Biology Transport in plants...Jun 27, 2020 · Biology Transport in plants WATER RELATIONS OF PLANTS PLANT PHYSIOLOGY INTRODUCTION – The study of various vial activities and metabolism

Biology Transport in plants

WATER RELATIONS OF PLANTS

PLANT PHYSIOLOGY

INTRODUCTION –

The study of various vial activities and metabolism of plant is known plant physiology.

Stephan Hales is known as fate of plant physiology.

J.C. Bose is known as father of Indian plant physiology.

Plants grow in solid and absorb water and minerals, which are available in soil. So that water has greater

importance for plant. Water forms 80-90% of fresh weight of plant body. The method or technique, plant

cell obtain water, comes under the heading of water relations.

To understand the plant water relations, we should know the following process:

DIFFUSION

“The movement of molecules or atoms or ion of a materials from an area higher concertation to

an area of their lower concentration is called diffusion.”

The diffusion is continue till the dynamic equilibrium is not established. At this stage the net movement of

molecules is equal to both direction.

The kinetic energy, which is present in the molecules of material is distributed equally in their available

space by their nature.

Diffusion rate → Gas > Liquid > Solid

DIFFUSSION PRESSURE

The diffused molecules or ions exert a pressure on the substance or medium in which diffusion

takes place, known as diffusion pressure.

This developed due to difference in the concentration of molecules of the material. Diffusion pressure of

pure solvent (1236 atm) is always higher than its solution.

Water molecules moves form their higher concentration to their lower concentration in plants.

The rate of diffusion decreases with increasing size of molecules/

Significance of diffusion:

(1) Exchange of gases like CO2, O2 take place through the diffusion.

(2) The distribution of hormones in the plants takes place through the diffusion

(3) The process of transpiration is a diffusion process. The evaporation of water from the intercellular

spaces is linked with diffusion during the transpiration.

(4) The ions of the minerals may diffused into the plant body.

(5) The process of osmosis is a special type of diffusion of solvent molecules through semi-permeable

membranes.


OSMOSIS

“Osmosis is defined at the special diffusion of solvent (water in this context) from the solution of

lower concentration to the solution of higher concentration when both the solutions are separed by

a semipermeable membrane”

Osmosis was discovered by Abbe Nollet.

The detailed explanation of osmosis was given by Traube and Duterochat.

Passing of water through the semipermeable membrane is the example of osmosis.

The water moves into the cell during the osmosis is called endosmosis.

Ex.: Resin & grapes placed in water.

When the water starts moving out of the cell then it is called exosmosis.

Ex.: grapes kept in salt solution.

PERMEABILITY

The exchange of materials in on through the membrane is called permeability.

The membranes are divided in the following types of the basis of permeability:

(i) Permeable membrane:

Such membranes are permeable for both - saluted and solvent. e.g. cell wall, filter paper.

(ii) Semipermeable membranes:

Such membranes allow diffusion of solvent molecules, but do not allow the passage of solutes e.g.

artificial membranes like Cellophane and Copper ferrocyanide membranes, porchment paper, goat

bladder.

(iii) Selective permeable membrane OR differentially permeable membrane:

Such membranes allow some selective solutes to pass through them along with the solvent molecules.

e.g. Cell membrane, tonoplast, Organeller membrane.

These membranes are permeable for CO2, N2, O2 gases, alcohol, ether and water, but impermeable for

polysaccharides and proteins.

(iv) Impermeable membrane - Rubber membrane, Al-foil, Suberized cell wall, cork wall.

OSMOTIC PRESSURE OR O.P.

Osmotic pressure is the pressure developed in a solution when solution, and water are separated

by semipermeable membrane

or

“O.P. of solution is equal to pressure, which required to be applied on a solution in order to

prevent as increase in its volume due to tendency of solvent to enter in when the two are separated

by a semipermeable membrane.”

The osmotic pressure of pure water is zero. O.P. is due to presence of solute into the solution.

The osmotic pressure of a solution is directly proportional to the concentration of solute in is.

The osmotic pressure shows maximum variation in the plants cell.


According to Hariss the osmotic pressure is highest in leaves and lowest in roots.

The highest osmotic pressure is found in the halophyte group. A triplex confortifolia (202 atm.)

The lowest osmotic pressure is found in aquatic plants or hydrophytes.

Hydrophytes < Mesophytes < Xerophytes < Halophytes.

Generally osmotic pressure is lesser during the night and higher at noon.

Osmotic pressure of a solution is measured by osmomemter, O.P. of cell is measured by incipient

plasmolysis. First osmometer was made by Pfeffer.

The osmotic pressure can be measured by various methods:

The formula of Vont Hoff for measuring O.P.:

Here - m = molar concentration

R = Gas constant [0.082 mole/molecules]

T = Absolute temperature

the osmotic pressure of 1 mole. glucose solution at 00C -

OP ⇒ 1 × 0.082 × 273 ⇒ 22.4 atm for non electrolytes

The O.P. of electrolytes is find out by the following formula

OP = MRT I

Where I is the constant of ionization of electrolytes.

The osmotic pressure of electrolytes is higher than that of non electrolytes.

For example - solution of 1 M NaCl and 1 glucose. The molar concentration of both solution are equal but

O.P. of 1 M Nacl is higher than solution of 1 M glucose.

Water moves from lower O.P. towards the higher O.P.

Significance of Osmosis:

(1) Root hairs of the roots absorb water from the soil through the process of osmosis.

(2) The conduction of water from one cell to another cell in plant and distribution of water in plant through

the osmosis.

(3) Turgidity is developed by the process of endosmosis, which helps o maintain a definite shape of

leaves, stem and flowers. Turgidity also provides mechanical strength to the plants.

(4) The opening and closing of stomata is also depends on the process of osmosis.

(5) The leaves of Miosa pudica (“Touch me not”) are dropping down only by contact and dehiscence of

fruits depends upon turgor change after osmosis.

(6) The resistance power increases due to high osmotic concentration against the dry climate and low

temperature.


TURGOR PRESSURE OR T.P. AND WALL PRESSURE OR WP

“When a cell is immersed in water, then water enter into the cell because osmotic pressure of the

cell sap is higher. The cell content press upon the wall or develop a pressure against the cell wall,

which is called turgor pressure.”

Turgor pressure is not applicable for free solution. this only applicable for osmotic system. Furgor

pressure is also known hydrostatic pressure.

The turgor pressure in encounter balanced by an equal but opposite pressure of the thick cell wall on the

enclosed solution or protoplasm is known as wall pressure. It means whatever the amount of pressure

exerted by cytoplasm on the cell wall is same and opposite direction s pressure exerted by the cell wall

towards the inner side on the cytoplasm.

Therefore, wall pressure and turgor pressure and equal to each other but W.P. is inward in direction.

TP = WP

Plant cells does not burst, when placed

in a pure water due to wall pressure, but

an animal cell burst when placed in pure

water because wall pressure is absent

due to absence of cell wall. for example

the consequence of endosomic is animal

cell can be demonstration by placing

RBCs of human blood is distilled water.

When examined after some time, the RBCs are found to have burst upon, leaving their cell membranes s

empty cases.

A flaccid cell has zero turgor pressure.

The highest value of turgor pressure is found in fully turgid cell and it is equal to the osmotic pressure.

Fully turgid cell has OP = TP

The value of turgor pressure is normally from zero to in between the osmotic pressure in plant cell.

The value of turgor pressure is assumed as negative (-ve) during the plasmolysis of the cell.

Significance of T.P.

(1) Protoplasm of the cell attached with the cell wall due to turgidity of the cell and cell is stretched

condition.

It maintains the normal shape of the cell in which physiological processes are going on.

