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Transport in Plants
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Which of the following helps in maintenance of the pressure gradient in sieve tubes?A Albuminous cellsB Sieve cellsC Phloem parenchymaD Companion cellsCompanion cells are closely associated with sieve tube elements and help maintain the pressure gradient required for translocation of food (loading and unloading of sugars) through the sieve tubes.
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Movement and accumulation of ions across a membrane against their concentration gradient can be explained byA Active TransportB OsmosisC Facilitated DiffusionD Passive Transport
Active transport uses energy to move substances against the concentration gradient.
Active transport is a type of cellular transport in which substances like ions, glucose and amino acids are transported across a biological membrane towards the region that already contains a lot of such substances. In active transport, chemical energy (e.g. ATP) is used to transport such substances against the concentration gradient. -
Given below are two statements: Statement I: The forces generated by transpiration can lift a xylem-sized column of water over 130 meters height. Statement II: Transpiration cools leaf surfaces sometimes 10 to 15 degrees, by evaporative cooling. In the light of the above statements, choose the correct answer from the options given below:A Statement I is incorrect but Statement II is correct.B Both Statement I and Statement II are correct.C Both Statement I and Statement II are incorrect.D Statement I is correct but Statement II is incorrect.
Transpiration pull can lift water over 130 m and evaporative cooling lowers leaf temperature.
A system of xylem vessels from the root to the leaf vein can supply the needed water. A pull force is created as water evaporates through stomata. These forces generated by transpiration can create pressure sufficient to lift a xylem-sized column of water over 130 metres high. Apart from creating transpiration pull for absorption and transport of plants it also helps in cooling leaf surfaces, sometimes 10 to 15 degrees by evaporative cooling. -
Match List-I with List-II
Column I
- A. Cohesion
- B. Adhesion
- C. Surface tension
- D. Guttation
Column II
- I. More attraction in liquid phase
- II. Mutual attraction among water molecules
- III. Water loss in liquid phase
- IV. Attraction towards polar surfaces
Correct answer: A → II, B → IV, C → I, D → III
Cohesion is mutual attraction of water molecules and adhesion is attraction to polar surfaces.
Cohesion: Mutual attraction between water molecules. Adhesion: Attraction of water molecules to polar surfaces. Surface Tension: Water molecules are attracted to each other in the liquid phase more than to water in the gas phase. Guttation: Water loss in its liquid phase near the tip of grass blades. -
Identify the correct statements regarding Mass flow hypothesis. (A) Mass flow is faster than diffusion. (B) Mass flow is the result of pressure difference between the end points. (C) Different substances involved in mass flow move at different paces. (D) Mass flow can result through either a positive or a negative hydrostatic pressure gradient. Choose the correct answer from the options given below:A (A), (C), (D) onlyB (B), (C), (D) onlyC (A), (B), (C) onlyD (A), (B), (D) onlyMass flow (bulk flow) is faster than diffusion (A is correct) and results from a pressure gradient (positive or negative) between the source and sink ends (B and D are correct). However, in mass flow, all substances move together at the same rate/pace (they are simply carried along in the bulk flow), not at different paces — so C is incorrect. Correct: A, B, D only.
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Given below are two statements: Statement I: The process of translocation through phloem is unidirectional but through xylem, it is bidirectional. Statement II: The most readily mobilized elements are phosphorus, sulphur, nitrogen and potassium. In the light of the above statements, choose the most appropriate answer from the options given below:A Statement I is correct but Statement II is incorrect.B Statement I is incorrect but Statement II is correct.C Both Statement I and Statement II are correct.D Both Statement I and Statement II are incorrect.Translocation through the phloem is actually bidirectional (can move up or down depending on source-sink relationships), while movement through the xylem is generally unidirectional (upward) — so Statement I, which states the opposite, is incorrect. The most readily mobilized mineral elements are indeed phosphorus, sulphur, nitrogen and potassium, so Statement II is correct.
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Which of the following is not observed during apoplastic pathway?A Apoplast is continuous and does not provide any barrier to water movement.B Movement of water occurs through intercellular spaces and wall of the cellsC The movement does not involve crossing of cell membraneD The movement is aided by cytoplasmic streaming
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"Girdling Experiment" was performed by Plant Physiologists to identify the plant tissue through which:A Osmosis is observedB Water is transportedC Food is transportedD For both water and food transportation
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Addition of more solutes in a given solution will:A Not affect the water potential at allB Raise its water potentialC Lower its water potentialD Make its water potential zero
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Match List-1 with List-2.
Column I
- A. Cohesion
- B. Adhesion
- C. Surface tension
- D. Guttation
Column II
- I. More attraction in liquid phase
- II. Mutual attraction among water molecules
- III. Water loss in liquid phase
- IV. Attraction towards polar surfaces
Correct answer: A → II, B → IV, C → I, D → III
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The process responsible for facilitating loss of water in liquid form from the tip of grass blades at night and in early morning is:A Root pressureB ImbibitionC PlasmolysisD Transpiration
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Select the incorrect statement.A Elements most easily mobilized in plants from one region to another are: phosphorus, sulphur, nitrogen and potassiumB Transport of molecules in phloem can be bidirectionalC Movement of minerals in xylem is unidirectionalD Unloading of sucrose at sink does not involve the utilization of ATPUnloading of sucrose at the sink (during phloem transport, the pressure flow/mass flow mechanism) does actively involve the utilization of ATP (active transport), so the statement that it does not involve ATP utilization is incorrect.
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Xylem translocates:A Water onlyB Water and mineral salts onlyC Water, mineral salts and some organic nitrogen onlyD Water, mineral salts, some organic nitrogen and hormones
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What is the direction of movement of sugars in phloem?A Non-multidirectionalB UpwardC DownwardD Bi-directional