Most Important Questions on Plant Physiology

In exams like SSC, Banking, Railways, and others, we find many questions from the General Science section. In this section, Biology topics are considered favorites. We will provide topic-wise practice questions so that students can be able to practice more and more and get most of the questions correct in this section. In this article, we will practice questions from the Plant Physiology section.

Important Questions on Plant Physiology:

Que 1. Why does a cell shrink when placed in saline solution?

(a) The cytoplasm is broken down 
(b) Mineral salt will break the cell wall
(c) Water comes out from the cell by osmosis
(d) Water comes out from the cell by exosmosis

Ans. (c) Water comes out from the cell by osmosis
Explanation- Cells shrink as the cytoplasm will decompose when placed in a salt solution. Mineral salts will break the cell wall, causing the cells to shrink. Saltwater enters the cell and breaks cell. Water comes out of the cell by osmosis, causing it to shrink.

Que 2. When a cell is placed in this solution it shrinks.

(a) Hypertonic solutions 
(b) Hypotonic solution
(c) Isotonic solutions 
(d) Saturated solutions 

Ans. (a) Hypertonic solutions
Explanation- If a cell is placed in a hypertonic solution, water will leave the cell, and the cell will shrink.

Que 3. Which of the following is present in the green pigment of the leaf?

(a) Mg
(b) P
(c) Fe
(d) Ca

Ans. (a) Mg
The explanation-Green pigment of the leaf is called chlorophyll. It has magnesium involved in the structure.

Que 4. Which of the following structures in a plant is responsible for transpiration?

(a) Xylem 
(b) Root
(c) Stomata
(d) Bark

Ans. (c) Stomata
Explanation- It is a process in which excess water is lost in the form of vapours from the aerial parts of the plant. Mainly through the stomates of leaves.

Que 5. Does plant cooling occur due to?

(a) Transpiration 
(b) Guttation
(c) Photorespiration
(d) Assimilation

Ans. (a) Transpiration
Explanation- Plant cooling is caused by transpiration and is similar to sweating occurring in humans after the fever begins to decrease. This sets natural body temperature.

Que 6. The instrument for measuring the rate of transpiration?

(a) Porometer
(b) Hygrometer
(c) Potometer
(d) Psychrometer

Ans. (c) Photometer
Explanation- The instrument used for measuring the rate of transpiration is called a Photometer.

Que 7. Name the gas which is important for photosynthesis.

(a) Oxygen 
(b) Carbon dioxide
(c) Nitrogen
(d) Carbon Monoxide

Ans.(b) Carbon dioxide
Explanation- photosynthesis is a chemical reaction that takes place inside a plant, producing food for the plant to survive.

Que 8. Which of the following is not plant hormone?

(a) Gibberellic 
(b) Auxins
(c) Cytokines
(d) Thyroxine

Ans. (d) Thyroxin
Explanation- Thyroxin is the main hormone secreted into the bloodstream by the thyroid gland. It plays vital roles in digestion, heart and muscle function, and the brain.

Que 9. Leaves are green because they…

(a) Absorb green light
(b) They do not absorb green light but reflect it 
(c) They use green light
(d) Absorb and reflect green light

Ans. (b) Do not absorb but reflect green light
Explanation- Leaves are green because they have chlorophyll in chloroplasts which absorb red and blue light but reflect green light.

Que 10. Plants purify the air by which process?

(a) Desiccation
(b) Respiration
(c) Photosynthesis
(d) Transpiration

Ans. (c) Photosynthesis
Explanation- During photosynthesis, carbon dioxide is reduced into carbohydrates, and oxygen is liberated, i.e., plants purify the air by the process of photosynthesis.

Que 11. Why is low temperature maintained for preservation?

(a) For easy digestion
(b) For easy cooking
(c) Bacterial attacks will be minimized
(d) All of these

Ans. (c) Bacterial attacks will be minimized
Explanation-Low temperatures are employed to stop chemical reactions and the action of enzymes in food and to stop or slow the development and activities of microorganisms found in food items. 

Que 12. The instrument used to measure the growth rate of plants?

(a) Potometer
(b) Auxanometer 
(c) Hydrometer 
(d) Osmometer

Ans. (b) Auxanometer 
Explanation- An auxanometer is an apparatus for measuring the increase of growth in plants.

Que 13. What are Auxins?

(a) Growth catalyzer
(b) Growth destroyer
(c) Growth inhibitor
(d) Growth hormones

Ans. (d) Growth hormones
Explanation- Auxins are growth hormones produced by plants.

Que 14. What is the fruit ripening hormone?
(a) Thyroxin 
(b) Collagen
(c) Ethylene 
(d) Kinetin

Ans. (c) Ethylene
Explanation- Ethylene is a gas and is known as the “fruit-ripening hormone.” Every fruit has a certain level of ethylene production throughout its lifecycle.

Que 15. Where is the concentration of auxin the highest?

(a) In growing tips
(b) In leaves
(c) At the base of the plant
(d) In xylem and phylum

Ans. (a) In growing tips
Explanation- The highest concentration of auxin exists in the growing tips of plants, both in root and shoot meristems.

Que 16. What is the type of movement that occurs during the opening and closing of a flower?

(a) Tactic movement
(b) Nastic movement
(c) Tropic movement
(d) Mutation

Ans. (b)  Nastic movement 
Explanation- The movement of the flowers during opening and closing is a type of nastic movement. 

Que 17. What are Photoperiodism effects?

(a) Fruiting 
(b) Vegetative growth
(c) Flowering 
(d) All of these

Ans. (c) Flowering
Explanation- Photoperiodism affects flowering by inducing the shoot to produce floral buds instead of leaves and lateral buds.

Que 18. What is an example of positive geotropism?

(a) Lateral growth of root
(b) Upward growth of stem
(c) Downward growth of root
(d) Closing of flower

Ans. (d) Closing of flower
Explanation- The movement of roots towards the soil is an example of positive geotropism. The movement of plant stems away from the soil in the upward direction is an example of negative geotropism.

Que 19. What is the role of Pneumatophores?

(a) Protect the plant from animals 
(b) Get oxygen from respiration
(c) Support plant in standing upright 
(d) Help plants with pollination

Ans..(b) Get oxygen from respiration
Explanation- Pneumatophores, commonly found in mangrove species that grow in saline mud flats, are lateral roots that grow upward out of the mud and water to function as the site of oxygen intake for the submerged primary root system.

Que 20. Which part of the plant helps in holding the plant firmly into the soil?

(a) Roots 
(b) Fruit
(c) Stem 
(d) Leaves

Ans. (a) Roots
Explanation- Roots of the plant help in holding the plant firmly into the soil.