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Q1. Munch hypothesis is based on

• Translocation of food due to turgor pressure gradient and imbibition force
• Translocation of food due to turgor pressure gradient
• Translocation of food due to imbibition force
• Translocation of organic solutes

Solution

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.

Q2. In the senescence stage of a plant, the rate of transpiration is

• High
• Low
• Unchanged
• Zero

Solution

The rate of transpiration reduces in the senescence stage.

Q3. Munch hypothesis is based on

• Translocation of food due to turgor pressure gradient and imbibition force
• Translocation of food due to turgor pressure gradient
• Translocation of food due to imbibition force
• None of the above

Solution

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.

Q4. Which of the following is impermeable?

• Cell wall
• Plasma membrane
• Cuticle
• Cellophane

Solution

The cuticle is impermeable, cellophane and the plasma membrane are semi-permeable, and the cell wall is permeable.

Q5. Cell A has an osmotic potential of −18 bars and a pressure potential of 8 bars, whereas cell B has an osmotic potential of −14 bars and a pressure potential of 2 bars. The direction of flow of water will be  

• From cell B to cell A  
• From cell A to cell B  
• No flow of     water  
• In both the directions  

Solution

In cell A,   In cell B,   So, water moves from a higher concentration to a lower concentration, i.e. from cell A to cell B.  

Q6. The root system in a plant is well developed

• Due to deficiency of auxins
• Due to deficiency of cytokinins
• Due to deficiency of minerals
• For increased absorption of water

Solution

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.

Q7. The most widely accepted theory for the mechanism of phloem translocation is

• Mass flow hypothesis
• Diffusion hypothesis
• Electro-osmotic theory
• Interfacial flow hypothesis

Solution

The most widely accepted theory for mechanism of phloem translocation is Munch’s mass flow hypothesis.

Q8. Lenticels are found in

• Young leaves
• Fruits
• Flowers
• Yellow leaves

Solution

Lenticels are found in fruits and woody cells and help in transpiration and gaseous exchange.

Q9. Passive absorption of water by the root system is the result of  

• Forces created in the cells of the root  
• Increased respiratory activity in root cells  
• Tension on the cell sap due to transpiration  
• Osmotic force in the shoot system  

Solution

Passive absorption occurs when the rate of transpiration is usually high. It occurs due to the tension created on the xylem by transpirational pull.  

Q10. The rate of transpiration will be less in a situation where

• Groundwater is sufficiently available.
• Wind is blowing.
• Environment is hot and dry.
• Relative humidity is high.

Solution

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.

Q11. 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  

• Increase in size  
• Decrease in size  
• Will be turgid  
• Will be plasmolysed  

Solution

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.  

Q12. The form of sugar transported through the phloem is

• Glucose
• Fructose
• Sucrose
• Ribose

Solution

Sucrose, which is formed by the plant during photosynthesis, is a sugar transported through the phloem of the plant.

Q13. When a cell is plasmolysed, it becomes  

• Flaccid and its TP becomes 0  
• Turgid and its TP becomes 0  
• Turgid and its TP becomes equal to OP  
• Flaccid and its DPD becomes 0  

Solution

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.  

Q14. Which one is an incorrect statement?  

• Movement of water is expressed in terms of free energy.  
• Free energy determines the direction by which physical and chemical changes should occur.  
• Water potential is the sum of free energy of water molecules in pure water and in any other system.  
• Water potential of pure water is zero.  

Solution

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.  

Q15. Water is released as droplets. This is known as  

• Root pressure  
• Transpiration  
• Guttation  
• Bleeding  

Solution

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.  

Q16. The rate of transpiration of a plant would gradually increase if

• Relative humidity increases
• Relative humidity decreases
• Relative humidity remains unchanged
• Water potential gradient remains unchanged

Solution

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.

Q17. Which one of the following will not directly affect transpiration?

• Temperature
• Light
• Wind speed
• Chlorophyll content of leaves

Solution

Chlorophyll content of leaves does not affect transpiration as it helps the plants during photosynthesis which is much required for transpiration.

Q18. Which of the following is not true about osmosis?

• It occurs through a selectively permeable membrane.
• It occurs in liquids and gases.
• It is a special type of diffusion.
• Only the solvent molecules move from a region of low concentration to high concentration.

Solution

Osmosis does not occur in any other medium except liquids.

