Further, the attraction between a water molecule and the wall of the xylem element is called adhesion. 6. Question 17. What is the difference between co – transport and counter transport? (b) about 10 – 14μ and 3 – 10μ respectively Aquaporin Is a water channel protein embedded in the plasma membrane. Pumping action of living cells should be in between two xylem elements (vertically) and not on lateral sides. (d) 1938 (c) J.C. Bose Osmotic pressure of mesophyll cells and that of root hair do not confirm the requirements. Explain Munch Mass Flow Hypothesis with its merits and objections. Answer: (d) Anti – transpirants reduce the enormous loss of wafer by transpiration in crop plants. (b) Acacia melanoxylon, (a) i – b; ii – d; iii – a; iv – c Answer: (c) Abscisic acid (e) The process is endo – osmosis because the solvent (water) moves inside the cell. (d) Overton (d) Von Mohl, Question 26. Answer: Answer: The guard cells already possess much amount of stored sugars. HARD. With the help of your teacher discuss the results. Root pressure definition, osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves. The main contribution of the root pressure is to establish the continuous movements of the water molecules in the xylem which can be affected by the transpiration. (d) all the three above, Question 2. Describe the theory of K+ transport theory of stomatal opening. Answer: Question 38. Give reasons. Based on the direction of movement of water or solvent in an osmotic system, two types of osmosis can occur, they are Endosmosis and Exosmosis: Question 5. (d) (i) and (iv) Question 1. Root pressure is totally absent in gymnosperms, which includes some of the tallest plants. Although, root pressure which is developed in the xylem of the roots can raise water to a certain height but it does not seem to be an effective force in ascent of sap due to the following reasons: (i) Magnitude of root pressure is very low (about 2 atms). Incipient wilting: Water content of plant cell decreases but the symptoms are not visible. (c) Root pressure is more during early morning than afternoon. Define active absorption of water. Question 2. Root pressures, measured with a bubble manometer, ranged from 2 kPa to a maximum of 148 kPa in Cissus ... Root pressures were absent in members of the Passifloraceae (five species of Passiflora), Aristolochiaceae (three Answer: Explain briefly. Give details of the types of osmosis in plants. The soil water is hypotonic and cell sap is hypertonic. (c) 0.5 Performance & security by Cloudflare, Please complete the security check to access. Even in the absence of transpiration, some water can move into the roots and partially up the xylem columns. (c) 75 cm / min, Question 23. Root canal therapy is performed when the pulp which is composed of nerves and blood vessels in the tooth becomes infected or damaged. Question 17. Explain the theory of photosynthesis in guard cells observed by Von Mohl with its demerits. Find the role of turgor pressure in sudden closing of leaves when we touch the ‘touch me not’ plant. Explain the term counter transport. Mention any two uses of anti – transpirants. (b) Godsey ... View Answer. Active absorption may be osmotic or non – osmotic. Explain in detail about the cohesion tension theory proposed by Dixon and Jolly (1894). 2. Give details of symplast route of water movement. d. proton pumps. (b) Root pressure cannot explain ascent of sap beyond 10 metres. In this condition the net movement of water molecule will be zero. Chamber “A” is analogous to mesophyll cells of the leaves which contain a higher concentration of food material in soluble form. Addition of solute to pure water: Question 25. The phenomenon of food transportation from the site of synthesis to the site of utilization is known as translocation of organic solutes. In the absence of transpiration (e.g. Answer: Thus, the rate of water absorption is equal to the rate of transpiration. Question 7. Atmospheric pressure: In low atmospheric pressure, the rate of transpiration increases. Answer: The term anti – transpirant is used to designate any Material applied to plants for the purpose of retarding transpiration. In the symplastic route, water has to cross plasma membrane to enter the cytoplasm of outer root cell; then it will move within adjoining cytoplasm through plasmodesmata around the vacuoles without the necessity to cross more membrane, till it reaches xylem. This theory was rejected because the magnitude of capillary force can raise water level only up to a certain height. (c) diffusion and absorption (a) increases the pH level (b) osmosis alone Give an account of active absorption theories with their demerits. (iv) root pressure is universal in all plants. Another predicted consequence of interrupted Casparian strips is an inability to build up root pressure, a process necessary for vascular transport of nutrients and water in the absence of transpiration and for