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Quiz 5
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Q.1
Which one is the driving force for the process of passive absorption of water in roots ... ...[ KCET 2010]
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a) Root pressure
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b) Transpiration in leaves
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c) Activity of aquaporins
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d) Increase in imbibition pressure in root cells
Explanation
Passive absorption is the type where the water absorption is through the transpiration pull. This creates tension or force that helps in the movement of water upwards into the xylem sap. Higher is the transpiration rate, higher is the absorption of water. Answer : (b)
Q.2
Water exudation through hydathodes is .... ... [ BHU 2000 ]
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a) Guttation
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b) Transpiration
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c) Hydrolysis
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d) Excretion
Explanation
Water exudation through hydathodes is Guttation Answer : (a)
Q.3
Stomata open by .... .... [ KCET 2012]
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a) Increasing solute concentration in guard cells
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b) Weakening of cell walls of guard cell to allow them to stretch
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c) Increasing water potential of guard cells
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d) Decreasing the solute concentration of guard cells
Explanation
An increase in solutes induces an influx of water across the guard cell membrane. As the volume of the guard cells increase, they “inflate” into two kidney-bean-like shapes. As they expand, they reveal the stoma opening in the center of the two guard cells Answer : (a)
Q.4
Cotton fibres dipped in water absorb water through ... ...[ RPMT 1996]
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a) Endosmosis
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b) Exosmosis
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c) Capillarity
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d) Imbibition
Explanation
Cotton fibres dipped in water absorb water through Capillarity Capillarity the tendency of a liquid in a capillary tube or absorbent material to rise or fall as a result of surface tension. Answer : (c)
Q.5
Which one is responsible for opening of stomata? .... ..[ Guj CET 2006]
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a) Decrease in CO2 concentration and increase in H+ ion concentration
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b) Decrease in CO2 concentration and decrease in H+ ion concentration
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c) Increase in CO2 concentration and increase in H+ ion concentration
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d) More free H+ ions and less Cl- ions
Explanation
If carbon dioxide concentrations inside the leaf start to fall, the plant will open its stomata so that more CO2 can enter The opening of gas exchange pores requires the uptake of potassium ions into guard cells. wihch decreases H+ ion concentration Answer : (b)
Q.6
In which type, the stomata are present exclusively on the upper surface of the leaves ... ...[ AMU 1991]
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a) Potato type
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b) Potamogeton type
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c) Barely type
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d) Water Lily type
Explanation
In lotus or Water Lily type, the leaves float on the surface of water. Theis lower surface is in touch with water and only upper surface is exposed. So all the three above mentioned functions are performed by stomata which are restricted to upper surface only Answer : (d)
Q.7
Plant cell kept in saline drop will ... .... [ Bih PMT 2004]
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a) Remain unchanged
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b) Decrease in size
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c) Increase in size
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d) Burst out
Explanation
When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become “flaccid”; this is the exact opposite of “turgid”. Answer : (b)
Q.8
Osmotic pressure is maximum in ... ... [ RPMT 1992]
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a) Hydrophytes
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b) Halophytes
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c) Xerophytes
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d) Mesophytes
Explanation
A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. To overcome this plants maintain a higher osmotic pressure in cell sap, so that they are able to absorb water inspite of high salt concentration in soil. Answer : (b)
Q.9
Stomata open during day due to ... ...[ Bih PMT 2002]
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a) Accumulation of K+ ion and sugar
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b) High pH
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c) Osmotic effect of ions present in guard cells
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d) None of the above
Explanation
Stomata open during day due to Accumulation of K+ ion and sugar Answer : (a)
Q.10
Latest explanation for closure of stomata is .... ... [ CPMT 2008]
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a) Starch glucose theory
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b) Active K+ ions theory
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c) ABA theory
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d) None of the above
Explanation
When turgor is lost, the stoma closes. In angiosperms and gymnosperms (but not in ferns and lycopsids), ABA is the hormone that triggers closing of the stomata when soil water is insufficient to keep up with transpiration. The mechanism: ABA binds to receptors at the surface of the plasma membrane of the guard cells Answer : (c)
Q.11
For the same amount of CO2 fixed, a C4 plant as compared to C3 plant loses only ... .... [ AMU 2009]
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a) Half amount of water
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b) Double amount of water
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c) Equal amount of water
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d) None of the above
Explanation
The water loss per g of biomass produced with C3 cycle is high (450 to 950) The water loss per g of biomass produced with C4 cycle is low (250 – 350) Answer : (a)
Q.12
Which one explains ascent of sap ... ...[ CPMT 1995]
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a) Cohesion-tension theory of Dixon and Joly
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b) Starch-sugar inter-conversion
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c) Photosynthesis
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d) None of the above
Explanation
