Transportation in plants

•Most plants have developed complex vascular system that move nutrients and water .

•Throughout the plant body through “tubes” of conductive cells.

•The vascular tissues of these plants are called xylem and phloem.

Transport system

Reason for transport system

•Unicellular organisms They can transport materials like oxygen and urea in and out of their bodies.•Multicellular organisms: Most of the cells inside the organisms are too far from the surface of their bodies and diffusion and osmosis are too slow to be relied on. A transportation system is required for food and oxygen to be brought efficiently from one place to another. Diffusion and osmosis would take place between the transport system and the cell.

Transport system in plants

There are two transport system in plants.

One that transports water and minerals from root to all other parts .These vessels are called xylem vessels.

Another vessels transport sugars (sucrose) and amino acids made in leaves to all the Other parts of plant. These are called phloem vessels.

•Xylem consist of mainly xylem vessels that are made up of dead cells.

•Xylem cells are elongated cells.

•Inner walls of xylem vessels are strengthened are lignin.

•Lignin deposited in the form of rings or spirals.

Xylem vessels

Adaptations of xylem vessels

Absence cross walls maintains a continuous lumen.Protoplasm disintegrate allows water to move efficiently.Dead empty tube maintains a continuous lumen.Lignified walls walls are rigid xylem will not collapse supports the plant

•Consists of man sieve tubes and companion cells .

•Sieve tubes consist of columns of sieve tube cells that are elongated and thin wall.

•Companion cells provide the nutrients and help the sieve tube cells transport .

•Manufactured food (sucrose)

Phloem cells

Adaptation of Phloem cells

Bi-directional sucrose flow Food can be transported to all parts of the plant.Cross walls perforated by sieve tubes Single row of thin elongated walls with minute pores Living cells to conduct the food in the tubeCompanion cell present Consists of protoplasm and mitochondria Assists sieve tubes in transport of food Provides energy required for active transport When dead, sieve elements will die off

XylemConduct water and mineral salts from roots to stem and leaves Provide mechanical support for plant.

PhloemConduct manufactured food(surose and amino acids)from the leaves to the other parts Of plants.

Functions of xylem and phloem

Root hair cells

Thin hairlike outgrowth of an epidermal cell just behind the tip; absorbs nutrients from the soil.Hair like structures found on the epidermis cells of the root that allow a much larger surface area for water to be absorbed and used by the plant

Plants absorb water and minerals from the soil through the root hairs.Root hair cells absorb water and nitrates from the soil efficiently.They help to hold the plant more firmly to the ground.

Adaptation of root hairs Finger-like extensions• Increases surface area to

volume ratio • To absorb water and mineral

salts at a faster rate Lower water potential• allow osmosis and diffusion

of nitrates to take place Large vacuole• To absorb as much water as

it can hold Is a living cell• carries out respiration• This provides energy for

active transport to take place when water potential

lower in the soil

Translocation

Translocation is the process of transporting food substances downwards from the leaves to All other parts of the plants, through the phloem.

How sugar

move In plants?

Translocation of organic solute

Phloem tubes are delicate structures, these tubes are punctured by a smallGreenish insect, aphid during its feeding from the young shoots of a plant.oAphids are fluid(phloem) feeders.They suck sugary substance from phloem tissues.The phloem contents are continued to come out .On examining the contents it is found that it contains up to 30percent sugars

(sucrose=glucose+fructose)remaining 70 percent is water.

Movement of water in plantsThe uptake or loss of water by cells

takes place by osmosis.

oThe movement of water molecules from higher concentration to a low concentration is called osmosis .if water moves by osmosis into a cell the process is called endosmosis.And if the water moves out of the cell it is called exosmosis.

Uptake of water by roots

oThe cell wall of epidermal cells of roots is freely permeable to water and other minerals.oThe cell membrane is however, is partially permeable to some substance.

oThe water which enters the epidermal cells moves along the concentration gradient and passes through cortex,endodermis,pericycle and ultimately to xylem cells.

There are three pathways taken by water to reach the xylem tissues:

Apoplast pathway

(cell wall to cell wall)

Symplast pathway (cytoplasm to

cytoplasm)

Vacuolar pathway (vacuole to

vacuole)

The movement of water takes place through TACT MechanismTranspirationAdhesionCohesionTension

Ascent of sap

The upward movement of water from the root to aerial parts of the plant body is called ascent of sap or often called translocation of water

TranspirationTranspiration is the evaporation of waterInto the atmosphere from the leaves and stems of plants.

Ascent of sap

Adhesion is the attractive force between water molecules and other substancesBecause both water and cellulose are polar molecules so there is the strong attraction for water within the hollow capillaries of the xylein.Adhesion also helps hold water in the xylem when transpiration is not occurring.

Adhesion:

Ascent of sap

It is attraction among water molecules which hold water together forming a solid chain- like column within the xylem tubes. The water molecules form hydrogen bonds between them.

Cohesion

TensionIt is provided when this water chain is pulled up in the xylem.Transpiration provides the necessary energy. Tension is between the molecules of water by hydrogen bonds.

Ascent of sap

Opening and closing of stomata

Low level of CO2

CO2+H2O (dissociate in ions)H⁺

HCO3

Activate the k+ channels (epidermal cells)

K+ move towards the guar cells

It flows the movement Of H2O

Stomata will open

Guard cells become turgid

ANY Question ???

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