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Class 10 SELINA Solutions Biology Chapter 5 - Transpiration

Transpiration Exercise Ex. 1

Solution A.1

(c) Transpiration

Solution A.2

(d) Exudation 

Solution A.3

(d) More from abaxial surface of a dicot leaf

Solution A.4

(c) Hydathodes 

Solution A.5

(d) Potometer 

Solution A.6

(c) Humidity 

Solution A.7

(b) Palisade cells

Solution A.8

(d) Translocation of food

Solution A.9

(d) Margins of leaves

Solution A.10

(c) Closed

Solution B.1

(a) Lenticels

(b) Guttation

(c) Potometer

(d) Nerium

(e) Ganong's potometer

(f) Stomata and cuticle

(g) Hydathodes

(h) Guttation

Solution B.2

(a) Transpiration is the loss of water as water vapour from the aerial parts of the plant.

(b) Closing of stomata and shedding of leaves reduce transpiration.

(c) Transpiration helps in creating suction force and in eliminating excess water (heat).

Solution C.1

(a) Hydathodes and guttation

(b) Leaf spines and protection and reduced transpiration

(c) Lenticels and transpiration

(d) Xylem and conduction of water and mineral salts

Solution C.2

(i) False. Most transpiration occurs at mid-day.


(ii) True.


(iii) True.


(iv) False. Atmospheric humidity reduces transpiration from a green plant.


(v) True.

Solution C.3

Column A Column B
(a) Hydathodes (v) Guttation
(b) Stomata (i) Photosynthesis
(c) Cuticle (iv) Reduces loss of water
(d) Lenticels (ii) Respiration
(e) Guard cells (iii) Regulates opening and closing of stomata

Solution C.4

(a) Stomatal transpiration, Cuticular transpiration and Lenticular transpiration

(b) Intensity of sunlight, Temperature and Wind velocity

(c) Thick cuticle, Sunken stomata and Narrow leaves

(d) Humidity, Carbon dioxide and Atmospheric pressure

(e) Farmer's potometer, Garreau's potometer, Ganong's potometer and Darwin's potometer

Solution D.1

(a) Transpiration: Transpiration is the loss of water in the form of water vapour from the aerial parts (leaves and stem) of the plant.


(b) Exudation: The process by which plants lose water or other fluids along with dissolved substances directly in liquid form and not as water vapour is called exudation.


(c) Potometer: Potometer is a device that measures the rate of water intake by a plant and this water intake is almost equal to the water lost through transpiration.


(d) Wilting: The collapsing of leaves due to excessive loss of water i.e. transpiration or due to some disease is called wilting.


(e) Hydathodes: Special pore-bearing structures present on the margins of the leaf to allow exudation are called hydathodes.


(f) Cuticle: Cuticle is a waxy layer secreted by the epidermis on the two surfaces of the leaf which prevents evaporation of water from the leaf surfaces.

Solution D.2

(a) Differences between stomata and lenticels:



1. They are minute openings in the epidermal layer of leaves.

1. They are minute openings on the surface of old woody stems.

2. Maximum transpiration occurs through stomata.

2. Lesser transpiration occurs through lenticels.


(b) Differences between guttation and bleeding:



1. It is the removal of excess of water from the plants because of excess water build-up in the plant.

1. It is the removal of water from the plant because of injury.

2. Water escapes from specialized structures called hydathodes.

2. Water escapes in the form of sap from the injured part of the plant.

3. It occurs during early mornings or late nights.

3. It occurs at the time of injury.


(c) Differences between transpiration and evaporation:



1. It is the loss of water in the form of vapour from the aerial parts of the plant.

1. It is the loss of water from the surface of water bodies in the form of vapour.

2. It is a slow process.

2. It is comparatively a faster process.


Solution D.3

(a) Nerium is a xerophyte with sunken stomata covered with hairs, which help limit water loss through transpiration. Also, the plant has narrow leaves, which reduce the surface area and limit the rate of transpiration.

(b) The rate of transpiration differs on the upper and the under surface of a dorsiventral leaf in a dicot plant. The undersurface of a dicot leaf has more stomata than its upper surface. Therefore, more transpiration occurs from the undersurface of a dicot leaf.

(c) If the wind blows faster, the water vapour released during transpiration is removed quicker, and the area outside the leaf is not saturated with water vapour. Hence, as the velocity of wind increases, the rate of transpiration also increases.

(d) Despite plenty of water in the soil, the leaves of some plants, such as balsam, wilt during the midday. This is because the rate of transpiration during midday exceeds the rate of water absorption by the roots. As a result, the cells lose turgidity. The stomata are constricted in the evening, and the temperature is not high. Therefore, there is no loss of water through transpiration, and the turgidity of the leaves is re-acquired. The plants thus recover and stand out erect.

