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100 questions in this collection · Page 2 of 10
Question 11 of 100
📘 CLASS XI
Transport In Plants
Examine the following statements about plant cells in different solutions:
I. Plasmolysis occurs when a plant cell is placed in a hypotonic solution, causing water to first exit the cytoplasm and then the vacuole. II. If the external solution balances the osmotic pressure of the cytoplasm, the surrounding solution is said to be isotonic. III. When water flows into and out of the cell in perfect equilibrium, the cells are described as flaccid. IV. In a plasmolysed plant cell, the space between the cell wall and the shrunken protoplast is occupied by a vacuum.
Which of the statements are correct?
Plasmolysis occurs in a hypertonic solution, not a hypotonic one. In an isotonic solution, cells become flaccid due to equal water movement. During plasmolysis, the space between the cell wall and protoplast is occupied by the external solution, not a vacuum.
Question 12 of 100
📘 CLASS XI
Transport In Plants
Study the physical effects of hypotonic solutions on plant cells:
I. When placed in a hypotonic solution, water diffuses into the cell, causing the protoplast to build up turgor pressure against the cell wall. II. The pressure exerted by the protoplast against the rigid cell wall is called solute potential (Ψs). III. Plant cells do not rupture in hypotonic solutions due to the structural rigidity of their cell walls. IV. Turgor pressure is ultimately responsible for the enlargement and extension growth of plant cells.
Which of the statements are correct?
Water enters plant cells in a hypotonic solution, producing turgor pressure (pressure potential, Ψp). The rigid cell wall prevents bursting, and turgor pressure is essential for cell enlargement and growth. Statement II is incorrect because the pressure developed is pressure potential, not solute potential.
Question 13 of 100
📘 CLASS XI
Transport In Plants
Consider the physical process of imbibition in plants:
I. Imbibition is a specialized type of active transport where water is absorbed by solid plant colloids. II. Classical examples of imbibition include the absorption of water by dry wood and seeds. III. A water potential gradient between the solid absorbent and the liquid imbibed is essential for the process. IV. Physical affinity between the adsorbant and the liquid is a mandatory pre-requisite for imbibition.
Which of the statements are correct?
Imbibition is a passive process, not active transport. It occurs in dry seeds and wood, requiring a water potential gradient and physical affinity between the adsorbent and the liquid. Hence Statements II, III and IV are correct.
Question 14 of 100
📘 CLASS XI
Transport In Plants
Examine the transport limitations in large multicellular plants:
I. Diffusion is a rapid process capable of moving water molecules across a 1-meter distance in a few hours. II. Long distance transport of water, mineral salts, and organic food proceeds via a mass or bulk flow system. III. Mass flow is driven by pressure differences between two distinct points. IV. In mass flow, substances in solution or suspension are swept along at the same velocity, unlike diffusion where solutes move independently.
Which of the statements are correct?
Diffusion is extremely slow and is unsuitable for long-distance transport in plants. Long-distance movement of water, minerals and food occurs by mass flow driven by pressure differences. In mass flow, all dissolved or suspended substances move together at the same velocity.
Question 15 of 100
📘 CLASS XI
Transport In Plants
Analyze the characteristics of apoplastic water movement in root layers:
I. The apoplast is the continuous system of adjacent cell walls throughout the plant, interrupted only by the endodermal Casparian strip. II. Apoplastic water movement occurs exclusively through cell walls and intercellular spaces without crossing cell membranes. III. This pathway is passive, gradient-dependent, and offers no resistance to water movement. IV. Water transport through the apoplast is slow and requires active metabolic energy to maintain mass flow.
Which of the statements are correct?
The apoplast consists of the continuous system of cell walls and intercellular spaces, interrupted by the Casparian strip. Water moves passively through this pathway without crossing membranes and encounters very little resistance. It does not require metabolic energy.
