Transpiration

A is True and R is False

Explanation
Lenticels are located on the surface of older woody stems. They remain open as they have no opening and closing mechanism like stomata.

A is False and R is True.

Explanation
Transpiration increases the amount of moisture in the atmosphere. Increased moisture in atmosphere helps in rain.

A is True and R is False.

Explanation
Nerium is adapted to dry environments and has sunken stomata and trichomes to reduce water loss. Nerium is not a hydrophytic plant (which lives in water-rich environments); it is actually a xerophytic plant adapted to arid conditions. The adaptations such as sunken stomata and trichomes help in minimizing water loss, not getting rid of excess water.

A is False and R is True.

Explanation
Transpiration helps in the ascent of sap by producing a suction force acting from the top of a plant.

(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 drying out, drooping and withering of the leaves of a plant due to inadequate water supply, excessive transpiration, or vascular disease.

(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.

(a) Difference between stomata and lenticels

(b) Difference between Guttation and Bleeding

(c) Difference between Transpiration and Evaporation

(a) Nerium loses less amount of water during transpiration because they have sunken stomata that are covered with hair like structures called trichome.

(b) More transpiration occurs from the under surface of a dicot leaf because the number of stomata is more on abaxial (lower) side of leaf.

(c) Transpiration increases with the velocity of wind because when wind blows faster, the water vapour released during transpiration is removed faster and the area outside the leaf does not get saturated with water vapour.

(d) Leaves of some plants wilt during midday due to high rate of transpiration. They usually recover by evening as the loss of water is compensated by absorption.

(e) Guttation normally occurs during early mornings or late nights when there is least transpiration. The hydrostatic pressure built, forces out the excess water directly from the tips of veins in the leaf.

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

Transpiration

Reason — Loss of water in form of vapour from aerial parts of plant through stomata, lenticel and cuticle is called Transpiration.

Exudation

Reason — Exudation refers to oozing out of fluids from plant either from hydathodes or from injured part.

More from abaxial surface of a dicot leaf

Reason — The lower or the abaxial side of leaf has more stomata which results in more transpiration.

Hydathodes

Reason — Hydathodes are small pores found in angiospermic plants (leaves) through which fluid oozes out in form of tiny droplets.

Potometer

Reason — Potometers are the devices to measure rate of transpiration.

Humidity

Reason — Humidity of the atmosphere decides the rate of transpiration. If the humidity is more then the diffusion of water vapour from sub stomatal space is slow.

Palisade cells

Reason — The upper layer of mesophyll in a leaf consists of elongated ground tissue called palisade mesophyll.

Translocation of food

Reason — Translocation of food is carried out by phloem tissue and is not dependent on transpiration.

Margins of leaves

Reason — Hydathodes are the tiny pores located on leaf margins. They are responsible for guttation.

Closed

Reason — When guard cells are flaccid, their inner wall is relaxed closing the stomata. Similarly, when the guard cells become turgid the inner wall is pulled outwards opening the stomata.

loss of water as vapour from the plants.

Cobalt chloride paper is an indicator of moisture. It is blue when dry but turns pink when exposed to moisture.

No, it will not serve the purpose because the number of stomata is much lesser on petals as compared to leaves. Moreover, there are no roots also to actively absorb water and increase the rate of transpiration. Hence, the water loss through transpiration will be negligible in this case.

Two limitations in the use of potometer are:

1. Introducing the air bubble is not very easy.
2. Any change in the outside air temperature may affect the position of the air bubble in the capillary tube.

Xylem vessels → mesophyll cells → intercellular space → substomatal space → stoma

Yes, diffusion plays a role in the passage of water vapour from the leaf during transpiration. The entire movement of water vapour from a cell into the outside atmosphere is a result of diffusion. The molecules of water vapour, like those of any gas, move from the region of their higher concentration to the region of their lower concentration.

In any experiment to demonstrate transpiration, the leaf must remain attached to its parent plant because on detachment the leaf may die and stomata gets closed.

