Long-Distance Transport Practice Questions
20 free Long-Distance Transport practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following processes is responsible for the movement of substances in bulk from one point to another due to pressure differences?
- A Simple diffusion
- B Facilitated diffusion process
- C Mass flow or bulk flow
- D Cytoplasmic streaming
Correct answer: Mass flow or bulk flow
Mass flow is the movement of substances in bulk as a result of pressure differences between two points. Unlike diffusion, substances in mass flow move at the same speed regardless of their size or concentration.
The long-distance transport of substances through the conducting tissues of plants is called:
- A Translocation
- B Transformation
- C Transduction
- D Translation
Correct answer: Translocation
Translocation is the term used for the long-distance transport of water, minerals, and food through the xylem and phloem. This process is much faster than diffusion over long distances.
In the roots, the pathway of water movement that occurs through the intercellular spaces and the walls of the cells is the:
- A Symplastic pathway
- B Apoplastic pathway
- C Vacuolar pathway
- D Transmembrane pathway
Correct answer: Apoplastic pathway
The apoplast is the system of adjacent cell walls that is continuous throughout the plant, except at the casparian strips of the endodermis. Water movement in the apoplast occurs through mass flow and does not cross cell membranes.
The symplastic system of water movement involves:
- A Non-living parts of the cell
- B Protoplasts joined by plasmodesmata
- C Cell walls and intercellular spaces
- D Lignified tracheary elements
Correct answer: Protoplasts joined by plasmodesmata
The symplast consists of the living parts of the plant. Water travels through the cytoplasm of cells, and inter-cellular movement occurs through the plasmodesmata.
Which structure in the endodermis blocks the apoplastic movement of water and minerals into the vascular cylinder?
- A Plasmodesmata
- B Stomatal pore opening
- C Sieve plates
- D Casparian strips
Correct answer: Casparian strips
Casparian strips are made of suberin, a waxy, water-impermeable material. They force water and solutes to cross the cell membrane and enter the symplast to reach the xylem.
Water movement through the symplastic pathway is relatively slower than the apoplastic pathway because:
- A Water must cross many cell organelles
- B The pathway is completely blocked by lignin
- C The cells involved are already dead
- D It must cross the membrane and cytoplasm
Correct answer: It must cross the membrane and cytoplasm
In the symplastic pathway, water must cross the selectively permeable plasma membrane and navigate through the relatively viscous cytoplasm. This provides more resistance compared to the porous cell walls of the apoplast.
A symbiotic association of a fungus with a root system that helps in the absorption of water and minerals is called:
- A Lichens
- B Rhizobium
- C Coralloid roots
- D Mycorrhiza
Correct answer: Mycorrhiza
Mycorrhizae are fungal associations where the fungal hyphae provide a very large surface area for absorbing water and minerals (like phosphorus) from the soil. In return, the plant provides sugars and nitrogen-containing compounds to the fungus.
Positive hydrostatic pressure developed in the xylem due to active transport of ions into the vascular tissue is called:
- A Transpiration pull
- B Imbibition pressure
- C Osmotic force
- D Root pressure
Correct answer: Root pressure
As ions are actively transported into the vascular tissues of the roots, water follows, increasing the pressure inside the xylem. This positive pressure is called root pressure and can push water up to small heights.
The loss of water in the form of liquid droplets from the margins of leaves of herbaceous plants is known as:
- A Transpiration
- B Evaporation
- C Bleeding
- D Guttation
Correct answer: Guttation
Guttation occurs during the night and early morning when evaporation is low and root pressure is high. Excess water is pushed out through specialized openings called hydathodes.
According to the widely accepted theory of water ascent in xylem, the main driving force for water movement in tall trees is:
- A Root pressure
- B Active pumping by xylem vessels
- C Transpiration pull
- D Capillary action alone
Correct answer: Transpiration pull
Transpiration from the leaves creates a negative pressure (tension) in the xylem. This 'pull' is transmitted down to the roots through a continuous column of water held together by cohesive forces.
