Multiple Choice Questions:
Put a tick mark against the correct alternative in the following statements:
1. Diffusion occurs when molecules move:
A. from lower concentration to higher concentration.
B. from higher concentration to lower concentration through a membrane.
C. from higher concentration to lower concentration.
D. when energy is used.
Solution: (C) from higher concentration to lower concentration.
2. Ascent of sap in plants takes place through.
A. Cortex
B. Epidermis
C. Xylem
D. Phloem
Solution: (C) Xylem
3. If the xylem vessels of a plant are plugged:
A. The leaves will turn yellow
B. No food will be made
C. The plant will wilt (shrivel)
D. The plant will continue to grow
Solution: (C) The plant will wilt (shrivel)
4. Force responsible for the ascent of sap is:
A. Capillary force
B. Root pressure
C. Transpirational pull
D. All the three
Solution: (D) All the three
5. Raisins swell when put in:
A. Rainwater
B. Tap water
C. Mustard oil
D. Saturated sugar
Solution: (A) Rainwater
6. The root-hairs are suited for absorbing water from the soil because:
A. They have a large surface area
B. They have a large surface area
C. They contain a Sol. of higher concentration than the surrounding water.
D. All the three.
Solution: (D) All the three.
7. Transpiration is defined as:
A. the rise of water up to the stem of a plant.
B. the elimination of water with dissolved water products.
C. the loss of water as water vapour from the aerial parts of a plant.
D. the loss of water as water vapour from the roots as well as the leaves of the plant.
Solution: (3) the loss of water as water vapour from the aerial parts of a plant.
8. Which one of the following favours the fastest transpiration rate?
A. A cool, humid, windy day,
B. A hot, humid, windy day,
C. A hot, humid, still day,
D. A hot, dry, windy day.
Solution: (D) A hot, dry, windy day.
Short Solution. Questions:
Question 1. An experiment was set up as shown in the figure below. After some time, the Water level in test tube A fell down but not in test tube B. Why was there a fall in the water level of test tube A and not in that of test-tube B?
Solution:
The plant in test tube A absorbed the water through its hidden roots, causing the water level to drop. Since there is oil present, there won’t be any water lost due to evaporation of the water’s surface. Since test-tube B doesn’t have a rooted plant in it, the water level there remains unchanged. The oil on the water’s surface stops the evaporation of the water.
Question 2. How are roots useful to the plants? Give any two points.
Solution:
Plants can benefit from roots in the following ways:
1. It moves water and minerals up to different regions of a plant by absorbing them from the soil.
2. The plant needs roots to become strongly rooted to the ground.
Question 3. What do xylem vessels carry?
Solution:
The xylem vessels transport the water and minerals that the roots have absorbed to the stem and leaves.
Question 4. Name the plant tissue which helps in carrying the food to different parts.
Solution:
Phloem tissue helps the plant in carrying the food to different parts.
Question 5. Define the terms:
(a) Semi-permeable membrane
(b) Osmosis
Solution:
(a) Semi-permeable membrane: The movement of solvent molecules is allowed through a membrane (like water molecules) but it prevents the movement of solute particles (like sugar or salt molecules).
For example: Egg membrane, Parchment membrane, Cellophane Paper etc. are semi-permeable membranes.
(b) Osmosis: Osmosis is the process of water molecules flowing from an area where it is more concentrated to a region where it is less concentrated through a semi-permeable membrane. Osmosis, then, is the flow of water via a semi-permeable membrane from its pure state or reduced Sol. into a stronger or concentrated Sol.
Question 6. Under what conditions do the plant transpire?
(a) more quickly and
(b) most slowly?
Solution:
(a) The plant transpiration is faster on hot summer days as compared to cold winters.
(b) The plant transpiration is decreased in humid air. When air is already filled with moisture, it cannot hold any more water molecules (humidity).
Question 7. Given here is an enlarged diagram of a part of the root. Draw arrows on the diagram to show the movement of water passing through different parts.
