Plant Physiology: II. Plant Nutrition

Total Questions: 25

1. Which of the following is not a correct match? [68ᵗʰ B.P.S.C. (Pre) 2022]

(a) Petiole : Attaches leaf to stem
(b) Thick, hard stem with branching near base : Tree
(c) Weak stem which cannot stand upright : Creeper
(d) More than one of the above
(e) None of the above

Correct Answer: (b) Thick, hard stem with branching near base : Tree

Solution:The correct matches are as follows:
Petiole : Attaches leaf to stem
Shrub : Thick, hard stem with branching near base
Tree : Thick, hard stem with branches high on the plant
Creeper : Weak stem which cannot stand upright
Hence, option (b) is the correct answer.

2. Stem of a plant helps in distributing food to all parts of the plant. It also helps in: [67th B.P.S.C. (Pre) 2022]

(a) storing the food
(b) shaping the plant
(c) respiration
(d) photosynthesis,
(e) None of the above/More than one of the above

Correct Answer: (e) None of the above/More than one of the above

Solution:Stem provides structure to the plant. It transports food from the roots to all parts of the plants and stores the food made by the leaves. Plant stems provide both shape and support for the other parts of the plant. This is the part of the plant that bears leaves, flowers, fruits, thus also helping in their vegetative reproduction.

3. The maximum amount of water, which plants need to grow, is absorbed by the following: [U.P.P.C.S. (Mains) 2007]

(a) Embryonic zone
(b) Growing point
(c) Zone of elongation
(d) Root hairs

Correct Answer: (d) Root hairs

Solution:The maximum amount of water is absorbed by root hairs. These are outermost layer of zone of cell maturation. Root hairs are thin, elongated extensions of epidermal cells, which are the outermost layer of the root. Their primary function is to increase the surface area available for water and mineral uptake from the soil. Water absorption by root hairs occurs through osmosis, where water moves from a region of high concentration (the soil) to a region of lower concentration (the root hair cell).

The numerous root hairs and their thin walls provide a large surface area for water and nutrient uptake, allowing plants to efficiently absorb water from the soil. Root hairs are primarily found in the root hair zone, which is located behind the root tip and is the region of the root where water absorption is most efficient.

4. Which of the following statements are true? [Chhattisgarh P.C.S. (Pre) 2022]

(i) Small pores in epidermis of leaf is called stomata.
(ii) Guard cells present in the stomata are helpful in exchange of gases with atmosphere.
(iii) Transpiration takes place through stomata.

Code:

(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (i), (ii) and (iii)

Correct Answer: (d) (i), (ii) and (iii)

Solution:Stomata are the small pores present on the epidermis of leaves. The stomata consist of minute pores called stomata surrounded by a pair of guard cells. Stomata open and close according to the turgidity of guard cells. Guard cells regulate the size of the stomatal opening. Exchange of gases with atmosphere and transpiration take place through stomata and guard cells play an important role in the working of stomata. Hence, all three statements are correct.

5. The stomata open or close due to change in the : [68ᵗʰ B.P.S.C. (Pre) 2022]

(a) position of nucleus in cells
(b) protein composition of cells
(c) amount of water in cells
(d) More than one of the above
(e) None of the above

Correct Answer: (c) amount of water in cells

Solution:The closing and opening of the stomata rely on the pressure that is caused by the water’s osmotic flow in the guard cells. The change in the guard cell's turgor pressure causes the stomata to open and close. Due to increased transpiration pull during the day, water is absorbed by the roots and transferred through the xylem to various areas of the plant causing the guard cell to swell and become turgid. The stomatal pore is open as a result. The guard cell shrinks and becomes stiff at night because the roots absorb less water. Consequently, stomatal pores close. So the correct option is (c).

6. Water reaches great heights in trees because of suction pull caused by : [68ᵗʰ B.P.S.C. (Pre) 2022]

(a) evaporation
(b) absorption
(c) transpiration
(d) More than one of the above

Correct Answer: (c) transpiration

Solution:Water reaches great heights in trees because of suction pull caused by transpiration. The loss of water vapour from the plant cools the plant down when the weather is very hot, and water from the stem and roots moves upward as it is 'pulled' into the leaves. On the other hand, plants absorb water and minerals from the soil via their roots but water does not move upward due to absorption. Similarly, water escapes the tree through evaporation. Hence, option (c) is the correct answer.

7. When the bark of a tree is removed in a circular fashion all around near its base, it gradually dries up or dies because — [I.A.S. (Pre) 2011]

(a) Water from soil cannot rise to aerial parts
(b) Roots are starved of energy
(c) Tree is infected by the soil microbes
(d) Roots do not receive oxygen for respiration

Correct Answer: (b) Roots are starved of energy

Solution:There are two types of transportation tissues in the bark of tree- (i) phloem, (ii) xylem. When the bark of a tree cut in circular form near the base of its stem, flow of nutrients (photosynthetic food from green leaves) stops towards the roots because phloem which is the transporting tissue for food is absent. In this way roots of the plant gets no energy. so the plant gradually dries up or dies.

8. Water is conducted in vascular plants by— [53ʳᵈ to 55ᵗʰ B.P.S.C. (Pre) 2011]

(a) Phloem tissue
(b) Parenchyma tissue
(c) Meristems
(d) Xylem tissue

Correct Answer: (d) Xylem tissue

Solution:Xylem is a specialized tissue that forms a continuous channel from the roots, through the stem, and into the leaves. The xylem carries water absorbed by the roots from the soil and, along with it, soluble mineral nutrients that are essential for plant growth and development.

The movement of water and minerals through the xylem is primarily driven by transpiration, the evaporation of water from leaves. This creates a negative pressure (or "suction") that pulls water upwards from the roots through the xylem vessels. This process is vital for the plant's ability to carry out photosynthesis, transport nutrients to all parts of the plant, and maintain overall plant health.

9. The ‘xylem’ in plants is responsible for transporting : [U.P. P.C.S. (Pre) 2023, U.P.P.C.S. (Pre) (Re. Exam) 2015]

(a) Water
(b) Oxygen
(c) Amino acid
(d) Food

Correct Answer: (a) Water

Solution:There are two types of transporting tissues found in vascular plants: (i) Phloem and (ii) Xylem. Xylem is the specialised tissue of vascular plants that transports water and minerals from plants - soil interface to stems and leaves and provides mechanical support and storage.

10. Water in plants is transported by : [66ᵗʰ B.P.S.C. (Pre) (Re. Exam) 2020]

(a) Xylem
(b) Epidermis
(c) Phloem
(d) Cambium
(e) None of the above/More than one of the above

Correct Answer: (a) Xylem

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