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1. PLANT PHYSIOLOGY
-deals with life functions
-includes functioning of cells, tissues, organs,
-organ-systems and the organismas a whole.
ROOTS
-fix the plant in the soil
-to absorb water and mineral nutrients
-conductinto the stem for supply
NEED OF WATER
-constituent of protoplasm,
-Photosynthesis: as a raw material in green leaves for the synthesis of glucose.
-Transpiration: for cooling in hot weather, ·for producing a suctionforce, etc by
evaporation as water.
-Transportation: of water solution containing, mineral salts fromthe roots
upward into the shoots, & Sugars etc fromleaves to other parts
-Mechanical:stiffness Provides turgidity (fully distended condition)
NEED OF MINERALS -absorbed fromthe soil by the roots as Salts (Phosphates,
sulphate, etc.) or as ions (potassium, calcium, magnesium, chlorine etc.)
-required as constituentsof cell and cell organelles
-in the synthesis of a variety of, compounds or enzymes in cells
CHARACTERISTICS. OF ROOTS
-(i)a huge surface area, shows a thick bunch of rootlets (Branch roots), each
rootlet show hundreds of root hairs.
-(ii)hairs contain solution (cell sap) which has concentration higher than that of
the surrounding soilwater, Root hairs are the extensions of the outer (epidermal)
cells of the root., they contain large vacuoles filled with solution called cell sap.
Cell sap has a concentrationhigher than that of th surrounding water.
-(iii)hairs having thin walls. Cell wall is thin and permeable allows movementof
water molecules and dissolved substances freely in and out of the cell.
PROCESSES RELATED TO ABSORPTIONOF WATER
1. IMBIBITION a phenomenon by which the living or dead plant cells absorbwater
by surface attraction.
-Cellulose andproteins are hydrophilic
-imbibe water or moistureand swellup,
-also, an important forcein the ascent of sap.

2. 2. DIFFUSION Thefree movement of molecules of substancefromthe region of
their higher concentration to the lower concentration when in direct contact
-solute molecules move away fromregion where they are more concentrated to
wherethey arefewer or absent
-movement continues until the molecules are uniformly distributed
3. OSMOSIS is the movement of water molecules fromtheir region of higher
concentration, to their region of lower concentration through a SEMI PERMEABLE
MEMBRANE.
-only the water molecules movefrom dilute side to concentrated side
-ENDOSMOSIS inward diffusion of water into root cells tends to swell up the cells
-EXOSMOSIS is the outward diffusion of water from rootcells, tends to cause
shrinkage of the cells
-SEMI-PERMEABLEMEMBRANE is one which, allows the passageof molecules
selectively, Itallows a solvent to pass through it freely butprevents thepassage
of the solute.
-osmosis can continue till solvent concentrationis equal (isotonic) or pressure in
the regions of higher concentrations of water molecules pushes back more water
molecules fromentering.
-OSMOTIC pressure is theminimum pressure thatmustbe exerted to prevent
the passageof the puresolvent into the solution when the two are separated by a
semi- permeable membrane. Is a measure of a solutions tendency to take in
water by osmosis,
-TONICITY Relative concentration of (two) solutions thatdetermine the direction
and extent of diffusion is called tonicity,3 types:
Isotonic: relative concentration is the same. Nonet movement of water
Hypotonic: solution outsidethe cell has a lower solute concentration than water
molecules will enter into the cell (endosmosis)
Hypertonic: solution outsidethe cell has a higher solute concentration than water
molecules will exit fromthe cell (exosmosis)
4. ACTIVE TRANSPORT Is thepassage of a substance (salt or ions) fromits lower
to higher concentration through a living cell membrane using energy fromthe
cell. ---Activetransportis in a directionopposite to that of diffusion.
-Certain nutrients such as ions of nitrates, sulphates, potassium, zinc, manganese,
have higher concentration within the cell.
-These ions have to be “forcibly”carriedintothe cell fromthe region of their
lower concentration
-This require energy to be supplied by the cell in the formof ATP

