water moves again to the next cell The water moves again to the next cell until it crosses the cortex tissue by osmosisuntil it crosses the cortex tissue by osmosis

Root PressureRoot Pressure … …contcont This water concentration gradient This water concentration gradient

existed in the cortex creates a force existed in the cortex creates a force called called root pressureroot pressure to push water to push water into xylem.into xylem.

H2O


Capillary actionCapillary action Capillary action is a combination force of Capillary action is a combination force of

cohesioncohesion and and adhesionadhesion which enable the which enable the water move up along the narrow xylem water move up along the narrow xylem vessel.vessel.

CohesiveCohesive force is the attraction of one force is the attraction of one molecule to other molecule of water.molecule to other molecule of water.

Meanwhile, Meanwhile, adhesiveadhesive force is the attraction force is the attraction between water molecules and the wall of between water molecules and the wall of xylem vessel.xylem vessel.

Therefore, xylem vessel forms a continuous Therefore, xylem vessel forms a continuous column of water from root through the stem column of water from root through the stem to the leaf.to the leaf.


Transpirational PullTranspirational Pull During the day, water During the day, water evaporates evaporates from from

the mesophyll cells into the the mesophyll cells into the intercellular space in the leaves.intercellular space in the leaves.

From here, the water vapour diffuses to From here, the water vapour diffuses to the surrounding air through the stoma.the surrounding air through the stoma.

The loss of water from the leaves to the The loss of water from the leaves to the atmosphere is called atmosphere is called transpirationtranspiration..

Transpiration in the leaves pull up the Transpiration in the leaves pull up the water from the soil, a force called water from the soil, a force called transpirational pulltranspirational pull..

Water Loss from the Plants Water Loss from the Plants (Transpiration)(Transpiration)

1.1. Definition: The loss of water in the Definition: The loss of water in the form of form of water vapourwater vapour from a plant to from a plant to the atmosphere.the atmosphere.Almost (99%) of the water taken by Almost (99%) of the water taken by plants is plants is evaporatedevaporated by transpiration, by transpiration, only 1% is used for only 1% is used for photosynthesisphotosynthesis and to remain and to remain turgidturgid..

2.2. About 90% of transpiration takes place About 90% of transpiration takes place through the through the stomatastomata, 5% through the , 5% through the cuticle cuticle and 5% evaporated from the and 5% evaporated from the lenticelslenticels of the stem. of the stem.

3.3. The importance of transpiration:The importance of transpiration:a)a) Creates a Creates a transpirational pulltranspirational pull that sucks that sucks

water and dissolved mineral salts from water and dissolved mineral salts from the soil. Mineral salts are used for the soil. Mineral salts are used for cell cell activitiesactivities while the water is used while the water is used photosynthesis and keeps the cells photosynthesis and keeps the cells turgid to give support to the leaves.turgid to give support to the leaves.

b)b) Maintains Maintains osmotic pressureosmotic pressure in the cells in the cells due to elimination of excessive water in due to elimination of excessive water in plant body.plant body.

c)c) Gives Gives cooling effectcooling effect due to absorption due to absorption of latent heat by water to evaporate.of latent heat by water to evaporate.

4.4. Measuring the rate of transpiration:Measuring the rate of transpiration:a)a) The pulling force developed by The pulling force developed by

transpiration can be demonstrated in transpiration can be demonstrated in an experiment by using an experiment by using potometerpotometer..

b)b) This potometer can also be used to This potometer can also be used to measure the rate of photosynthesis measure the rate of photosynthesis under different environmental under different environmental condition.condition.

c)c) From the diagram above, the rate of From the diagram above, the rate of water loss is indicated by the speed of water loss is indicated by the speed of which the air bubble moves along the which the air bubble moves along the graduated capillary tube (from X to Y)graduated capillary tube (from X to Y)

A potometer

Capillaries tube with

scale

Resevoir

Air bubble

Water

Leafy shoot

Y X

Rate of = Distance X – Y (cm)

water loss time

d)d) Notice that, the potometer does Notice that, the potometer does not measure transpiration directly not measure transpiration directly and will give an accurate and will give an accurate indication only if the rate of water indication only if the rate of water loss is precisely equal to the rate loss is precisely equal to the rate of water uptake. However, for of water uptake. However, for most purpose the estimated of most purpose the estimated of transpiration obtained from the transpiration obtained from the experiment is satisfactory.experiment is satisfactory.

Factors Affecting the Rate of Factors Affecting the Rate of TranspirationTranspiration

1.1. Air movementAir movement Water vapour that Water vapour that

diffuses out of stomata diffuses out of stomata accumulatesaccumulates around the around the leaf surface.leaf surface.

Moving air carries water Moving air carries water vapour away. This vapour away. This createscreates the the concentration gradient concentration gradient between water vapour between water vapour inside the leaf and inside the leaf and outside the leaf. Hence, outside the leaf. Hence, the rate of transpiration the rate of transpiration is increased.is increased.

Air movement

Tran

spira

tion

rate

The rate of transpiration increases when the movement of air is increased.

Factors Affecting the Rate of Factors Affecting the Rate of TranspirationTranspiration

2.2. TemperatureTemperature An increase in An increase in

temperature, temperature, increase the rate of increase the rate of transpiration due to:transpiration due to:

Increase in water Increase in water evaporationevaporation rate rate

Increase in diffusion Increase in diffusion raterate

Decrease Decrease in humidity in humidity of surrounding airof surrounding air

Air movement

Tran

spira

tion

rate

The rate of transpiration increases when the temperature

is increased.

chap 1 transport in plant

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