Case Study Questions Class 11 Biology Transport in Plants

Case Study Questions Class 11 Biology Chapter 11 Transport in Plants

CBSE Class 11 Case Study Questions Biology Transport in Plants. Important Case Study Questions for Class 11 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Transport in Plants.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

CBSE Case Study Questions Class 11 Biology Transport in Plants

CASE 1

The behaviour of the plant cells or tissues with regard to water movement depends on the surrounding solution. If the external solution balances the osmotic pressure of the cytoplasm, it is said to be isotonic. If the external solution is more dilute than the cytoplasm, it is hypotonic and if the external solution is more concentrated, it is hypertonic. Cells swell in hypotonic solutions and shrink in hypertonic ones.

Plasmolysis occurs when water moves out of the cell and the cell membrane of a plant cell shrinks away from its cell wall. This occurs when the cell (or tissue) is placed in a solution that is hypertonic (has more solutes) to the protoplasm. Water moves out; it is first lost from the cytoplasm and then from the vacuole. The water when drawn out of the cell through diffusion into the extracellular (outside cell) fluid causes the protoplast to shrink away from the walls. The cell is said to be plasmolysed. The movement of water occurred across the membrane moving from an area of high water potential (i.e., the cell) to an area of lower water potential outside the cell.

When the cell (or tissue) is placed in an isotonic solution, there is no net flow of water towards the inside or outside. If the external solution balances the osmotic pressure of the cytoplasm it is said to be isotonic. When water flows into the cell and out of the cell and are in equilibrium, the cells are said to be flaccid.

The process of plasmolysis is usually reversible. When the cells are placed in a hypotonic solution (higher water potential or dilute solution as compared to the cytoplasm), water diffuses into the cell causing the cytoplasm to build up a pressure against the wall that is called turgor pressure. The pressure exerted by the protoplasts due to entry of water against the rigid walls is called pressure potential Ψp . Because of the rigidity of the cell wall, the cell does not rupture. This turgor pressure is ultimately responsible for enlargement and extension growth of cells.

1.) When the external solution osmatic pressure is the same to the osmatic pressure of cytoplasm within cell, such condition is referred as ____________

a) Isotonic

b) Hypotonic

c) Hypertonic

d) None of the above

2.) When water movers from an area of high water potential to an area of lower water potential this phenomenon is known as _____________

a) Hypotonic

b) Plasmolysis

c) Deplasmolysis

d) Crenation

3.) What come off when the cells are placed in a hypotonic solution?

4.) What come off when the cells are placed in a isotonic solution?

5.) How cell become plasmolysed cell?

Answer key

1.) a

2.) b

3.) When the cells are placed in a hypotonic solution which have higher water potential as compared to the cytoplasm, water diffuses into the cell causing the cytoplasm to build up a pressure against the wall. That pressure is called turgor pressure.

4.) When the cell is placed in an isotonic solution, there is no net flow of water towards the inside or outside. Because solution osmatic pressure is the same to the osmatic pressure of cytoplasm within cell.

5.) Whenwater drawn out of the cell through diffusion into the outside cell causes the protoplast to shrink away from the walls and cell become plasmolysed.

CASE 2

Transpiration is the evaporative loss of water by plants. It occurs mainly through stomata. Besides the loss of water vapour in transpiration, exchange of oxygen and carbon dioxide in the leaf also occurs through these stomata. Normally stomata are open in the day time and close during the night. The immediate cause of the opening or closing of stomata is a change in the turgidity of the guard cells.

Transpiration is affected by several external factors: temperature, light, humidity, wind speed. Plant factors that affect transpiration include number and distribution of stomata, per cent of open stomata, water status of the plant, canopy structure etc.

The transpiration driven ascent of xylem sap depends mainly on the following physical properties of water:

Cohesion – mutual attraction between water molecules.

Adhesion – attraction of water molecules to polar surfaces.

Surface Tension – water molecules are attracted to each other in the liquid phase more than to water in the gas phase

These properties give water high tensile strength, i.e., an ability to resist a pulling force, and high capillarity, i.e., the ability to rise in thin tubes. In plants capillarity is aided by the small diameter of the tracheary elements – the tracheids and vessel elements. The process of photosynthesis requires water. The system of xylem vessels from the root to the leaf vein can supply the needed water. As water evaporates through the stomata, since the thin film of water over the cells is continuous, it results in pulling of water, molecule by molecule, into the leaf from the xylem. Also, because of lower concentration of water vapour in the atmosphere as compared to the substomatal cavity and intercellular spaces, water diffuses into the surrounding air. This creates a ‘pull’. Measurements reveal that the forces generated by transpiration can create pressures sufficient to lift a xylem sized column of water over 130 metres high.

1.) ________________ is the site for gaseous exchange and evaporation of water in the form of vapours i.e. transpiration.

a) Leaf

b) Leaf surface

c) Stomata

d) All of the above

2.) Hydrophilic mutual attraction between water molecules is termed as,

a) Cohesion

b) Adhesion

c) Surface tension

d) Both a and c

3.) Identity the correct statement

Statement 1 – Cohesion is mutual attraction between water molecules.

