Transport in Plants

Both A and R are false.

Explanation — Plants utilize sunlight, water and carbon dioxide as raw materials to create glucose (their food), and release oxygen and water vapour as by products during the process of photosynthesis.

Both A and R are false.

Explanation — The food prepared by leaves is transported to all parts of the plant including the roots. Roots absorb water and minerals from the soil. Water is the raw material used to prepare food (glucose) by photosynthesis.

A is false and R is true.

Explanation — Transportation of water in plants from roots to leaves is carried out by the conducting tissue xylem, not phloem. Phloem is responsible for transporting prepared food throughout the plant.

Both A and R are true.

Explanation — The minerals have to be absorbed from a level of lower concentration (soil) to a level of higher concentration (cell). This movement of molecules from their lower concentration to a higher concentration requires energy and the process is called Active Transport.

A is true and R is false.

Explanation — Nitrogen is macronutrient, which means it is required in larger concentration by the plants.

A is true and R is false.

Explanation — The outermost layer of the root hair cell is the cell wall, but the cell wall is fully permeable, not semi-permeable. The cell membrane, located beneath the cell wall, is semi-permeable and is responsible for controlling the entry of water via osmosis.

1. Transportation in plants is carried out by a conducting system.

2. The upward movement of sap that contains water and minerals is called ascent of the sap.

3. Transpiration is more when the wind is blowing fast.

4. Most water gets evaporated from the plant from its leaves.

5. Transpiration is reduced if the air is humid.

Test tube A contains plant, therefore, the water level in test tube A falls because the water is absorbed by the plant through the roots dipped in the water. Since the test tube contains oil, no water loss occurred due to evaporation because oil prevents water molecules from evaporating. In test-tube B the water level remains the same because there is no plant present as well as oil refrains the water to evaporate.

(a) The main objective of the given experiment is to show how the water is transported in plants.

(b) The tissue which is responsible for the process shown in the figure is xylem.

(c) Two dyes which can be used in the above experiment to make a coloured solution are Eosin and Red ink.

(a) Transpiration is being demonstrated here.

(b) The pot and its soil were left uncovered by the polythene bag because in the experiment we need to observe the loss of water occurred by plants. If the pot is covered, the water from the soil may also get evaporated and we will not get accurate results.

(c) In sunlight, the rate of transpiration is faster as the stomata are open to allow inward diffusion of carbon dioxide for photosynthesis. Hence, the plant was left in sunlight.

(d) If the pot was placed inside a dark room, transpiration will hardly occur as the stomata of the plant are closed. Hence, negligible water droplets will get condensed on the inner side of polythene bag.

As water evaporates from the leaves during transpiration, it creates a suction force or tension in the xylem vessels. As a result of transpiration, a suction force is created in the xylem vessel. This force causes the water to be pulled up from the xylem in the roots to the stem and then to the leaves. This suction force helps draw more water up through the stem, which in turn causes the roots to absorb more water from the soil. This pulling force is called transpirational pull.

1. Temperature — Higher temperatures increase the rate of transpiration due to faster evaporation of water.
2. Light intensity — With Sunlight the rate of transpiration is faster as stomata are open to allow inward diffusion of carbon dioxide for photosynthesis. During night time, the stomata remain closed and hence transpiration hardly occurs.
3. Wind — Transpiration is more when the wind is blowing faster as water vapour moves away faster from the surface of leaves.

Magnified view of the root hair with its parts labelled is shown below:

(a) Outermost layer of the root — Cell wall

(b) Unicellular outgrowth — Root Hair / Epidermal cell

(c) Part that is freely permeable — Cell wall

(d) Part that is semi-permeable — Cell membrane

Phloem carries the food to different parts of the plant.

Two conducting tissues of the plants are:

1. Xylem
2. Phloem

The four components of Xylem tissue are:

1. Tracheids
2. Vessels
3. Xylem Parenchyma
4. Xylem Sclerenchyma

The four components of Phloem tissue are:

1. Sieve Tubes
2. Companion Cells
3. Phloem Fibres
4. Phloem Parenchyma

The three factors which increase the rate of transpiration are:

1. Light intensity
2. Wind speed
3. High Temperature

Three macro-nutrients are:

1. Nitrogen
2. Phosphorus
3. Potassium

Three micro-nutrients are:

1. Zinc (Zn)
2. Iron (Fe)
3. Manganese (Mn)

from higher concentration to lower concentration.

Reason — The movement of molecules (gas, liquid or solid) from higher concentration to lower concentration is called diffusion.

Xylem

Reason — Xylem the vascular tissue is responsible for the transport of water and minerals.

The plant will wilt (shrivel)

Reason — The xylem vessel of the plant is responsible for the conduction of the water and mineral salt in the plant body. So if the xylem vessels of the plant are plugged then the conduction of water will be stopped and then the plant will wilt.

All the three

Reason — Ascent of sap takes place through xylem. Forces like capillary force, root pressure, transpirational pull helps in this unidirectional movement of water.

