Q1. Which of the following is not true about osmosis?
- 1) It occurs in liquids and gases.
- 2) Only the solvent molecules move from a region of low concentration to high concentration.
- 3) It is a special type of diffusion.
- 4) It occurs through a selectively permeable membrane.
Osmosis does not occur in any other medium except liquids.
Q2. Water is released as droplets. This is known as
- 1) Bleeding
- 2) Root pressure
- 3) Transpiration
- 4) Guttation
The loss or excretion of water in the form of liquid droplets from the leaves and other parts of an uninjured plant is called guttation.
Q3. A cell when kept in a sugar solution gets dehydrated. Then the solution is
- 1) None of the above
- 2) Hypertonic
- 3) Hypotonic
- 4) Isotonic
Hypertonic solutions have a higher solute concentration which causes the water inside a cell to get out of the cell by osmosis.
Q4. The rate of transpiration will be less in a situation where
- 1) Wind is blowing.
- 2) Groundwater is sufficiently available.
- 3) Relative humidity is high.
- 4) Environment is hot and dry.
The rate of transpiration is inversely proportional to relative humidity which means that the rate of transpiration is lower when the relative humidity is higher and vice versa.
Q5. Carbohydrates in the phloem are transported as
- 1) Sucrose
- 2) Starch
- 3) Fructose
- 4) Galactose
Carbohydrates synthesised in the leaves by photosynthesis are transported through the phloem in the form of sucrose.
Q6. A typical root hair has thickness of about
- 1) 10 μm
- 2) 100 μm
- 3) 1 μm
- 4) 1 mm
A typical root hair is about 1 mm to 1 cm in length and about 10 μm in diameter.
Q7. The rupture and fractionation do not usually occur in the water column in vessel/tracheids during the ascent of sap because of
- 1) Lignified thick wall
- 2) Cohesion and adhesion
- 3) Transpiration pull
- 4) Weak gravitational pull
There are a large number of treachery elements running together, the blockage of one or a few of them does not cause any breakage in the continuity of the water column. The column of water does not fall under the impact of gravity because forces of transpiration provide energy. Water molecules remain attached to one another by strong mutual forces of attraction called cohesion and adhesion forces.
Q8. Water potential is expressed in
- 1) Pascal
- 2) Pascal2
- 3) Newton
- 4) N/m2
The water potential is expressed in Pascal.
Q9. Water is lost in a liquid state in some plants through hydathodes. These hydathodes
- 1) Always remain open
- 2) Do not show any specificity in opening and closing
- 3) Remain closed during the day
- 4) Remain closed at night
Hydathodes remain open because they are a structural part of a plant found mostly in grasses. There is no such regulation process of its opening or closing as in stomata. Guttation occurs through hydathodes.
Q10. Plasmolysis will occur when the cell is placed in
- 1) Isotonic solution
- 2) Hypertonic solution
- 3) Hypotonic solution
- 4) Hypotonic and isotonic solutions
A hypertonic solution causes exosmosis or withdrawal of water from the cytoplasm. The pressure on the wall is simultaneously reduced, and the elastic wall contracts causing a reduction in cell size which is called plasmolysis.
Q11. The osmotic pressure of mesophyll cells of the leaf increases due to
- 1) Continuous synthesis of carbohydrates
- 2) Continuous exposure to wind
- 3) Continuous exposure to light which increases transpiration
- 4) Continuous uptake of salts from neighboring cells
The osmotic pressure of mesophyll cells of the leaf increases because of the continuous synthesis of carbohydrates by photosynthesis.
Q12. What will happen to the solute potential inside the cell if the cell is kept in a hypertonic solution?
If the cell is kept in a hypertonic solution, then the solute potential inside the cell will increase.
Q13. Plasmolysis is the result of
- 1) Diffusion
- 2) Exosmosis
- 3) Reverse osmosis
- 4) Endosmosis
Plasmolysis is the result of exosmosis or the withdrawal of water from the cytoplasm. The pressure on the wall is simultaneously reduced, and the elastic wall contracts causing a reduction in cell size.
Q14. Which form of carbon was used in isotopic studies to determine the role of phloem in the transport of food through the plant?
- 1) 14C2
- 2) 13C2
- 3) 12C2
- 4) 15C2
14C2 is a radioactive form of carbon which was used in isotopic studies to determine the role of phloem in the transport of photosynthetic products through the plant.
Q15. The main significance of facilitated diffusion is
- 1) Absorption of mineral ions by plant roots
- 2) Excretion of urea and hydrogen ions by mammalian kidneys
- 3) Absorption of fructose and nucleotides in the small intestine
- 4) Absorption of amino acids from the gut
Facilitated diffusion helps in the transportation of glucose in liver cells and also helps in the absorption of fructose and nucleotides in the small intestine.
Q16. When a plant undergoes senescence, the nutrients may be
- 1) Exported
- 2) Translocated
- 3) Absorbed
- 4) Withdrawn
When any plant undergoes senescence, nutrients may be withdrawn from senescent regions and moved to the growing parts. The mineral ions are transferred to the apical and lateral meristems, young leaves, developing fruits, seeds and storage organs by the process of diffusion and active uptake by the cells of growing regions.
Q17. Water potential of pure water at standard temperature is equal to
- 1) −10
- 2) 10
- 3) Zero
- 4) 20
Water potential is the difference in the free energy or chemical potential per unit molal volume of water in a system and that of pure water at the same temperature and pressure. Water potential of pure water at normal temperature and pressure is zero.