(2) The 3-D structure of mitochondria, chloroplast and micro bodies is maintained due to turgor

pressure, which is essential for their physiological activities.

(3) Turgor pressure is essential for maintaining definite shape of delicate organs

(4) Turgor pressure helps in cell elongation or growth of cell.

(5) Plant movement like, movement of guard cells of stomata, wilting movements and semimonastic

movements etc. depend upon turgor pressure.


(6) Turgor pressure provides essential power to the plumule to coming out from the solid and help in

penetration of radicle into the soil.

DIFFUSION PRESSURE DEFICIT (DPD) OR SUCTION PRESSURE (SP)

DPD: The difference between the diffusion pressure of the solution and it’s pure solvent at

particular temperature is called DPD

or

The DPD of any solution is the difference between the diffusion pressure of the water, which is

present in the solution and diffusion pressure of pure water.

The term Diffusion pressure deficit [DPD] is used by B.S. Meyer Renner named as Suction Pressure

(S.P.) in cell.

DPD determines the direction of osmosis and it is the power of absorption of water for the cell. (Suction

pressure)

This is also known as demand of water in cell. DPD ∝ concentration of solute.

The diffusion of water takes place from the region of lower DPD to the region of higher DPD in the

process of osmosis.

Normally, osmotic pressure is greater than the turgor pressure in a cell. The difference between

osmotic pressure and turgor pressure is called suction pressure or DPD.

DPd = OP - TP or WP

The DPD of any free solution is equal to the osmotic pressure of the that solution.

DPD = OP

(i) DPd in partially turgid or normal cell:

DPD = OP – TP

(ii) DPd for fully turgid cell:

When a cell placed in pure water or hypotonic solution then water enter into the cell, results turgor pressure

develops in the cell. The ell starts swelling due to the turgor pressure. Simultaneously, concentration of cell

sap decreases dur to continuous inflow of water. Therefore, OP is goes on decreasing and T.P.

increases due to At this stage cell becomes fully turgid. Therefore, in a fully turgid cell

Cell-

DPD = OP - TP

When, OP = TP or OP - TP =

So that DPD = 0

(iii) DPD in flaccid cell:

if, the cell is in flaccid state then its T.P. or WP would be zero and value of DPD would be equal to OP.

TP or WP =O

Therefore, DPD or S.P. – OP


If a flaccid cell placed in water, then waters enter into cell because DPD of the cell sap is higher.

(iv) DPD for plasmolysed cell:

Sometimes the value of turgor pressure in negative as in plasmolysed cell. In this state

DPD = OP - TP

∴ [TP = - Ve]

DPD = OP - [-TP] = OP + TP

So that the DPD of the plasmolysed cell is greater than osmotic pressure.

It means- DPD - OP + TP

Demand of water = Plasmolysed cell > Flaccid cell > Partially turgid cell > Fully turgid cell

The demand of water in plasmolysed cell is highest.

It means, when the osmotic pressure and turgor pressure will be equal, then the DPD will be zero. Water

will not enter in this type of cell and cell become fully turgid.

But, when turgor pressure is lesser than the osmotic pressure, in normal cell then some DPD will be

definitely present in the cell and water would enters into the cell

For Ex.

WATER POTENTIAL OR 𝛙𝐖

“The difference between the free energy of molecules of pure water and free energy of the solution

is called water potential of the system:’’

Now a days according to concept of free energy and thermodynamics DPD of a solution is also represented

by water potential.

(Given by Taylor and Slatyer).

The water potential of pure water is maximum the pure water has greater free energy. The free energy,

lower down by addition of solute.

Water always flows from higher water potential to lower water potential

Water potential is represented by Greek word ψ (Psi)/ ψW and it is measured in bars or Pascal (Pa).

Water potential is equal to DPD, but opposite is sign. Its value is negative.


Water potential has following components:

1. Osmotic potential ψS

Osmotic potential or solute potential represents the concentration of the solute. Water potential (ψW) is

negative in the present of solutes. So that osmotic potential is also negative.

According to thermodynamics, osmotic pressure is called solute potential or osmotic potential. it is

represented by ψS nd shwon by negative sign (-ve) or it is better to say osmotic potential on the basis of

free energy.

Osmotic potential or solute potential measured in bars. [1 Bar = 0.987 atmospheric pressure].

OP = 22.4 atm = > osmotic potential = -22.4 atm. (1 M glucose solution)

2. Pressure potential (ψP):

Turgor pressure is known as pressure potential. It is shown by positive sign (+ve).

1 Bar = 106 dynes/sq. cm. or 0.987 atm. (1 megapascal = 10 bars)

According to this concept their relation is as follows.

Water potential = Osmotic potential + pressure potential + matric potential

Δψ or ψW = ψS + ψP + ψm

ψW = ψS + ψP As ψm and ψg (Matric potential and gravitational potential) are negligible

ψW = −ve

ψS = −ve

ψP = −ve

According to the above concept the relation of the three phases of the cell by the water potential will be as

follows:

[A] In case of fully turgid cell –

There is no flow of water in a turgid cell, because the cell is in equilibrium condition with water which is

present outside the cell. So that water potential will be zero at this state, because osmotic pressure

potential is equal in the cell.

For example - if the value of osmotic potential of a cell is - 10 and pressure potential (ψP) is + 10, then

water

potential will be zero as –

[B] In case of flaccid cell:

Turgor pressure is zero at this stage. It means pressure potential is zero. If osmotic potential of the cell is -

10

bars then ψW = ψS


[C] In Plasmolysed cell:

The pressure potential ψP) means turgor presure is negative in this stage. Therefore water potential (ψW) of

the cell will be more negative [more - ve]

If the value of osmotic potential is - 10 bar of a plasmolysed cell and value of pressure potential is - 2 bars

then its water potential (ψW ) will be - 12 bars.

So, this is the conclusion that water always move from higher water potential towards the lower water

potential.

For example if the water potential of ‘A’ cell is -10 bars and water potential of ‘B’ cell is - 12 in to cells,

then water will be flow from ‘A’ cell to the ‘B’ cell.

TYPES OF SOLUTIONS

[i] Isotonic solution:

If solution in which a cell is placed, has equal osmotic concentration to that of cell sap, the outer solution is

called isotonic solution

[ii] Hypotonic solution:

If the osmotic concentration of outer solution is lesser than that of the cell sap, the outer solution is called

hypotonic solution. If a cell is placed in such solution endosmosis takes place, results, cell swells up e.g.

Swelling of dried grape (resins).

[iii] Hypertonic solution:

If the osmotic concentration of a solution is higher than that of the other (cell sap), solutions known as

hypertonic solution

If a cell placed in this type of solution, exosmosis take place. It means water of the cell sap diffused out

into the outer solution, resulting cell become flaccid.

e.g. Grapes placed in higher concentration of sugar solution becomes flaccid (contracts).

PLASMOLYSIS

If a plant cell placed in a hypertonic solution, water molecules diffused out from the cell. As a result

of exosmosis, the protoplasm of the cell detached from the cell was and starts shrinking. this is

called plasmolysis.

The various sequences of plasmolysis are as follows:

(i) In a trugid cell, the cell sap pushed away the protoplasm so that it is in close contact with cell wall.

(ii) When it placed in a hypertonic solution, the volume of the cell reduces due to shrinking of cell because

some amount of water of sap diffused out by exosmosis. Turgor pressure decreases by which cell wall is

not pushed by the protoplasm, so that shrinking cell membrane reduces in total volume of the cell. This

situation, is called the first stage of plasmolysis or limiting plasmolysis.


(iii) If the diffusion of water to the

outside is continue by the

exosmosis then central vacuole

contracts and with this protoplasm

also shrinks but cell wall is not

contracting. So that protoplasm is

seems to detach from the

corners of cell wall. This

condition is known as second

phase of the plasmolysis or

incipient plasmolysis.

