As osmotic pressure builds up the phloem sap will move to areas of lower pressure. In transpiration water is lost in the form of water vapour. Water enters the osmometer A because of osmosis resulting in mass flow from A to C and finally B. (April 85, 88, 90, 2001, Oct. 1997, M.Q.P., July 2008) Answer: During the day CO2 is used in photosynthesis, concentration is low in guard cells, as a result, the pH rises to 7.0. Expand DPD (M.Q.P.) Answer: of water occurs in this region. (1) Guttation If the cut end is contracted to a rubber tube, the liquid can be collected and the rate of exudation measured. Answer: MiC generated fluid flow in part of the apical ramification with negative apical pressure values but low shear stress and velocity. What is hypertonic solution? Zero. Answer: Question 5. The plasmodesmata allow the direct flow of small molecules such as sugar, amino acids and ions between cells. Question 16. (Apr. It the pressure exerted on the liquid contents of the cortical cells of the roots, under fully turgid condition this root pressure pushes the water up the xylem vessels to the aerial parts. In liquid and gaseous form they are in random motion that is both rapid and constant. F.B. (March 2011) Enzyme is activated and starch is hydrolysed to glucose phosphate. (a) Water is lost in vapour form. Give reason: The water when drawn out of the cell through diffusion into the extracellular fluid causes the protoplast to shrink away from the walls. Larger molecules, including transcription factors and plant viruses ! Aim: Why is diffusion important to plants? When a particular tree is chopped or saw down, we can generally see a stump that bleeds sap. Question 14. To demonstrate ascent of sap using a Balsam or Peperomia plant. 07) Transpiration takes place through stomata, cuticle and lenticel. Root pressure provides the impetus for this flow. It is also called Starch Sugar interconversion. Answer: Just below the air chamber there is a group of loosely arranged thin walled, colourless cells (parenchyma like cells) are called epithem (Epithem are loosely arranged thin walled parenchyma cells present just below the air chamber of hydathode). (July 2007) Fill the glass tube with coloured water. Question 4. We tested this hypothesis by resurrecting excised fronds using either simulated root pressure or capillary action alone. Answer: Sir. Proton Transport or Active potassium mechanism: This theory was explained by Levitt. Which theory was proposed by Dixon and Jolly? Factors affecting Transpiration: Temperature, light, humidity and wind speed. ... root pressure as the pressure developed in the tracheary element of the xylem as a result of metabolic activity of the root. Xylem sap will exude from the cut stem for hours or days due to root pressure. 90) (M.Q.P.,April 96, 99, 03, 2006, Oct. 97, 2003) Leaf surface are dotted with openings called stoma that are bordered by guard cells. Question 3. Answer: Answer: Question 2. 'Root Pressure'. A manometer can be attached to a plant stem to measure the root pressure. Expert Answer: Root pressure is the positive pressure that develops in the roots of plants by the active absorption of nutrients from the soil. Since the source-sink relationship is variable, the direction of movement in the phloem can be bi-directional. (3) Seen in some herbaceous plants only. The pressure of exudation can be demonstrated by placing a graduated glass tube to the cut end of the stem. The fungus provides minerals and water to the roots, in turn, the roots provide sugars and Nitrogen-containing compounds to the mycorrhizae. Epidermal cells in a leaf can have pressures ranging from 1.5 to 2.0 MPa. Please enable Cookies and reload the page. (4) Occurs only in the early morning time. Considering both the lack of K leaf recovery as measured with the RKM (in which no positive pressure was applied during rehydration), as well as the observed recovery of embolism following positive-pressure rehydration, it is possible that B. vulgaris requires positive root pressure to regain conductance and also to reverse embolization. Describe 3 properties of water responsible for transpiration driven ascent of sap. Question 10. Following changes bring closing of stomata. 91, 93, M.Q.P.) (c) Universal occurrence. If environmental conditions cause rapid water loss, plants can … Question 1. Click here to get an answer to your question ️ what is root pressure? So maximum absorption . The transport of a water column up a very tall tree can be explained by _____. Adhesion – an attraction of water molecules to polar surfaces. Exchange of oxygen and carbon dioxide in the leaf also occurs through stomata. Lopez, G.F. Barclay, in Pharmacognosy, 2017. The addition of solutes to water lowers its potential just as increase in pressure increases its potential. Mention any 2 theories on mechanisms of Phloem conduction. Fig. Question 5. In addition, for any substance to imbibe any liquid, affinity between the adsorbent and the liquid is also a prerequisite. Chemicals secreted into the soil by roots are referred to as root exudates. Answer: Transpiration is the evaporation of water from the aerial parts of plants, especially leaves but also stems flowers and roots. Distinguish between endosmosis and ex-osmosis. What are the factors affecting the rate of diffusion? Because of transpiration pull the water (eosin solution) rises into the root, through the stem leaves and because of the transparent stem Xylem appears red. (e) Apoplast and Symplast pathways of movement of water in plants. You can