The cohesion-tension theory (C-T theory) by Boehm (1893) and Dixon and Joly (1894) postulates that the water ascent in trees is exclusively due to the transpirational pull from continuous water columns in the xylem conduit running from the roots to the leafs Answer : (a)
Q.13
Which of the following is not the purpose of transpiration .... ... [ kerala 2010]
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a) Supplies water for photosynthesis
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b) Maintains shape and structure of plants
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c) Helps in translocation of sugar from source to sink
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d) Cools leaf surface
Explanation
The mechanism by which sugars are transported through the phloem, from sources to sinks, is called pressure flow. At the sources (usually the leaves), sugar molecules are moved into the sieve elements (phloem cells) through active transport. Hence translocation of sugar from source to sink has no relation with transpiration Answer : (c)
Q.14
The principal pathway of water translocation in angiosperms is ... ... [ BHU 2012]
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a) Sieve cells
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b) Sieve tube elements
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c) Xylem vessel system
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d) Xylem and phloem
Explanation
Xylem forms vascular bundles with the phloem and helps in the conduction of water and minerals from the root to the other parts of the plant. Xylem tissue consists of a variety of specialized, water-conducting cells known as tracheary elements. Answer : (c)
Q.15
Maximum water loss occurs through .... ... [ Har PMT 2005]
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a) Lenticels
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b) Hydathodes
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c) Stomata
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d) Cuticle
Explanation
Answer : (c)
Q.16
In guard cells when sugar is converted into starch, the stomatal pore ... .... [ CBSE 1992]
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a) Closes completely
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b) Opens partially
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c) Opens fully
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d) Remains unchanged
Explanation
According to starch-sugar interconversion theory, during night the glucose 1-phosphate (sugar) converts into starch in guard cells and thus increasing the osmotic potential. The guard cells release water, become flaccid and stomata closes. Answer : (a)
Q.17
Value of osmotic potential (π) and pressure potential (p) of cell a, b, c, d are given Identify the correct sequence for movement of water ... ... [ EAMCET 2005]
cell
π
p
a
-1.0
0.5
b
-0.6
0.3
c
-1.2
0.6
d
-0.8
0.4
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a) b → c → d → a
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b)c → b → a → d
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c) d → c → a → b
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d) b → d → a → c
Explanation
The formula for calculating water potential is ψ = π + p. Water always moves from the system with a higher water potential to the system with a lower water potential. cell a water potential = -0.5 cell b water potential = -0.3 cell c water potential = -0.6 cell d water potential = -0.4 Note the more solute there is, the more negative ψ becomes Now water will move from lower solute water to higher solute water Cell c have higest solute while cell b have lowest solute Water will move from cell b to other cells Answer : (d)
Q.18
Osmosis is defined as ... ... [ MPPMT 1998]
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a) Flow of solvent (water) through a semipermeable membrane from less concentrated solution to more concentrated solution
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b) Flow of solute from a semipermeable membrane
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c) Flow of water without a membrane
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d) None of the above
Explanation
Answer : (a)
Q.19
A leaf with more stomata on lower surface belongs to ... .... [ AMU 2002]
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a) Potato type
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b) Oat type
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c) Apple - mulberry type
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d) Nymphaea type
Explanation
Depending upon the distribution and arrangement of stomata in the leaves five categories of stomatal distribution have been recognized in plants Apple or mulberry (hypostomatic) type : Stomata are found distributed only on the lower surface of leaves, e.g., apple, peach, mulberry, walnut, etc. Oat (amphistomatic) type: Stomata are found distributed equally upon the two surfaces, e.g. maize, oats, grasses, etc. Water lily (epistomatic) type: Stomata are found distributed only on the upper surface of leaf, e.g., water lily, Nymphaea and many aquatic plants. Potamogeton (astomatic) type: Stomata are altogether absent or if present they are vestigeal. e.g., Potamogeton and submerged aquatics. Answer : (c)
Q.20
A cell placed in hypotonic solution will .... ...[ Odisha 2000 ]
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a) Shrink
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b) Show exosmosis
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c) Show endosmosis
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d) No change in shape or size
Explanation
When a cell is placed in hypotonic solution (dilute solution), water enters into the cell, hence cell will show endosmosis. Answer : (c)
Q.21
Select the correct evens leading to stomatal opening ... ... [ kerala 2009] a) Decline in guard cell solutes b) Lowering of osmotic potential of guard cells c) Rise in K ions in guard cells d) Movement of water from neighboring cells into guard cells e) Guard cells become flaccid
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a) a, e
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b) b, c, d
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c) a, c, d
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d) b, d, e
Explanation
When the concentrations of solutes decrease in guard cells in the cases of ABA and elevated CO2, water potential increases in the cells and water flows out, causing a decrease of turgor pressure and closure of the pores. statement "a" not related to stomata opening When guard cells losses water, causes the cells to become flaccid and the stomatal opening to close Answer : (b)
Q.22
Rate of water absorption is slow near freezing point because ... ... [ AMU 1997]
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a) Water absorption is a metabolic process
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b) Cell growth stops
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c) Transpiration is reduced
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d) Cell membranes become more viscous
Explanation