(iv) The shrinking of protoplasm is

continuous due to continuous

exosmosis, it detaches from the

cell wall and assumed a spherical

shape. This phase is known as

evident plasmolysis/full

plasmolysis.

Hypertonic solution is

present in between the cell

wall and protoplasm.

Plasmolysis:

A-A cell in normal stage, B-A cell placed in pure water and resulting in increased turgor pressure and, C-A

cell placed in strong salt solution leading to plasmolysis.

Significance of plasmolysis:

[i] A living cell is distinguished from the nonliving [dead] cell through the plasmolysis. Because plasmolysis

does not occur in dead cell.

[ii] The osmotic pressure of any cell can be measured by incipient plasmolysis.

[iii] If the plasmolysis remains for long duration in a cell then it dies. To destroy the weeds, salts puts in their

roots.

[iv] Fishes and meat are prevented from spoilage by salting, which inhibits the growth of bacteria and

fungus.

[v] Higher concentration of sugar in jams and jellies stops the growth of bacteria and fungus.

[vi] High amount of chemical fertilizers near the root causes death or browning of the plant due to

plasmolysis.

[vii] The fresh water growing plants are either wilted or die when they are kept in marine water.


IMBIBITION

Adsorption of undissolved liquid by a solid material is called imbibition or adsorption of water by

hydrophilic colloids is known as imbibition.

This is a physical process by which as dry soli collide material swells up by adsorption of water.

The cell wall is made up of colloidal substances as cellulose, pectin, hemicellulose etc. All they are in

nature. Therefore, they imbibe water.

Proteins, Agar - agar, starch etc, these are all imbibant materials.

Agar-agr can adsorbs 99 times more water than that of its weight. Some of the proteins adsorb 15 times

more water. Affinity must be between imbibant and liquid material and movement of water occurs in

order of water potential gradient.

Imbibition power = Agar - Agar > Pectin > Protein > Starch > Cellulose

The heat released during the imbibition is called heat of wetting.

A huge pressure is developed in material due to imbibition. This pressure is called Imbibition pressure

(IP).

IP is also called as matric potential which respect to water potential. DPD - IP or ψw = ψm

Dry wood is filled in the natural grooves of rocks and watered them. The rocks and broken due to their

swelling.

The imbibition is less compact arranged material like wood, and more is lighter or soft material lke gelatin.

Imbibition decreases with increasing pressure on imbibant material.

Significance of Imbibition :

(1) Absorption of water during the seed germination is only initiate through the imbibition.

(2) Breaking of seed coat during the seed germination is due to imbibition process. Proteins fats and start

is present in the kernel. This kernel swells up more as compared to the seed coat which break the seed

coat.

(3) Initial process of water absorption in roots by root hirs is imbibition.

(4) Resurrection in many plants like Selaginella, Lichen, Takes place due to the process of imbibition.

(5) The water enter into the aerial roots and dry fruits is due to imbibition.

(5) Newly formed wood swells up in rainy season


ABSORPTION OF WATER BY PLANTS

Water in an excellent solvent and essential for the physiological process and helps in up take and

distribution of nutrients and solutes for growth and development of plants.

Water participates in many vital activates of the plant. All the organic and inorganic material are

translocated only through the water. The cells of the plant remain in turgid condition due to water. It helps

the growth of the plant. Water is essential for germination seeds. All the enzyme action only takes place in

the presence of water. Plant movements is due to the turgidity of the cells. Translocation nutrients and

chemical reaction of plants take place in aqueous solution.

FORMS OF WATER

Water is mainly obtained through rain. Some of the water greed into the water reservoirs. This is called run

off water. Rest of the water enter into the land. Water present in soil is following types →

(a) Gravitational water:

From of water, which reaches at the soil water table due to the gravitational force after the rainfall. This

form is not available to plants but available by mechanical methods or by tube well irrigation. Some plants

can absorbed this water - Calotropis, Prosopis, Caparies, etc.

(b) Hygroscopic water:

This film of water is tightly held by the soil particles is called hygroscopic water. This water is also not

available to the plants.

ψw of hygroscopic water is highly negative or very low.

(c) Chemically combined water:

The amount of water present in the chemical compounds, which are present in the particles of soil. This is

not available to the plants ...... 24 H2O, ....... 7 H2O

(d) Capillary water:

Water exists between soil particles in small capillary pores is called capillary water. It is the most

available form to the plants. Plants only absorb this from of water.

(e) Atmospheric humidity:

This is water vapor present in air, which can be absorbed by hanging roots of the epiphytes due to

presence of velamen tissue.

Holard : it is the total amount of water present in the soil.

Holard = Chresard + Echard

Chresard : This is the water available to the plants.

Echard : This water is not available to the plants


ORGAN FOR WATER ABSORPTION

Water is absorbed by either the whole surface or by the rhizoids

in lower plant but in ptreidophytes and spermatophytes

absorption of water takes place through the root.

[i] Root cap region

[ii] Meristematic region

[iii] Elongation region

[iv] Root hair region

[v] Maturation region

The maximum absorption of water takes place from root hair

region.

These root hairs increase the absorption area of root.

Transplated plant cannot grow easily a root hairs are damaged.

Osmotic pressure of cell sap is greater than that of osmotic pressure of soil solution. The osmotic

pressure of cell sap is about 3 atm.

PATH OF WATER ABSORPTION

Soil solution → Root hairs → Epiblema/Epidermis → cortex → (Epiblema) → Cortex → Endodermis

(Passage cells) → Pericyle cells → Protoxylem → Metaxylem.

The water situated in the soil is to be reach up

to the xylem of root. Root hairs remains in the

contact of water. First of all, water is absorbed

on pectin wall of root hairs, then water

entered into the epidermis of root hairs. From

here water reaches up to the endodermis are

suberized. But cells lie in front of the protoxlem

are thin walled known as passage cells. These

cell transfer water to the xylem. From here water reached to the xylem from endodermal cell through the

thin walled pericycle cells.

(a) Symplast :

A sustainable living part is known as symplast. This is the living passage. The movement of water from

cell to cell through plasmodesmata is called symplastic path in plant. This movement of water through cell

membrane is also called as transmembrane pathway.

(b) Apoplast :

This is the non living path is plants Watered cell wall,

intercellular space and xylem cavity associated together to

form apoplast.


Term “apoplast” & “symplast” given by Munch

The path of water from root hair to cortex, may be apoplastic or symplastic. Casparian strips blokc the

apoplast, thus water must pases through pasage cells via symplast.

MECHANISM OF WATER ABSORPTION

Water is absorbed by two differnt ways :

(1) Active water absorption (2) Passice water absorption.

Mechanism

Term active & passive absorption was proposed by Tenner.

1. Active abosrption of water → Acco. to the method water is absorbed due to the activity of roots or by

expenditure of ATPs.

I. Osmotic active → This is given by Atkins & Priestly. Acco. to this method water is absorbed due to the

osmotic activity of roots in order to O.P. & D.P.D. No direct ATP are consumed in this method.

II. Non osmotic Active → Propsoed by Theimam, Bennet-Clark. According to this method

absorption of water occurs against the osmotic concentration by direct investement/expenditure of

metabolic energy in the form of ATPs. Generally this process present in Halophytes.

Only 4% of total obsrobed water is taken by this proces.

2. Passive abosorption of water →

According to this method forces for the

absorption of water organates in aerial

parts by rapid transpiration & root remain

as passive organ.

According to Kramer water absorption in

plants in followed by transpiration. About

96?% of wter is absorbed by passvie

method. Due to rapid transpiration, D.P.D.

of leaf cells ↑ result in suction force, which

suck the water from roots.