Solution:
Path of water through the root hair to the xylem vessels.
Question 8. Why is the structure of the root hair quite suitable for absorbing water from the soil?
Solution:
The root hair is suitable for absorbing water from the soil in the following three ways:
1. There are root hairs on a large surface. Greater absorption results from larger surface areas.
2. The semi-permeable membrane is formed by the plasma membrane surrounding the vacuole and the permeable membrane is composed of the cellulose-based cell wall.
3. The content of Sol. (cell sap) in root hairs is higher than that of the nearby soil water.
Unicellular root hairs navigating the soil particles
Question 9. Briefly explain, how transpiration helps in upward conduction of water in plants?
Solution:
(a) The plants continuously absorb water through their roots. All plant parts, including the leaves, receive this water through the stem. The plant only uses a small amount of water for photosynthesis or for storage. The remaining part evaporates as water vapour into the atmosphere through cell walls found in the epidermis of the plant’s leaves and other aerial components. As a result, a suction pressure is created, drawing water up from the roots’ xylem and moving it to the stem and then the leaves.
(b) The force will be stronger because xylem tissues, which take the form of capillary tubes (level of capability and fibres), have a smaller diameter. Water from below rises into the xylem vessels by a capillary force whenever they are empty, such as when water is lost during transpiration. Water evaporates from the leaves’ surface during the day as a result of transpiration. Due to their ability to keep joined water molecules, more and more of them are pulled up throughout this process (cohesion). In the case of tall trees where water conducts upward, this pulling force produced by the leaves is important.
Question 10. How does temperature, light intensity and wind affect transpiration?
Solution:
Temperature: Transpiration moves more quickly on hot summer days than it does on chilly winter ones.
Brightness level: The rate of evaporation increases as the light intensity rises. During the day, the rate of evaporation rises in the sunshine. The stomata remain open to permit the inward flow of carbon dioxide for photosynthetic bacteria during the night, which is when evaporation is least likely to occur.
Wind: When the wind is blowing more fast, water evaporates from leaves more quickly.
Question 11. The set up shown alongside was kept in sunlight for an hour. It was observed that drops of water appeared on the inside of the polyethylene bag.
(a) Name the process which is being demonstrated.
(b) Why was the pot and its soil left uncovered by the polythene bag ?
(c) Why was the pot left in the sunlight?
(d) Suppose the pot in this experiment was placed inside a dark room instead of placing it in sunlight for some time. What difference will be noticed?
Solution:
(a) The approach demonstrates that the water loss responsible for the polythene bag seeming dry is transpiration. The potted plant wrapped with the polythene bag will lose water while it is kept in the sun through the stomata on its leaves. The water drops will appear within the polythene bag as a result of the stomata losing water. This is caused by transpiration.
(b) Given that the potted plant is under sunlight. The moist soil and the pot will also release water vapors. These vapors (water droplets) will also go into the polythene if it is used to cover the pot and the soil. We removed the polythene bag from the container and soil in order to see the water loss from the plant’s aerial portions, which were covered with it. This proves that the polythene bag’s water collection is a result of the plant’s aerial parts.
(c) As we keep the container in the light, the stomata will open, allowing water to evaporate from the aerial parts of the potted plant and the stomata. The polythene bag will soon fill with water vapor in the sun due to increased water loss (transpiration).
(d) As long as the pot is kept within the room, the rate of water loss will be very low, and since the stomata won’t fully open, no water vapors will escape into the polythene bag. Retaining the pot in the area will drastically cut down on water loss, which will also drastically cut down on transpiration.
Question 12. State whether the following statements are true or false. Rewrite the false statements correctly.
(a) Water absorption mainly occurs through the root-hair.
(b) Water enters the root-hair by osmosis.
(c) Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant.
(d) A semi-permeable membrane allows larger molecules to pass through, but prevents the smaller ones.(e) Transpiration is the loss of water from the roots of the plant.
(f) Transpiration cools the plant when it is hot outside.
(g) During transpiration, the leaves lose more water from their upper surface.