Q18. The root system in a plant is well developed
- 1) Due to deficiency of cytokinins
- 2) For increased absorption of water
- 3) Due to deficiency of minerals
- 4) Due to deficiency of auxins
Water in land plants is mainly absorbed through the roots, especially at the tips in the region of root hair. Therefore, the root system in a plant is well developed for increasing absorption of water.
Q19. The process of penetration of ions of living cells from the surrounding through a selective membrane is called
- 1) Active transport
- 2) Absorption
- 3) Diffusion
- 4) Endosmosis
During absorption, the ions or molecules penetrate the inner space of the living cells or tissues from the surrounding medium through a selective membrane. The movement of dissolved substances into and out of cells is also called transport or flux.
Q22. What is translocation?
Translocation is the bulk movement of substances through vascular tissues of plants.
Q21. Name the element which cannot be remobilised.
Q22. Distinguish between osmosis and diffusion.
Osmosis Diffusion It is the movement of solute molecules across a concentration gradient. It is the movement of solvent molecules across the concentration gradient. It does not require any membrane. It occurs through a semipermeable membrane.
Q23. According to Munch’s hypothesis, when the plant is defoliated,
- 1) Negative concentration gradient disappears
- 2) Negative concentration gradient decreases
- 3) Positive concentration gradient increases
- 4) Positive concentration gradient disappears
According to Munch’s hypothesis, the positive concentration gradient disappears when the plant is defoliated.
Q24. When a cell is plasmolysed, it becomes
- 1) Flaccid and its TP becomes 0
- 2) Turgid and its TP becomes 0
- 3) Flaccid and its DPD becomes 0
- 4) Turgid and its TP becomes equal to OP
In plasmolysis, the pressure potential or the turgor pressure (TP) is zero, and the osmotic concentration of the cell interior is equal to that of the external solution, making the cell flaccid.
Q25. The process by which water is absorbed by solids such as colloids causing them to increase in volume is called
- 1) Imbibition
- 2) Plasmolysis
- 3) Diffusion
- 4) Osmosis
Imbibition is the absorption or adsorption of water by certain colloids, with resultant swelling of tissues as in seeds.
Q26. Absorption of diffusible ions by cells against the concentration gradient is called
- 1) Donnan equilibrium
- 2) Passive absorption
- 3) Active absorption
- 4) Osmosis
The absorption of cells against the concentration gradient is said to be active absorption.
Q27. Differentiate between simple diffusion and active transport.
Simple Diffusion Active Transport The movement of molecules is along the concentration gradient. The movement of molecules is against the concentration gradient. Energy is not required for the transport of substances. Energy is used in the form of ATP.
Q28. Passive absorption of water by the root system is the result of
- 1) Forces created in the cells of the root
- 2) Tension on the cell sap due to transpiration
- 3) Increased respiratory activity in root cells
- 4) Osmotic force in the shoot system
Passive absorption occurs when the rate of transpiration is usually high. It occurs due to the tension created on the xylem by transpirational pull.
Q29. Which of the following is not a purpose of transpiration?
- 1) Supplies water for photosynthesis
- 2) Prevents loss of water
- 3) Helps in absorption and transport in plants
- 4) Cools leaf surfaces
- 5) Maintains shape and structure of plants by keeping the cell turgid
Transpiration is necessary for (i) Transporting minerals from the soil to the plant parts (ii) Cooling the plant (iii) Moving sugars and plant chemicals (iv) Maintaining turgor pressure by keeping the cell turgid Transpiration is eventually the loss of water in the vapour form from the exposed parts of the plant which cannot be prevented.
Q30. Which one of the following will not directly affect transpiration?
- 1) Chlorophyll content of leaves
- 2) Wind speed
- 3) Temperature
- 4) Light
Chlorophyll content of leaves does not affect transpiration as it helps the plants during photosynthesis which is much required for transpiration.
Q31. Water reaches the top of a plant due to
- 1) Root pressure
- 2) Transpiration
- 3) Diffusion
- 4) Capillarity
Water reaches the top of a tree through capillary action due to the ascent of sap. This can be explained by the theory of root pressure which develops in the treachery elements of xylem due to the metabolic activities of roots. This pressure of water is known as root pressure which is responsible to raise water up to a certain height.
Q32. Stomata of CAM plants
- 1) Open during the day and close at night
- 2) Open during the night and close during the day
- 3) Are always open
- 4) Never open
Crassulacean acid metabolism (CAM) plants open stomata only at night, because at night, the temperature is low and the humidity is high, causing lesser loss of water. Examples: Agave, Opuntia
Q33. Of the total amount of water absorbed by the plant,
- 1) 5% is used by the plant and 95% is lost
- 2) 65% is used by the plant and 45% is lost
- 3) 45% is used by the plant and 65% is lost
- 4) 95% is used by the plant and 5% is lost
Of the total amount of water absorbed by the plant, 5% is used by the plant and 95% of the absorbed water is lost.
Q34. When is a solution called a hypertonic solution?
When the external solution is more concentrated than the content of the cytoplasm, a solution is called a hypertonic solution.
Q35. Consider the following statements about facilitated transport: (A) Requires ATP energy (B) Transport saturates (C) Highly selective (D) Requires special membrane, properties (E) Uphill transport Of the above statements,
- 1) C, D and E are relevant, but A and B are irrelevant.
- 2) B, C and D are relevant, but A and D are irrelevant.
- 3) B, C and E are relevant, but A and E are irrelevant.
- 4) A, B and C are relevant, but D and E are irrelevant.
- 5) A, D and E are relevant, but B and C are irrelevant.
Facilitated diffusion is specific as it allows the cell to select substances for uptake. It is sensitive to inhibitors, but there is no requirement of energy. Active transport is also called uphill transport.
Q36. Define isotonic solution.
