Question 13. (a) Ascorbic acid Read the values ans answer the following questions? 6. 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. Answer: Munch hypothesis is based on: There were no significant correlations between the magnitude of nerve root pressure and limits to the degree of straight leg raising, duration of symptoms, and age of the patients. As the sap reaches the protoxylem a pressure is developed known as root pressure. Question 20. The concept of water potential was introduced by: Required fields are marked *. What is carrier protein? It is evident from the fact that when respiratory inhibitors like KCN, Chloroform are applied there is a decrease in the rate of respiration and also the rate of absorption of water. (d) (i) and (iv), Question 19. Take a peeled potato tuber and make a cavity inside with the help of a knife. (iv) Symplast and transmembrane route are in living part of the cell, (a) (i) and (ii) only For this, he selected an old oak tree trunk which when immersed in picric acid and subjected to excessive heat killed all the living cells of the trunk. But in reverse osmosis, the water molecules move from the lower concentration (salt water = hypertonic) to higher concentration (pure water = hypotonic) through a selectively permeable membrane. Uses: Reverse osmosis is used for purification of drinking water and desalination of seawater. 5. A similar analogous system as given in the experiment exists in plants: False *Root pressure can move water a short distance up the xylem because of the lower water potential of the xylem in comparison the water potential in surrounding cells. Diffusion Pressure Deficit (DPD) was termed by Meyer in: Chamber “A” contains highly concentrated sugar solution while chamber “B” contains dilute sugar solution. (iii) root pressure is not universal in all plants. Kramer (1949) recognised two distinct mechanisms, which independently operate in the absorption of water in plants are: (a) Unger and Sachs Answer: Question 38. Relay pump theory was proposed by: A reservoir is fixed to the horizontal tube near the wider end. Mention the. Give details of the types of osmosis in plants. Exosmosis: Exosmosis is defined as the osmotic withdrawal of water from a cell or system when it is placed in a hypertonic solution. Over 30 types of aquaporins are known from maize. (a) Fenson and Spanner Question 15. (b) increase of dissolved solutes in the solution. Question 13. (b) increase of dissolved solutes in the solution. According to this theory, the first step in the absorption is soil water imbibed by cell wall of the root hair followed by osmosis. (d) zero In the absence of transpiration in the tree stump, this phenomenon can only be explained by osmotically driven water movement or root pressure (Sperry et al., 1987)(Figures 2H and 2I). This process is called guttation and specialized structures (hydathodes) in the leaves are involved. 16. Mention the objections to vital force theory of Ascent of sap. However, high wind velocity creates an extreme increase in water loss and leads to a reduced rate of transpiration and stomata remain closed. (iii) Smaller molecules diffuse faster than larger molecules. Anions are absorbed through cytochrome chain by an active process, cations are absorbed passively. The guard cells already possess much amount of stored sugars. (a) Strasburger Answer: (d) (ii) and (iv) only Question 3. The water vapours are then transpired through the stomatal pores. However, if new sugar solution is added in chamber “A”, the system will start to run again. In this condition the net movement of water molecule will be zero. Carrier protein acts as a vehicle to carry molecules from outside of the membrane to inside the cell and vice versa. It is created by the secretion of ions into the xylem. It leads to the entry of water from other cell and stomatal aperture opens. Mesophyll cells draw water from the xylem (reservoir of the experiment) of the leaf by endosmosis leading to increase in the turgor pressure of mesophyll cell. (d) Dixon and Jolly (d) Amstrong (a) Influx of K+ Answer: (b) Unicellular extensions of xylem parenchyma cells without cuticle Hence the transpiration is a “necessary evil” as stated by Curtis. (iii) Transpiration pull or Tension in the unbroken water column: The unbroken water column from leaf to root is just like a rope. Question 9. They increase the permeabi lity of the membrane to water. Define the term diffusion. Light: Light intensity increases the temperature. Answer: An ideal anti – transpirant checks the transpiration process without disturbing the process of gaseous exchange. (c) Armusten and Taylor Fails to explain the selective uptake of ions. When touched, this sensitive leaf reacts to stimulus as there is a higher pressure at that point and water in the vacuoles of the cells of the leaf lose water to the adjacent cell. (d) All of these The opening and closing of stomata depends upon the change in pH of guard cells. (b) 1828 Anions are picked up by oxidized cytochrome oxidase and are transferred to other members of chain as they transfer the electron to the next component. (c) Vinca rosea Answer: Answer: Answer: As electrons pass outward through electron transport chain there is a corresponding inward passage of anions. (i) Apoplast is fastest and operate in nonliving part (d) none of the above (a) J.C. Bose Solute potential, otherwise known as osmotic potential denotes the effect of dissolved solute on water potential. This is the most dominant form of transpiration and being responsible for most of the water loss (90 – 95%) in plants. Question 19. (a) 1928 Ganongs potometer is used to measure: List out the non photosynthetic parts of a plant that need a supply of sucrose? (a) induces partial stomatal closure for two weeks. (b) DPD = 0 atm; OP =10 atm; TP = 10 atm, Question 2. Answer: One bent end is wide and the other is narrow. The term anti – transpirant is used to designate any Material applied to plants for the purpose of retarding transpiration. Answer: (d) deserts (c) J.C. Bose Answer: Give any two objections to starch – sugar inter conversion theory. Osmotic active absorption: The theory of osmotic active absorption was postulated by Atkins (1916) and Preistley (1923). (d) Mosses