TRB BT Assistant - Plant Physiology and Water Relations Online Test (MCQ Quiz)

1. Which of the following processes is the primary mechanism for water absorption by plant roots?

A) Active transport B) Facilitated diffusion C) Osmosis D) Pinocytosis

2. The movement of water from a region of higher water potential to a region of lower water potential across a semipermeable membrane is called:

A) Transpiration B) Guttation C) Imbibition D) Osmosis

3. What is water potential (Ψw) primarily influenced by in plant cells?

A) Temperature and pressure B) Solute potential and pressure potential C) Humidity and light intensity D) Soil pH and nutrient availability

4. Solute potential (Ψs) is always:

A) Positive B) Negative C) Zero D) Variable

5. Pressure potential (Ψp), also known as turgor pressure, is typically:

A) Negative in xylem B) Positive in root cells C) Zero in plasmolysed cells D) Always zero in mature plant cells

6. When a plant cell is placed in a hypotonic solution, water will move:

A) Out of the cell, causing plasmolysis B) Into the cell, causing turgor C) Equally in both directions, with no net movement D) Out of the cell, causing the cell to shrink

7. Plasmolysis occurs when a plant cell is placed in a solution that is:

A) Hypotonic B) Isotonic C) Hypertonic D) Neutral

8. The pathway through the root cortex where water moves via the cell walls and intercellular spaces is known as the:

A) Symplast pathway B) Apoplast pathway C) Transmembrane pathway D) Endodermal pathway

9. Water movement from cell to cell through plasmodesmata is called the:

A) Apoplast pathway B) Symplast pathway C) Vacuolar pathway D) Cortical pathway

10. The Casparian strip, located in the endodermis, is crucial because it:

A) Facilitates rapid water entry into the stele B) Blocks the apoplast pathway, forcing water into the symplast C) Increases the rate of transpiration D) Promotes nutrient uptake from the soil

11. The bulk flow of water through the xylem is driven by:

A) Root pressure B) Capillarity C) Transpiration pull D) Active transport by xylem parenchyma

12. Transpiration is the process of:

A) Water absorption by roots B) Water movement from root to leaf C) Water loss in the form of vapor from aerial parts of the plant D) Water storage in plant tissues

13. Which plant structure is primarily responsible for controlling transpiration?

A) Root hairs B) Stomata C) Lenticels D) Trichomes

14. The opening and closing of stomata are regulated by changes in the turgor of which cells?

A) Epidermal cells B) Mesophyll cells C) Guard cells D) Xylem vessels

15. During stomatal opening, guard cells become:

A) Flaccid and lose potassium ions B) Turgid due to influx of potassium ions and water C) Plasmolysed D) Dehydrated

16. The cohesion-tension theory explains water transport in xylem based on:

A) Root pressure and guttation B) Capillary action and osmotic gradients C) Cohesion of water molecules and tension created by transpiration D) Active pumping by xylem parenchyma cells

17. Cohesion refers to the attraction between:

A) Water molecules and xylem walls B) Water molecules themselves C) Solute molecules and water D) Xylem walls and surrounding tissues

18. Adhesion in the context of water transport refers to the attraction between:

A) Water molecules and other water molecules B) Water molecules and the walls of xylem vessels C) Xylem vessels and surrounding tissues D) Solute molecules and water

19. What is the primary driving force for the ascent of sap in tall trees?

A) Root pressure B) Capillary action C) Transpiration pull D) Osmotic pressure of leaf cells

20. Root pressure can push water up to a certain height, but it is generally not sufficient to explain the transport of water to the:

A) Root hairs B) Root cortex C) Shoot apex of tall trees D) Vascular tissues in the root

21. Guttation is the loss of water in liquid form from plant leaves, typically occurring when:

A) Transpiration rate is very high B) Soil is dry and humidity is low C) Transpiration is inhibited (e.g., at night) and root pressure is high D) Stomata are widely open during the day

22. The process by which plants absorb water from the soil into their roots is primarily driven by:

A) Active transport of water molecules B) Differential water potential between soil and root cells C) Pressure build-up in the soil D) Evaporation from root surfaces

23. Which of the following factors generally increases the rate of transpiration?

A) High humidity B) Low temperature C) High wind speed D) Low light intensity

24. Waterlogging of soil can lead to wilting because:

A) The soil becomes too cold B) There is an excess of water, reducing water potential in roots C) Oxygen supply to roots is reduced, inhibiting active water absorption D) Salt concentration in the soil increases

25. The ability of plants to absorb water from dry soil is related to their:

A) High solute potential in root cells B) Low solute potential in root cells C) High pressure potential in root cells D) Low transpiration rate