(e) Guttation is more common in plants that thrive in a warm and humid climate. It frequently happens at night or in the morning when the rate of water absorption by the roots surpasses the rate of water transpiration from the leaves. This builds up a significant hydrostatic pressure within the plant and forces out excess water directly from the hydathodes.

(f) Plants lose water in the form of water vapour into the atmosphere daily through transpiration. Vast stretches of fields, particularly forests, release a large amount of water due to transpiration. This increases the amount of moisture in the atmosphere, resulting in more rainfall.

Solution E.1

(i) Leaf D: i.e. the leaf with no greasing on either surfaces would dry first because it would lose water from both surfaces i.e. it would lose maximum quantity of water.


(ii) Leaf A: which was coated with grease on both the surfaces would dry last because greasing prevents evaporation of water and transpiration occurs through stomata which are present more on the lower surface of the leaf.

Solution E.2

(a) Ganong’s potometer

(b) Ganong’s potometer is used to measure the water intake of a plant which is almost equal to the water lost through transpiration.

(c) The movement of the air bubble and its position in the capillary tube indicates the volume of water lost through transpiration in a given time.

(d) The water in the reservoir can be released into the capillary tube by opening the stop cock. This allows the air bubble to restore back to its original position.


(i) If the apparatus is kept in the dark, there will be no transpiration as the stomata would be closed. As a result, there would be no movement of the air bubble and it would remain stable.

(ii) If the apparatus is kept in bright sunlight, the rate of transpiration will be more. As a result, the movement of the air bubble would be larger since there would be more loss of water due to transpiration. 

(iii) If the apparatus is kept in front of a fan, the rate of transpiration will be more. As a result, the movement of the air bubble would be larger since there would be more loss of water due to transpiration as the velocity of wind/air increases. 

Solution E.3

(a) Blue.

(b) The experimental leaf is a dicot leaf as it shows reticulate venation and there are more number of stomatal openings on the undersurface of a dicot leaf. Hence, transpiration is more and can be easily observed.

(c) Glass slides are placed over the dry cobalt chloride papers so as to retain the strips in their position.

(d) The cobalt chloride paper on the dorsal side will turn less pink or turns pink in a much longer time; while the one on the ventral side will turn more pink. This occurs because the ventral surface has more number of stomata as compared to the dorsal surface. As a result, the rate of transpiration is more on the ventral side than on the dorsal side of a dicot leaf. 

Solution E.4

(a) A is transpiration. Transpiration is the evaporative loss of water from the aerial parts (leaves and stem) of the plants.


(b) Significance of transpiration for the plants:

 Cooling effect

 Suction force

 Distribution of water and minerals


(c) Arrow B indicates water passing up the trunk and the phenomenon is lenticular transpiration/ascent of sap. Arrow C indicates water absorbed by roots from the soil and the phenomenon is called endosmosis.


(d) Opened stomata:


Solution E.5

(a) Transpiration

(b) Transpiration is a process by which water is lost in the form of water vapour from aerial parts of the plant. 

(c) Weight of test tube A before the experiment was more than its weight after the experiment. This is because water from test tube A has evaporated due to transpiration.

Weight of test tube B remains the same before and after the experiment, because no loss of water occurs in test tube B.

(d) Test tube B is used here as a control. This makes the observation of the change in test tube A easy.

(e) Oil is added in the test tube to prevent the loss of water by evaporation.

Solution E.6

(a) Transpiration

(b) Transpiration is a process during which water is lost in the form of water vapour through aerial parts of the plant. 

(c) The pot is covered with a plastic sheet to prevent evaporation of water from the soil.

(d) A control for this experiment will be an empty polythene bag with its mouth tied.

(e) Transpiration is beneficial to plants in the following ways:

  • It creates a suction force in the stem which enables the roots to absorb water and minerals.
  • It helps in cooling the plant in hot weather.

(f) Adaptations in plants to reduce transpiration are 

  • Leaves may be modified into spines as in cactus or into needles as in pines.
  • The number of stomata is reduced and they may be sunken in pits.
  • Leaves may be folded or rolled up.

Solution E.7

(a) A- Guard cell, B- Stoma

(b) Stomata are located in the epidermal layer of leaves.

(c) Guard cells (structure A) regulate the rate of transpiration by the opening and closing of stomata.

(d) Important roles of stoma (structure B):

 Helps in the exchange of gases by opening and closing the pores. 

 It aids in the removal of excess water from the leaves through transpiration. 

 It releases oxygen and takes in carbon dioxide during photosynthesis.

(e) Guard cell in flaccid condition:


When the water content of the leaf falls down, the guard cells lose turgidity and become flaccid, i.e. they shrink, thereby closing the stomatal pores.

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