Absorption of Water
Multiple Choice Questions and Answers
1. Root cap has no role in absorption because it has
(a) no direct connection with vascular system
(b) loosely arranged cells
(c) no cells containing chloroplasts
(d) no root hairs
Answer: (d) no root hairs
2. Wilting of the plant occurs when
(a) phloem is blocked
(b) xylem is blocked
(c) both xylem and phloem are blocked
(d) a few old roots are removed
Answer: (b) xylem is blocked
3. Which of the following is a rapid type of absorption?
(a) passive absorption
(b) active absorption
(c) root absorption
(d) salt absorption
Answer: (a) passive absorption
4. Xylem transport of water in tall trees appears to be mainly due to
(a) metabolic activity in xylem cells
(b) root pressure
(c) capillary rise in xylem open pipes
(d) transpiration pull and cohesion of water molecules
Answer: (d) transpiration pull and cohesion of water molecules
5. In active absorption of water
(a) energy is not used
(b) the transpiration pull provides force for absorbing water
(c) the root respiration gives energy
(d) the photosynthesis provides energy
Answer: (c) the root respiration gives energy
6. Water available to the plants is
(a) runoff water
(b) gravitational water
(c) hygroscopic water
(d) capillary water
Answer: (d) capillary water
7. The main source of water for the soil is
(a) precipitation
(b) capillary water
(c) hygroscopic water
(d) estuarine water
Answer: (a) precipitation
8. The process by which water enters the roots due to diffusion is termed as
(a) endocytosis
(b) active absorption
(c) osmosis
(d) passive absorption
Answer: (c) osmosis
9. Root pressure is maximum when
(a) transpiration is very high and absorption is very low
(b) transpiration is very low and absorption is very high
(c) both transpiration and absorption are very high
(d) both the absorption and transpiration are very low
Answer: (b) transpiration is very low and absorption is very high
10. Passive absorption of water from the soil by root hair is mainly affected by
(a) respiratory activity of root
(b) typical tissue organisation of root
(c) tension on the cell sap due to transpiration
(d) root pressure developed in the cortical cells of the roots
Answer: (c) tension on the cell sap due to transpiration
11. The entry of water from soil up to xylem elements of roots is because of
(a) ion concentration in water
(b) turgor pressure
(c) gradient of suction pressure
(d) degree of imbibition
Answer: (c) gradient of suction pressure
12. Water potential of the root hair cells is
(a) equal to soil water
(b) more negative than that of soil water
(c) more positive in comparison to soil water
(d) none of the above
Answer: (b) more negative than that of soil water
13. Water will be absorbed by the root hairs when the external medium is
(a) isotonic
(b) hypertonic
(c) hypotonic
(d) viscous
Answer: (c) hypotonic
14. Which of the following plants absorb water from the air?
(a) Orchids
(b) Ficus
(c) Cuscuta
(d) Brassica
Answer: (a) Orchids
15. Active absorption of water by roots from the soil is mainly affected by
(a) osmotic concentration of cell sap
(b) tension in cell sap due to transpiration
(c) sucking power of the root hairs
(d) typical tissue organisation
Answer: (a) osmotic concentration of cell sap
16. After heavy torrential rain much of the water flows through the surface of soil and accumulates in ponds, lakes, rivers and oceans. This water is known as
(a) gravitational water
(b) runaway water
(c) hygroscopic water
(d) capillary water
Answer: (b) runaway water
17. Absorption of water through roots can be increased by
(a) increased transpiration
(b) increased rate of photosynthesis
(c) decreased transpiration
(d) decreased absorption of ions
Answer: (a) increased transpiration
18. In comparison to clay, the water holding capacity of sand is
(a) more
(b) less
(c) equal
(d) none of the above
Answer: (b) less
19. When the concentration of soil solutes is low, the absorption of water
(a) retards
(b) increases
(c) remains same
(d) stops completely
Answer: (b) increases
20. In roots, root hairs occur in the zone of
(a) cell division
(b) cell elongation
(c) cell maturation
(d) none of the above
Answer: (c) cell maturation
21. Which of the following statements is correct?
(a) carbon dioxide in soil has greater inhibitory effect on water absorption
(b) carbon dioxide causes an increase in the viscosity of protoplasm
(c) carbon dioxide causes decrease in the root’s permeability to water
(d) all of the above
Answer: (d) all of the above
22. When the wall of the root hairs becomes lignified and suberized with advancing age
(a) they show rapid absorption of water
(b) they become more elastic
(c) their ability to absorb water becomes limited
(d) they show increase in the uptake of solutes
Answer: (c) their ability to absorb water becomes limited
23. If the water potential of the soil solution is more negative than the cell sap of the root cells, what response do you expect?