Because permeability of cell membrane decreases as both membrane and water become viscous. At low temperature, the fatty acid tails of the phospholipids move less and become more rigid. This decreases the overall fluidity or become viscous of the membrane Answer : (d)
Q.23
Osmometer having 0.5M solution can be made to shrink when immersed in solution ... ...[ KCET 2012]
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a) 0.05M
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b) 0.75M
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c) 0.5M
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d) Distilled water
Explanation
Osmometer will shrink when it is placed in a hypertonic solution. It loses water due to osmosis and shrinks. So the only solution which is hypertonic to the osmometer is 0.75 M. Answer : (b)
Q.24
Water rises in the stem due to ... ..... [ RPMT 2000 ]
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a) Cohesion and transpiration pull
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b) Turgor pressure
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c) Osmotic pressure
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d) None of the above
Explanation
Transpiration pull,Cohesion is the phenomenon of attraction between similar molecules. The water molecules remain attracted by the cohesive force and cannot be easily separated from one another Due to cohesion between water molecules and transpiration pull, water rises upwards in the stem. Answer : (a)
Q.25
Which ones are true and false? a) Positive hydrostatic pressure is called turgor pressure b) Wall pressure exerts to prevent the increase of protoplasm size c) Diffusion of water through a semipermeable membrane is called imbibition d) Osmosis is movement of substances which takes place along a diffusion gradient ... ...[ kerala 2006]
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a) a and b are true but c, d are false
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b) a and c are true but b, d are false
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c) a and d are true but b, c are false
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d) a is true but b, c and d are false
Explanation
The diffusion of water through a selectively permeable membrane is called osmosis. Statement (c) is NOT correct Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes.Statement (d) is NOT correct Answer : (a)
Q.26
Which is produced during water stress that brings stomatal closure ... ... [ BHU 1991]
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a) Ethylene
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b) Abscisic acid
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c) Ferulic acid
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d) Coumarin
Explanation
Abscisic acid (ABA) inhibits light-induced stomatal opening through calcium- and nitric oxide-mediated signaling pathways. Answer : (b)
Q.27
The most widely accepted theory for ascent of sap in trees is ... ... [ BHU 1996]
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a) Capillarity
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b) Role of atmospheric pressure
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c) Pulsating action of living cell
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d) Transpiration pull and cohesion theory of Dixon and Joly
Explanation
The most widely accepted theory for ascent of sap in trees is, transpiration pull and cohesion theory of Dixon and Joly Answer : (d)
Q.28
Stomata generally operate in response to ... ... [ CPMT 2005]
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a) Atmospheric humidity
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b) Soil temperature
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c) Atmospheric temperature
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d) Light
Explanation
Stomatal responses to light and humidity (vapor pressure difference, VPD) are important determinants of stomatal conductance. Stomatal movements induced by light are the result of a transduction of the light stimulus into modulated ion fluxes in guard cells and concomitant osmotic adjustments and turgor changes. Answer : (d)
Q.29
Osmotic pressure in a vacuolated plant cell is .. ... [ BHU 1991]
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a) Equal to W.P.
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b) Equal to T.P.
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c) More than D.P.D
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d) Less than D.P.D
Explanation
Under optimal conditions, the vacuoles are filled with water to the point that they exert a significant pressure against the cell wall Osmotic pressure is the pressure required to prevent fluid diffusing through a semipermeable membrane separating two solutions containing different concentrations of solute molecules. The difference between diffusion pressure of pure water and solution is called diffusion pressure deficit (DPD). The DPD of a cell is influenced by both osmotic pressure and wall pressure (turgor pressure) which opposes the endosmotic entry of water, i.e. DPD = OP - TP(wall pressure). Turgor Pressure(T.P) is defined as the amount of pressure inside a cell solely due to its water content. When a cell is fully turgid, its OP is equal to TP and DPD is zero Answer : (b)
Q.30
In order to demonstrate root pressure, the plant is given a cut ... ...[ Har. PMT 2003]
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a) At the tip
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b) Transition zone
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c) A few centimeters above the soil
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d) A few centimeters below the soil
Explanation
EXPERIMENT TO DEMONSTRATET THE ROOT PRESSURE THEORY Root pressure is defined as hydrostatic pressure developed in the root due to accumulation of absorbed water. 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. It shows that water absorption is an active process. Experiment on root pressure: The root pressure can be demonstrated in a plant by the following experiment. Apparatus required: A well watered herbaceous plant, a knife, a rubber tube, a narrow glass tube and colored water. Procedure: Water a potted herbaceous plant. Keep it over night. Next morning, cut off the stem a few centimeters above the soil level or near to the root. Fix a long and narrow glass tube to the cut end of the stump with the help of rubber tubing. Pour a little colored water in the glass tube and mark its level. The glass tube is connected to a manometer and whole setup is then left for observation. Observation: After some time the level of the colored water rises in the tube. And rise in the level of the mercury of the manometer shows the measurement of root pressure. Result and conclusion: A rise in the level of water in the glass tube is due to the pressure exerted by water exuded from the cut part of the stem. The exuding of water from the cut end of the stem is called bleeding. The flow of water from the cut surface or bleeding when measured by mercury manometer is estimated to 3-5 atmospheres only. Answer : (c)
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