MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Transport in Plants Class 11 Important Questions Very Short Answer Type

Question 1.
Which factors effect rate of diffusion?
Answer:
Factors affecting the rate of diffusion are :

  • Concentration of the medium,
  • Solubility of solutes,
  • Temperature,
  • Size and mass of diffusing particles,
  • Permeability of the separating membrane.

Question 2.
What is Porin? Give its role in diffusion.
Answer:
Porin is a type of protein, which forms pore in the outer membrane of plastids, mitochondria and bacteria, so that protein molecules can pass through them.

Question 3.
Which part of the roots absorb water from the soil?
Answer:
Root hair zone of the roots absorb water from the soil.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 4.
Which soil water is absorbed by the roots?
Answer:
Roots absorb capillary water.

Question 5.
What is Guttation?
Answer:
The process of loss of water in the form of water droplets through the hydath- odes of herb plants is called as Guttation.

Question 6.
What is semipermeable membrane?
Answer:
Membranes which allow only the solvent to pass through them not the solute particles are called as semipermeable membrane

Question 7.
Name the tissue helps for conduction of water in plants.
Answer:
Xylem helps for conduction of water and minerals in plants.

Question 8.
What is Transpiration pull?
Answer:
Due to continuous loss of water vapour through stomata during transpiration process tension is created on unbroken water column in the Xylem, which remain continuous due to cohesive force of water molecules, thus water ascend in the plants in upward direction through Xylem. This is called as Transpiration pull.

Question 9.
What is Wilting?
Answer:
When rate of transpiration is very high and rate of absorption fails to keep balance with the loss of water, a kind of water deficit takes place in plants. This condition is called as Wilting. Plant cells become flaccid in this condition.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 10.
What do you mean by antitranspiration substance?
Answer:
Substance which reduces rate of transpiration without effecting gaseous exchange in plants is called as Antitranspiration substance e.g. Phenyl mercuric acetate.

Question 11.
What is ascent of sap?
Answer:
The upward movement of water from the root towards the top of the plant is known as ascent of sap. Sap is water with dissolved ingredients (Minerals). Ascent of sap takes place through tracheary elements of Xylem.

Question 12.
Define DPD.
Answer:
The amount by which the diffusion pressure of the solution is lower than that of its solvents at the same temperature and atmospheric pressure is called as diffusion pressure deficit (DPD). DPD is the index of absorbing power of a solution, it is also called as suction pressure.

Question 13.
Define osmotic pressure.
Answer:
A pressure which is developed in a solution when it is separated from its solvent by a semipermeable membrane due to presence of dissolved solutes in it. This is called osmotic pressure (OP).

Transport in Plants Class 11 Important Questions Short Answer Type

Question 1.
Explain role of protein pump during active transport in plants.
Answer:
Absorption of substances which occurs with expenditure of energy through plasma membrane is called as active absorption.

Cell is surrounded by a lipo-protein membrane, which is impermeable to free ions. But some carrier compounds (protein in nature) acts as carrier to carry ions by binding with ions. Carrier combines with ions to form carrier-ion complex, which can move across the membrane with the expenditure of metabolic energy (ATP) of respiration. On the inner surface of the membrane this complex breaks releasing ions into the cell while the carrier goes back to the outer surface to pick fresh ion.

Question 2.
Why water potential of pure water is highest? Explain.
Answer:
Kinetic energy of water molecule is more. If concentration of water is more in any system then its kinetic energy will be more, thus its water potential or osmotic potential is high. Addition of solvent to pure water lowers its osmotic potential. It is represented by Greek symbol psi (Ψ) and its value is equal to osmotic pressure. Its unit is Pascal (Pa).

Question 3.
Explain Water Potential. What are the various factors which effect it? Explain relationship between water potential, solute potential and pressure potential.
Answer:
Water travels from high energy area to low energy area. Kinetic energy of pure water is highest. Water move from one place to other place according to concentration gradient or potential gradient. Water potential of pure water is highest, its value is equal to zero. Addition of solute to pure water lowers its free energy therefore reduces value of water potential, thus its value become negative (-ve).
The differences between the free energy of water molecule is pure and any other system is called as water potential. It is represented by (Ψw).
The amount of solute present in water is called solute potential (Ψs).
Pressure potential is equal to osmotic pressure, when cell is in turgid condition. Pressure potential is represented by sign Ψp.
The water potential (Ψw) is actually the sum of other two potentials.
Ψw = Ψs + Ψp

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 4.
What will happen if pressure more than atmospheric pressure is applied to the pure water or solvent?
Answer:
If pressure more than atmospheric pressure is applied in pure water then its water potential increases. Its value is equal to the amount of water pumped from one place to the other place. When water enters into a cell, it apply pressure on the cell wall. Cell become turgid. It increases pressure potential. Generally, water potential is positive. Water potential is represented by sign Ψp.