Download Chapter 11 Transport in Plants Questions and Answers, 1st PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations. (d) Imbibition and Diffusion (2) Loss of water takes place through hydathodes. If there is no restriction on flow, water molecules will proceed from the locus of pure water to the more negative water potential of the solution. Humidity: higher the humidity the rate of transpiration decreases i.e. (June 2009) Answer: Root pressure can be demonstrated in the following ways: Choose a well-watered soft-stemmed plant; Cut the stem horizontally near the base with sharp blade. Answer: Wind: When the wind velocity is high the rate of transpiration increases. Further water loss causes plasmolysis-pressure decreases to the point where the protoplasm of the cell peels away from the cell wall leaving gaps between the cell wall and the membrane, Eventually cytorrhysis- the complete collapse of the cell wall can occur. Whereas, cell becomes flaccid due to exosmosis. But, the source and sink may be reversed depending on the plant’s needs. Answer: Cohesion-tension theory. (Apr. Answer: Then connect a glass tube by means of a strong rubber tubing as shown in the figure. When there is a high soil moisture level, water will enter plant roots, because water potential of roots is lower than soil solution. It results in the opening of stomata. The mercury enables root pressure to be measured. How is it demonstrated experimentally? Answer: Imbibition is a special type of diffusion when water is absorbed by solids colloids causing them to enormously increase in volume. Arts: (b) Comparison of Munch Hypothesis in Plants A mycorrhiza is a symbiotic association of a fungus with a root system. Water potential of a cell is affected by both solute and pressure potential. During day time, guard cells consume (use) CO, Glucose -1 – P is convented into glucose -6 – phosphate in the presence of. According to this theory following changes bring the opening of stomata. The greatest contribution is to re-establish the continuous chains of water molecules in the xylem which often break under the enormous tensions created by transpiration. They are the ends of the xylem tissue of the veins. Give reason. Write any four significances of transpiration. (Oct. 2003) This theory was proposed by Dixon and Jolly (1894). As sugars are removed, the osmotic pressure decreases and water moves out of the phloem. 98, 02, Oct. 04, July 2011) Answer: C. Bose, Question 17. This dissociates into H+ and Malate ions and by using ATP exchange H+ for K+ to form Potassium malate. The theories put forth to explain Phloem conduction are, 1st PUC Biology Transport in Plants Three Marks Questions, Question 1. cause of the opening or closing of the stomata is a change in the turgidity of the guard cells. Guttation. When would you observe a positive root pressure? While this pressure is insufficient to refill embolisms in tall trees, it is adequate to repair embolisms in herbaceous crops. Surface tension – Water molecules are attracted to each other in liquid phase more than water in gaseous phase. (Oct. 98, March 09) What is Endosmosls? Increase the rate of water and mineral absorption. Water flows into the xylem by osmosis, pushing a broken water column up through the gap until it reaches the rest of the column. The significance of diffusion in plants is. Drops of fluid ooze out of the cut stem indicates a positive hydrostatic pressure, the root pressure. 272 Root pressure . Procedure: Give reason: Girdling experiment cannot be performed in sugarcane plants. Water enters the osmometer A because of osmosis resulting in mass flow from A to C and finally B. Question 7. This pressure can be demonstrated by cutting a stem, from which water will exude. Question 18. What is osmosis? • The water will accumulate in plant, creating a slight root pressure. lncreases rate of water absorption and mineral absorption. This, however, is the accepted model of phloem transport. The aerial parts of vascular plants are supplied with water and nutrients via the xylem conduit, a network of pipelines extending from roots to leaves. Material required : A potted plant, knife, rubber tube, glass tube, coloured water. Imbibition results in a pressure called imbibitional pressure of high magnitude and is defined as “the potential maximum developed in the imbibant due to entry of water.” Example: Wooden doors and windows absorb moisture in monsoon. The significance of transpiration are. Water molecules possess kinetic energy. Answer: Question 12. This process of loading at the source produces a hypertonic condition in the phloem. This process continues (evaporation absorption of water from the adjacent cells evaporation) upto the xylem vessels of leaf, then to the xylem vessels of petiole, stem and root. A manometer can be attached to a plant stem to measure the root pressure. Cell becomes turgid due to endosmosis. During the dark Photosynthesis decreases, CO2 concentration increases and PH decreases to 5.0. Imbibition is the absorption of water by hydrophilic colloids. erate to rapid no root pressure or exudation can be demonstrated. Unlike water, all minerals cannot be passively absorbed by the roots. The fungal filaments form a network around the young root or they penetrate the root cells. Hence different proteins in the membrane play a major role in both active as well as passive transport. Osmosis happens across a semipermeable membrane. Question 5. Question 5. Question 9. Imbibition is also diffusion since water movement is along a concentration gradient, the seeds and other such materials have almost no water hence they absorb water easily. when the atmosphere is saturated with water vapour) the root can maintain a positive pressure in the xylem sufficient to push water upwards against the gravitational field of the earth, thus providing the shoot with water required to maintain growth. The entire system is left in a trough D containing water. (March 2011) Define Plasmolysis? Answer: The hydathodes are present at the tips of the veins It consists of pore in the epidermis and it is guarded by guard cells. Transport of food material from one sieve-tube to the other. Answer: (March 2010) Root pressure can only provide a modest push in the overall process of water transport. 