When the external solution balances the osmotic pressure of the cytoplasm, the solution is called an isotonic solution.
Q37. Munch’s hypothesis failed to explain
- 1) Unidirectional movement of metabolites
- 2) Movement of growth hormones
- 3) Bidirectional movement of metabolites
- 4) Movement of viruses in the plant
Munch’s hypothesis failed to explain the bidirectional movement of metabolites in plants, which is most commonly observed.
Q38. In which region of the plant, the apoplast is absent?
Apoplast is absent in the casparian strip of the endodermis in the roots.
Q39. Cohesion-tension theory is related to
- 1) Transpiration
- 2) Ascent of sap
- 3) Photosynthesis
- 4) Respiration
Cohesion-tension theory is called Dixon’s theory of ascent of sap because it was put forward by Dixon and Jolly in 1894. This theory is based on the features of cohesion, adhesion and tension.
Q40. What is the effect of turgor pressure in Munch hypothesis?
- 1) Independent to water potential gradient
- 2) Increase of turgor pressure
- 3) Decrease of turgor pressure
- 4) No change in turgor pressure
Carbohydrates are synthesised in the mesophyll cells of leaves. Osmotic pressure of these cells is increased which then absorbs water from neighbouring cells leading to an increase in the turgor pressure.
Q41. Greater the concentration of the solute particles,
- 1) Closer the value of osmotic potential towards zero on the negative side
- 2) Greater the value of osmotic potential on the positive side
- 3) Closer the value of osmotic potential towards zero on the positive side
- 4) Greater the value of osmotic potential on the negative side
Greater the concentration of the solute particles, greater the value of osmotic potential on the negative side.
Q42. Which of the following is an example of imbibition?
- 1) Swelling of seed when put in soil
- 2) Exchange of gases in stomata
- 3) Uptake of water by root hair
- 4) Opening of stomata
Imbibition is the absorption or adsorption of water by certain colloids, with resultant swelling of the tissues as in seeds. Imbibition causes swelling of seeds when put in soil because when mature seeds are soaked in water at room temperature, they imbibe water and swell.
Q43. The cell wall of a root hair has two distinct layers, of this, the inner layer is made of
- 1) Chitin
- 2) Pectin
- 3) Lipids
- 4) Cellulose
The cell wall of a root hair has two distinct layers, of this, the inner layer is made of cellulose and the outer layer is made of pectic substances.
Q44. What is guttation?
When the rate of evaporation is low, at night or in the early morning, excess water gets collected in the form of droplets at the special openings of veins of leaves of many herbaceous plants. Such water loss in its liquid phase is called guttation.
Q45. The most widely accepted theory for ascent of sap in trees is
- 1) Transpirational pull and cohesion theory of Dixon and Jolly
- 2) Role of atmospheric pressure
- 3) Capillarity
- 4) Pulsating action of living cell
The transpirational pull and cohesion theory was put forward by Dixon and Jolly in 1894. According to this theory, water rises due to the transpiration pull, continuity of the water column and cohesive power of water molecules from the lower part of the roots to the higher peaks of the trees.
Q46. Which one of the following is not a characteristic of active transport?
- 1) Insensitive to inhibitors
- 2) Transport saturates
- 3) Highly selective
- 4) Uphill transport
The rate of active transport depends on the carrier proteins which are highly specific like enzymes. They are sensitive to inhibitors which react with protein side chains.
Q47. Define the following with respect to plants: Source Sink
Source – It is a part of the plant which synthesises food. Sink – The parts of the plant which require food or store food.
Q48. Which of the following statements does not apply to reverse osmosis?
- 1) It is a passive process.
- 2) It is used for water purification.
- 3) In this technique, pressure greater than osmotic pressure is applied to the system.
- 4) It is an active process.
Reverse osmosis is the expulsion of pure water from a solution through a semipermeable membrane with a higher osmotic pressure. It is used for the purification of water, and it is an active process which requires energy. A passive process is any process which occurs without an input of energy. Diffusion is the process of a substance moving from an area of high concentration to an area of low concentration in order to obtain equilibrium.
Q49. Choose the correct option: Mycorrhiza is a symbiotic association of fungus with root system which helps in (A) Absorption of water (B) Mineral nutrition (C) Translocation (D) Gaseous exchange Options:
- 1) Only A
- 2) Both A and B
- 3) Only B
- 4) Both B and C
Mycorrhiza is a mutualistic symbiosis between the root system of higher plants and fungal hyphae. It increases the surface area for absorption of minerals and water.
Q50. Main function of lenticels is
- 1) Transpiration
- 2) Guttation
- 3) Gaseous exchange
- 4) Bleeding
The primary function of lenticels is gaseous exchange. Transpiration takes place mostly through stomata. Guttation and bleeding occur through hydathodes.
Q51. Which of the following is impermeable?
- 1) Cuticle
- 2) Plasma membrane
- 3) Cellophane
- 4) Cell wall
The cuticle is impermeable, cellophane and the plasma membrane are semi-permeable, and the cell wall is permeable.
Q52. During the process of respiration, the movement of CO2 and O2 out and inside the cell is achieved by
- 1) Active transport
- 2) Both active and facilitated diffusion
- 3) Facilitated diffusion
- 4) Independent diffusion
The inside and outside movement of CO2 and O2 during respiration and photosynthesis is achieved by independent diffusion.
Q53. Lenticels are found in
- 1) Yellow leaves
- 2) Young leaves
- 3) Fruits
- 4) Flowers
Lenticels are found in fruits and woody cells and help in transpiration and gaseous exchange.