26. What happens to the water potential of a plant cell when it absorbs solutes?

A) It increases B) It decreases C) It remains unchanged D) It becomes zero

27. The primary function of water in plants, besides being a solvent and reactant, is:

A) Providing structural support through turgor pressure B) Producing energy through photosynthesis C) Absorbing light for photosynthesis D) Transporting minerals from the soil

28. Xylem vessels are dead cells that are hollow tubes, which facilitates:

A) Active transport of water B) Bulk flow of water with minimal resistance C) Storage of water D) Exchange of gases within the xylem

29. Phloem is primarily responsible for the transport of:

A) Water and minerals B) Sugars (photosynthates) C) Hormones and enzymes D) Oxygen and carbon dioxide

30. The movement of photosynthates from source (e.g., leaves) to sink (e.g., roots, fruits) through the phloem is explained by the:

A) Cohesion-tension theory B) Pressure-flow hypothesis C) Root pressure theory D) Capillary rise theory

31. In the pressure-flow hypothesis, the loading of sugars into the phloem sieve tubes at the source leads to:

A) An increase in water potential, causing water to leave the phloem B) A decrease in water potential, causing water to enter the phloem C) A decrease in pressure potential, driving flow towards the sink D) An increase in pressure potential, driving flow towards the sink

32. When a plant wilts, its leaves lose turgor pressure because:

A) The cells are gaining water B) The cells are losing water and pressure potential drops C) The solute concentration in the cells increases significantly D) Photosynthesis has stopped

33. Which of the following is NOT a function of water in plant physiology?

A) Reactant in photosynthesis B) Solvent for mineral nutrients C) Medium for metabolic reactions D) Primary source of energy for respiration

34. The rate of transpiration is generally higher during which part of the day?

A) Night B) Early morning C) Midday D) Late evening

35. What type of solution would cause a plant cell to become flaccid?

A) A hypotonic solution B) An isotonic solution C) A hypertonic solution D) A solution with zero solute potential

36. The movement of water across the root endodermis is primarily through the symplast pathway due to the presence of:

A) Plasmodesmata B) Casparian strips C) Root hairs D) Xylem vessels

37. Abscisic acid (ABA) is a plant hormone that generally:

A) Promotes stomatal opening B) Inhibits stomatal opening and promotes closure C) Increases the rate of transpiration D) Reduces the water potential in guard cells

38. The bulk flow of water in the xylem is a passive process driven by:

A) ATP hydrolysis B) Proton pumps C) Water potential gradients D) Active transport of water

39. Water moves from the soil into root hair cells primarily due to:

A) Higher water potential in root hair cells than in the soil B) Lower water potential in root hair cells than in the soil C) Active pumping of water by root hair cells D) Evaporation from the root surface

40. Which of the following is an adaptation of plants living in arid environments to reduce water loss?

A) Large, thin leaves B) Numerous, sunken stomata C) Shallow root systems D) Open stomata during the day

41. The process of imbibition is crucial for:

A) Water transport in xylem B) Water absorption by dry seeds C) Transpiration D) Guttation

42. When a plant cell is in equilibrium with its surroundings, its water potential is:

A) Positive B) Negative C) Zero D) Equal to the solute potential

43. The tension created by transpiration pulls water up the xylem. This tension is a form of:

A) Positive pressure B) Negative pressure C) Osmotic pressure D) Turgor pressure

44. What is the role of aquaporins in plant water relations?

A) They block water movement across membranes B) They facilitate rapid water transport across membranes C) They actively pump water against its potential gradient D) They regulate the concentration of solutes in cells

45. The rate of transpiration is inversely proportional to:

A) Wind speed B) Temperature C) Humidity D) Light intensity

46. Which component of water potential is most likely to be zero in an open container of pure water at standard atmospheric pressure?

A) Solute potential (Ψs) B) Pressure potential (Ψp) C) Matric potential (Ψm) D) Osmotic potential (Ψo)

47. The movement of water into the phloem sieve tube elements at the source is primarily driven by:

A) High pressure potential B) Low solute potential C) High solute potential D) Active transport of water

48. During the process of osmosis, water moves from:

A) Higher solute concentration to lower solute concentration B) Lower water potential to higher water potential C) Higher water potential to lower water potential D) Lower solute concentration to higher solute concentration

49. The overall process of water uptake by roots, transport through xylem, and loss from leaves is known as:

A) Photosynthesis B) Respiration C) Transpiration stream D) Mineral uptake

50. Which of the following conditions would favor the highest rate of transpiration?

A) A cool, humid, windless day B) A hot, dry, windy day C) A cool, dry, windless day D) A hot, humid, windy day

Plant Physiology and Water Relations - Online Test

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