Factors affecting water absorption :

[1] Available soil water :

Plant absorbs capillary water, which is present in soil. Aborption of wter depends on the amount of

capillary water present in the soil. Absorption increases by increasing amount of capiallry water.

If, water is present in higher amount in the soil then such type of soil is called “Water logged soil”. This

soil is physilogically dry and lack oxygen. Because of this anaerobic respiration takes place in roots, and

alcohol is formed. Roots can be degenerte due to form alcohol. (Dry soil is physically dry).


[2] Soil temperature :

Soil temperature affects the folloiwn gmechanisms :

(i) Low temerature decreases the permeability of cell membrane.

(ii) It is essential for the activity of enzymes for the formatioin of root hairs.

(iii) At low temperature viscosity of capillary water is increased.

Generally, normal absorption of wter take plce at temperature of soil between 20 - 350C.

Increasing or decreasing soil temperature, lower down the rate of absorption of water.

Col soil is a physiologically dry.

[3] Soil Air :

Absorption of water proceeds more rapidly in well aerated sol. Deficiency of oxgygen in soil causes

improper respiration in roots.

Poorly aerated soil is physiologically dry.

[4] Soil Concentration :

The rate of the absorption is inversely proportional to the concentration of minerals present in soil.

Water absorption is only take place in appropriate soil solution. If the concentration of soil minerals is

high, it decreases the rate of absorption. Therefore saline soil is physiologically dry. Halophytes can

grown only in this soil.

[5] Transpiration :

According to Krmer the rate of water absorption is directly proportional to the rate of transpiration. The

rate of absorption increases due to increases in the transpiration. Because passiv e waer absorption

increases due to transpiration.

OTHER METHODS OF WATER ABSORPTION

(a) By mycorrhiza:

The root hairs are not developed in some of conifer plants thus water is absorbed with the help of

mycorrhizal assocation.

These fungus myecilium absorb water and minerals and transfers to the roots.

These fungus myecilium obtain their food from the roots.

(b) By Velamen :

Velamens are found in epihytes such as Orchids.

Absroption of water vapur of air takes place in these plants through the hanging roots. These roots have

specialised tisue on the out side of their cortex is called velamen.

(C) By Hygroscopic hairs :

Hairs are arises from the aerial parts of the epiphytic plants which absorbs atmospheric moisture are

called hygroscopic hairs.


ASCENT OF SAP

Upward movement of absorbed water against the gravitaional force upto top parts of plants in

called as acent of sap.

Xylem is water conducting tissue in plnats.

Evidence for this : Experimenets which that xylem is water conducting tisue of the plants :

(i) Girdling or ringing exp. Malpighi, Hartig and Stephen hales.

(ii) Experiment on Balsam plant - By using eosin dye and found that xylem is water conducting tissue.

(iii) Blockage experiments By Dixon -Xylem was blosked by using wax.

Mechanism : Various theories are given to explain the mechanism of ascent of sap.

(A) Vital force theories : Accoring to these theories living cells involved in ascent of sap.

(1) Wastermainer (1883) : According to him ascent of sap is due to the activity of xylem parenchyma

cells.

(2) Godlewski’s theory (1884) : According to his the ascent of sap is due to rhythemic change of

osmotic pressure of xylem parenchyma & medullary cells.

This theory is also known as ‘Relay pump theory’ or Clambering hypothesis.

(3) Pulsation theory : By Sir J.C. Bose : According to this theory ascent of sap is due to the

pulsatory activity of the inner most layer of cortex.

Bose explains his theory with hel of galvanometer or electric probe.

Objection :

According to Strasburger ascent of sap is continue after the living cells of xylem killes by poisen picric

acid It means ascent of sap is through the non living elements of xylem i.e. vessels & tracheids.

(B) Root pressure theory : By Priestely.

According to it, a positive pressure is develop in to xylem sap, due to turgidity or activity of root cells

(cortical cells), is called root pressure, which pushed water upwards is xylem.

Term root presure & phenomenon was discovered by Stephen Hales.

Objection :

(i) Root presure is absent in woody plants.

(ii) When root pressure is high, during night, the accent of sap is low.

(C) Physical force theories :

(1) Capillary force theory : By Boehm - According to this cesels & trachieds acts as capillaries & ascent of

sap takes place due to capillary force.

(2) Imbibition force theory : By Unger & Von Sachs - According to it ascent of sap is due to the imbibition

force of xylem wall.

(3) Chain theory : By Jamin - According to it a chain of alternate layers of water and air are formed in

xylem. When layer of air is expands than water will move upwards.

(4) Transpiration pull & cohesion force theory : By Dixon & Jolly

Most accepted or universally accepted theory of ascent of sap.


According to it 3 component are involved in ascent of sap.

(a) Cohesion : Mutual attraction between the water molecule is known as cohesioin, which from a

contunous water column in xylem elements.

(b) Adhesion : Attraction between xylem walls & wter molecules is called adhesion force, which helps in

maintance of water coloumn of xylem.

(c) Transpiration Pull : A tension or negative pressure dvelops in xylem, due to rapid tanspiration in

leaves (because of high DPD), this crates a tarnspiration pull, which is responsible for the pulling up of

water column in xylem. So ascent of sap is constitutive efect of cohesion, adhesion & adhesion &

transpiration pull.

FOOD TRNASLOCATION IN PLANTS

Food/organix material conduction in plants mainly occurs by phloem. (Proved by Girdlin experiment).

Food conduction occurs in between source and sink. Source is net exporter while sink is net importer.

Generally green photosynthetic palnt parts act as source like leaves while non photosyntehtic parts like

root, shoot, fruits acts as sink.

Foor conduction may be in any required directio unlike the water conduction which is a unidirectional

process.

Translocaetion of food mainly occurs in the form of source or it is non-reducing sugar and chemicall yinert

in it’s pathway of conduction

Phloem loadin/surcose loadin at source → it is an active process helped by carrier molecules. At

source due to phloem loading concentration of sieve cell increase, results in increases in osmotic

pressure and water will moves from neary xylem into sieve cells results in increase in turgor pressure


T.P.) and increase in water potential( w). It establish a higher T.P. at source and in seive tubes.

Surcrose moves from source in sieve tubes sink form high T.P./High ψω to towards the low T.P./low ψW .

Phloem unloading/sucrose unloading at sink It is an active process helped by carrier molecules. At sink

surcrose is unloaded results in decrease in osmotic pressure (O.P.), it results in exits of water into near

by xylem leasds to decrease in Turgor pressure (T.P.) and water potential (ψW) of phloem). In sink cell

the unloaded sucrose is either changed into starch (as starch not change O.P.) or consumed, to maintain

low O>p. and continuous unloading.

So the process of sucrose loading at source and unloading at sink continues. This turgor pressure

difference will maintained and water will continue to move in at source and out at sink.

This mechanism was experimentally demonstrated by Bimodel exp. of Munch.

According to evidences of modern research phloem conduction is an active process and it required

metabolic energy in phloem cells.

TRANSPIRATION

Loss of water in form of vapour, from the aerial pars (organs) of living plants is known as

Transpiration.

Only few percetage [1-2%] of absorbed water is used by the plants, while remaining (98-99%) of water

lost atmosphere.

“Transpiration is an essential evil” - by Curtis

“Transpiration is an unavoidable evil” - by Steward.

The minimum transpiration is found i succulent xerophytes & no transpiration is submerged hydrophytes.

Maximum trnspiration is found is mesophytes.


TYPES OF TRANSPIRATION

Transpiration is of the following three types :-

[i] Stomatal transpiration :

Transpiration takes place through the stomata which are present on the leaves of the plants and delicate

organs, is called stomatal transpiration. The maximum amount of water is lost by this transpiration.

about 80% to 90% transpiration is occurs through the stomata.