(a) water will move out of the plant instead of being absorbed
(b) water will move inside the plant
(c) there will be no reaction
(d) root growth will increase
Answer: (a) water will move out of the plant instead of being absorbed
24. The soil factors that affect absorption of water by root are
(a) temperature
(b) osmotic potential of the soil solution
(c) aeration and availability of water
(d) all of the above
Answer: (d) all of the above
25. Low temperature reduces the absorption of water because
(a) at low temperature solution becomes more viscous and its mobility retards
(b) at low temperature protoplasm is less permeable to water and root growth is inhibited
(c) both a and b
(d) none of the above
Answer: (c) both a and b
26. Symplast includes
(a) cell wall
(b) cell wall+ intercellular spaces
(c) living protoplast
(d) protoplast+xylem elements
Answer: (c) living protoplast
27. The apoplast is discontinuous because of
(a) endodermis
(b) pericycle
(c) both a and b
(d) none
Answer: (a) endodermis
28. Which of the following plant is expected to cause dryness of soil?
(a) Eucalyptus
(b) Ficus
(c) Eichhornia
(d) Azadirachta (Neem)
Answer: (a) Eucalyptus
29. In water logged fields, crops show signs of wilting, because
(a) soil is more aerated
(b) soil gets cool
(c) amount of CO2 increases in the soil
(d) all of these
Answer: (c) amount of CO2 increases in the soil
30. Field capacity is
(a) the same as permanent wilting point
(b) the amount of water in soil available to plants
(c) the amount of water in the soil after drainage takes place
(d) higher for sandy soils than clay soil
Answer: (c) the amount of water in the soil after drainage takes place
31. Apoplastic moment of water and minerals in the root is stopped at
(a) cortex
(b) pericycle
(c) endodermis
(d) protoxylem elements
Answer: (c) endodermis
32. The soil water easily available to the root system is
(a) capillary water
(b) imbibitional water
(c) hygroscopic water
(d) gravitational water protoplast
Answer: (a) capillary water
33. The transport of water and salt takes place through
(a) phloem
(b) xylem
(c) sieve tubes
(d) sclerenchyma
Answer: (b) xylem
34. 3In root hair, water enters due to
(a) osmotic concentration
(b) turgor pressure
(c) wall pressure
(d) diffusion pressure
Answer: (a) osmotic concentration
35. Many transplanted seedlings may not survive because
(a) they do not like the new soil
(b) they do not get the required mineral salts
(c) the leaves get damaged during the transfer
(d) most of the root hairs are lost during transplantation
Answer: (d) most of the root hairs are lost during transplantation
36. In root hair, water enters due to
(a) Diffusion
(b) W.P
(c) T.P
(d) O.P
Answer: (d) OP
37. Passive water absorption by roots system is due to
(a) forces created in the cells of the root
(b) osmotic force in the shoot system
(c) increased respiratory activity in the cell of the root
(d) tension in the sap due to transpiration
Answer: (d) tension in the sap due to transpiration
38. Most water flow in root occurs via apoplast as
(a) cortical cells are living cells
(b) cortical cells are loosely arranged
(c) cortical cells are thin walled
(d) all the above
Answer: (c) cortical cells are thin walled
39. Attraction of water molecules to polar surface is known as
(a) adhesion
(b) tensile strength
(c) surface tension
(d) cohesion
Answer: (a) adhesion
40. The path of water and solutes from the soil to the conducting tissue of the root is
(a) soil → root hair→ cortex→ endodermis → pericycle → proto xylem → phloem
(b) soil → root hair→ cortex → endodermis → pericycle → proto xylem → meta xylem
(c) soil → root hair → cortex→ pericycle → endodermis → proto xylem → meta xylem
(d) none
Answer: (b) soil→ root hair → cortex → endodermis → pericycle → proto xylem → meta xylem
41. Water will be absorbed by root hairs when
(a) concentration of salts in the soil is high
(b) concentration of solutes in the cell sap is high
(c) the plant is rapidly respiring
(d) they are separated from the soil by a semipermeable membrane
Answer: (b) concentration of solutes in the cell sap is high
42. Which of the following statements is wrong?
(a) plants absorb only one thing at a time- water or inorganic salt
(b) water and inorganic salts are taken in simultaneously by root hairs
(c) plants take in a small quantity of mineral salts through root hairs
(d) roots are one of the main absorbing organs of the plant
Answer: (b) water and inorganic salts are taken in simultaneously by root hairs
43. Root hairs absorb water from the soil with the help of
(a) root pressure
(b) suction pressure
(c) TP
(d)OP
Answer: (b) suction pressure
44. Entry of water from soil to xylem is through
(a) gradient of imbibition
(b) gradient of suction pressure
(c) gradient of turgor pressure
(d) gradient of ion concentration
Answer: (b) gradient of suction pressure
45. Presence of auxins …….. the rate of water absorption
(a) increases
(b) decreases
(c) has no effect
(d) none of the above
Answer: (a) increases
46. Sand has low water holding capacity because of
(a) pore spaces
(b) air spaces
(c) intercellular spaces
(d) none
Answer: (a) pore spaces
47. Which of the following statement is true?
(a) water is absorbed by the roots and aerial parts of the plants
(b) the principal source of soil water is rain
(c) all forms of water present in the soil are collectively known as combined water
(d) all of the above
Answer: (b) the principal source of soil water is rain
48. Name the specific part of the root which is concerned with the absorption of water
(a) zone of elongation
(b) zone of maturation
(c) root hair cell
(d) all of the above
Answer: (d) all of the above
49. Which of the following statement is true?
(a) Tonoplast is a selectively permeable membrane.
(b) Symplastic and apoplastic movement of water occurs simultaneously.
(c) The absorption is maximum in a well aerated soil.
(d) all of the above
Answer: (d) all of the above
50. Root pressure is responsible for …… absorption of water
(a) passive
(b) active
(c) both a and b
(d) none
Answer: (a) passive