Q54. The rate of transpiration of a plant would gradually increase if
- 1) Relative humidity decreases
- 2) Relative humidity remains unchanged
- 3) Relative humidity increases
- 4) Water potential gradient remains unchanged
The rate of transpiration is inversely proportional to relative humidity which means that the rate of transpiration is higher when the relative humidity is lower and vice versa.
Q55. Explain the mechanism of the pressure flow hypothesis.
When glucose is prepared at the source by photosynthesis, it is converted into sucrose. Sucrose is then transported into the companion cells and then into the phloem sieve tube cells by active transport. This is called loading of the source. Loading creates a hypertonic condition in the phloem due to which water from the adjacent xylem cells moves into the phloem by osmosis. As the osmotic or hydrostatic pressure builds up inside the phloem, the sap moves to the surrounding areas of the lower osmotic pressure, i.e. the sink. As the sucrose moves into the sink, the water potential in the phloem increases which again moves water into the xylem.
Q56. Guard cells help in
- 1) Protection against grazing
- 2) Fighting against infection
- 3) Transpiration
- 4) Guttation
Guard cells help in transpiration. Transpiration is the evaporation of water from the aerial parts of plants, especially leaves, but also stems, flowers and roots. The stomatal opening facilitated by guard cells allows the diffusion of carbon dioxide and oxygen during photosynthesis.
Q57. The cells of the cortex of the xylem tissue are connected by means of
- 1) Antiporter channels
- 2) Casparian strips
- 3) Plasmodesmata
- 4) Symporter channels
The cells of the cortex of the xylem are living cells and the cell walls of these cells are connected to each other by means of plasmodesmata.
Q58. Veins in the leaves are useful for
- 1) All of the above
- 2) Transport of water and minerals
- 3) Mechanical support
- 4) Transport of organic food material
Leaves have veins for the support of the leaf blade and for transport of food and water in the leaf. In most leaves, the veins form a netlike pattern, with several large veins connected by smaller ones which supply every part of the blade with water.
Q59. Compare the statements A and B. Statement A: To counteract the increase in turgor pressure in plant cells, the cell wall produces an equal and opposite pressure, i.e. wall pressure. Statement B: When plant cells undergo endosmosis, they swell but do not burst.
- 1) Both statements A and B are correct, and A is not the reason for B.
- 2) Both statements A and B are correct, and A is the reason for B.
- 3) Statement A is correct and B is wrong.
- 4) Statement A is wrong and B is correct.
When water enters the living cell, a pressure is developed within the cell due to turgidity. The hydrostatic pressure developed inside the cell on the cell wall due to endosmosis is called turgor pressure. When the wall pressure equals the turgor pressure, the entry of water into the cell stops. Therefore, the cell wall does not burst and the cells swell.
Q60. Define uphill transport.
Uphill transport is the transport of substances from their low concentration to their high concentration.
Q61. An increase in temperature increases the rate of diffusion because
- 1) The kinetic energy of the molecules increases
- 2) The molecules try to move to a region of lower temperature
- 3) The space between the molecules increases
- 4) All of the above
With an increase in temperature, the rate of diffusion increases as the kinetic energy of the diffusing molecules increases.
Q62. The hydathode helps in
- 1) Photosynthesis
- 2) Transpiration
- 3) Guttation
- 4) Respiration
Hydathodes are usually found on the margins and tips of leaves. So, the excretion of water is due to the development of a positive pressure in the xylem present in the vein ending. The pressure forces the liquid out through the hydathode which is called guttation.
Q63. The total amount of water in the soil available for the plant is called
- 1) Golard
- 2) Chresard
- 3) Echard
- 4) Holard
In the soil, the total amount of water present is called holard, the total amount available to the plant is called chresard and the water which cannot be absorbed by the plant is called echard.
Q64. Who gave the idea that energy released during respiration is responsible for absorption of water?
- 1) B. S. Meyer
- 2) Priestley
- 3) Kramer
- 4) Thimann
Thimann observed that absorption rate and respiration rate are closely related which gave the idea that energy released during respiration is responsible for absorption of water.
Q65. Name the two pathways by which water is moved when absorbed by the roots.
Pathways by which water is moved when absorbed by the roots are Apoplast pathway Symplast pathway
Q66. Potometer works on the principle of
- 1) Amount of water absorbed equals to the amount transpired
- 2) Root pressure
- 3) Potential difference between the tip of the tube and that of the plant
- 4) Osmotic pressure
A potometer is a device used to measure the rate of transpiration, or the rate of loss of water, from the leaves of a plant. A potometer experiment can be performed for measuring the amount of water lost per unit time when different environmental aspects are varied. Plants when exposed to variations in the environmental conditions will transpire at different rates from those at normal room conditions.
Q67. Cohesion and adhesion theory is otherwise called
- 1) Pulsation theory
- 2) Transpiration pull theory
- 3) Relay pump theory
- 4) Root pressure theory
The upward movement of water is mainly due to the creation of a negative force or tension attributed to the continuous evaporation of water at the surfaces of leaves in the process of transpiration. As molecule after molecule of water evaporates through the stomata, it creates a pulling action on the next molecule of water in the transpiration stream. This pulling force, otherwise called transpiration pull, is strong enough to overcome the force of gravity which is responsible for the tendency of water to move downward.
Q68. Distinguish between hypertonic and isotonic solutions.
Hypertonic Solution Isotonic Solution The solution does not balance the osmotic pressure of the cell, because its water potential is lesser than the cytoplasm of the cell. The solution balances the osmotic pressure of the cell. There is a flow of water outside the cell, and the cell shrinks. There is no net flow of water inside or outside, and the cell remains flaccid.