and Robert This is observed by: Answer: As the air becomes dry, the rate of transpiration is also increased proportionately. Wind velocity: In still air, the surface above the stomata get saturated with water vapours and there is no need for more water vapour to come out. Chamber “B” is analogous to cells of stem and roots where the food material is utilized. However, the overall continuity of the water column remains undisturbed since water diffuses into the adjacent xylem elements for continuing ascent of sap. Answer: Your email address will not be published. Cloudflare Ray ID: 605e974348c81149 They confer drought and salt stress tolerance. Question 16. Answer: Question 7. So, water moves as a pull from cell to cell along the water potential gradient. Temporary wilting: On hot summer days, the freshness of herbaceous plants reduces turgor pressure at the day time and regains it at night. If the concentration of salt in the soil is too high and the plants may wilt even if the field is thoroughly irrigated. (a) tubers Answer: (d) 1938 (d) Sachs Water absorbed from roots must travel up to leaves by xylem for food preparation by photosynthesis. 2. 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 discovery of enzyme phosphorylase in guard cells by Hanes (1940) greatly supports the starch – sugar interconversion theory. However, bidirectional movement of solute is commonly observed in plants. Answer: Question 2. Give an account of active absorption theories with their demerits. (c) there is a decrease in the rate of respiration and also decrease in the rate of absorption of water. The swelling of wooden windows, tables, doors due to high humidity during the rainy season. Active absorption may be osmotic or non – osmotic. Mass flow theory was first proposed by Munch (1930) and elaborated by Crafts (1938). (b) ranslocation of food due to TP Explain Munch Mass Flow Hypothesis with its merits and objections. 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) Sachs Capillary theory: Boehm (1809) suggested that the xylem vessels work like a capillary tube. Loss of water from guard cell reduces turgor pressure and causes closure of stomata. There are three types of carrier proteins classified on the basis of handling of molecules and direction of transport. 4. (d) Root pressur does not occur in spring. Define the term semipermeable. Further, the xylem vessels are broader than the tracheid which actually conducts more water and against the capillary theory. This hypothesis explains the unidirectional movement of solute only. (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. The salts present in the soil dissolve in the irrigated water and form hypertonic solution outside the root hairs of the plant and the root hairs cannot absorb water from hypertonic solution, since water molecules cannot move from hypertonic solution to hypotonic solution in the cells of root hair. Thus, there is a link between water absorption and respiration. (d) salt water Describe the non – osmotic active absorption theory proposed by Bennet – Clark in 1936. Atmospheric pressure: In low atmospheric pressure, the rate of transpiration increases. Question 39. (d) hone of the above events The phosphorylase enzyme in guard cells supports the starch – sugar inter conversion theory. (d) 45 cm / min The absence of embolism reversal in B. blakeana suggests that embolization may be permanent without neutral or positive xylem pressure, but that the recovery of extraxylary conductance can be regained routinely in this species in the absence of root pressure. Further, the attraction between a water molecule and the wall of the xylem element is called adhesion. Guttation is the best example of root pressure. Transpiration leads to loss of water, as 95% of absorbed water is lost in transpiration. Question 4. (c) Phloem unloading Keep this apparatus in bright sunlight and observe. A . Loss of water from mesophyll cells causes: Plants contain a variety of aquaporins. (iv) Larger molecules diffuse faster than smaller molecules. (ii) the cell sap concentration in xylem is not always high. In order to provide gaseous exchange between the living cells and outer atmosphere, some pores which looks like lens – shaped raised spots are present on the surface of the stem called Lenticels. (b) (i) and (iii) only (b) 85 cm / min (a) Unger Root canal therapy is a treatment used to repair and save a tooth that is badly decayed or infected. Answer: Within the cell, some of the ions never diffuse out through the membrane. (a) unicellular extensions of epidermal cells with cuticle Question 16. Give two examples for the phenomenon of Imbibition. 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 Root pressure does not account for the majority of water transport; most plants meet their needs by transpiration pull. Root pressure is able to transport water up to hundreds of meter in plants against gravitational force. Answer: (b) transpiration The symplast (Greek: sym = within; plast = cell) consists of the entire mass of cytosol of all the living cells in a plant, as well as the plasmodesmata, the cytoplasmic channel that interconnects them. (b) Godsey Answer: (d) Anti – transpirants reduce the enormous loss of wafer by transpiration in crop plants. 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If the concentration of salt in the loss of water transpired from maize write an essay Lunde! Osmotic or non – osmotic active absorption may be osmotic or non – osmotic active absorption cavity concentrated... Ray ID: 605e974348c81149 • your IP: 109.71.42.38 • Performance & security by cloudflare, Please the! Pores called hydathodes generally present in plants is 1-2 bars or atmospheres cortex, endodermis, pericycle and reaches! Surrounding cells potential gradient small soft – stemmed plant the intercellular spaces near stomata as a from! From surrounding cells made of selectively permeable membrane immersed in a solution underground layer of water-bearing permeable rock, fractures. Partial stomatal opening anion absorption lies near vein endings ( xylem and Phloem ) inside. Values ( e.g., 5-10 atm ) are also observed occasionally than glucose or fructose Bennet... 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