Question 5.
How does mycorrhiza helpful to plant in absorption of water and minerals?
Answer:
There are fungi which live in intimate association with some other unlike living organisms, both being beneficial to each other, the process being called symbiosis. A symbiotic, non-pathogenic or weakly pathogenic association of various fungi and bryophytes, pteridophytes or flowering plants is known as mycorrhiza. Most of these associations are not specific. A fungus can associate with many plants and a plant can associate with many fungi. The fungus may grow within the root surface or may grow around the root surface.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 1

The fungal partners are usually those that can breakdown the plant cell wall only in a limited way. The fungus takes its nutrition from the damaged portion and grow, but the growth of the fungus within the plant does not damage it. The fungus remains in a restricted area. The plants are benefitted as the fungi spread in soil, absorbs water, nitrogen and other minerals from the soil. The fungi also produce various growth promoting substances and antimicrobial substances. The fungi use carbohydrates produced by other plant partner.

Question 6.
Give role of endodermis in absorption of minerals in plants.
Answer:
Many transport proteins are found embedded in the plasma membrane of endodermal cells of the roots of the plants, which allow only few particles to pass through them.
Transport protein of endodermal cells of roots of the plants can bind to selected solute particles only based on the shape and utility of the mineral ions for the plants. They also control quantity and type of ions to be absorbed.

Question 7.
Derive relationship between osmotic pressure, turgor pressure and suction pressure or diffusion pressure deficit.
Answer:
To understand relationship between OP, TP, and DPD, we must see first what are these.
Osmotic pressure (OP) :
A pressure which is developed in a solution, when it is separated from its solvent by a semipermeable membrane.

Turgor pressure (TP):
When a cell is placed in distilled water, it absorbs water by the process of osmosis and become turgid and the contents of cell exert a pressure against cell wall which is known as turgor pressure.

Diffusion pressure deficit (DPD) :
The amount by which the diffusion pressure of the solution is lower than that of its solvent at the same temperature and atmospheric pressure is called as Diffusion pressure deficit or Suction pressure.
Relationship between Diffusion Pressure Deficit, Osmotic Pressure and Turgor Pressure : When a cell absorbs water the turgor pressure of cell is increased but cell wall also applies an equal but opposite pressure called wall pressure (WP) against the turgor pressure (TP). Therefore, actual force responsible for entry of water into the cell will be OP-TP (or WP). The relationship between DPD, OP, TP and WP can be expressed as follows :
DPD(SP) =OP-WP
or
DPD = OP – TP, (∵ TP = WP)
Due to endosmosis of water the OP of the cell sap, decreases while WP is increased, so that in fully turgid cell TP is equal to OP.
OP = TP (in fully turgid cell)
Hence, DPD (SP) = 0 (zero)

Thus, there will be no absorption of water by the cell in fully turgid cell.
On the other hand, the removal of water from cell sap (exosmosis) results in the increase of its OP and decrease of TP so much so that cell becomes flaccid (fully plasmo- lyzed) and the value of turgor pressure becomes zero.
TP = 0 (in fully flaccid cell)
Hence, DPD (SP) = OP
Consider that a plant cell with OP = 10 atm is immersed in pure water. In beginning, TP inside the cell will be zero, i.e., DPD = OP = 10 atm.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 8.
What is Osmosis? Give impotance of osmosis process in plants.
Answer:
Osmosis :
The process of movement of solvent from higher concentration to lower concentration through a semipermeable membrane is called as Osmosis.
It is of following types :

1. Endosmosis :
It is the movement of the solvent molecules from outside to inside the cell through semipermeable membrane (SPM). e.g., Some raisins when kept in water for few hours, they swell as they contain sugar solution of higher concentration.

2. Exosmosis :
It is the movement of solvent molecules from inside to outside the cell through semipermeable membrane (SPM). e.g.,

(i) Swollen raisins shrink if kept in a sugar solution of higher concentration.
(ii) If erythrocytes are placed in 2% NaCl solution, they quickly lose water, shrink up and assume the wrinkled appearance.
Significance of Osmosis :

  •  It helps in the absorption of water and minerals from the soil by roots.
  • Osmosis helps in the movement of water from one cell to another.
  • The phenomenon of plasmolysis is dependent on osmosis.
  • It develops turgidity and turgor pressure in plant cell and hence the shape or form of organs is maintained.
  • Opening- and closing of stomata is regulated by the osmotic entry and exit of water in guard cells.
  • The resistance of plants to drought and frost increases with increase in osmotic pressure of their cells.

Question 9.
What is the role of root pressure in transport of water in plants?
Answer:
According to Priestley (1916), upward flow of water is due to development of a hydrostatic pressure, which is developed in root system. The hydrostatic pressure developed due to accumulation of water absorbed by root, is called root pressure. This pressure is developed in the tracheal elements of the Xylem as a result of metabolic activities of roots. This led to the view that root pressure can raise water in tall trees.