3. 5 PASSIVETRANSPORT Similar to diffusion. Passivebecause no input of energy is
required. Itis s a free movement of molecules fromtheir higher concentration to
their lower concentration.
Diffusion Osmosis Active transport
Diffusion is the transportof
gases or dissolved
substances in solution from
a region of concentration to
a region of low concentrator
when the two are in direct
contact,
Osmosis is the transport
of water through a semi-
permeable membrane
froma solution of low
concentration to a
solution of high
concentration
Active transportis the
passageof salt or ion
through a living
membrane fromlower
to higher
concentration using
energy from the cell
Liquids and gases can diffuse
over considerable distances
Water only transported
over a short distance.
Cell energy needed for
transportation (ATP)
Move. of solute or solvent. Movement of water only Movement of ions only
3. Rapid in gases, butslow
in solutions.
slow in solutions. Rapid process
Highto low concentration water froma solution of
low concentration
(dilute) to that of high.
Movement of Mole-
clues against a conc-
entration gradient.
Without a non-living
permeable membrane.
living or non-living semi-
permeable membrane
needed .
A living selective
membrane is essential.
5. TURGIDITYAND FLACCIDITY(PLASMOLYSIS)
TURGIDITY: When a cell reaches a state whereit cannot accommodate any more
water, i.e., it is fully distended, itis called turgid and the condition is called
turgidity. Cell wall is rigidand stretched by an increase involume of vacuoles
due to the absorption. When turgid, the cell is in balanced condition, turgor
pressurecounter balances thewall pressureand no further absorption of water
takes place.
TURGOR PRESSURE is the pressure of the cell contents on thecell wall
WALL PRESSURE: is the pressureexertedby the cell wall on the cell contents
If cell wall is unable to bear turgor pressure, itruptures
PLASMOLYSIS is the contractionof cytoplasm fromthe cell wall caused due to
the withdrawal of water when placed in a strong (hypertonic) solution. When
cytoplasmshrinks theplasma membrane withdraws from the cell wall.

4. DEPLASMOLYSIS is recovery fromor thereversal of plasmolysis
FLACCIDITY is the condition in which the cell content is shrunken and the cell is
no more tight.
USES OF TURGIDITY
1 Provides rigidity tosoft tissues such leaves
2 Turgor pressurehelps to pushthrough the hard ground
3 Turgor in rootcells builds up root pressure
4 Turgor in the opening and closing of stomata:
5Turgor Movement:
The rapid drooping of leaves of the sensitive plant
Turgor movements in insectivorous plants whoseleaves doseup to entrap a
living prey.
ROOTPRESSURE - heavy pressurefromtheroots causing upward flow of water
-is built up due tocell-to-cellosmosis in the roottissue
-Turgid cell presses thenext cell, the force of the flow of water increases inwards
-Finally, water reaches the xylemvessel (centrally placedvertical channels) with
considerableforce.
-The root pressureis one of the forces to raise water up through the stem into
the leaves
GUTTATION: loss of excessivewater is called guttation.
- high root pressureforces water all the way throughthe stem which comes out
throughthe ends of leaf veins.
ROOTHAIRS AND THE UPWARD MOVEMENTOF ABSORBWATER AND MINERALS
Differencein concentration of salts in cell sap sets off osmosis and water from
soil diffuses into the root hair
-mineral elements areabsorbed by active transport by thecells and as ions
rather than as salts.
-water and minerals are passedcell tocells and finally enter the xylem vessels
and upward flow occurs throughthe xylem.
FORCES CONTRIBUTING TO ASCENTSAP
1. Root pressure
2. Capillarity (narrow diameter) of xylem vessel, exerting a force called
capillary force.
3. Transpirationpull- as the water is lost by leave, Cohesion (tendency water
molecules to remain joined) pulls up more water molecules, to producea
continuous column of water through the stem

5. 4. Adhesion Causes the water to stick to the surfaceof cells thus drawing
more water molecules frombelow when the leaf cells lose water due to
transpiration, this force is importantin tall tree
Experiment 2. WATER IS CONDUCTED UPWARDS THROUGH THEXYLEM.
-balsam plant is uprooted
-placed in a beaker containing a staineosinsolution(pink)
-roots completely submerged
-kept aside for 3-4 hrs
-taken out, washed in tap
-a transvers section of the roots, stemand leaves is made and examined under a
microscope
-Xylem, vessels will appear distinct fromthe becausethese will be stainedred by
the dye.
Experiment 3 CONDUCTIONOF WATERTHROUGH XYLEM
-Two leafy shoots balsam plant, cut under water to prevent any air bubbles
- Keep lower ends dippedin water.
- In the one beaker remove about3cm outer ring (phloem) of the stem in one of
them. (girdling)
-In the other beaker removean equal lengthof the central part after incising the
stem. Xylem are located in the core of a stem.
-fix on stand and allowed to remain for about two days with their lower ends
immersed in water.
-firsttwig (with Xylem intact) remains turgid and stand out almostnormally
-second twig with (Xylemremoved) get wiltedand droop down.
• Structureof a single full-grown roothair –
Pericycle
Root hair
Endodermis
Water entering root hair
Epidermis
Cortex
Phloem
Xylem