91,92,98, M.Q.P.) What role do they play in diffusion? Answer: It is a passive process. So turgor pressure is developed in the guard cells. The immediate It quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure or matrix effects including surface tension. What is Epithem? Root pressure usually develops during the night when absorption is maximum and transpiration is … can also be transported through with the help of actin structures. During night CO2 accumulates in guard cells and is converted to carbonic acid, PH decreases to 5.0 and causes the conversion of sugar to starch. Root pressure can be demonstrated in the following ways: Question 3. 87) Question 8. What happens to the plant cell when it is plasmolyzed? Question 1. If a well-aerated plant growing vigorously in spring is cut off slightly above the ground, water is seen to exude from the cut end of the stump through the xylem. From this observation, it is easy to conclude that here is the explanation for sap flow in maple, sap rising to the top of tall trees, and sap movement comes from a “pump” in the roots. The transport of a water column up a very tall tree can be explained by _____. What are the factors influencing transpiration? This occurs when the cell is placed in a solution that is hypertonic to the protoplasm. Answer: It is also believed that the force lifting the fluids is generated by transpiration and evaporation of water from the leaves and they are aided by the adhesive and cohesive forces of the molecules in the fluids and possibly with other factors, which all help to move fluids up the plant. Normally stomata are open in the day time and close during the night. (b) Loss of water takes place through stomata. explain with activity !!!! Question 7. Answer: Transport rate reaches a maximum when all the protein transporters are being used or are saturated. Explain Munch Hypothesis. Specific proteins in the membranes of root hair cells actively pump ions from the soil into the cytoplasms of the epidermal cells. The Xylem of the stem T.S. Photometer. Question 21. Question 25. A red streak can be seen through the transparent stem. The terms isotonic, hypotonic and hypertonic describe the difference in osmotic pressure between the solutions with a certain osmotic potential. Question 1. Importance of Transpiration: Transport of liquids and minerals is facilitated because of transpiration. (M.Q.P.) Question 4. The phenomenon is produced by the root cells having a solute concentration gradient which increases from outside the root towards the centre of the root. The phenomenon of guttation can be demonstrated by a simple experiment (see Fig. Water potential gradient between the absorbent and the liquid imbibed is essential for imbibition. Explain the cohesion tension theory; and mention its merits and demerits. Question 7. it has the same solute concentration as the cytoplasm. The upward movement of sap (mainly water) through the xylem from the base to the tip of the plant is called ascent of sap. Excessive use of chemical fertilizers result in wilting of plants. Another way to prevent getting this page in the future is to use Privacy Pass. Discuss any three environmental factors affecting transpiration. A growing root cell's turgor pressure can be up to 0.6 MPa, which is over three times that of a car tire. Write its one merit and one demerit (Oct. 99, July 2011) The water from B is forced out because of pressure created due to mass flow. Munch used a model system to explain the translocation of solutes. During guttation. DPD. Positive xylem sap pressure, usually attributed to root pressure (as opposed to stem pressure in maples), has been observed in grape vine (Sperry et al. Procedure: Take a regularly watered potted plant and cut the stem portion 1 cm above the ground level. Fresh grapes shrink in salt solution. What role does root pressure play in water movement in plants? Question 6. Root hairs provide enormous surface area for absorption. lf transpiration exceeds rate of absorption it results in death due to wilting. root pressure a force exerted within a plant root that pushes water up towards the stem. Water is drawn into the guard cells from the surrounding subsidiary cells. Cohesion – mutual attraction between water molecules. (Oct. 97, Apr. ‘A’ filled with concentrated sugar solution and ‘B’ with dilute sugar solution. Root pressure can be demonstrated in the following ways: Choose a well-watered soft-stemmed plant; Cut the stem horizontally near the base with sharp blade. (Oct. 87, M.Q.P., Apr. Shrinking of Protoplasm due to exosmosis when cells are placed in a Hypertonic solution. : ( July 2008 ) as the wind velocity is high the of... The swell up name and define the phenomenon of guttation can be in... 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