Objections to root pressure theory :

  • Root pressure has not been found in all plants.
  • No or little root pressure has been observed in gymnosperms which have some of the tallest trees of the world.
  • Water continues to rise upwards even in the absence of roots.
  • It was observed that, root pressure by itself cannot be held responsible for the ascent of sap in tall trees.Because its maximum value does not normally exceed two atmospheric pressure, hence it can raise the sap up to 15-30 m.

Experiment 1.

Demonstration of root pressure in plants.
Requirements :
Potted Tomato, Balsam or Biyophyllum plant, rubber tube, knife, narrow gas tube, coloured water, petridish, non-drinking oil.
Method:
Take a previously well-watered potted plant of Tomato, Balsam or Bryophyllum. Cut their stem 5-8 cm above the soil level particularly in the morning. Fix a narrow glass tube to the cut end of stem with the help of rubber tube and fill it with coloured water. Cover the glass tube with a small petridish in order to prevent evaporation. A drop of non-drying oil can also be used over the surface of water to prevent evaporation.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 2

Question 10.
Describe the factors affecting Ascent of sap through Xylem in plants.
Answer:
Ascent of sap through Xylem in plants depends on following physical factors :

  • Cohesion: Water molecules has tendency to link with each other by force of attraction.
  • Adhesion: An attraction exists also between water molecules and the elements of the Xylem wall called as adhesion.
  • Surface tension : Molecules of water has more attraction in liquid state as compared to gaseous state.

Water molecules are in a continuous movement strongly attracted to each other to form a continuous column of water in Xylem elements, which help them to move in upward direction through Xylem.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 11.
Give role of transpiration pull in transport of water. What are the factors affecting transpiration ? Which factors are useful for plants?
Answer:
Transpiration pull or Tension on the unbroken water column :
As a result of transpiration, water is lost from mesophyll cells to the intercellular spaces. The water vapours move out of the plant through stomata. The DPD of mesophyll cells increases.

With the increase in DPD, these cells absorb water from adjoining cells, ultimately the water is absorbed from Xylem elements of vascular bundles of leaf. Since the xylem elements are filled with continuous water column this tension of pull is transmitted down from petiole to stem and finally to roots leading to upward movement of water.

Thus, water ascends in the plants because of transpiration pull and the column of water remains continuous because of cohesive force of water molecules. This theory is the most accepted theory at the present time.
Factors affecting transpiration : Transpiration is influenced by a number of factors both external and internal. A brief account of them are given below :

[A] External factors :
1. Humidity :
If the plant is surrounded by a saturated atmosphere, there can be no escape of water vapour from the intercellular spaces of the leaf to the outside atmosphere. On the other hand, if the atmosphere is less humid, transpiration goes on at a rapid rate.

2. Temperature :
Rise in temperature reduces the relative humidity of the air as a result, the rate of transpiration increases.

3. Wind :
Wind has a direct influence on humidity. Dry air lowers the amount of air moisture and increases the rate of transpiration, whereas humid air decreases the rate of transpiration.

4. Light:
The rate of transpiration increases markedly in light and decreases in the dark. Light affects transpiration into two ways : Firstly, it increases transpiration by raising the temperature of leaves. Secondly, there is a close relationship between the opening of stomata and light as the stomata opens in day and gets closed in night.

5. Available soil water :
If available soil water is such that the rate of absorption of water is slowed down, the rate of transpiration is correspondingly decreased. Higher con-centration of salts in the soil water reduces the absorption rate and thereby the rate of transpiration.

6. Atmospheric pressure:
At lower atmospheric pressure at the altitudes, the rate of transpiration is increased but the decrease in rate occurs due to the prevailing low tempera-ture at these heights.

[B] Internal factors:
The histological and internal physiological conditions influence the rate of transpira-tion to a great extent. The following structures of the leaves influence the rate of transpiration :

  • Presence of thick cuticle and deposition of wax on epidermis, decreases the rate of transpiration.
  • Presence of hair on the outer surface of stomata also reduces the rate of transpiration.
  • The rate of transpiration depends upon size, position and distribution of the leaves.
  • The rate of transpiration is directly proportional to the water contents of the mesophyll tissue.

Question 12.
Xylem transport is unidirectional and phloem transport is bidirectional. Explain.
Answer:
In Xylem transport of water and minerals is unidirectional, i.e. from root to top part of the plant (upward) because suberin layer found in the endodermis of roots causes active transport of ions in one direction.

Whereas in phloem transport of food occurs bidirectional. Generally, food is prepared in the green parts of the plants which contain chlorophyll and then it is collected in sink, which is to be distributed to all parts of the plant. Young buds act as sink. In plants, source and sink for transport of food is changeable as it changes with season thus phloem shows bidirectional movement of food.

Question 13.
Give reason for opening and closing of guard cells during transpiration.
Answer:
Opening and closing of stomata :
Opening and closing of stomata depends upon the activity of guard cells. Guard cells are crescent like or kidney shaped. Their concave wall are thicker than convex which face each other. The opening and closing of stomata depend upon the turgidity of the stomata, when guard cells become turgid, stomata open while guard cells become flaccid, stomata closed. Guard cells contain chloroplast hence they synthesize food by photosynthesis, using CO2 during day time.