Q19. Greater the concentration of the solute particles,

• Greater the value of osmotic potential on the negative side
• Greater the value of osmotic potential on the positive side
• Closer the value of osmotic potential towards zero on the negative side
• Closer the value of osmotic potential towards zero on the positive side

Solution

Greater the concentration of the solute particles, greater the value of osmotic potential on the negative side.

Q20. The process of penetration of ions of living cells from the surrounding through a selective membrane is called

• Absorption
• Endosmosis
• Diffusion
• Active transport

Solution

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.

Q21. The hydathode helps in

• Transpiration
• Guttation
• Photosynthesis
• Respiration

Solution

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.

Q22. Which of the following is a hydrophilic substance?

• Wax
• Methane
• Silica
• Grease

Solution

Silica is a hydrophilic substance, while the rest are hydrophobic in nature.

Q23. Water reaches the top of a plant due to

• Root pressure
• Capillarity
• Transpiration
• Diffusion

Solution

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.

Q24. Main function of lenticels is

• Transpiration
• Guttation
• Gaseous exchange
• Bleeding

Solution

The primary function of lenticels is gaseous exchange. Transpiration takes place mostly through stomata. Guttation and bleeding occur through hydathodes.

Q25. 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.  

• a and b are true, and c, d and e are false.  
• a and c are true, and b, d and e are false.  
• a and d are true, and b, c and e are false.  
• a and e are true, and b, c and d are false.  
• c, d and e are true, and a and b are false.  

Solution

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.   

Q26. The rate at which solutes move in translocation is about

• 100 m/hr
• 200 m/hr
• 100 cm/hr
• 200 cm/hr

Solution

The rate at which solutes move in translocation is about 100 cm/hr.

Q27. 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.  

• A and B only  
• B and D only  
• A, C and D only  
• A, B and D only  

Solution

Adding solutes can only decrease water’s free energy because water molecules interact with solute molecules and cannot diffuse easily.  

Q28. Cohesion and adhesion theory is otherwise called  

• Relay pump theory  
• Pulsation theory  
• Root pressure theory  
• Transpiration pull theory  

Solution

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.  

Q29. Water in the soil available to plants is

• Gravitational water
• Capillary water
• Hygroscopic water
• None of the above

Solution

The water present in narrow soil spaces is called capillary water, which is available to plant roots for absorption.

Q30. Water potential is expressed in

• Newton
• N/m²
• Pascal
• Pascal²

Solution

The water potential is expressed in Pascal.

Q31. Which one of the following theories for ascent of sap was proposed by the eminent Indian scientist J. C. Bose?  

• Pulsation theory  
• Relay pump theory  
• Transpiration pull theory  
• Root pressure theory  

Solution

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.  

Q32. Which form of carbon was used in isotopic studies to determine the role of phloem in the transport of food through the plant?

• ¹²C₂
• ¹³C₂
• ¹⁴C₂
• ¹⁵C₂

Solution

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.

Q33. In a girdled plant, which part dies first?

• Leaves
• Stem
• Roots
• Phloem

Solution

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.

Q34. The cell wall of a root hair has two distinct layers, of this, the inner layer is made of

• Pectin
• Cellulose
• Chitin
• Lipids

Solution

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.

Q35. Which of the following statements does not apply to reverse osmosis?  

• It is used for water purification.  
• In this technique, pressure greater than osmotic pressure is applied to the system.  
• It is a passive process.  
• It is an active process.  

Solution

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.  

Q36. The cells of the cortex of the xylem tissue are connected by means of

• Casparian strips
• Plasmodesmata
• Antiporter channels
• Symporter channels

Solution

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.

Q37. The main significance of facilitated diffusion is  

• Absorption of mineral ions by plant roots  
• Excretion of urea and hydrogen ions by mammalian kidneys  
• Absorption of fructose and nucleotides in the small intestine  
• Absorption of amino acids from the gut  

Solution

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.  

Q38. During the process of respiration, the movement of CO₂ and O_­2 out and inside the cell is achieved by

• Active transport
• Facilitated diffusion
• Independent diffusion
• Both active and facilitated diffusion

Solution

The inside and outside movement of CO_2­ and O₂ during respiration and photosynthesis is achieved by independent diffusion.

Q39. Which of the following is not a purpose of transpiration?

• Helps in absorption and transport in plants
• Prevents loss of water
• Maintains shape and structure of plants by keeping the cell turgid
• Supplies water for photosynthesis
• Cools leaf surfaces

Solution

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.

Q40. The rate of diffusion will be less in

• Concentrated solution
• Dilute solution
• Neutral solution
• Rate of diffusion is not affected by the concentration of solution

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