transport into non-transpiring organs (Wegner, 2014). (b) does not change water potential. (d) The cell become more turgid. In short “B” is consumption end called “sink”. (c) about 10 – 40μ and 3 – 10μ respectively, Question 24. What is meant by phloem unloading? ii. (b) there is an increase in the rate of respiration and decrease in the rate of absorption of water. Hence the transpiration is a “necessary evil” as stated by Curtis. Two hours and discuss with your teacher: Question 1. According to this hypothesis, organic substances or solutes move from the region of high osmotic pressure (from mesophyll) to the region of low osmotic pressure along the turgor pressure gradient. Question 6. Chamber “B” is analogous to cells of stem and roots where the food material is utilized. (a) Unger (d) all the three above The loss is compensated by water absorption through the xylem portion of the twig. (d) all the three above, Question 32. Question 12. Predawn root pressure, as evidenced by xylem sap exudation from cut stems, was observed in 61 species. (c) Crafts and Munch Question 23. (a) increases water potential Answer: Define the term Ion – Exchange. Question 9. Answer: The liquid coming out of hydathode is not pure water but a solution containing a number of dissolved substances. (iii) root pressure is not universal in all plants. (a) 1.0 Your email address will not be published. (i) Apoplast is fastest and operate in nonliving part It does this in order to promote or discourage nutrient uptake. (d) (i) and (iv), Question 19. Answer: Furthermore, the fact that root pressures tend to be lowest when water loss from leaves (transpiration) is highest, which is exactly when plants most need water, shows that … (b) Lenticular If the concentration of salt in the soil is too high and the plants may wilt even if the field is thoroughly irrigated. Cloudflare Ray ID: 605e974348c81149 (ii) Continuity of the water column in the plant: An important factor which can break the water column is the introduction of air bubbles in the xylem. Likewise, food prepared from leaves has to travel to all parts of the plant including roots. (b) hydrolyses reaction The loss of water from lenticels is very insignificant as it amounts to only 0.1% of the total. Question 11. Guttation is the best example of root pressure. Xylem sap will exude from the cut stem for hours or days due to root pressure. (b) developing fruits Answer: (d) the rate of transpiration Root pressure is not universal in all plants especially in trees. (a) Strasburger Due to association with molecules to be transported, the structure of carrier protein gets modified until the dissociation of the molecules. 16. Hills favour high transpiration rate due to low atmospheric pressure. By correlating two factors, water potential is written as, Ψw = Ψs + Ψp. What are the types of osmosis based on the direction of the movement of water? Temperature: With the increase in atmospheric temperature, the rate of transpiration also increases. A delayed response in pressure at the opposite end of a root segment could be caused by the capacitance of the root pressure probes, which would dampen the effect on P r . (a) unicellular extensions of epidermal cells with cuticle (high solute and low solvent) placed in the water, it swells up due to turgidity. (b) Acacia melanoxylon Explain the term reverse osmosis. 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. Question 19. Sucrose has low viscosity even at high concentrations and has no reducing ends which makes it inert than glucose or fructose. The trunk when dipped in water, the ascent of sap took place. Exosmosis: Exosmosis is defined as the osmotic withdrawal of water from a cell or system when it is placed in a hypertonic solution. Answer: (c) green Diffusion Pressure Deficit (DPD) was termed by Meyer in: Ψw = 0, Ψs = 2, Ψp = 0. Define the term Imbibition. Answer: (c) a solution containing a number of dissolved substances, Question 40. Apparatus consists of a horizontal graduated tube which is bent in opposite directions at the ends. Choose the correct answer (1 Mark) (a) two different molecules are transported in opposite direction. The term symport is used to denote an integral membrane protein that simultaneously transports two types of molecules across the membrane in the same direction. Near stomata as a result root pressure is absent in active absorption theories with their demerits plant that need a supply sucrose... Its surroundings a woody or herbaceous plant is girdled, the epidermis replaced... Root pressure ( b ) two different molecules are transported in opposite root pressure is absent in at narrow... Examples for the phenomenon is imbibition change in pH of guard cells Hanes... Observed a correlation between respiration and decrease in the rate of absorption of.... So, water potential ( Ψw = Ψs + Ψp indicate the correct answer ( Mark! 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