Thus, due to lack of CO2 the pH value of the cell increases (7.5 pH). At this pH starch produced during photosynthesis reacts with inorganic phosphate in presence of phosphorylase enzyme to form glucose-1-phosphate, which is soluble in water thus concentration of the cell sap of the guard cell increases. This lead to absorption of water by the guard cells from neighbouring cells by osmosis, thus increasing turgor pressure due to which the outer thinner wall of the guard cells stretches out and stomata open for diffusion of water vapour.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 3
In dark the reverse reactions occur in the guard cells. During this period photosynthesis does not occur and respiration releases CO2, thus reducing the pH of guard cell towards acidic side (pH 5.0).
Now soluble carbohydrates are converted into insoluble starch by the enzyme phosphorylase. This brings about rapid fall of the osmotic concentration of cell sap of guard cell which become flaccid, thus closing the stomatal aperture.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Transport in Plants Class 11 Important Questions Long Answer Type

Question 1.
(a) Describe the process of plasmolysis with labelled diagram.
(b) What will happen if a plant cell is kept in high water potential solution?
AnsWER:
(a) Plasmolysis :
When a living cell is placed in a hypertonic solution then exosmosis of water takes place hence the water of cell comes out into outer solution. Due to exosmosis of water the protoplasm shrinks away from the cell wall and an irregular mass at the centre. This shrinkage of protoplasm is known as plasmolysis.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 4

When plasmolysed cell is placed in water, the water enters into the cell sap, the cell becomes turgid and the protoplasm again assumes its normal sap and position. This phenomenon is called as deplasmolysis.

(b) When a plant cell is kept in high water potential solution, i.e. hypotonic solution then endosmosis occurs. Cell become turgid. Protoplasm apply pressure on the cell wall called as Turgor pressure. Pressure of the protoplasm against cell wall is called as pressure potential (ΨP). This turgor pressure is responsible for increased size of the cell.

Question 2.
Explain hypothesis of translocation of organic substances in plants.
Answer:

Munch mass flow hypothesis :
This theory was proposed by Munch (1930). According to this theory, translocation occurs on mass along a gradient of turgor pressure from supply end to the consumption end and which can be established by the following arrangement.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 5

Two bulbs ‘A’ and ‘B’ with semipermeable membrane walls are – connected with a tube ‘C’ containing water to form a closed system. Bulb ‘A’ contains more concentrated solution than bulb ‘B’ and are dipped in water. Now due to higher osmotic pressure of the concentrated sugar solution in ‘A’, water enters into it by endomosis, increasing turgor pressure. This will result in mass flow of sugar solution to bulb ‘B’ through the tube ‘C’ till the concentration of sugar solution in both become equal. If in the above, it could be possible to maintain continuous supply of sugar in ‘A’ and its utilization in ‘B’, the process will go on indefinitely.

According to Munch, similar arrangement exists in plants. Due to photosynthesis, the mesophyll cells of the leaves have higher concentration of sugar solution in soluble form corresponding to bulb ‘A’ and is utilized by different parts (bulb ‘B’). The sieve tubes of the phloem act as tube ‘C’.

In plants mesophyll cells draw water from the xylem of leaf, due to high osmotic and suction pressure or DPD of their cell sap, increasing their turgor pressure. The turgor pressure in the cells of stem and roots are comparatively low hence, the soluble organic solute begins to flow from mesophyll through phloem down to the cells of stem and roots under the gradient of turgor pressure. These organic materials are either consumed or stored and water returns back to the xylem.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 3.
Write differences between following :
(a) Diffusion and Osmosis,
(b) Transpiration and Evaporation,
(c) Osmotic pre-ssure and Osmotic potential,
(d) Diffusion and Imbibition,
(e) Apoplast and Symplast pathway,
(f) Guttation and Transportation,
(g) Transpiration and Guttation,
(h) Endosmosis and Exosmosis.
Answer:
(a) Differences between Diffusion and Osmosis

Diffusion Osmosis
1. Molecules move from higher concentration to lower concentration. Molecules move from higher osmotic pressure to lower osmotic pressure.
2. Semipermeable membrane is not required. Semipermeable membrane is required.
3. It occurs in solid, liquid and gas. It occurs only in liquid.
4. It is a fast process. It is a slow process.

(b) Differences between Transpiration and guttation

Transpiration Evaporation
1. Transpiration is a vital process. Evaporation is a physical process.
2. It takes place only in living plants. It occurs in both, living and non-living things.
3. In this process, loss of water in the form of water vapour takes place specially through the leaves. Evaporation takes place through any surface of living or non-living thing.
4. The process of transpiration is regulated by the activity of guard cells. Guard cells are not involved in this process.
5. Transpiration is largely dependent upon absorption of water from the soil. Evaporation continues as long as water is available on the surface.