Solution:
(a) Water absorption mainly occurs through the root-hair. (True)
(b) Water enters the root-hair by osmosis. (True)
(c) Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant. (True)
(d) A semi-permeable membrane allows larger molecules to pass through, but prevents the smaller ones. (False)
(e) Transpiration is the loss of water from the roots of the plant. (False)
(f) Transpiration cools the plant when it is hot outside. (True)
(g) During transpiration, the leaves lose more water from their upper surface. (False)
Question 13. Fill in the blanks with suitable terms given below:
(Fast, Leaves, Stomata, Conducting, Ascent, Humid)
(a) Transportation in plants is carried out by a __________ system.
(b) The upward movement of sap that contains water and minerals is called __________ of sap.
(c) Transpiration is more when the wind is blowing __________.
(d) Most water gets evaporated from the plant from its __________.
(e) Transpiration is reduced if the air is__________ .
(f) The leaves have more __________ on their lower surface.
Solution:
(a) Transportation in plants is carried out by a conducting system.
(b) The upward movement of sap that contains water and minerals is called ascent of sap.
(c) Transpiration is more when the wind is blowing fast.
(d) Most water gets evaporated from the plant from its leaves.
(e) Transpiration is reduced if the air is humid.
(f) The leaves have more stomata on their lower surface.
Long Solution Questions:
Question 1. Draw a magnified view of the root-hair, and describe, how it helps in the absorption of water from the soil.
Solution:
The above image shows a enlarge image of root hair. It is the elongated protuberance of a cell. This cell contains a material known as cell sap, which is more concentrated than the soil water nearby. The root hair is shielded by a very thin membrane on the ceiling that permits water molecules to flow through but prevents larger molecules from doing so. Osmosis enables soil water to reach the root hairs as a consequence.
Question 2. How does transpiration help the roots absorb water and minerals from the soil?
Solution:
In plants, the transpiration mechanism creates a suction pressure that pulls water up from the roots’ xylem to the stem and subsequently to the leaves. The tracheids and fibers that make up the xylem tissues are shaped like capillary tubes, where the force rises as the diameter decreases. Every time the xylem vessels are empty, such as when water is lost during transpiration, water from below rises into them by a capillary force. Transpiration draws up more and more water molecules because of the propensity of water molecules to stay together (cohesion). This pulling force created by the leaves is essential for tall trees where water conducts upward.
Question 3. Define the three processes by which plants absorb water and minerals from the soil.
Solution:
Following are the tree processes which help the plants to absorb water and minerals from the soil.
1. Diffusion: When we add sugar to milk, the sugar molecules are evenly dispersed throughout the milk and fill the intermolecular gaps. Through the process of diffusion, water from the soil moves from a higher concentration to a lower concentration and enters the root hairs.
2. Osmosis: Both the cell sap and the cell walls function as semi-permeable and permeable membranes, respectively. In comparison to the soil’s water + minerals, the concentration of cell sap is higher. As a result, osmosis allows water and dissolved minerals to reach the roots.
3. Active transport: Minerals and water are absorbed from the soil via root hairs. Since there is a higher concentration of water than root hair, water diffuses into the root hairs. However, in the case of minerals, they shift from molecules with lower concentration to those with greater concentration. Water then moves into the roots together with the minerals from the soil. Therefore, this is energy-intensive active transport moving in the opposite direction.
Question 4. How water absorbed by the roots is important for the plants?
Solution:
The water absorbed by the roots is important for the plant in three main ways:
1. Transportation: Substances in solution are moved from one area of the plant body to another by the water present there.
2. Food production: When sunshine is present, water is combined with carbon dioxide from the air to produce food (photosynthesis).
3. Cooling: When it’s hot outdoors, water is utilized to chill the plant by evaporating through the leaves.
Question 5. Name the factors which affect the rate of transpiration? State their role in each case.