Stomata are absent in algae, fungi and submerged aquatic plants.

Foliar transpiration : Total transpiraion takes plave through the leaves is called as foliar transpiration.

Foliar transpiration = Stomatal + Cuticular, for the leaves.

[i] Cuticular Transpiration :

Loss of water through the cuticule wihich present on the herbaceous stem and leaves. Cuticle is a wax like

thin layer present on epidermis. About 9% transpiration is cuticuler.

[ii] Lenticular Transpiration :

Minute pore like structure found on the stem of some woody plants and epidermis of some of some fruits

called lenticles. Some amount of water is lost by lenticels is kown as lenticular tranpiration. However it is

approximately .1% to 1% of the total water lost

STRUCUTRE OF STOMATA

Stomata are found on teh aerial delicate organs and outer surface of the leaves in the form of minute

pores. Stomatal pore is surrounded by two specialised epidermal cells called as guard cell. They are

kidney shaped. The number of guard cells are two.

The structure of guard cells in monocots (Gramineae) is dumbel shaped.

Guard cells are epidermal cells. But due to presence of chloroplast they are different from that of

epidermal cells.

The outer wall of the guard cells is thin and elastic, while inner wall is thick and non elastic.


Guard cells are surrounded by some specialized epimdermal cells called subsidiary cells are

accessory cells.

Stomata are found on both upper and lower surface. Stomata attache with air chambers and fomrs a

cavity is called sub-stomatal-cavity.

In xerophytic plants position of stomata is deep in the surface of the leaf. Stomata are present in this

position are called suken stomata.

TYPES OF STOMATA

(A) Based on distribution :

(1) Apple and Mulberry type → When the stomata present on the lower (Dorsal/abaxil) surface of the leaf

e.g. - Oxali, Peach, Nausturtium, Morus etc.

(2) Potato type → When stomata present mainly on the lowre surface but some stomata are present on the

upper surface (Adaxialy) also. e.g. - Tomato, Brinjal, Cabbage, Pea etc.

(3) Oat type → When stomata are almost equally distribued on both surface of the leaf. e.g. Monocots

(4) Water lily type → When stomata present only on the upper surface of the leaf. (Aquatic plants with

floating leaves)

(5) Potamogeton type → The stomata in this type are either absent or rudimentary or functionless e.g.

Submerged hydrophytes.

(B) Based on time of opening & closing ⇒ By Loftfiel

(1) Alfa-alfa type → Stomata are opened in day and closed in night.

Ex.- Mesophytes as Pea, Bean, Radish, Grapes, Apple etc.

(2) Potato type → Stoamta always open except evening time.

Ex. - Onion, Potato, Cabbage, Banana etc.

(3) Equisetum type → Always opened stomata. Amphibious plants.

(4) Barely type → Stomata always closed except few hurs in day time. Wheat, Maize etc.

(5) Scotoactive opening → Stoamta closed in day and opened in night

Ex. Succelents - Opnutia.

(C) Stomata based on structure and number of accessory cells :

(1) Anomocytic → Subsidiary cells - 5 ot 6 and same in strucutre.

(2) Anisocytic → Subsidiary cell-3 and one cell smaller than two. Ex. - Cruciferae

(3) Paracytic → Subsidiary cells - and parallel to guard cells. Ex. Rubiaceae

(4) Diacytic → Longitudinally situated nd 2 accessory cells.

Ex, - Caryophyllaceae.


MACHANISM OF OPENING AND CLOSING OF STOMAT OR

STOMTAL MOVMENT AND MECHANISM OF TRANSPIRATION

Stomata generally open during the day & closed during the night with new execptions. The important

theories of stomatal movments are as follows –

(1) Photosynthesis is guard cell hypothesis :

This theory was proposed by Schwendener & Von mohl. According to this theory guad cell

chloroplastperform photosynthesis during the day time. this produce sugar in guard cell which increases the

O.P. of GC, compared to adjacet epidermal cell (subsidiary cells). Water enters in guard cells form

subsidiary cells by endomosis, due to this guard cells become turgid & stomata will open.

Objections -

(i) In CAM plants stomata open during dark/night

(ii) Chloroplastof monocot guard cells are non-functional (inacive) photosynthetically

(2) Starch Sugar interconversion theory :

This theory was propsed by Sayre (1926). First of all Lloyd states taht amount of sugar in GC is increases

during th eday time & starch in nigh.

Detail study of this change was done by Syre & given Strch hydrolysis theory. Acco. to Syre, strach

converts in to sugars during day time when pH of guard cell is high. Sugar changes in to starch during

night as low pH in guard cells (Supported by Scarth). Sayre clarified that CO2 reacts with water during

night.

Dut to accumulation of H2CO3, pH in guard cell is decreases.

Hanes -States that this chagne takes place by phosphorylase enzyme.

Yin & Tung reported the presence of phosphorylase enzyme in guard cells.


Stewards modification -

Acco. to Stewrd (1967) appriciable change in O.P. of GC is possible after the conversion of glucose - 1 P

into Glucose & ip (inorganic phosphate)

Steward gave stomatal mechanism as following

Objections -

(i) Starch is absent in GC of some monocots like onion

(ii) Formation of organic acids is observed during stomatal opening.

(3) Active 𝐊+ ⇄ 𝐇+ exchange theory or active proton transport mechanism –

Given by Levitt (1973-74). This is modern & most accepted theory for stomatl opnening & closing.

Fist of all Funjino observed that influx of K+ ions in guard cells during stomatal opening. (Supported by

Fisher & Hsiao.) Detail study of this pnenomenon was done by Levit, who proposed this theory. Acco. to

him stomata opens by followin mechanism

Closing of stomata : Plant hormone ABA-acts on

guard cells, which interfere the exchagne of K+ ⇄ H+

ions in guard cells, result in reverse of rxn. of opening

of stomat, hence stomat closed. pH of guard cells is

decrese dring night, which favours tomatal closing.

High concentration of K+ ions in guard cells in

electrically balanced by uptake of Cl- and malate ions

in guard cell.

(4) Ca-ABA second messenger model -

Given by Desilva & Cowan (1985) this is modern

explaination of stomatal closing only


Ramdas & Raghvandra Suggested that ATPs for stomatal movement comes from cyclic ETC.

Bowlings : Malate switch hypotehsis.

Raschke : K+ ions in guard cells comes from subsidiary cells.

Stomata opoens during the night in suculent plants and closed during the day. This nature of stomata in

opuntia is called sctotoacive stoamta.

In CAM plants organic acid is formed during night which broken down during day & Co2 is liberated which

is used in photosynthesis.

Factors affecting stomatl opening and closing :

[1] Light :

In most of the plants stomate open during th eday except succulent xerophytic plants and close during the

dark. Opening of stomata completes in the presence of blue and red light. Blue light is mot effective and

causing stomatal opening.

[2] Temperature :

Loft Field show temperature quotient of opening of stomata is [𝐐𝟏𝟎] = 2

[3] 𝐂𝐨𝟐 concentration :

Stomata opens at low concentration of CO32 while clsoed at high concentration of CO2

CO2 is antitranpiration gas.

[4] Growth Hormones :

Cytokinin hormone induce opening of stomata. It increase the influx of K+ ions and stimulate the

stomata for opening.

While ABA stimualte the stomata for closing. This hormone oppose the induction effect of cytokinin.

ABA effect the permeability of the guard cells. Ir precent the out flux of H.+ ions and increase the out flux

of K+ ions. Because of this pH of the guard cells decreased.

Cl− ions also plays important role is stomatal movment.

Above mentioned effects also found in high amoun of CO2

ABA is formed due to high water stress in chloroplast of leaves.