(c) Differences between Osmotic Pressure and Osmotic Potential

Osmotic Pressure Osmotic Potential
1. Pressure which is developed in a solution, when it is.kept separated from its solvent by a semipermeable membrane is called as Osmotic pressure. Osmotic potential is that quantity of water which may reduce pressure of solute.
2. Its value is positive. Its value is negative.

(d) Differences between Diffusion and Imbibition

Diffusion Imbibition
1. Movement of molecules or particles from a region of higher concentration to a region of lower concentration is called as diffusion. It is the process of absorption of solvent by a solid substance.
2. It helps for gaseous exchange through stomata, lenticels, passive absorption of water by roots etc. It helps in initiation of water absorption by roots, absorption of water by germinating seeds etc.

(e) Differences between Apoplast and Symplast Pathway

Apoplast Pathway Symplast Pathway
1. Pathway of movement of water through cell wall without crossing plasma membrane is called as Apoplast pathway. Pathway of movement of water through plasmodesmata of the plasma membrane is called as Symplast pathway.

(f) Differences between Guttation and Transportation

Guttation Transportation
1. Water is lost in the form of water droplets  from the margin of leaves through hydathodes in this process. Movement of materials in plants from one part to other part is called as transportation.
2. Guttated water contains many minerals,salts and forms a solution. Transported materials are water, minerals, organic food etc.
3. It occurs through hydathode. It occurs through xylem and phloem.
4. It occurs at night. It may occur at any time.

(g) Differences between Transpiration and Guttation

Transpiration Guttation
1. Water is lost in the form of vapour through stomata, cuticle or lenticel. Water is lost in the form of water droplets from the margins of leaves through hydathodes.
2. Transpired water vapour is pure. Guttated water contains many mineral salts and forms a solution.
3. This process is regulated by the act kity of guard cells and occurred during day time only. Guard cells do not involve in this process and it takes place during night time only.
4. Root pressure does not affect this process. Transpiration takes place in all terrestrial plants. Root pressure affects this process and it takes place only in herbaceous plants.

(h) Differences between Endosmosis and Exosmosis

Endosmosis Exosmosis
1. The diffusion of water or solvent molecules takes place from external cell to the cell. The diffusion of water or solvent molecules takes place from cell to external solution.
2. It takes place when the concentration of cell solution is higher than the concentration of outer solution. It takes place when the concentration of external solution is higher than the concentration of outer solution.
3. Cells become turgid after endosmosis. Cells become flaccid after exosmosis.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 4.
What is ascent of sap? Explain the view of Dixon and Jolly regarding the ascent of sap.
Or,
Explain the cohesion theory of ascent of sap.
Answer:
Ascent of sap :
The mechanism of upward translocation of water from the roots to the top of the plant is still a mystery. The upward movement of water from the root towards the top of the plant is known as ascent of sap. Sap is water with dissolved ingredients (minerals). The ascent of sap takes place through the tracheary elements of xylem. The mechanism involved in the transport of water from the roots to the leaves of plants, some of them being more than 200 metre high (e.g., Sequoia, Gigantia, Eucalyptus), is still unresolved.

Transpiration pull and cohesion of water theory :
This theory was proposed by Dixon and Jolly in 1894. According to this theory, water molecules are in a continuous movement strongly attracted to each other to form a continuous column of water in xylem elements. The process of transpiration pulls up the water. This theory has the following three essential features:

(A) Strong cohesion force or tensile strength of water :
The principle is mairily based on the facts that:

  • Water molecules have strong mutual attraction (cohesion) with each other and cannot be easily separated from one another.
  • An attraction exists also between water molecules and the elements of the xylem wall (cohesion). These cohesive and adhesive attractions together maintain water column in xylem tracheids.

(B) Continuity of water column in the plant:
A strong objection against the theory has been the evidence for the occurrence of air bubbles in the water column of xylem elements. They disturb the continuity of the water column.

(C) Transpiration pull or tension on the unbroken water column :
As a result of transpiration, water is lost from mesophyll cells to the intercellular spaces. The water va¬pours move out of the plant through stomata. The DPD of mesophyll cell increases. With the increase in DPD These cells absorb water from adjoining cells, ultimately the water is absorbed from xylem elements of vascular bundles of leaf. Since, the xylem elements are filled with continuous water column. This tension or pull is transmitted down from petiole to stem and finally to roots leading to upward movement of water.

Question 5.
By giving significance of transpiration explain that “Transpiration is a necessary harm”. Give factors affecting transpiration.
Answer:
Significance of Transpiration :
It is one of the most controversial issues for the physiologists. Some consider it a very’ significant and beneficial process but many other consider it as entirely harmful and useless as plants. Spend energy to absorb water continuously but 90% of absorbed water is lost by transpiration process. The significant role of transpiration are as follow:

  • Excess amount of water is removed from the plant tissues.
  • Bring coolness for the foliage and thus help them in maintaining their vigour in sunlight.
  • Causes transpiration pull, through which water is conducted to all parts of the plant.
  • Helpful in the absorption of water and minerals.
  • Helpful to maintain the concentration of cell sap.
  • Saturate the atmosphere with water vapour and regulate the water cycle of the atmosphere.
  • Certain plants liberate certain hygroscopic salts with transpired water, which accumulates on the leaf surface. These salts absorb water from the atmosphere and this saves the plant from wilting.