Q69. Water potential is expressed in terms of pressure units, one of which is bar. 1 bar is equal to
- 1) 750 mmHg
- 2) 250 mmHg
- 3) 25 mmHg
- 4) 75 mmHg
1 bar = 750 mmHg
Q70. Transport saturation does not occur in
- 1) Both facilitated diffusion and active transport
- 2) Active transport
- 3) Simple diffusion
- 4) Facilitated diffusion
In simple diffusion, saturation of diffusion does not occur.
Q71. Which of the following substances is found as a coating on leaves of certain plants?
- 1) Resin
- 2) All of the above
- 3) Wax
- 4) Suberin
Wax, suberin and resin are some of the substances which occur as leaf coating.
Q72. Which of the following statements are true? (A) The apoplastic movement of water occurs exclusively through the cell wall without crossing any membranes. (B) Solutes present in a cell (or in any solution) increase the free energy of water or water potential. (C) The symplastic movement occurs from cell to cell through the plasmodesmata. (D) Membrane permeability depends on membrane composition and the chemical nature of the solute.
- 1) B and D only
- 2) A, B and D only
- 3) A and B only
- 4) A, C and D only
Adding solutes can only decrease water’s free energy because water molecules interact with solute molecules and cannot diffuse easily.
Q73. Guttation is the result of
- 1) Diffusion
- 2) Transpiration
- 3) Osmosis
- 4) Root pressure
Guttation usually occurs during periods of active growth when conditions favour more water absorption and less transpiration. Due to the high root pressure, water is forced out into the intercellular space and flows out of the hydathodes.
Q74. Movement of H20 through the cell wall is
- 1) Apoplast
- 2) Tonoplast
- 3) Symplast
- 4) None of the above
The passing of water from root hair to xylem through the walls of intervening cells without crossing any membrane or cytoplasm is called the apoplast pathway.
Q75. State the rate of the upward flow of water in the xylem of plants.
The rate of the upward flow of water in the xylem of plants is 15 metres per hour.
Q76. Which one is an incorrect statement?
- 1) Water potential of pure water is zero.
- 2) Movement of water is expressed in terms of free energy.
- 3) Water potential is the sum of free energy of water molecules in pure water and in any other system.
- 4) Free energy determines the direction by which physical and chemical changes should occur.
The free energy of water is the movement of water molecules in a system. The movement of water molecules determines the free energy, which in turn signifies the physical and chemical changes. The water potential of pure water at normal temperature and pressure is zero. The water potential is the total of solute potential, matric potential and pressure potential of pure water.
Q77. In facilitated diffusion, the channels which regulate the transport of water are made of
- 1) Porins
- 2) Aqua channels
- 3) Aquaporins
- 4) Water channels
In facilitated diffusion, the channels which regulate the transport of water are made of 8 aquaporins.
Q78. Select the correct statement:
- 1) The translocation in phloem is unidirectional, whereas it is bidirectional in the xylem.
- 2) The apoplast is a system of interconnected protoplasts.
- 3) Pinus seeds cannot germinate and establish without the presence of mycorrhizae.
- 4) Absorption of water by seeds and dry wood is an example of facilitated diffusion.
Pinus has obligate association with mycorrhizae. The Pinus seeds germinate only when they get associated with mycorrhizae.
Q79. Phloem sap is mainly made of
- 1) Water and sucrose
- 2) None of the above
- 3) Water and minerals
- 4) Oligosaccharides and hormones
In the phloem sap, water and sucrose are carried throughout the parts of the plant by the vascular system.
Q80. What kinds of substances are transported by facilitated diffusion?
Substances which are hydrophilic and cannot pass through the plasma membrane easily are transported by facilitated diffusion.
Q81. Which of the following is a hydrophilic substance?
- 1) Methane
- 2) Grease
- 3) Wax
- 4) Silica
Silica is a hydrophilic substance, while the rest are hydrophobic in nature.
Q82. The rate at which solutes move in translocation is about
- 1) 100 cm/hr
- 2) 200 cm/hr
- 3) 100 m/hr
- 4) 200 m/hr
The rate at which solutes move in translocation is about 100 cm/hr.
Q83. Differentiate between hypotonic and hypertonic solutions.
Hypotonic Solution Hypertonic Solution It has more water potential than the cytoplasm of the cell. It has less water potential than the cytoplasm of the cell. When the cell is kept in a hypotonic solution, the cell becomes turgid. When the cell is kept in a hypertonic solution, the cell shrinks.
Q84. In plants, there is a complex traffic of compounds. Justify.
In plants, water and minerals are transported in one direction from the roots to the stems or the growing regions in the upward direction through the xylem. Organic compounds formed during photosynthesis are exported from leaves to other parts of the plants including storage organs. From the storage organs, the organic compounds are later re-exported. This means the organic compounds are transported in different directions. When a plant undergoes senescence, nutrients are withdrawn from the part of the plant undergoing senescence and are moved to growing parts. Growth regulators are also transported sometimes either in one direction, i.e. from the region where they are synthesised to the parts of plants where they are required. There are many substances which are constantly transported in different directions at a time in plants. Hence, it can be said that in plants, there is a complex traffic of compounds.
Q85. Define imbibition. State the prerequisite factors for imbibition to occur.
Imbibition is a type of diffusion where water is absorbed by solids or colloids and results in an increase in their volume. Prerequisites for imbibition are The water potential gradient between the adsorbent and the liquid to be imbibed. Affinity between the adsorbent and the liquid.
Q86. Which theory did Crafts elaborate on?
- 1) Activated diffusion theory
- 2) Munch’s hypothesis
- 3) Diffusion hypothesis
- 4) Electro-osmotic theory
Munch proposed the mass flow theory (Munch’s theory) in 1930, which Crafts elaborated on in 1938.