Solution:
The following are the main factors that affect the rate of transpiration:
1. Sunlight: During daytime, the rate of transpiration is faster. This is because the stomata remain open to allow the inward diffusion of carbon-dioxide for photosynthesis. During dark, the stomata are closed, and hence transpiration hardly occurs at night.
2. Temperature: Transpiration is faster on hot summer days as compared to cold winter.
3. Wind: Transpiration is more when the wind is blowing faster as water evaporates faster from the leaves.
4. Humidity: Transpiration is reduced if the air is humid. Air cannot hold any water molecules when it is already laden with moisture (humidity).
5. Low atmospheric pressure: The rate of transpiration increases when the pressure is low.
Question 6. Mention the two ways in which transpiration helps the plants.
Solution:
Transpiration helps the plants in the following ways:
1. Cooling effect: The plant evaporates water during transpiration. The plant can cool itself while it’s hot outside since the heat needed for this evaporation comes from the plant itself (latent heat).
2. Transpiration helps in maintaining the concentration of the sap inside the plant body: Water is still being taken up by the roots from the earth. If extra water is not evaporated off, the sap will get diluted and won’t be able to absorb any more water or the nutrients the plant needs.
Question 7. Describe an experiment to show that the plant loses water through its leaves.
Solution:
Experiment: To demonstrate that the plants lose water through its leaves.
• Select a single little potted plant with a few branches that is well-watered. As indicated in A, place a polythene bag over the tree’s one branch and secure it with a rubber band.
• Another branch (B) of the same plant should have all of its leaves removed. This branch should also be covered with a polythene bag and secured with a rubber band.
• Place the plant in the sun, and check it again in four to six hours. You’ll see that drips have developed on the polythene bag’s inside surface over branch A, but not on branch B.
• This arrangement shows that the plant’s leaves are where the majority of water evaporation occurs.
Question 8. Name any three minerals whose deficiency causes diseases in plants. Give the symptoms of each deficiency.
Solution:
Minerals, or nutrient elements, are necessary for plants to grow healthily and successfully complete their life cycles. There are two primary groups for the minerals:
(i) Macro-Nutrients: They are acquired from soil and are needed in higher quantities. The following three macronutrients (minerals) are necessary for healthy plant growth and development.
1. Nitrogen (N) – Leaf yellowing and cereal grain wrinkles.
2. Phosphorus (P) – Delays in seed germination are caused by purple and red patches on leaves.
3. Potassium (K) – Bad Growth
(ii) Micro Nutrients: They are only sometimes needed, and soil is where they are also found.
The three minerals (micronutrients) whose deficiencies result in illnesses in plants are:
1. Iron (Fe) – Yellowing of Leaves.
2. Manganese (Mn) – Yellowing of leaves, with grey spots.
3. Zinc (Zn) – Desphaped leaves, yellowing of leaves, stunted plant growth.
Question 9. List out the differences between xylem and phloem.
Solution:
The Xylem tissue consists of four types of cells:
1. Tracheids: They are dead cells that are extended and have tapered ends. Their primary job is to support mechanically and carry water upward.
2. Vessels: They resemble tube-like structures that are stacked one on top of the other to create lengthy channels. Additionally to supporting mechanically, they move water and mineral salts laterally and vertically upward.
3. Fibres: They have a long, thin profile with tapered ends. They solely offer mechanical assistance.
4. Parenchyma: They are living cells that aid in the transport of minerals and water as well as the storage of meals.
The Phloem tissue consists of four types of cells:
1. Seive tubes: They make up the primary conducting component of the phloem and are composed of two cells each. These are vertical rows of linked end-to-end cylindrical cells. Seive plates are the end walls of these objects that have pores in them. Seive pilates aid in the transportation of dietary components between cells.
2. Companion Cells: They are connected to sewer tunnels. It facilitates the movement of food particles via sieve tubes.
3. Parenchyma: It is made up of unspecialized, thin-walled parenchymatous cells that store food.
4. Phloem fibres: They are elongated cell-based dead sclerenchyma fibers. These offer mechanical sturdiness.