Thus, transpiration seems to be of much significance in the life of plants. However, excessive transpiration may cause permanent wilting and death of the plant. Therefore, “transpiration is a necessary harm” for the plants.

Factors affecting Transpiration :
Transpiration pull or Tension on the unbroken water column :
As a result of transpiration, water is lost from mesophyll cells to the intercellular spaces. The water vapours move out of the plant through stomata. The DPD of mesophyll cells increases.

With the increase in DPD, these cells absorb water from adjoining cells, ultimately the water is absorbed from Xylem elements of vascular bundles of leaf. Since the xylem elements are filled with continuous water column this tension of pull is transmitted down from petiole to stem and finally to roots leading to upward movement of water.

Thus, water ascends in the plants because of transpiration pull and the column of water remains continuous because of cohesive force of water molecules. This theory is the most accepted theory at the present time.
Factors affecting transpiration : Transpiration is influenced by a number of factors both external and internal. A brief account of them are given below :

[A] External factors :
1. Humidity :
If the plant is surrounded by a saturated atmosphere, there can be no escape of water vapour from the intercellular spaces of the leaf to the outside atmosphere. On the other hand, if the atmosphere is less humid, transpiration goes on at a rapid rate.

2. Temperature :
Rise in temperature reduces the relative humidity of the air as a result, the rate of transpiration increases.

3. Wind :
Wind has a direct influence on humidity. Dry air lowers the amount of air moisture and increases the rate of transpiration, whereas humid air decreases the rate of transpiration.

4. Light:
The rate of transpiration increases markedly in light and decreases in the dark. Light affects transpiration into two ways : Firstly, it increases transpiration by raising the temperature of leaves. Secondly, there is a close relationship between the opening of stomata and light as the stomata opens in day and gets closed in night.

5. Available soil water :
If available soil water is such that the rate of absorption of water is slowed down, the rate of transpiration is correspondingly decreased. Higher con-centration of salts in the soil water reduces the absorption rate and thereby the rate of transpiration.

6. Atmospheric pressure:
At lower atmospheric pressure at the altitudes, the rate of transpiration is increased but the decrease in rate occurs due to the prevailing low tempera-ture at these heights.

[B] Internal factors:
The histological and internal physiological conditions influence the rate of transpira-tion to a great extent. The following structures of the leaves influence the rate of transpiration :

  • Presence of thick cuticle and deposition of wax on epidermis, decreases the rate of transpiration.
  • Presence of hair on the outer surface of stomata also reduces the rate of transpiration.
  • The rate of transpiration depends upon size, position and distribution of the leaves.
  • The rate of transpiration is directly proportional to the water contents of the mesophyll tissue.

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 6.
Explain the pathway of water absorption in plants with the help of diagram.
Answer:
In plants, water is absorbed from root hairs. These root hairs absorb the capillary water of the soil by the process of osmosis. Each root hair possessing a vacuole which is filled with cell sap. The cytoplasm of the root hairs functions like that of a semipermeable membrane. These root hairs are associated with the cortical cells. Cortical cells are elaborated up to endodermis. The absorbed water is passed into xylem through root hairs to cortical cells. Cortical cells to pericycle and pericycle to vascular tissues of the stem.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 6

Question 7.
What is Transpiration? What are its types?
Or,
Write three types of transpiration process.
Answer:
Transpiration :
The process of loss of water in the form of water vapour from aerial parts of the plant is known as transpiration. There are three types of transpiration based on plant surface :

1. Stomatal or foliar transpiration :
The loss of water which takes place through specialized apertures which are present in leaves is called foliar transpiration. Most of the (80-90%) foliar transpiration takes place through stomata is called stomatal transpi-ration.

2. Cuticuiar transpiration :
Transpiration through cuticle is called the cuticular transpiration. Cuticular transpiration is only 3-10% of the total transpiration. It is continuous throughout day and night.

3. Lenticular transpiration :
Loss of water through the lenticels of fruits and woody stem is called the lenticular transpiration. The lenticular transpiration is only 0-1 % of the total transpiration. It however, continues day and night because lenticels have no mechanism of closure.

Question 8.
Describe Starch ⇌ Sugar interconversion hypothesis of opening and closing of stomata.
Answer:
Starch ⇌ Sugar interconversion hypothesis :
(i) This theory was proposed by Lloyd in 1908. According to him, the turgidity of guard cells is controlled by changes in OP, caused by interconversion of starch and sugar. He found that the amount of starch in guard cells increased by night and decreased by day.