Rain water

Reason — When raisins are placed in rain water, they absorb water through Osmosis as rain water serves as a dilute solution in comparison to the contents of raisins. In case of saline water and saturated sugar solution, they are more concentrated than the raisins hence Osmosis doesn't take place. As Mustard oil is not water, so it is not absorbed by the raisins.

All the three

Reason — Root hairs are long and thin so they can penetrate between soil particles and they have a large surface area for absorption of water which in return, increases the speed at which water and nutrients can be absorbed. The cell sap in the root hair cell is said to be of a high concentration as it contains more solutes compared to the surrounding soil water. This promotes water absorption.

the loss of water as water vapour from the aerial parts of a plant.

Reason — Transpiration is the loss of water in the form of water vapour from the aerial parts of a plant.

A hot, dry, windy day.

Reason — Transpiration is mainly affected by the temperature, humidity, and wind speed. On a hot, dry, windy day transpiration increases.

Both (1) and (2)

Reason — The decrease in water level is due to both absorption by the plant and transpiration through the leaves.

Only P and R

Reason — The root hairs are well-suited for absorption of water from soil due to their larger surface area, higher concentration of cell sap, and semi permeable nature of the cell membrane.

Only Q and R

Reason — The Xylem tissue consists of tracheids, vessels, wood parenchyma and wood fibres. Sieve tubes and companion cells are part of phloem, the tissue responsible for transporting prepared food, not water.

A semi-permeable membrane is a membrane which allows the passage of molecules selectively. It allows a solvent such as water molecules to pass through it freely but prevents the passage of the solute (sugar or salt molecules in solution).

Osmosis is the movement of water molecules from their region of higher concentration (dilute solution or with a lower solute concentration) to their region of lower concentration (concentrated solution or with a higher solute concentration) through a semi permeable membrane.

Diffusion is defined as the free movement of molecules of a substance (solute or solvent, gas, liquid) from the region of their higher concentration to the region of their lower concentration when the two are in direct contact.

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

The upward movement of water and dissolved inorganic particles from the roots to the leaves through the xylem tissue against gravity is called ascent of sap.

Translocation of food refers to the movement of food and other nutrients from one part of a plant to another.

A root hair is a long protuberance (extension) of an epidermal cell of the root that helps in increasing the surface area for absorption of water and nutrients from soil.

Two functions of Xylem are:

1. Transportation of water and minerals from roots to the aerial parts.
2. Tracheids, vessels and xylem sclerenchyma provide physical support.

Two functions of Phloem are:

1. Transportation of food prepared by leaves to all parts of plant.
2. Storage of food by phloem parenchyma.

Two functions of Root are:

1. Absorption of Water and Nutrients from the soil.
2. Roots anchor the plant firmly to the ground, providing stability.

Roots are useful to the plants in the following ways:

1. Roots absorb water and minerals from the soil.
2. Roots fix the plant firmly in the ground.

Xylem vessels carry water and mineral salts from the roots to the aerial parts of the plant.

(a) Plants transpire more quickly on hot, dry, windy days as Sunlight, higher temperatures, fast winds and low humidity increase the rate of transpiration.

(b) Transpiration is most slow on cool, humid, still days as lower temperatures, still winds and high humidity decrease the rate of transpiration.

Two ways in which transpiration helps the plants:

1. Cooling effect — Transpiration from the aerial parts of the plant, cools down the plant surface.
2. Ascent of sap and distribution of minerals — Transpiration results in the development of low water potential in the leaf tissues. Thus, water moves from the xylem tissue to the leaf cells and helps in the ascent of sap. Mineral ions also move up along with water due to the transpiration pull.

Three important uses of water in the plants are:

1. Transportation of food/sugars or minerals occur in solution form.
2. Water is required for photosynthesis.
3. Transpiration of water helps to keep the plant cool.

The three special features of root hairs which make then suitable for the absorption of water from the soil are:

1. The numerous root hairs provide a large surface area. More the surface area, greater is the absorption.
2. Root hairs contain cell sap which is of a higher concentration than the surrounding soil water.
3. The cell wall is freely permeable, i.e., permits movements of all types of substances. But the cell membrane is semi-permeable. It allows only some substances to pass through it.

On a humid day, air already contains moisture. This reduces the concentration gradient between the leaf's internal air spaces and the external environment. Therefore, transpiration is reduced if the air is humid.

Despite resulting in loss of water, transpiration remains a crucial process for the overall well-being of the plant because:

1. Transpiration provides cooling effect helping the plant to cool itself when it is hot outside.
2. Transpiration helps in maintaining the concentration of the sap inside the plant body.
3. Transpiration creates the suction force called transpirational pull that is necessary for ascent of sap.

1. True

2. True

3. True

4. False
   Corrected statement — A semi-permeable membrane allows smaller molecules to pass through but prevents the larger ones.

5. False
   Corrected statement — Transpiration is the loss of water from the aerial parts of the plant.

6. True