1. Stomatal transpiration
2. Cuticular transpiration

(i) Still air — decreases transpiration

(ii) Midday high temperature — increases transpiration

(iii) Dry air — increases transpiration

(iv) Dim sunlight — decreases transpiration

(v) Insufficient absorption of water by the roots — decreases transpiration

1. Sunken stomata covered by hairs.
2. Fewer Stomata
3. Narrow leaves (reduce the surface area)

Four advantages of transpiration to the plants are:

1. It has a cooling effect on leaf surface. This cooling effect helps the plant withstand the heat. Intense heat can destroy the enzymes.
2. It maintains the suction force due to transpirational pull and thus maintains ascent of sap.
3. Regular ascent of sap results in proper absorption and distribution of water and minerals.
4. Transpiration also maintains the turgidity of plant cells.

Plant release a large quantity of water vapour into atmosphere. For instance, an apple tree may lose 30 litres of water per day and a maize plant can lose 2 litres of water per day. Therefore, the large stretch of field and dense forests contribute a huge quantity of moisture through transpiration. This moisture further bring the rains.

Plants when injured, ooze out cell sap from the ruptured surface due to root pressure. This is very similar to bleeding in animals. Therefore, the term bleeding is used for it.

(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.

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

(ii) True

(iii) True

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

(v) True

(a) Three kinds of transpiration:

1. Stomatal transpiration.
2. Lenticular transpiration.
3. Cuticular transpiration.

(b) Three external factors which increase the rate of transpiration:

1. Increase in intensity of Sunlight.
2. Low humidity.
3. Increase in velocity of wind.

(c) Three intrinsic features which reduce the rate of transpiration:

1. Sunken stomata.
2. Narrow leaves.
3. Thick cuticles.

(d) Three extrinsic factors which decrease the rate of transpiration:

1. Increase in humidity.
2. Increase in carbon dioxide level in atmosphere.
3. Increase in temperature.

(e) Four potometers named after their discoverers :

1. Farmers's potometer
2. Ganong's potometer
3. Darwin's potometer
4. Garreau's potometer

(i) Leaf D — 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 — It was coated with grease on both the surfaces. Hence, it 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.

(a) Name of the apparatus is Ganong's potometer.

(b) Ganong’s potometer is used to measure the rate of water intake by a plant.

(c) The air bubble which was introduced into the horizontal graduated capillary tube moves along as transpiration proceeds. As the water is lost from the twig, a suction force is set up which pulls the water from the beaker and the bubble in the capillary tube moves along.

(d) Reservoir is used to release the water into the capillary tube by opening the stop cock.

(e) The movement of air bubble is affected as follows:

1. 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.
2. During the day, the stomata are open to facilitate the inward diffusion of CO₂ for photosynthesis. At night they are closed. Therefore, more transpiration occurs during the day. As a result, the movement of the air bubble would be larger since there would be more loss of water due to transpiration.
3. 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.

(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.

(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:

1. Cooling effect.
2. Creating suction force.
3. Distribution of water and minerals.

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

(d) Below diagram shows an opened stomata:

(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) The purpose of putting oil in the test tube is to prevent loss of water from the test tube by evaporation.

(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:

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

(f) Some plants have developed adaptations to reduce transpiration to cut down loss of water such as:

1. Sunken stomata
2. Narrow leaves
3. Reduced exposed surface by rolling or folding of leaves.

(a) The guidelines A and B are:

• A → Guard cells
• B → Stoma

(b) Most of them are found under the leaf i.e. abaxial side of leaf.

(c) It regulates the opening and closing of the stomata.

(d) Three important roles of structure B are:

1. Transpiration.
2. Intake of carbon dioxide for photosynthesis.
3. Respiration.

(e) The flaccid condition occurs when there is less absorption of water. In such condition the cells lose their turgidity and the stomata closes.

(a) These tiny openings are called lenticels.

(b) Two functions of lenticels -

1. They facilitate transpiration.
2. They allow exchange of gases.
   s (c) Stomata and hydathodes.

(a) Lenticels.

(b) Guttation.

(c) Potometer.

(d) Nerium.

(e) Ganong's potometer.

(f) Stomata and Cuticle.

(g) Hydathodes.

(h) Guttation.

(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).