During day time the guard cells of the stomata contain sugar synthesized by their chloroplasts by the use of light. The sugar is soluble and increases the concentration of the sap of guard cells. Due to higher concentra¬tion of the cytoplasm of guard cells, the water comes to them from the neighbouring cells by osmosis and they become turgid with the result the stomata remain open.

(ii) According to Sayre (1926), stomata open at pH 4-2 to 4-4 when starch contents is very low. The closure of stomata is always associated with an increase in starch contents. Sayre thought that utilization of C02 during photosynthesis during day time will cause the increase of pH resulting in the conversion of starch into sugar.

(iii) According to Hanes, enzyme phosphorylase catalyses the interconversion of starch and sugar.
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 7

(iv) According to this hypothesis, CO2 liberated from respiration is used in photosynthesis by mesophyll cells in daytime. This leads to the lowering of acidity (H+ ion concen-tration) of the guard cells. As the H+ ion concentration (acidity) decreases the pH increases and the enzymatic interconversion of starch into sugar is favoured.

During night (darkness) CO2 released from respiration, accumulates in the intercellular spaces increasing the H+ ion concentration (lowering the pH) this favours the conversion of sugar into starch.

(v) According to Steward (1964), OP of guard cells is not affected unless glucose-1- phosphate is further converted into glucose and inorganic phosphate.
According to Steward :
(A) At higher pH stomata opens in the following manner :
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 8

(B) At low pH closing of the stomata will be take place in the following manner:
MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants 9

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Transport in Plants Class 11 Important Questions Objective Type

1. Choose the correct answers:

Question 1.
Transpiration occurs through :
(a) Stomata
(b) Lenticel
(c) Cuticle
(d) All of these.
Answer:
(d) All of these.

Question 2.
Stomata opens during day time because the guard cells have :
(a) Outer membrane is thin
(b) Kidney shaped
(c) Chloroplast is present
(d) Large nucleus is found.
Answer:
(a) Outer membrane is thin

Question 3.
Rate of transpiration increases due to :
(a) Drought
(b) High temperature
(c) Moist soil
(d) Slow speed of wind.
Answer:
(c) Moist soil

Question 4.
Rate of transpiration is measured by :
(a) Potometer
(b) Porimeter
(c) Photometer
(d) None of these.
Answer:
(a) Potometer

Question 5.
When temperature rises, rate of transpiration :
(a) Increases
(b) Decreases
(c) Transpiration stops
(d) None of these.
Answer:
(a) Increases

Question 6.
Stomata closes due to lack of water. This condition is created due to :
(a) Formation of cytokinin
(b) Formation of Auxin
(c) Formation of ethylene
(d) Formation of Abscisic acid.
Answer:
(b) Formation of Auxin

Question 7.
Which of the following reason decreases rate of transpiration :
(a) Wind
(b) Increase in temperature
(c) Decrease in light intensity
(d) Absorption of water by plants.
Answer:
(c) Decrease in light intensity

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 8.
Water reaches the upper part of the plants by :
(a) Root pressure
(b) Cell pressure
(c) Evaporation
(d) Diffusion.
Answer:
(c) Evaporation

Question 9.
Maximum water is absorbed by plants through :
(a) Root cap
(b) Root hair
(c) Root hair area
(d) Division area.
Answer:
(c) Root hair area

Question 10.
Plants only utilize this water present in the soil:
(a) Runaway water
(b) Gravitational water
(c) Vapourised water
(d) Capillary water.
Answer:
(d) Capillary water.

Question 11.
When the cell is completely turgid which of the following pressure becomes zero :
(a) Turgor pressure
(b) Cellular wall pressure
(c) Vapour pressure
(d) Osmotic pressure.
Answer:
(b) Cellular wall pressure

Question 12.
Stomata are open in day time in most of the plants, such stomata are called :
(a) Photoactive type
(b) Potato type
(c) Barley type
(d) Dark active type.
Answer:
(a) Photoactive type

Question 13.
Which type of stomata is found in the lower surface of leaves :
(a) Appie type
(b) Potato type
(c) Oat type
(d) None of these.
Answer:
(b) Potato type

Question 14.
In which type of plants Sunken stomata is found :
(a) Xerophytes
(b) Hydrophytes
(c) Mesophytes
(d) Sporophytes.
Answre:
(a) Xerophytes

Question 15.
What will happen if a plant cell is kept in concentrated salt solution :
(a) Plasmolysis
(b) Turgid
(c) Contraction
(d) Deplasmolysis.
Answer:
(a) Plasmolysis

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 16.
Reason for Root pressure is :
(a) Passive absorption
(b) Active absorption
(c) Increase in transpiration
(d) Decrease in rate of photosynthesis.
Answer:
(b) Active absorption

Question 17.
Potometer is used for measurement of:
(a) Rate of absorption
(b) Rate of transpiration
(c) Rate of photosynthesis
(d) Phototropism.
Answer:
(b) Rate of transpiration