Q87. When a molecule moves across a membrane independent of other molecules, the process is called
- 1) Antiport
- 2) Uniport
- 3) Symport
- 4) Cotransport
Movement of a molecule across a membrane independent of other molecules is called uniport.
Q88. The instrument used for measuring the rate of transpiration is
- 1) Photometer
- 2) Lactometer
- 3) Potometer
- 4) Porometer
A potometer is a device used to measure the rate of transpiration or the rate of loss of water from the leaves of a plant.
Q89. Who among the following experimentally demonstrated that tension develops in the xylem during rapid transpiration?
- 1) Munch
- 2) Casper
- 3) Priestley
- 4) Scholander
Scholander demonstrated that tension develops in the xylem during rapid transpiration.
Q90. Name the elements which are easily remobilised in plants.
Elements which are easily remobilised in plants are phosphorus, sulphur, nitrogen and potassium.
Q91. Explain the three physical properties of water which help in the ascent of sap in plants.
Properties of water which help in the movement of ascent of sap are as follows: Mutual attraction between water molecules. This property is called cohesion. Attraction of water molecules to polar surfaces such as the surface of tracheary elements. This attraction is also called adhesion. Water molecules are attracted to each other more in the liquid phase than in the gas phase. This property is called the surface tension of water. All the above properties help to form a continuous passage of water molecules in the xylem which moves upwards due to the transpiration pull.
Q92. A cell when dipped in 0.5 M sucrose solution has no effect, but when the same cell is dipped in 0.5 M NaCl solution, the cell will
- 1) Will be turgid
- 2) Increase in size
- 3) Decrease in size
- 4) Will be plasmolysed
A hypertonic solution such as sucrose causes exosmosis or withdrawal of water from the cytoplasm. The pressure on the wall is simultaneously reduced and the elastic wall contracts causing a reduction in cell size which is called plasmolysis.
Q93. Describe the structure of guard cells.
Guard cells are two bean-shaped cells present on either side of the stomatal aperture. The inner walls of the guard cells are thick and elastic, while the outer walls are thin. Cellulose microfibrils are present in guard cells. These fibrils are arranged radially. Change in the turgidity of guard cells and radial orientation of cellulose microfibrils control the opening and closing of stomata.
Q94. The most widely accepted theory for the mechanism of phloem translocation is
- 1) Interfacial flow hypothesis
- 2) Electro-osmotic theory
- 3) Mass flow hypothesis
- 4) Diffusion hypothesis
The most widely accepted theory for mechanism of phloem translocation is Munch’s mass flow hypothesis.
Q95. Munch hypothesis is based on
- 1) Translocation of food due to imbibition force
- 2) Translocation of food due to turgor pressure gradient
- 3) None of the above
- 4) Translocation of food due to turgor pressure gradient and imbibition force
The movement of sugars in the phloem begins at the source where sugars are loaded (actively transported) into a sieve tube. Movement occurs by bulk flow (mass flow); phloem sap moves from sugar sources to sugar sinks by turgor pressure, also known as hydrostatic pressure.
Q96. What are control proteins?
Control proteins are transport proteins of endodermal cells at which plants adjust the quantity and type of solutes which reach the xylem.
Q97. Which of the following statements are true/false? a. The positive hydrostatic pressure is called turgor pressure. b. Wall pressure is exerted to prevent the increase of protoplasm size. c. Diffusion is more rapid in liquids than in gases. d. Diffusion of water through a semi-permeable membrane is called imbibition. e. Osmosis is the movement of substances which occurs along a diffusion gradient.
- 1) a and d are true, and b, c and e are false.
- 2) a and c are true, and b, d and e are false.
- 3) c, d and e are true, and a and b are false.
- 4) a and b are true, and c, d and e are false.
- 5) a and e are true, and b, c and d are false.
a. Turgor pressure is the water pressure of the cell vacuole pushing against the cell wall. b. As turgor pressure exerts its impact on to the cell wall, the cell wall, being plastic, exerts a counter pressure which is called wall pressure which prevents an increase of protoplasm size. c. Diffusion depends on the number of particles per unit volume, density of medium, temperature and pressure. Therefore, gases diffuse more rapidly than liquids. d. The absorption or adsorption of water by certain colloids, as in seeds, with resultant swelling of the tissues is called imbibition. e. Osmosis is a type of diffusion of water which occurs through a semi-permeable membrane.
Q98. In a girdled plant, which part dies first?
- 1) Leaves
- 2) Stem
- 3) Roots
- 4) Phloem
In a girdled plant, the roots die first. This is because the xylem of the plant transports water and minerals from the soil to the upper part of the plant. However, because of the absence of phloem, there is no transport of food to the lower part of the plant, resulting in its death.
Q99. Give two examples of imbibition.
Two examples of imbibition are as follows: Absorption of water by seed and Absorption of water by dry wood
Q100. The rate of diffusion will be less in
- 1) Concentrated solution
- 2) Dilute solution
- 3) Neutral solution
- 4) Rate of diffusion is not affected by the concentration of solution
The rate of diffusion will be less in a concentrated solution.
Q101. The root pressure theory was proposed by
- 1) None of the above
- 2) Dixon
- 3) Priestley
- 4) Joly
Priestley proposed the root pressure theory in 1916.
Q102. The pressure flow hypothesis was proposed by
- 1) Munch
- 2) Sayer
- 3) Crafts
- 4) Steward
The pressure flow hypothesis or the mass flow theory was first proposed by Munch in 1930 and was elaborated by Crafts in 1938.
Q103. Why is imbibition said to be a type of diffusion?
During imbibition, the movement of water occurs along the concentration gradient; hence, it is said to be a type of diffusion.