[5] Atmospheric humidity :

Atomata opens for long duration and more widen in the presence of humid atmosphere, while stomata

remains closed in dry atmosphere or partial opening at higher atm. humidity transpiration will be stop but

stomata remain completly open

Factors affecting the rate of transpiration.

Factors effecting the rate of transpiration are divided into two type :

[A] External factors (Environmental factor)

[B] Internal Factors


[A] External factors :

[1] tmospheric humidity :

This is the msot important factor. The rate of transpiration is higher in low atmospheric humidity while at

higehr atmospheric humidity, the atmosphere is moistened, resulting decreasing of rate of transpiration.

Therefore, the rate of transpiraion is high during the summer and low in rainy season.

[2] Temperature :

The value of Q10 for transpiration is 2. It means by increasing 1000C temperature, the rate of transpiration

is approximately double. (By Loftfied)

Water vapour holding capacity of air increased at high temperature , resulting the rate of transpiration

increased.

On contrary vapour holding capacity of air decreased at low temperature so that the rate of transpiration

is decreased.

[3] Light :

Light stimulates, transpiration by heating effect of leaf.

Action spectrum of transpiration is blue and red.

Rate of transpiration is faster in blue light than than of red light. Because stomata are completely opened

as their full capacity in the blue light.

[4] Wind velocity :

Transpiration is less in constant air but if wind velocity is high the rate of transpiration is also high,

because wind removes humid air (saturated ait) around the stoamta.

Transpiration increases in teh beginning at high wind velocity [30-35 km./hour] But latter on it cause

closure of stomata due to mechanical effect and transpiration decrease.

[5] Atmospheric Pressure :

The speed of the air increase at low atmospheric pressure, due to this rate of the diffusion increase which

increase the rate of transpiration.

The rate of transpiration is found maximum in the high intensity of light at high range of hills.

By carrying a plant form Kota, to hill station, rate of transpiration increased.


[6] Anti transpirants :

Chemical sustances whcih reduce the rate of transpiration are known as antitranspirants. Anti transpiratns

are as follows :

Phenyl Mercuric Acetate [PMA[, Aspirin (Salicylic acid), Abscisic Acid [ABA], Oxi-ethylene, Silicon

oil, 𝐂𝐎𝟐 and low viscous wax

PMA closed the stomata for more than two weeks partially.

Antitranspirants are used in dry farming.

[B] INTERNAL FACTORS :

These factors are concerned with structure of plants. These are following types :

[1] Transpirin area :

Pruning increase the rate of transpiration per leaf but overall reduce the transpiration.

[2] Anatomical characteristics of leaf and leaf orientation :

Several strucutres of leaf effect the transpiration as follows :

Stomatal characteristics of leaf and leaf orientation :

Several structures of leaf effect the transpiration as follows :

Stomatal characteristics :

Transpiration is effected by the struture of stomata, position of stomata, distance between the stomata,

number of stomata per unit area and activity of the stomata.

By Salisbury - Stomatal Index (SI) =S

E+S

SI - Stomatal index S = No. of stomata/unit area

E = No. of epidermal cells in same unit aea

[3] Water status of Leaves

[4] Root - Shoot Ratio :

The rate of transpiration decreses with decreases in root - shoo ratio.

The ratio of transpiration increases with increase root - shoot ratio.

The following characteristics are found in leaf to recude the transpiration.

(i) Leaves modify in spines.

(ii) Leaves transformed into needle e.g. Pinus.

(iii) Folding and unfolding of leaves by bulliform cellls. eg. Amophilla, Poa etc.

(iv) Small size of the leaves.

(v) Presence of thixk waxy layer on leaves.

e.g. banyan tree.

Significance of traspiration :

[1] In regulation of temperature :

Cooling effect on teh surface of leaves is produced by the process of transpiration, due to which

temperature remains contant in plants.


The plants re protected fromt he burining of heat due to transpiration. Evaporation of water produce cooling

effect.

[2] In mineral absorption :

Mass flow of water is found during the passive absorption of water. Hence it is assumed that minerals enter

the roots through the water.

[3] In ascent of sap

[4] In water absorption

[5] Distribution of absorbed salts

[6] Gaseous exchange

[7] Control of hydrological cycle.

GUTTATION

Loss of wate form the uninjured part of maring of leaves of the plant in the form of water droplets is

called as guttation.

The term “Guttation” was coined by Burgerstein.

xuded liquid of gattation along with water contains some organic and inorganic (dissolved) substances. It

means it is not pure water.

Normally, gutation proces is found in herbacious plants like grases, tomats, balsum, Naustertium,

Colocasia, Sexifraga and in some of the plants of Cuburbitceae family.

Guttation occurs from the margins of the leaves through the special pore (always open) like strucutre are

called hydathodes or water stomata.

Generally guttaion occurs during mid night or early morning.

Parenchymatous and loose tissue are lie beneath the hydathode, which are known as epithem or transfer

tissues.

The process of guttation take place due to root pressure, develope in cortex cells of root.

BLEEDING

Fast flowing of liquid from the injured or cut parts of the plants in called bleeding or exudation.

This process takes place due to high root pressure.

Sugar is obtained from the Sugar mapple by this process.

The highest bleeding is found in Caryota urens (Toddy plam) (about 50 liter per day).

Bleeding is important in economic biology, because Opium, Latex of rubber is obtained by this.


WILTING

Droping of soft plarts of the plants due to loss of turgidity in their cells is called wit\lting. Wilting is caused

due to high rate of transpiration during mid-day or deficiency of water in soil and also in prolonged

drought conditioin.

Wilting may be temporary or permanent.

Incipient wilting : This is the starting of wilting wihtou any external symptom is called incipient wilting

SPECIAL POINTS

The main reason of osmotic pressure for stomata is potassium chloride or potassium malate.

Porometer is used to find out the ara of stomata on the leaf.

Transpiration measuring intrument is called potometer. The rate of absorption of water is measured

through this instrument. In potometer rate of water absorption is proportional to the rate

transpiration.

Cobalt - chloride test : This method is used for the comparision of transpiration at both the surface of

the leaves. it is firsdt of all shwon by Stall.

Stomata covers 1-2% of total leaf area. Size of stomata is 10-40 μ (lenght) × 3 12 μ (width).

The photophosphorylation process in the guard cells is a energy metabolic process, not CO2 – metabolic

process. (Cyclic photophosphorylation)

The rate of transpiration of C4 plants is les as compared to C3 plants. In CAM plants minimum

transpiration occurs.

Manometer is used to measure root pressure.

Distribution of Stomata on leaf surfaces :

MINERAL ABSORPTION AND NUTRITION OF PLANTS

MINERAL ABSORPTION

Soil is the main source of mineral salts. These mineral salts are mainly absorbed by the (Sub terminal)

meristemetic region of roots.

Mineral salts are present with soil particcles in colloidal form and in water as soil solution. Conduction of

mineral salts is done through the xylem.

Mineral absorption is done in form of ions mainly form meristemetic zone.

Absorption of mineral is plant is an active process. There are two methods of absorption of mineral salts


(A) Passive absorption of minerals : (Without expenditure of ATP)

(1) By Simple diffusion : According to this method mineral ions may diffuse in root cells from the soil

solution.

(2) By mass flow : According to this method mineral ions absorption occurs with flow of water under the

influence of transpiration.

(3) By ion exchange : This is exhcange of mineral ions with the ions of same charge.

(i) By contact exchange : When the mineral ion exchgne occurs with the H+ and OH- ions.

(ii) carbonic acid exchange : When the mineral ion exchange takes place with the ions of carbonic acid.