Statement 2 – Adhesion is attraction of water molecules to polar surfaces.

Statement 3 – Transpiration is the evaporative loss of water by plants.

Statement 4 – water molecules are attracted to each other in the liquid phase more than to water in the gas phase

a) Only 1

b) Only 2

c) Only 3 & 4

d) All of the above

4.) What is the reason behind immediate opening or closing of stomata?

5.) Enlist the properties that give water high tensile strength.

6.) Define cohesion and adhesion.

Answer key

1.) c

2.) a

3.) d

4.) The reason behind immediate opening or closing of stomata is the turgidity of the guard cells. A change in the turgidity of the guard cells cause immediate opening or closing of stomata.

5.) Properties that give water high tensile strength;

  • Cohesion
  • Adhesion
  • Surface Tension

6.) Cohesion – is defined as the hydrophilic mutual attraction between water molecules.

Adhesion – is defined as attraction of water molecules to polar surfaces.

CASE 3

As various ions from the soil are actively transported into the vascular tissues of the roots, water follows (its potential gradient) and increases the pressure inside the xylem. This positive pressure is called root pressure, and can be responsible for pushing up water to small heights in the stem. Effects of root pressure is also observable at night and early morning when evaporation is low, and excess water collects in the form of droplets around special openings of veins near the tip of grass blades, and leaves of many herbaceous parts. Such water loss in its liquid phase is known as guttation.

Root pressure can, at best, only provide a modest push in the overall process of water transport. They obviously do not play a major role in water movement up tall trees. The greatest contribution of root pressure may be to re-establish the continuous chains of water molecules in the xylem which often break under the enormous tensions created by transpiration. Root pressure does not account for the majority of water transport; most plants meet their need by transpiratory pull.

Despite the absence of a heart or a circulatory system in plants, the upward flow of water through the xylem in plants can achieve fairly high rates, up to 15 metres per hour. A long standing question is, whether water is ‘pushed’ or ‘pulled’ through the plant. Most researchers agree that water is mainly ‘pulled’ through the plant, and that the driving force for this process is transpiration from the leaves. This is referred to as the cohesion-tension-transpiration pull model of water transport.

Water is transient in plants. Less than 1 per cent of the water reaching the leaves is used in photosynthesis and plant growth. Most of it is lost through the stomata in the leaves. This water loss is known as transpiration.

1.) Identify the correct statement

Statement 1 – Circulatory system is present in plants in the form of xylem and phloem.

Statement 2 –Root pressure maintain the continuous chains of water molecules in the xylem.

Statement 3 – Water loss in the form of vapour is known as guttation.

Statement 4 – Guttation is the result of turgor pressure

a) Statement 1 is correct

b) Statement 2 and 3 are incorrect

c) Statement 1 and 4 are correct

d) Statement 2 is correct

2.) Root pressure produced in root that push absorbed fluidand minerals toward the _________________in upward direction.

a) Xylem

b) Phloem

c) Root hairs

d) Both xylem and phloem

3.) Explain how dew drops develop on tip of the grass?

4.) What is cohesion-tension-transpiration pull model of water transport?

5.) Name the vascular tissue which play key role in transportation water.

Answer key

1.) d

2.) a

3.) Effects of root pressure is observable at night and early morning when evaporation is low, and excess water collects in the form of droplets around special openings of veins near the tip of grass blades, and leaves of many herbaceous parts. Such water loss in its liquid form is known as guttation.

4.) The upward flow of water through the xylem in plants can achieve fairly high rates, up to 15 metres per hour. The driving force for this process is come from transpiration at the leaves. This is referred to as the cohesion-tension-transpiration pull model of water transport.

5.) Xylem is the key vascular tissue which play very important role in water transport, as phloem translocate the food from source to sink.

CASE 4

Water potential (Ψw) is a concept fundamental to understanding water movement. Solute potential (Ψs) and pressure potential (Ψp) are the two main components that determine water potential. Water molecules possess kinetic energy. In liquid and gaseous form they are in random motion that is both rapid and constant. The greater the concentration of water in a system, the greater is its kinetic energy or ‘water potential’. If two systems containing water are in contact, random movement of water molecules will result in net movement of water molecules from the system with higher energy to the one with lower energy. Thus water will move from the system containing water at higher water potentialto the one having low water potential. This process of movement of substances down a gradient of free energy is called diffusion. Water potential is denoted by the Greek symbol Psi or Ψ and is expressed in pressure units such as Pascal (Pa).

If some solute is dissolved in pure water, the solution has fewer free water molecules and the concentration (free energy) of water decreases, reducing its water potential. Hence, all solutions have a lower water potential than pure water; the magnitude of this lowering due to dissolution of a solute is called solute potential or Ψs . Ψs is always negative. The more the solute molecules, the lower (more negative) is the Ψs .For a solution at atmospheric pressure (water potential) Ψw = (solute potential) Ψs

If a pressure greater than atmospheric pressure is applied to pure water or a solution, its water potential increases. It is equivalent to pumping water from one place to another. Pressure can build up in a plant system when water enters a plant cell due to diffusion causing a pressure built up against the cell wall, it makes the cell turgid;this increases the pressure potential. Pressure potential is usually positive, though in plants negative potential or tension in the water column in the xylem plays a major role in water transport up a stem. Pressure potential is denoted as Ψp .

