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Class 10 SELINA Solutions Biology Chapter 5 - Transpiration

Transpiration Exercise Ex. 1

Solution A.1

(a) Open stomata, dry atmosphere and moist soil

Solution A.2

(a) increase

Solution A.3

(c) sunken stomata

Solution A.4

(d) hydathodes

Solution A.5

(d) hot, dry and windy

Solution A.6

(b) Lenticels

Solution A.7

(b) evaporation of water from the aerial surfaces of a plant

Solution B.1

(a) Lenticels

(b) Guttation

(c) Potometer

(d) Nerium

(e) Ganong's photometer

(f) Stomata and cuticle

(g) Hydathodes

(h) Guttation

Solution B.2

(a) vapour, aerial

(b) stomata, transpiration

(c) suction, water (heat)

Solution C.1

(a) guttation

(b) protection and reduced transpiration

(c) transpiration

(d) 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

(a) Transpiration increases with the velocity of wind. If the wind blows faster, the water vapour released during transpiration is removed faster and the area surrounding the transpiring leaf does not get saturated with water vapour.


(b) When the rate of transpiration far exceeds the rate of absorption of water by roots, the cells lose their turgidity. Hence, excessive transpiration results in wilting of the leaves.


(c) Plants absorb water continuously through their roots, which is then conducted upwards to all the aerial parts of the plant, including the leaves. Only a small quantity of this water i.e. about 0.02% is used for the photosynthesis and other activities. The rest of the water is transpired as water vapour. Hence water transpired is the water absorbed.


(d) There are more stomatal openings on the lower surface of a dorsiventral leaf. More the number of stomata, higher is the rate of transpiration. Hence more transpiration occurs from the lower surface.


(e) The stomata in most plants are more numerous on the lower surface of a leaf as compared to the upper surface because lower surface does not face direct sunlight. This arrangement helps to reduce the rate of transpiration.


(f) Due to transpiration, huge quantities of water are released into the atmosphere by vast stretches of filed particularly forests. Thus, transpiration increases the moisture in the atmosphere and brings more rain.


(g) On a bright sunny day, the rate of transpiration is much higher than any other days. The leaves of certain plants roll up on a bright sunny day to reduce the exposed surface and thus reduce the rate of transpiration.

Solution C.2 old

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

(ii) True

(iii) True

(iv) False. Potometer is an instrument used for measuring the rate of transpiration in green plants.

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

Take the small potted rose plant and cover it with a transparent polythene bag. Tie its mouth around the base of the stem. Leave the plant in sunlight for an hour or two.

Drops of water will soon appear on the inner side of the bag due to the saturation of water vapour given out by the leaves. A similar empty polythene bag with its mouth tied and kept in sunlight will show no drops of water. This is the control to show that plants transpire water in the form of water. If tested with dry cobalt chloride paper, the drops will be confirmed as water only.

Solution D.4

Transpiration occurring through lenticels i.e. minute openings on the surface of old stems is called lenticular transpiration.

Stomatal transpiration is controlled by the plant by altering the size of the stoma, where as this does not happen in case of lenticular transpiration. This is because the lenticels never close, but remain open all the time.

The amount of stomatal transpiration is much more than the amount of lenticular transpiration.

Solution D.5

No, they are not dew drops.

This is water given out by the plant body through guttation. Since the banana plant is growing in humid environment, transpiration is hampered. But the roots continue to absorb water from the soil. This builds up a huge hydrostatic pressure within the plant and forces out the excess water from the hydathodes, which are pores present at the tips of veins in the leaf. This is observed especially during the mornings.

Solution D.6

(a) Intensity of light - During the day, the stomata are open to facilitate the inward diffusion of carbon dioxide for photosynthesis. At night they are closed. Hence more transpiration occurs during the day. During cloudy days, the stomata are partially closed and the transpiration is reduced.

(b) Humidity of the atmosphere - When the air is humid; it can receive very less water vapour. Thus, high humidity in the air reduces the rate of outward diffusion of the internal water vapour across stomata, thereby reducing the rate of transpiration.

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) 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.3

(a) CaCl2 is a hygroscopic compound that absorbs moisture/water without changing its state. CaClvials inside the cup to absorb water.

(b) Yes, after few hours the weight of the CaCl2 vials will increase because they will absorb water lost by the leaf of the plant due to transpiration.

(c) Manometer is used to measure the pressure. In order to measure the pressure exerted by the fluid, the fluid is allowed to exert pressure on one of the closed ends of the tube. Under the effect of the pressure, the liquid inside the manometer tube gets displaced and the amount of displaced liquid is measured.

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

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 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) 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.

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