(4) By Donnan equilibrium : This theory explain the passive accumultion of ions against the concentration

gradietn ro electrochemical potential (ECP) withut ATP. At the inner side of cell membrane, which

separates form outside (external medium), these are some anion,s which are fixed or non diffusible and

membrane is impermeable to these anions. While cations are diffusible.

In such condition, for maintenance of equilibrium additional cations are needed to balance negative

charges of anions (at inner side of membrne). Thus some cations moves, inside the cell from soil solution.

So according to this theory Donnan equilibrium is attained, if the anions and cations in the internl solution

become equal to the anions and cations in external solution.

Objections for passive mineral absorption / evidences in facvour fo active mineeral absorption :

(1) Absorption of K+ ions in Nitella algae is observed against the concentration gradient.

(2) Rate of respiration of a plant is increases, when plant transferred to mineral solution. (Salt respiration)

(3) Factors like deficienty of oxygen, CO, CN, which inhibits rate of respiration, these factors also inhibit the

absorption of mineeral ions in plants.

Thus ion abosorption in plants is considered mainly as an active process.

(B) Active ion absorption : (By expenditure of ATPs)

(1) Cytochrome pump theory : By Lundegargh and Burstrom (1933) according to this theory, only

anions are absorbed by active mechanism through cytochrome pumping and absorpition of cation is

passive process.

According to cytochrome pump theory salf respiration is called as anion respiration.

(2) Carrier concent : By Vanden Honert. According to this theory some specific carrier molecules made

up of proteins are present in cell membrane of root ell, which absorb both the ions and forms ion-carrier

complex. This complex is broken inside the cell membrane with the use energy.


(3) Protein - lecithin theory : By Bennet Clark

According to this theory a phospholipid lecithin in root cell membrane works as carrier for both type of

ions.

Lecithin has two type of groups.

Goldacre - A contractile protein is associated, with absorption of minerals.

Minerals absorbed by the roots of plants are carried by xylem by to pathways, apoplastic and symplastic

pathway.

P.R. Stout and Hoagland (1939) proved that mineral salts are translocated through xylem along with

transpiration pull (exp. with help of radiosiotopes)

MINERAL NUTRITION

About 50-60 elements are present in plant body but only 16/17 elements are considered as essential

elements. According to Arnon-Criteria of essentiality of minerals :

(i) The element must be necessary for normal growth and reproduction fo all plants.

(ii) The requirement of the element must be specific for plant life. That is indespensible element to plant.

(iii) The elements must be direct ly involved in metabolism of plant.

C, G, O, N, K, S, Ca, Fe, Mg, P, Cu, Mn, B, Cl, Zn, Mo, Ni

Arnon divides these necessary elements in to two group on the basis of requirement of plant

(i) Major element/Macro nutrients : Concentration must be 1010 μg 𝐋−𝟏 / 10 m mole 𝐤𝐠−𝟏 of dry matter

(mmole-Milimolar)

C,H,O,N,K,S, Ca, Fe, Mg, P

(ii) Minor element/micro nutrients : (Concentration present less than 1.0-0.1 μg 𝐥𝟏−/𝟏𝟎 m mole

𝐤𝐠−𝟏 per gram of dry matter)

Cu, Zn, B, Cl, Mn, Mo, Ni

Some physiologist consider Fe as micronutrient

Common Role :

1. Constituent of protoplasm - C, H, O, N, P, S are porotoplamic elements.

2. Maintain the osmotic pressure of cell

3. In redox process - (In ETS) - Fe, mN, Cu, Cl.

4. Antagonistic role (balancing function) - Ca, K neutralize the toxicity of harmful substance.

5. Control permeability of cell mebrane - 𝐂𝐚+, 𝐊+

6. As cofactors or activator - Mg, Fe, Ca, Zn, Cu, K, Mn, Mo

Benificial nutrients : Mineral elemetns other than essential elements, which satisfy specific additinal

nutrient requirement of some specific plants.


Ex. Na - halophytes (eg. Atriplex - helps in C4 pathway)

Si - grasses (Provides mechanical strength)

Se - astragalus

Co - leguminous plants (root nodule formation)

Toxic elements / Toxicity - Any mineral ion concentration in plant tissue that reduces the dry weight of

tissue by about 10 percent is considerd as toxic or toxic element and this effect is called toxicity.

Most of the micronutrients become toxic as their required amount for plants is very low. This excess

concentration inhibits activity of other essential elements.

Ex : Excess Mn (Manganese) may induce deficiency of iron, magnesium and calcium casue appearance of

brown spots surrounded by chlorotic veins, Mn competes with iron (fe) and magnesium (Mg) for uptake and

with Mg for biding to enzymes. Mn also inhibits, calcium translocation into the shoot apex and causes

disease ‘Cricke leaf’. So the dominant symptoms of Mn toxicity may actually be the symptoms of Fe, Mg

and Ca deficiency.

The dificiency symtoms of highly mobile elements in plnats like N,P,K, and Mg first appear in older plant

parts. These minerals are presnet as structural constituent of biomolecules of mature plant parts and

when plant part become older, these biomolecules broken down making these elements available for

younger plant parts.

The deficiency symptoms of immobile elements like Ca, S first appear in young plant parts, as they are

not transported from older plant plarts.


MINERAL – NUTRITION

NAME ROLE/FUNCTION DEFICIENCY SYMPTOMS

NITROGEN

(Imp. in growth, metabolism,

heridity reproduction)

No3− form (Nitrate)

(i) Imp. constituent of proteins

(A), RNA, DNA

(ii) Present in porphyrins of

Chlorophylls & Cytochromes,

thus active role in photocynthesis

& respiration. (ETS).

(iii) Parts of vitamins, Co

enzymes (NAD, NADP) &

alkaloids.

(iv) Constituent of plant

hormonesIAA, & AT Ps.

(v) Absorbed from soil as

No3− NO2, NH4+ some plants from

air by nitrogen fixeres (Rhizobia,

Azolla, fungi)

(i) Chlorosis (yellowing) in older

leaves (highly mobile)

(ii) Anthocyanin formed in stem,

petioles & leaf. (tomato etc.)

(iii) Plant growth student (cell div.

& respiration reduced).

(iv) Protein synthesis, cell

enlargement, chl-cynthesis

decreases.

(v) Late floweing & plant become

more suceptible to fungal

disease due to excessive

nitrogen.

(vi) Seed dormany increased.

SULPHUR

SO42− (Sulphate) form

(i) Part of cystine, cystein, &

methionine amino acids.

(ii) Vit. biotene, thiamine, Co -A

in respiration.

(iii) Disulphide linkage (-S-S-) for

protein orientation.

(iv) Role in oil synth,

chlorophyll synthesis & prt of

ferredoxin

(vi) Root nodule formation.

(i) Chlorosis in yellowing in

younger leaves, with

anthocynain.

(ii) Stem & rotos become woody

(Hard) because sclerenchyma

development.

(iii) Tip. & margins of leafs

curbed inwardly “tea yellow

disease”

(iv) Cell div. reduced & chek

fruting.

PHOSPHORUS

𝐇𝟐𝐏𝐨𝟒 -and 𝐇𝐏𝐎𝟒 -

(Orthophosphate anion

form)

(i) Very imp. to RNA, DNA

(heredity) Phospholipid (Cell

membrane) NADP (Co-enzyme)

ATP (Energy reaction)

(ii) Imp. in Photo synthesis

(NADP), protein synth. (DNA,

RNA ATP, AA)

(iii) In oxidation-reduction

reactions, fat metabolism,

(i) Premature leaf fall, necrosis,

anthocyanin formation.

(ii) Protein synthesis decreases

(iii) Growth of roots, Shoots

checked delay in flowering

(iv) Xylem & phloem

differentiation reduces.

(v) Inhibits seed germination.