Water potential of a cell is affected by both solute and pressure potential. The relationship between them is as follows: Ψw = Ψs + Ψp

The plant cell is surrounded by a cell membrane and a cell wall. The cell wall is freely permeable to water and substances in solution hence is not a barrier to movement. In plants the cells usually contain a large central vacuole, whose contents, the vacuolar sap, contribute to the solute potential of the cell. In plant cells, the cell membrane and the membrane of the vacuole, the tonoplast together are important determinants of movement of molecules in or out of the cell. Osmosis is the term used to refer specifically to the diffusion of water across a differentially- or selectively permeable membrane. Osmosis occurs spontaneously in response to a driving force. The net direction and rate of osmosis depends on both the pressure gradient and concentration gradient.

1.) Greater the concentration of water in a system, the greater its ______________

a) Solute potential

b) Pressure potential

c) Water potential

d) All of the above

2.) When some solute is dissolved in pure water, it results into ______________

a) Reducing its water potential

b) Reducing free water molecules

c) Decrease in Water potential

d) All of the above

3.) Name the components that determine water potential.

4.) What is tonoplast?

5.) Write equation which represent the relationship between components of water potential.

6.) Give the unit of water potential.

Answer key

1.) c

2.) d

3.) Solute potential (Ψs) and pressure potential (Ψp) are the two main components that determine water potential.

4.) Tonoplast is the semi permeable membrane surrounding vacuole in plant cell.

5.) Solute potential (Ψs) and pressure potential (Ψp) are the two main components that determine water potential. Water potential of a cell is affected by both solute and pressure potential. The relationship between them is as follows: Ψw = Ψs + Ψp

6.) Water potential is denoted by the Greek symbol Psi or Ψ and is expressed in pressure units such as Pascal (Pa).

CASE 5

The responsibility of absorption of water and minerals is more specifically the function of the root hairs that are present in millions at the tips of the roots. Root hairs are thin-walled slender extensions of root epidermal cells that greatly increase the surface area for absorption. Water is absorbed along with mineral solutes, by the root hairs, purely by diffusion. Once water is absorbed by the root hairs, it can move deeper into root layers by two distinct pathways: apoplast pathway and symplast pathway

The apoplast is the system of adjacent cell walls that is continuous throughout the plant, except at the casparian strips of the endodermis in the roots. The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells. Movement through the apoplast does not involve crossing the cell membrane. This movement is dependent on the gradient. The apoplast does not provide any barrier to water movement and water movement is through mass flow. As water evaporates into the intercellular spaces or the atmosphere, tension develop in the continuous stream of water in the apoplast, hence mass flow of water occurs due to the adhesive and cohesive properties of water.

The symplastic system is the system of interconnected protoplasts. Neighbouring cells are connected through cytoplasmic strands that extend through plasmodesmata. During symplastic movement, the water travels through the cells – their cytoplasm; intercellular movement is through the plasmodesmata. Water has to enter the cells through the cell membrane, hence the movement is relatively slower. Movement is again down a potential gradient. Symplastic movement may be aided by cytoplasmic streaming. You may have observed cytoplasmic streaming in cells of the Hydrilla leaf; the movement of chloroplast due to streaming is easily visible.

1.) Symplastic system is the system of

a) Interconnected cell wall

b) Interconnected plasmodesmata

c) Interconnected protoplasts

d) Interconnected cytoplasm

2.) Apoplastic movement of water occurs through the _________ and the cell walls and cell membrane.

a) Intracellular spaces

b) Intercellular spaces

c) Plasmodesmata

d) Cytoplasmic strands

3.) Explain how water travels during symplastic movement of water.

4.) Give the example of cytoplasmic streaming.

5.) Why water movement in symplastic movement is relatively slower.

6.) Define apoplast pathway and symplast pathway.

7.) What is root hair?

Answer key

1.) c

2.) b

3.) Symplastic system is the system of interconnected protoplasts. Cells are connected through cytoplasmic strands that extend through plasmodesmata. During symplastic movement, the water travels through the cells – their cytoplasm. Intercellular movement take place through the plasmodesmata. Water has to enter the cells through the cell membrane, hence the movement is relatively slower.

4.) Cytoplasmic streaming is observed in cells of the Hydrilla leaf.The movement of chloroplast due to streaming is easily visible in it.

5.) In symplastic movement, water travels through the cytoplasm of cell. Intercellular movement occurs through the plasmodesmata. Water has to enter the cells through the cell membrane, because of this the movement is relatively slower.

6.) Apoplast pathway – The movement of water exclusively through cell wall without crossing cell membrane, is called apoplast pathway.

Symplast pathway – The movement of water through the cell membrane is called transmembrane pathway or symplast pathway.

7.) Root hairs are thin-walled slender extensions of root epidermal cells that provides more surface area for absorption. Water is absorbed along with mineral solutes, by the root hairs.

Updated: April 4, 2022 — 1:43 pm

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