Q104. What is a flaccid cell?
When the water moves into the cell and out of the cell, and the cell is in equilibrium, it is called a flaccid cell.
Q105. Differentiate between symplast and apoplast.
Symplast Apoplast Movement occurs through cell walls and intercellular spaces. Movement occurs through the cytoplasm and plasmodesmata by cutting the plasma membrane. Water movement is faster. Water movement is slower.
Q106. Define root pressure.
When different ions are transported actively from the soil to root hair, water follows a potential gradient, i.e. moves from its higher potential region (soil) to its lower potential region (root tissues). This increases a positive pressure inside the roots called root pressure.
Q107. Munch hypothesis is based on
- 1) Translocation of organic solutes
- 2) Translocation of food due to imbibition force
- 3) Translocation of food due to turgor pressure gradient and imbibition force
- 4) Translocation of food due to turgor pressure gradient
Munch hypothesis is a mass flow or pressure flow hypothesis in which the organic substances move from the region of high osmotic pressure to the region of low osmotic pressure in a mass flow due to the development of a gradient of turgor pressure.
Q108. Write the external factors which affect the rate of transpiration.
External factors which affect the rate of transpiration are Temperature Light Humidity Wind speed
Q109. How much water can a mature plant absorb in a day?
A mature plant can absorb 3 litres of water in a day.
Q110. Water in the soil available to plants is
- 1) Hygroscopic water
- 2) Gravitational water
- 3) Capillary water
- 4) None of the above
The water present in narrow soil spaces is called capillary water, which is available to plant roots for absorption.
Q111. Define the following terms about water: Capillarity Tensile strength
Capillarity – It is the ability of water molecules to rise in thin tubes. Tensile strength – It is the ability of water molecules to resist a pulling force.
Q112. When a cell was kept in a solution, its solute potential decreased. Identify the type of solution in which the cell was kept?
The cell was kept in a hypotonic solution.
Q113. Define plasmolysis.
Plasmolysis is the process in which the water moves out of the plant cell, and the cell membrane shrinks away from the cell wall.
Q114. Differentiate between simple diffusion and facilitated diffusion.
Simple Diffusion Facilitated Diffusion Carrier proteins are not involved in the transport of substances. Carrier proteins help in the transport of substances across the membranes. Non-polar substances are easily transported. Polar substances are transported across the membrane.
Q115. Define osmosis.
Osmosis is the diffusion of water molecules across a semipermeable membrane from the region of higher chemical potential to the region of lower chemical potential until its equilibrium is reached.
Q116. Which of the following chemical serves as an antitranspirant in plants?
- 1) Potassium iodide
- 2) Phenyl mercuric acetate
- 3) Dimethyl mercury
- 4) Cobalt chloride
Substances which reduce the rate of transpiration are called antitranspirants. The most used transpirant is phenyl mercuric acetate (PMA). PMA increases the leaf resistance to water vapour diffusion without affecting carbon dioxide uptake.
Q117. Which one of the following theories for ascent of sap was proposed by the eminent Indian scientist J. C. Bose?
- 1) Relay pump theory
- 2) Transpiration pull theory
- 3) Root pressure theory
- 4) Pulsation theory
The theory of ascent of sap was put forward by J. C. Bose in 1923 which is called the vital force theory or pulsation theory. The theory says that the innermost cortical cells of the root absorb water from the outer side and pump the same into xylem channels.
Q118. State the factors which regulate the opening and closing of stomata.
Factors which regulate the opening and closing of stomata are as follows: Change in the turgidity of guard cells. Radially arranged cellulose microfibrils in the walls of the guard cells.
Q119. State the names of two components which determine the water potential.
The components which determine the water potential are as follows: Solute potential and Pressure potential
Q120. State the factors which affect the rate of diffusion.
Factors affecting the rate of diffusion are as follows: Concentration gradient Permeability of the membrane Temperature Pressure
Q121. Which material can be easily diffused across the cell membrane?
- 1) Proteins
- 2) Glucose
- 3) Lipid-soluble substances
- 4) Hydrophilic substances
Lipid-soluble substances or lipophilic substances can easily pass through the cell membrane as lipids form the major component of the cell membrane.
Q122. A raisin was a kept in a bowl containing a solution for two hours. After two hours, there was increase in the volume and size of the raisin. Identify the type of solution in which the raisin was placed.
Because the raisin swelled up after two hours, it was kept in a hypotonic solution.
Q123. Define turgor pressure. How is it useful for plants?
Turgor pressure is the pressure exerted by the protoplast against the rigid cell wall due to the entry of water. Turgor pressure helps plants in enlargement and extension growth of cells.
Q124. Define osmotic pressure.
Osmotic pressure is the pressure developed by the solute molecules to prevent the inward diffusion of water molecules or solvent molecules.
Q125. How much water can a mustard plant absorb in 5 hours?
A mustard plant can absorb water equal to its own weight in five hours.
Q126. Transpiration supplies water for photosynthesis. Justify.
The concentration of water vapour in the atmosphere is lower than that in the stomata and intercellular spaces. This results in the loss of water to the surrounding air. When water evaporates through the stomata, it results in the pulling of water, molecule by molecule, from the xylem into the leaf, thus making water available for plant cells which can be used for photosynthesis.
Q127. Which does not pertain to facilitated transport?
- 1) Requirement of special membrane
- 2) Uphill transport
- 3) High selectivity
- 4) Transport saturation
Facilitated transport is the transport of substances along the concentration gradient through fixed membrane transport proteins without involving energy expenditure, but it is not uphill transport. It is otherwise called active transport which employs ATP energy for transport across the membrane.