(iv) In growth of roots, dev. of leaf

form of seeds and crop yeild.

(v) Important for endergonic &

exergonic reaction.

CALCIUM

𝐂𝐚++ form

(i) Imp. for mechanical strength,

because Ca is contituent of

middle Lamella (Ca- pectate in

cell wall)

(ii) Permeability of

biomembrane

maintained by calcium.

(iii) Stability of chromosome

structure

& in spindle formation (Hewit

1963)

(iv) Detoxification (Oxalic Acid →

Ca-Oxalate), Na+, K+,

(v) Activator of enxymes

Phospholipae, arginin kinase,

ATPase, amylase

(vi) essential for growth of apical

meristems.

(i) Disintegration of growin

apices (root, shoot, leaf apex).

(ii) Irregular cell division

(mitosis)

and death of meristem.

(iii). Chlorosis on margins of

younger

leaves, malformation.

(iv) Flower falling necrosis.

(v) Abnomalities in

chromosomes.

MOLYBDENUM

𝐌𝐨𝐎𝟒𝟐− form

(Molybate ion)

(i) Role as prosthetic grown of

nitrate reductase and

nitrogenase in nitrogen

metabolism.

(ii) Tanin synthesis process.

(i) Interveinial chloroise e.g.

Lemon.

(ii) Whip tail of cauliflower.

(iii) Inhibition of flowering

POTASSIUM

𝐊+ is only Monovalant cation

in Free form

(i) Not a essential constituent of

organic meter but im. For

respiration photosynthesis,

protein synth. And DNA

synthesis as activator

(ii) Key role in stomatal

movement and transpiration

(iii) In starch synthesis &

distribution, regulation of

permeability and charge of cells

(Cation- anion balance)

(i) Mottled (interveinal)

chlorosis, & shorter the

internodes. (bushy habit)

(ii) “die-back” desease,

(iii) Necrosis & blight effect on

leaf tips, margin curved

downward.

(iv) Stop the carbohydrate

metabolism, storage of

carbohydrate in potato, beet.

inhibited


(v) Decrease the apical

dominance, seeds less

developed.

MAGNESIUM

𝐌𝐠++ from

(i) Constituent of Chlor-ophyll

and in ribosomal units binding.

(ii) Essentil for phosphate

transfer reactions (P-

metabolism).

(iii) Activator of many enzymes

in Carbohydrates metabolism.

hexokinase

(iv) In cell wall formation

(i) Interveinal chlorosis on

large scale and form. Of

anthocyanin in older leaves.

(ii) Necrotic spots

(iii) Inhibition of glycolysis Krebs

cycle (Carbhohydrate

metabolism)

IRON(Fe)

Absorption in 𝐅𝐞++ (us) form,

which is active form.

(i) Absorption in acidic soil,

because present in soluble form.

(ii) Iron-porphyrin protein for

cytochromes, Peroxidase,

Catalases (Photorespiration)

(iii) Fe imp. to ferredoxin →

biological N2 fixation & ETS.

(iv) Essential role in chlorophyll

synthesis.

(v) In aconitase enzyme of Krebs

cycle.

(i) Rapid Interveinal chlorosis

(New leaves)

(ii) Inhibition of respiration.

(iii) Disintegration of chloroplast.

MANGANESE

𝐌𝐧++ form

(i) Mn++ is activator of many

enzymes – Nitrite reductase,

hydroxyl amine reductase

decarboxylase, dehydrogenase

(ii) Essentil for O2 evolution and

photolysis of water in light

reaction (M++ & Cl− H2O to e− Ps

II on transfer )

(iii) Chlorophyll & IAA formation.

(iv) Respiratory metabolism.

(i) Deficiency cause chlorotic &

necrotic spots on leaves. (Mosaic

pattern)

(ii) Chlorophyll & starch

disappear form plastids

(iii) Marsh spot of pea, and grey

speak of oat.

(iv) Chlorosis in young & older

leaves

BORON 𝐇𝟑𝐁𝐎𝟑− or 𝐁(𝐎𝐇)𝟑 Or

𝐛𝐨𝟑−𝟑 (Borate)

(i) B is only micronutrient, which

not asso. With enzymes

(ii) Key role in sugar translocation

(Phyloem conduction)

(iii) Must for cell division,

flowering, fruiting, active salt

(i) Stem and root tips (apex) dies.

root growth stunted.

(ii) Flowr formation supp-resed.

(iii) EMP pathway change in

HMP (PPP) pathway

(iv) Physiological diseases – top


SPECIAL POINTS

C,H,O, N and P are main constituents of protoplasm (organic meterils). So they are called protoplasmic

elements C,N & O from atmosphere and H2O form soil for H & O.

C, H and O re the main components of nucleic acid, proteins, enxymes, carbohyddrates, fats (frame

work elements)

Mostly soil is deficient of NPK and these elements are knowna s critical elements, NP K-fertilizer is good

for crop yiels.

Co is part of Vit. 𝐁𝟏𝟐, which acts as coenzyme, Cobalt also used in cancer therapy and γ -garden of

crop improvement.

Silica (SiO2) is present in cell wall of diatoms grasses and paddy straw.

Al-present in pteridophytes i.e. - Lycopodium.

Mo. requires in minimum quantity.

Hydroponics/solution culture / soil les growth / tank farming and ash analsis is a technique which

determines the role of nutrients in plants. (By Geriack)

Gold (Au) present in Equisetum, mustars plants.

Plants grown in moistened air with nutrients is aeroponic.

absorption, nodule formation in

legumes

(iv) B is essential in pollen tube

formation

(v) Lethal effect at carbo hydrate

metabolic site

rotten in tobaccom water core

in turnip, brown heart rot of

beets, Brittleness of Celeary

stem, Heart rot in carrot &

marigold, fibers in apple fruit.

COPPER

𝐂𝐮++ form

‘toxic in High cons.

(i) Oxi-Reduction Process, as

parts of Enzymes, cytochromes

(PC & a)

(ii) Vit.-c (ascorbic Acid)

formation.

(i) Necrosis of tip in young leaves

(wither tip)

(ii) “Die-back of citrus” and

other fruit trees Exanthema in

tress.

(iii) Reclamation disease of

cereals and legume crops.

ZINC

𝐙𝐧++ form

(i) Specific role in Auxin (IAA)

Hormone synthesis in cell.

(ii) Activator of Carbonic

anhydrse, alcohol

dehydrogenase, Peptidase

(iii) In seed formation

(i) Checked veg. growth and

shorter the internoded leaf

deformation.

(ii) Mottle leaf disease in fruit

trees Little leaf disease.

(iii) ‘Khaira disease of paddy’

Rosset disease in walnut.

(iv) Inhibit seed formations,

white bud disease in maize.


Root meristem is important is storage and absorption of minerals.

Na+ found in halophytes for their growth (marine plants).

Trace- element are micro-nutrients, while tracer-elements are radio-isotopes.

Mg present in chlorophyll, as non-ionic form

Mg remians after chlorophyll burning.

Minerals and organic matter regulates the osmotic concentration of cell.

Mo in nitrogen metabolism.

One abundant and stable form of Fe in leaves in stored in chloroplasts as an iron protein complex called

phytoferritin (Seckback 1983).

C,H,O, are provided by H2O,O2 nd CO2 but 13 elements essential to all plants are absorbed as ion from

the soil solution is called a solution mining. (N2 from soil & atm.)

Putrifiction/proteolysis : Becillus, Pseudomonas, Cllostridium.

Proteins Proteases→ peptides

Peptidase→ amino acids (conversion of proteins in to amino acids) smell of dead

bodies.

Deaminaion : Removal of amono group as NH3 from an amino acid.

Root pressure is measured by manometer

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