Question 18.
In guttation process loss of water occurs through :
(a) Stomata
(b) Hydathodes
(c) Wound
(d) Lenticels
Answer:
(b) Hydathodes

Question 19.
Which wall of the guard cells is thick :
(a) Outer
(b) Inner
(c) Lateral
(d) All of these.
Answer:
(b) Inner

Question 20.
When a cell is at equilibrium then :
(a) DPD = 0
(b) DPD = TP
(c) OP = TP
(d) DPD=OP.
Answer:
(c) OP = TP

Question 21.
What will happen if a plant cell is kept in pure water :
(a) Turgid
(b) Flaccid
(c) Plasmolysis
(d) Impermeable.
Answer:
(a) Turgid

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

Question 22.
Water potential of cell become positive in plant cell due to :
(a) Transpiration
(b) Low transpiration
(c) High absorption
(d) Guttation.
Answer:
(c) High absorption

Question 23.
Meaning of Osmosis is :
(a) Diffusion of dissolved particles from higher to lower concentration
(b) Diffusion of dissolved particles from lower to higher concentration
(c) Diffusion of water from higher to lower concentration
(d) Diffusion of water from lower to higher concentration.
Answer:
(c) Diffusion of water from higher to lower concentration

Question 24.
Guttation occurs due to :
(a) Transpiration
(b) Osmosis DPD
(c) Root pressure
(d) Osmotic pressure.
Answer:
(c) Root pressure

Question 25.
Transfer of water from one cell to other cell and direction of water flow depends on:
(a) WP
(b) TP
(c) DPD
(d) Primary plasmolysis.
Answer:
(c) DPD

2. Fill in the blanks:

1. The cavity and loose tissues present below the hydathodes is called ………………….
Answer:
Epithem

2. …………………. gave the name protoplasm.
Answer:
Purkinje

3. …………………. gave the K+ exchange process for opening and closing of stomata.
Answer:
Levitt

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

4. The guard cells for dicot stomata are ………………….
Answer:
Kidney shaped

5. Osmoscope is used to measure ………………..
Answer:
Osmosis

6. Parchment paper, is an example of …………………… membrane.
Answer:
Semipermeable

7. DPD = OP – …………………..
Answer:
TP

8. The cavity present below hydathodes is called ………………..
Answer:
Epithem

9. Loss of water from the margin of leaves in the form of water droplets is called………………….
Answer:
Guttation

10. In osmosis, diffusion of solvent takes place through ………………….
Answer:
Semipermeable membrane

11. The DPD of a fully turgid cell is always …………………..
Answer:
0

12. The DPD of a solution is ……………….. to its concentration.
Answer:
Proportional

13. ………………… is an instrument which is used to measure the rate of transpiration.
Answer:
(b) Potometer

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

14. The transport of water and mineral salts takes place through …………………
Answer:
Xylem

15. Absorption of water with use of energy is known as …………………..
Answer:
Active absorption

16. In plants, rate of transpiration is measured with the help of ……………….
Answer:
Potometer

17. Loss of water in the form droplets from the margin of leaves is called ……………….
Answer:
Guttation

3. Match the following:

(A)

Column ‘A’ Column ‘B’
1. Transpiration (a) Semipermeable membrane
2. Guttation (b) Stomata
3. Bleeding (c) Hydathode
4. Hydathode (d) Injured part
5. Osmosis (e) Epithem.

Answer:
1. (b) Stomata
2. (c) Hydathode
3. (d) Injured part
4. (e) Epithem
5. (a) Semipermeable membrane

(B)

Column ‘A’ Column ‘B’
1. Pulsation theory (a) Pnestley
2. Active water absorption (b) Dixon and Jolly
3. Root pressure theory (c) Godlewski
4. Transpiration pull theory (d) Atkins and Priestley
5. Relay pump theory (e) J. C. Bose.

Answer:
1. (e) J. C. Bose,
2. (d) Atkins and Priestley
3. (a) Pnestley
4. (b) Dixon and Jolly
5. (c) Godlewski

MP Board Class 11th Biology Important Questions Chapter 11 Transport in Plants

4. Answer in one word:

1. Which part of the root take part in water absorption?
Answer:
Root hairs

2. What type of water is absorbed by roots?
Answer:
Capillary water

3. From which tissue of the plant body, translocation of water takes place?
Answer:
Xylem

4. Name the pressure responsible for stomatal opening.
Answer:
Turgor Pressure

5. “Transpiration is a necessary evil”, who stated it?
Answer:
Kartis

6. The pressure exerted in plant cells due to the absorption of water.
Answer:
Osmotic pressure

7. What will be the DPD of a fully turgid cells?
Answer:
Zero

8. Name the water absorbing part of the roots.
Answer:
Root hair

9. Name the process of loss of water from the aerial part of the plant body in the form of water vapour.
Answer:
Transpiration

10. Name the enzyme which converts starch into glucose, 1-phosphate.
Answer:
Phosphorylase

MP Board Class 11th Biology Important Questions

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