NIOS Class 12 Biology Chapter 8 Solution – Absorption, Transportation and Water Loss (Transpiration) in Plants
NIOS Class 12 Biology Solution Chapter 8 Absorption, Transportation and Water Loss (Transpiration) in Plants . NIOS Class 12 Biology Chapter 8 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
INTEXT 8.1
1.) Define diffusion.
Ans: . The movement of molecules from their higher-concentration region to their lower-concentration region is called diffusion. Diffusion is an effective method of transport of matter over short distances
2.) Give one point of difference between osmosis and diffusion.
Ans: the main difference between osmosis and diffusion semipermeable membrane is required for osmosis and not necessarily for diffusion
3.) Name the process because of which crystals of KMnO4 added to water makes it purple.
Ans: Diffusion is the process because of which crystals of KMnO4 added to water makes it purple
4.) If blood cells are placed in salt water what will happen to them ? Based on your answer state if salt solution is isotonic, hypotonic or hypertonic?
Ans: If blood cells are placed in salt water , the water will move out from the blood cells and they will shrink. The salt solution is Hypertonic because solution outside has higher solute concentration than inside the cell
5.) When does plasmolysis occur in plant cells?
Ans: When a cell is placed in a hypertonic solution, or when the outside solution’s concentration is higher than the cell sap, water from the cell moves out, causing the protoplasm in the cell’s centre to shrink. This is called as Plasmolysis. The bathing solution fills the area between the cell wall and protoplast because the dead cell wall is permeable to the external solution.
6.) Name the phenomenon which makes it difficult to close a wooden door after monsoon?
Ans: The phenomenon which makes it difficult to close a wooden door after Monsoon is Imbibition
INTEXT 8.2
1.) Which part of the plant absorbs water and minerals?
Ans: Roots absorbs water and minerals
2.) What are plasmodesmata?
Ans: Plasmodesmata is Cytoplasmic connections between plant cells.
3.) How does translocation occur in plants?
Ans: . Translocation occur in plants hrough the phloem
4.) What is the process of ascent of sap?
Ans: Movement of minerals and water from the earth to the plant’s apex, or from the roots to the leaves is called ascent of sap
5.) Which are three different forms in which water is present in the soil?
Ans: Gravitational, Hygroscopic and capillary are the three different forms in which water is present in the soil.
INTEXT 8.3
1.) Name the pressure in guard cells responsible for opening and closing of stomata.
Ans: Turgor pressure responsible for opening and closing of stomata
2.) Mention the shape of guard cells in monocots and dicots.
Ans: The shape of guard cells in Dicot is Kidney shaped and in Monocots is Dumb bell shaped
3.) Give a point of difference between a stoma and a hydathode
Ans: Stomata, which are pores on the surface of leaves, allow water to evaporate.
Special pores called hydathodes, located on the leaf margins, allow water to evaporate as water droplets.
TERMINAL EXERCISE
1.) Name two types of passive absorption in plants.
Ans: Through osmosis and root hair cells the absorption occurs in plants.
2.) In what ways diffusion is important to a plant ?
Ans: With the help of diffusion , the movement of water from one cell to another can be possible.
3.) Name various factors that affect osmosis in plants.
Ans: The process of water molecules diffusing through a semipermeable membrane from a location of high concentration to a region of low concentration is known as osmosis.The factors affecting are concentration gradient, temperature, pressure etc.
4.) Differentiate between turgor pressure and wall pressure.
Ans:
Turgor pressure | Wall presure |
Turgor Pressure is the pressure exerted by the protoplasm against the cell wall. | Wall pressure is the pressure exerted by the cell wall against the protoplasm |
Cell burst when turgor pressure is more | Cell do not burst when wall pressure is more |
5.) Discuss the mechanism of stomatal opening in dicot plants.
Ans: Stomata open and close depending on alternately turgid and flaccidity in guard cells and subsidiary cells. The guard cells in dicotyledonous plants are kidney-shaped. The stoma’s inner walls are thicker than its outer walls. Wgen turgor pressue in guard cell increases, it expands. The tough inner walls become convex and these way stomata opens. After this, the pressure in guard cell decreases , the guard cells sag and the inner wall come closer and hence the stomata gets close.