The property of water molecules being attracted to each other in the liquid phase is called:
- A Adhesion
- B Surface tension
- C Tensile strength
- D Cohesion
Correct answer: Cohesion
Cohesion is the mutual attraction between water molecules. This property is crucial for maintaining a continuous column of water within the xylem tracheids and vessels.
Which property of water allows it to resist a pulling force and gives it high tensile strength?
- A Adhesion and Cohesion
- B Guttation
- C Root pressure mechanism
- D Imbibition
Correct answer: Adhesion and Cohesion
Cohesion (attraction between water molecules) and Adhesion (attraction to polar surfaces like tracheary walls) provide water with high tensile strength. This allows the water column to withstand the tension created by transpiration pull.
Which of the following cells are the main conducting elements of the xylem in angiosperms?
- A Sieve tubes and companion cells
- B Xylem parenchyma and fibers
- C Tracheids and vessels
- D Albuminous cells
Correct answer: Tracheids and vessels
Tracheids and vessels are elongated, dead cells with lignified walls that form continuous tubes. They are the primary channels for the long-distance translocation of water and minerals.
During the process of water absorption by roots, most of the water flow in the cortex occurs via the apoplast because:
- A The cortical cells are loosely arranged
- B The cortical cells are already dead
- C The symplast pathway is blocked by suberin
- D Root pressure levels are too high
Correct answer: The cortical cells are loosely arranged
In the root cortex, the cells are loosely arranged, offering very little resistance to the movement of water through the cell walls and spaces (apoplast).
Transpiration and photosynthesis represent a 'compromise' because:
- A Stomata must open for CO2 despite water loss
- B Plants need to stop photosynthesis to save water
- C Water is required for the dark reaction only
- D Transpiration provides the energy for photosynthesis
Correct answer: Stomata must open for CO2 despite water loss
For photosynthesis to occur, stomata must open to allow CO2 entry. However, this inevitably leads to the loss of water vapor via transpiration, creating a constant balance the plant must maintain.
The upward movement of water in the xylem is achieved by a 'pull' rather than a 'push'. This 'pull' can reach pressures up to:
- A 10-20 atmospheres
- B 1 atmosphere
- C 100-130 atmospheres
- D 500 atmospheres
Correct answer: 10-20 atmospheres
Measurements show that the transpiration pull-generated tension is sufficient to lift a column of water over 130 meters high. The force generated can create a pressure of roughly 10-20 atmospheres.
Which of the following is a physical property of water that contributes to capillarity in plants?
- A Small diameter of tracheary elements
- B High specific heat
- C Large vacuoles inside tracheid cells
- D Photosynthetic rate
Correct answer: Small diameter of tracheary elements
Capillarity is the ability of water to rise in thin tubes. The small diameter of xylem vessels and tracheids aids this process, supported by the adhesion of water to the cell walls.
In Pinus, the seeds cannot germinate and establish without the presence of:
- A Rhizobium bacteria
- B Mycorrhizal association
- C Sustained high root pressure
- D Frequent guttation
Correct answer: Mycorrhizal association
Pinus has an obligate association with mycorrhizae. Without the fungal partner, the seedling cannot absorb enough water and minerals to survive and grow.
The effect of root pressure is most observable:
- A At noon when transpiration is maximum
- B During the night and early morning
- C In very tall redwood trees
- D During the peak of summer
Correct answer: During the night and early morning
Root pressure is easiest to see when transpiration is low (night/early morning). The positive pressure causes water to accumulate and exude from cut stems or hydathodes.
Which of the following statements about translocation is true?
- A Xylem translocates only pure water and absolutely nothing else
- B Phloem translocates only inorganic nitrogen compounds
- C Xylem also carries minerals, organic nitrogen, and hormones
- D Translocation in the xylem is always bi-directional
Correct answer: Xylem also carries minerals, organic nitrogen, and hormones
The xylem is not just a water pipe; it also carries dissolved mineral salts, small amounts of organic nitrogen (amino acids), and plant hormones from the roots to the aerial parts.