Question 1

Question 1Define the following terms:(a) Transpiration(b) Exudation(c) Potometer(d) Wilting(e) Hydathodes(f) Cuticle

Accepted Answer

(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.

Question 2

Question 2Distinguish between the following pairs:(a) Stomata and Lenticels(b) Guttation and Bleeding(c) Transpiration and Evaporation

Accepted Answer

(a) Difference between stomata and lenticelsStomataLenticelsThey are minute openings in the epidermal layer of leaves.They are minute openings on the surface of old woody stems.Maximum transpiration occurs through stomata.Lesser transpiration occurs through lenticels.(b) Difference between Guttation and BleedingGuttationBleedingIt occurs from the edges of leaves by hydathodes in uninjured plants.It occurs from any cut or injured part of a plant.The exudate is mainly water with some dissolved mineral salts.The exudate is mainly plant sap and sugars.It occurs during early mornings or late nights.It occurs at the time of injury.It happens in certain plants like Banana, Nasturtium, Strawberry.It occurs in all plants that have been cut or injured.(c) Difference between Transpiration and EvaporationTranspirationEvaporationIt is the loss of water in the form of vapour from the aerial parts of the plant.It is the loss of water from the surface of water bodies in the form of vapour.It is a slow process.It is comparatively a faster process.

Question 3

Question 3Give reason/suitable explanation for each :(a) Nerium loses less amount of water during transpiration.(b) More transpiration occurs from the under surface of a dicot leaf.(c) Transpiration increases with the velocity of wind.(d) Leaves of some plants wilt during midday and recover in the evening.(e) Guttation normally occurs during early mornings or late nights.(f) Forests tend to bring more rains.

Accepted Answer

(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.

Question 4

Question 9Hydathodes are located on:At the petioleUpper surface of leavesLower surface of leavesMargins of leaves

Accepted Answer

Margins of leavesReason — Hydathodes are the tiny pores located on leaf margins. They are responsible for guttation.

Question 5

Question 10When guard cells are flaccid, the stoma must be:OpenNeither open nor closedClosedNone of these

Accepted Answer

ClosedReason — 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.

Question 6

Question 4An outline sketch of a tree is shown in a diagram below. Study the same and answer the questions that follow:(a) Name and define the phenomenon labelled A in the diagram.(b) Write the significance of the process mentioned in A for the plants.(c) What do the direction of arrows in B and C indicate? Name the phenomenon.(d) Draw a neat and labelled diagram of an opened stomata.

Accepted Answer

(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.Creating suction force.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:

Question 7

Question 5The figure given below represents an experimental set up with a weighing machine to demonstrate a particular process in plants. The experimental set up was placed in bright sunlight. Study the diagram and answer the following questions.(a) Name the process intended for study.(b) Define the above mentioned process.(c) When the weight of the test tubes A and B is taken before and after the experiment, what change is observed? Justify.(d) What is the purpose of keeping the test tube B in the experimental setup?(e) What is the purpose of putting oil in the test tube?

Accepted Answer

(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.

Question 8

Question 6An apparatus as shown below was set up to investigate a physiological process in plants. The setup was kept in sunlight for two hours. Droplets of water were then seen inside the bell jar. Answer the questions that follow:(a) Name the process being studied.(b) Explain the process named above in (a).(c) Why was the pot covered with a plastic sheet?(d) Suggest a suitable control for this experiment.(e) Mention two ways in which this process is beneficial to plants.(f) List three adaptations in plants to reduce the above mentioned process.

Accepted Answer

(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) Some plants have developed adaptations to reduce transpiration to cut down loss of water such as:Sunken stomataNarrow leavesReduced exposed surface by rolling or folding of leaves.

Question 9

Question 7Given below is the figure of a stoma. Study the same and answer the following questions:(a) Label the guidelines A and B.(b) Write the exact location of the above mentioned structures.(c) Mention one important role of structure A.(d) Write three important roles of structure B.(e) Redraw the same figure when structures A are in flaccid condition. When does flaccid condition occur ?

Accepted Answer

(a) The guidelines A and B are:A → Guard cellsB → 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:Transpiration.Intake of carbon dioxide for photosynthesis.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.

Question 10

Question 8The figure given below is a transverse section of an old woody stem. It shows very minute openings labelled - A on its surface.(a) What are these tiny openings called?(b) Mention two significant functions of these openings.(c) Name two other tiny openings which can be found on the surface or margins of leaves.

Accepted Answer

(a) These tiny openings are called lenticels.(b) Two functions of lenticels -They facilitate transpiration.They allow exchange of gases.s (c) Stomata and hydathodes.

Transpiration

Descriptive Type

Multiple Choice Type

Structured Application Skill Type