6.) Explain any four factors that affect transpiration in plants.
Ans: The loss of water from aerial parts of the plant in the form of water vapour is termed transpiration. The factors that affecting transpiration are
- Temperature: A rise in temperature causes the rate at which water evaporates from cell surfaces to increase, while a fall in atmospheric humidity, to increase the rate of transpiration.
- Light: Light does not directly alter the rate of transpiration, but it does so indirectly through two different mechanisms: first, by regulating the stomatal opening, and second, by influencing the temperature. Because the stomata open and the temperature rises with an increase in light intensity, the rate of transpiration also increases.
- Water availability: A lack of water in the soil slows down the rate of absorption, which in turn slows down the rate of transpiration. The plants wilt when there is too much of a water shortage in the soil, and they cannot recover until water is added to the soil.
- Atmospheric pressure: Lowering atmospheric pressure lowers the density of the outer atmosphere, allowing for faster water diffusion. Because high-altitude plants transpire at a higher rate, they exhibit xerophytic characteristics.
7.) Describe an experiment to demonstrate osmosis by potato osmometer
Ans: To demonstrate the phenomenon of osmosis through plant membrane a potato osmoscope is used.An experiment is done on the potato whose one side is cut into a flat surface and on another side a cavity is made which is filled by sugar solution. Keep the potato in a beaker containing a small amount of water which is lower than the sugar solution.After sometime the level of sugar solution in the cavity rises. This is because the living cells of potato tuber collectively act as differentially permeable membrane, Water molecules continue to move through the cell-membranes, into the sugar solution till the concentration of water molecules in the beaker becomes equal to that in the cavity of the osmoscope.
8.) Discuss the cohesion tension theory for uptake of water in plants.
Ans: This theory accounts for the physical forces that carry water to enormous heights in extremely tall trees. Cohesion force (attraction between water molecules), adhesion force (attraction between water and lignocellulose walls of xylem), and transpiration pull (which raises the water column by inducing tension inside the xylem vessel) are the three forces that work in this. From the mesophyll intercellular space of the leaf to the xylem of the leaf, through the stem and root, to the water in the soil, water forms an uninterrupted column. A water potential gradient exists between the leaf and the root, and transpiration causes a pull on the entire water column. Water is raised by the force of transpiration pull as long as the column is continuous from the outer atmosphere through the plant and down to the soil.
9.) Describe the mechanism of translocation of solutes. Name the most appropriate theory for the translocation of solutes in plants. Who proposed this theory?
Ans: The mechanism of translocation of solutes is that between the source (leaf) and sink (storage) cells, a water potential gradient is produced that causes the sugar solution in the phloem sieve tube to flow.In this instance, we observe a massive migration of sugar solution from the leaf mesophyll to leaf sieve tubes, and subsequently to all areas of the plant.
The most reliable theory for phloem translocation is this one, also referred to as the Munch hypothesis or the mass flow theory.It was proposed by Ernst Munch.
11.) Define transpiration.
Ans: Transpiration is the word used to describe the loss of water from a plant’s aerial portions as water vapour. Various environment factors like temperature, light, wind, humidity and internal Plants and animals factors like structure of leaf and root-shoot ratio affect the transpiration
12.) Name the holes in the bark through which transpiration in the bark of old trees takes place ?
Ans: Through lenticels ,the transpiration in the bark of old trees takes place
13.) Why is transpiration considered to be a necessary evil ?
Ans: Stomata remain open throughout the day to allow for the crucial photosynthesis process of absorbing carbon dioxide and releasing oxygen. Water vapour escape cannot be controlled when the stomata are left open for this crucial gaseous exchange. Therefore, water loss is a wasteful process that cannot be prevented since stomata must remain open in order to perform a task that is more crucial: absorbing carbon dioxide during the day to support photosynthesis. For this reason, transpiration was described by Curtis as a necessary evil in 1926.
14.) Give one way by which desert plants prevent transpiration
Ans: The plants present in the desert have their leaves in the shape of needle, which prevents transpiration.
15.) State one point of difference between transpiration and guttation.
Ans:In transpiration water is loss in the form of water vapour while in guttation it is loss in the form of water dropes.
Also See: Next Chapter No. 9 Question Answer