Question 16 of 100
📘 CLASS XI
Transport In Plants
Consider the mechanisms of symplastic water transport in plants:
I. The symplastic system is a pathway of interconnected protoplasts linked by cytoplasmic strands called plasmodesmata. II. Symplastic water movement is faster than apoplastic transport because water travels directly through cells. III. Symplastic transport is entirely passive, moving down a potential gradient. IV. Symplastic movement can be actively aided by cytoplasmic streaming, which is visible in Hydrilla leaves.
Which of the statements are correct?
The symplast consists of interconnected living protoplasts joined by plasmodesmata. Water movement through the symplast is passive and occurs down a water potential gradient. Cytoplasmic streaming may assist movement. It is slower than apoplastic transport because water must cross membranes.
Question 17 of 100
📘 CLASS XI
Transport In Plants
Study the structural and functional features of root endodermis and xylem:
I. Most of the water flow in the root cortex occurs via the symplast because cortical cells are loosely packed. II. The endodermis is impervious to water due to a band of suberised matrix called the Casparian strip. III. Water molecules are forced to cross membranes to bypass Casparian strip regions, making endodermal flow symplastic. IV. Xylem vessels and tracheids are living conduits that form a continuous part of the symplast in young roots.
Which of the statements are correct?
Water movement through the cortex occurs mainly through the apoplast because cortical cells are loosely packed. The Casparian strip blocks apoplastic flow at the endodermis, forcing water to cross cell membranes into the symplast. Mature xylem vessels and tracheids are dead and belong to the apoplast.
Question 18 of 100
📘 CLASS XI
Transport In Plants
Examine the following statements regarding mycorrhizae and water absorption:
I. A mycorrhiza is a symbiotic association formed between a fungus and a root system. II. Fungal hyphae have a very high surface area to absorb water and mineral ions from a larger soil volume than roots alone can access. III. The host plant roots provide sugars and nitrogen-containing compounds to the symbiotic fungus. IV. Pinus seeds can germinate and establish successfully even without the presence of mycorrhizae.
Which of the statements are correct?
Mycorrhiza is a mutualistic association between fungi and plant roots. Fungal hyphae greatly increase the absorptive surface area for water and minerals, while the plant supplies sugars and nitrogen-containing compounds. Pinus has an obligate association with mycorrhizae and cannot establish successfully without them.
Question 19 of 100
📘 CLASS XI
Transport In Plants
Analyze the positive pressure systems in plants:
I. Root pressure is a positive pressure that builds in xylem when ions are actively transported into the vascular cylinder and water follows. II. Root pressure is the main driving force for water transport up tall forest trees. III. Guttation is the loss of liquid water droplets from special vein openings near leaf tips when soil moisture is high and transpiration is low. IV. The major contribution of root pressure is re-establishing the continuous chains of water molecules in xylem that break under high tension.
Which of the statements are correct?
Active accumulation of ions in the root xylem draws water into the vascular cylinder, generating positive root pressure. Root pressure is insufficient to lift water in tall trees, where transpiration pull is the dominant force. Guttation is the exudation of liquid water through hydathodes when soil moisture is high and transpiration is low. Root pressure also helps restore broken water columns in the xylem.
Question 20 of 100
📘 CLASS XI
Transport In Plants
Examine the physical principles governing transpirational pull:
I. Cohesion is defined as the physical attraction of water molecules to polar surfaces like tracheary walls. II. Adhesion is defined as the mutual attraction between individual water molecules. III. Surface tension ensures that water molecules are attracted to each other more in the liquid phase than in the gas phase. IV. Narrow diameters of tracheids and vessels provide water with high capillarity and tensile strength to resist pulling forces.
Which of the statements are correct?
Cohesion is the attraction between water molecules, whereas adhesion is the attraction between water molecules and polar surfaces such as xylem walls. Surface tension and the narrow diameter of tracheids and vessels provide high tensile strength and capillarity, enabling the water column to withstand transpirational pull.