ICSE Class 10th Biology- Absorption By Roots & Transpiration Online Assessment

Wind velocity affects transpiration because it increases the rate of evaporation from the leaves. When wind blows over the surface of the leaves, it removes the water vapor that has evaporated from the stomata, creating a lower concentration of water vapor around the leaves. This difference in concentration causes more water to evaporate from the leaves, leading to an increase in transpiration. Therefore, higher wind velocity results in higher transpiration rates.

The term "bleeding" refers to the loss of water through a cut stem. When a stem is cut, it can lead to the release of sap or water from the vascular tissues, resembling the process of bleeding in animals. This loss of water can occur due to the damaged xylem vessels, which transport water and nutrients in plants. Therefore, "bleeding" is the appropriate term to describe this phenomenon.

Guttation is the correct answer because it refers to the process of exudation of xylem sap droplets on the edges of leaves. This typically occurs during the night when the root pressure is high and the stomata are closed. As a result, excess water is forced out through specialized structures called hydathodes, forming droplets on the leaf edges. Transpiration, diffusion, and condensation are not the correct answers as they do not specifically describe this process of sap exudation on the edges of leaves.

Xylem is the tissue concerned with the upward conduction of water in plants. It is responsible for transporting water and minerals from the roots to the rest of the plant. Xylem consists of specialized cells called tracheids and vessel elements that form long tubes, allowing for efficient water transport. Phloem, on the other hand, is responsible for the transportation of sugars and other organic compounds in plants. Therefore, the correct answer is Xylem.

The statement "Most transpiration occurs at midnight" is incorrect. Transpiration is the process by which water is evaporated from plants, mainly through their leaves. Transpiration rates are influenced by various factors such as temperature, humidity, wind speed, and sunlight. During the night, when temperatures are lower and sunlight is absent, transpiration rates are typically lower compared to daytime. Therefore, the correct answer is False.

Guard cells regulate transpiration by controlling the opening and closing of stomata, which are tiny pores on the surface of leaves. When guard cells are turgid, the stomata open, allowing for the exchange of gases and the release of water vapor through transpiration. Conversely, when guard cells are flaccid, the stomata close, reducing water loss. Therefore, the movement of guard cells directly influences the rate of transpiration in plants.

Active transport is a process in which molecules or ions move across a cell membrane against their concentration gradient, requiring the use of energy. Diffusion, on the other hand, is the passive movement of molecules or ions from an area of higher concentration to an area of lower concentration. Therefore, the direction of active transport is opposite to that of diffusion, as active transport moves substances against their concentration gradient while diffusion moves substances down their concentration gradient.

Imbibition is the correct answer because it refers to the process of absorption of water by plant cells through surface attraction. It occurs when the solid particles of a substance attract and hold water molecules, causing the substance to swell and expand. This process is important for the germination of seeds and the movement of water in plants. Diffusion, osmosis, and endosmosis are different processes that involve the movement of substances across a membrane, but they do not specifically refer to the absorption of water by plant cells through surface attraction.

Hydathodes are specialized structures found in the leaves of plants that allow for the release of excess water in the form of droplets. This process is known as guttation. Unlike stomata, which primarily regulate gas exchange, hydathodes specifically facilitate the excretion of water from the plant. Lenticels are small openings in the bark of woody plants that aid in gas exchange, but they do not play a role in guttation. Similarly, while the lower epidermis of leaves contains stomata, guttation primarily occurs through hydathodes.

Living cells placed in an isotonic solution tend to retain their shape and size because of osmosis. Osmosis is the movement of water molecules across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. In an isotonic solution, the concentration of solutes outside the cell is the same as inside the cell, creating an equal balance of water movement. Therefore, there is no net movement of water, and the cell retains its shape and size.

When the atmospheric pressure is low, the rate of transpiration will increase. This is because transpiration, which is the process of water loss from plants through their leaves, is driven by the difference in water vapor concentration between the inside and outside of the leaves. When the atmospheric pressure is low, the concentration of water vapor outside the leaves is also low, creating a larger concentration gradient and thus increasing the rate of transpiration.

Turgidity refers to the state of a cell where the cell wall is rigid and stretched due to the absorption of water. When water enters the cell, it exerts pressure on the cell wall, causing it to become firm and swollen. This state of turgidity is important for plant cells as it helps maintain the shape and structure of the cell, allowing it to provide support to the plant.

Osmosis is the process by which water enters root hairs. Osmosis is the movement of water molecules from an area of higher water concentration to an area of lower water concentration through a semi-permeable membrane. In the case of root hairs, they have a higher solute concentration than the surrounding soil, creating a lower water concentration in the root hairs. This causes water to move into the root hairs through osmosis, allowing the plant to absorb water and nutrients from the soil.

A hypertonic salt solution refers to a solution with a higher concentration of salt compared to the concentration inside the plant cell. Plasmolysis occurs when a plant cell is placed in a hypertonic solution, causing water to move out of the cell and the cell membrane to shrink away from the cell wall. Therefore, the plant cell getting plasmolysed suggests that it was placed in a hypertonic salt solution.

The characteristic "Grow downward into the soil" is not related to the suitability of roots for absorbing water because the direction of root growth does not determine its ability to absorb water. The other characteristics mentioned, such as tremendous surface area, higher concentration of cell sap, and thin cell walls of root hairs, are all directly related to the root's ability to absorb water efficiently.

Girdling around the trunk of a tree disrupts the flow of water and nutrients between the roots and the rest of the tree. This interruption in the transport system can cause the tree to stop absorbing water and nutrients, leading to its eventual death. If the tree cannot regrow to bridge the wound caused by girdling, it will be unable to sustain its growth and survival, ultimately resulting in its demise.

Sieve elements are responsible for the transport of food materials in higher plants. These cells form the phloem tissue, which is responsible for the translocation of sugars and other organic compounds from the leaves to other parts of the plant. Sieve elements are specialized cells that are connected end-to-end to form sieve tubes. These tubes allow for the movement of food materials through small pores called sieve plates. The movement of sugars and other nutrients is facilitated by pressure gradients and the activity of companion cells, which are closely associated with sieve elements.

Mycorrhizae is a symbiotic association between the roots of plants and fungi. It is estimated that nearly 90% of the flowering plants form mycorrhizal relationships. These relationships are beneficial for both the plants and the fungi involved, as the plants receive nutrients from the fungi while the fungi receive carbohydrates from the plants. Therefore, the correct answer is Mycorrhizae.

Steroid hormones are lipid soluble, which means they can easily pass through the plasma membrane through simple diffusion. This is because the plasma membrane is composed of a phospholipid bilayer, and lipid-soluble molecules can dissolve in and pass through this lipid layer without the need for transport proteins or energy. Steroid hormones are derived from cholesterol and have a hydrophobic structure, allowing them to dissolve in the lipid bilayer and enter the cell. Once inside, they can bind to specific receptors in the cytoplasm or nucleus and initiate various cellular responses.