Q128. All the minerals cannot be passively absorbed by the roots. Justify.
Minerals are present in the soil as charged particles which cannot move across the cell membranes. The concentration of minerals in the soil is usually lower than the concentration of minerals in the root. Hence, all the minerals cannot be passively absorbed by the roots.
Q129. Explain the movement of water by apoplast and symplast in roots to reach vascular bundles.
Due to loosely packed cortical cells, the water in root hair cells is transported by apoplasts. The inner boundary of roots contains casparian strips in the endodermis. These strips are impermeable to water. Hence, water is redirected to the cells through regions where casparian bands are absent. The water then moves through symplasts, i.e. through interconnected protoplasts of the cells to reach the xylem.
Q130. In the senescence stage of a plant, the rate of transpiration is
- 1) Low
- 2) High
- 3) Zero
- 4) Unchanged
The rate of transpiration reduces in the senescence stage.
Q131. Name the plant which establishes a symbiotic relationship with mycorrhizae.
Pinus establishes a symbiotic relationship with mycorrhizae.
Q132. Name the plant tissue system responsible for carrying out long-distance transport of substances in plants.
The vascular plant tissue system is responsible for carrying out long-distance transport of substances in plants.
Q133. The pathway of the movement of water through the cell wall only is called
- 1) Apoplast pathway
- 2) Symplast pathway
- 3) Plasmodesmata pathway
- 4) Vacuolar pathway
The passing of water from root hair to xylem through the walls of intervening cells without crossing any membrane or cytoplasm is called the apoplast pathway.
Q134. State the relation between the concentration of water in a system and its kinetic energy.
Greater the concentration of water in a system, higher is its kinetic energy.
Q135. Define imbibition.
Imbibition is a type of diffusion where water is absorbed by solids or colloids and results in an increase in their volume.
Q136. The form of sugar transported through the phloem is
- 1) Fructose
- 2) Glucose
- 3) Ribose
- 4) Sucrose
Sucrose, which is formed by the plant during photosynthesis, is a sugar transported through the phloem of the plant.
Q137. In what way is transpiration significant for plants?
Significance of transpiration: It creates a water column in the xylem and thus makes the water available for photosynthesis. It creates the transpiration pull required for absorption and transportation in plants. It cools the leaf surfaces by evaporation of water through stomata. The shape and structure of plants are maintained as transpiration keeps the cells turgid. Transports minerals from the soil to all parts of the plant.
Q138. Name the component of the plant cell which prevents the cell from rupturing when kept in a hypotonic solution.
The cell wall prevents the cell from rupturing when kept in a hypotonic solution.
Q139. State the unit used to measure the water potential.
The unit which is used to measure the water potential is pascal (Pa).
Q140. Name the protein which forms huge pores in the outer membranes of mitochondria.
Q141. Write any one similarity found between enzymes and carrier proteins.
Like enzymes, carrier proteins carry specific substances across the cell membrane. Carrier proteins are sensitive to inhibitors. (Write any one similarity)
Q142. Write two similarities between diffusion and facilitated diffusion.
Both are passive transport processes and do not require energy. The movement of substances occurs along the concentration gradient, i.e. from higher concentration to lower concentration.
Q143. Properties of substances affect the rate of their diffusion. Justify.
The size of substances affects the rate of diffusion. Small molecular size substances diffuse faster than large molecular size substances. Substances which are soluble in lipids are transported faster across the plasma membrane. Substances which are hydrophilic need carrier proteins for their transport across the cell membrane.
Q144. State the difference between diffusion and imbibition.
Diffusion Imbibition It is the movement of solutes, solids or gaseous along the concentration gradient. It is the movement of water molecules along the concentration gradient. Adsorbent is not involved. Adsorbent is involved.
Q145. What will happen to the pressure potential of the cell if it is kept in a hypotonic solution?
If the cell is kept in a hypotonic solution, then the pressure potential inside the cell will increase.
Q146. Differentiate between hypotonic and isotonic solutions.
Hypotonic Solution Isotonic Solution The solution does not balance the osmotic pressure of the cell, because its water potential is greater than the cytoplasm of the cell. The solution balances the osmotic pressure of the cell. There is a flow of water inside the cell, and the cell swells up. There is no net flow of water inside or outside, and the cell remains flaccid.
Q147. Name the process by which unloading of minerals occurs in plant cells.
The process by which unloading of minerals occurs by plant cells is through diffusion.
Q148. How does turgidity of guard cells help stomata to open or close?
When the turgidity inside the guard cells increases, the outer thick walls of the guard cells bulge out. This creates a force on the inner walls of the guard cells and they become crescent shape resulting in the opening of stomata. When the guard cells lose their turgor due to water loss, the inner walls gain their original size. The guard cells become flaccid resulting in the closing of the stomata.
Q149. The direction of movement of food in the phloem can be bidirectional. Justify.
Usually, the source is the part of a plant where food is synthesised and the sink is the part of the plant where the food is required or stored. However, it can be reversed, especially during seasonal changes or according to the plant’s need. In the early spring, sugar stored in the roots is sometimes used and acts as a source, and the buds of trees which need energy for growth and development of the photosynthetic apparatus act as a sink. Hence, the source-sink relationship is variable in plants, and the direction of movement of food in the phloem is bidirectional.
Q150. What is apoplast?
Apoplast is the system in which adjacent cell walls are continuous except at the casparian strips of the endodermis in the roots.
Q151. State the characteristic features of transport proteins.
Characteristics of transport proteins are as follows: They are selective and specific to the substances, i.e. each protein will carry only a specific substance across the membrane. They are liable to saturate. They respond to inhibitors. Their actions are controlled by hormones.