Prepare for NEET with Botany-specific practice questions. Covering all major Botany chapters, this is perfect for your NEET Biology needs.
Girdling experiments, where the bark of a tree is removed in a ring around the trunk, demonstrate the importance of phloem for translocation. Which observation is NOT expected after girdling?
Accumulation of sugars above the girdle.
Swelling of the bark above the girdle.
Eventual death of the roots due to lack of nutrients.
Increased sugar concentration above the girdle and decreased sugar concentration below the girdle, with no effect on xylem function.
The cohesion-tension theory explains the ascent of sap in tall trees. Which of the following factors LEAST contributes to the maintenance of the continuous water column?
Active transport of water into xylem vessels
Cohesion between water molecules
Adhesion of water molecules to xylem walls
Transpiration pull generated by evaporation from leaves
Which factor does not significantly influence the rate of diffusion of a solute in a liquid?
Temperature of the liquid
The size and shape of the solute molecules
The presence of other non-interacting solutes
The viscosity of the liquid
Which of the following experimental manipulations would MOST effectively demonstrate the contribution of root pressure to xylem sap ascent in a small herbaceous plant?
Submerging the roots in a hypertonic solution and observing changes in leaf turgor
Measuring the rate of transpiration under varying light intensities
Removing the apical bud and observing the effect on guttation
Measuring exudation rate from a cut stem stump after applying a respiratory inhibitor to the roots
Which factor does NOT influence the rate of facilitated diffusion?
The concentration gradient of the transported substance
The number of carrier proteins in the membrane
The amount of ATP available
The temperature
A plant is exposed to for a short period. After 5 minutes, the radioactive carbon is detected in the phloem sieve tubes near the source. After 20 minutes, it's found further down the stem in the phloem. Which observation MOST directly contradicts the mass flow hypothesis?
Sucrose moves bidirectionally in the phloem, sometimes against the concentration gradient.
ATP is required for active loading of sucrose into the sieve tubes.
The concentration of sucrose is higher in the source than in the sink.
Water moves from xylem to phloem at the source and from phloem to xylem at the sink.
Which experimental observation would be MOST difficult to reconcile with the mass flow hypothesis?
A higher concentration of sucrose in source tissues compared to sink tissues.
A positive correlation between the rate of transpiration and the rate of translocation.
Bidirectional movement of different solutes within the same sieve tube element.
The presence of a pressure gradient between source and sink tissues in the phloem.
A researcher observes that applying a metabolic inhibitor to the sink tissues of a plant reduces the rate of translocation. How does this observation relate to the mass flow hypothesis?
It refutes the hypothesis, as metabolic energy should not be required for passive flow.
It supports the hypothesis, as reduced sink activity would decrease the pressure gradient driving flow.
It is irrelevant to the hypothesis, as the inhibitor's effect is localized to the sink.
It partially supports the hypothesis, suggesting an additional active component to the predominantly passive flow.
A researcher modifies a plant's guard cells to overexpress aquaporins. Under water-deficient conditions, which of the following is the MOST LIKELY consequence?
Increased stomatal opening
Increased transpiration
Increased water uptake
Increased stomatal closure
Consider a plant exhibiting guttation. Which of the following statements regarding the xylem sap at night is MOST accurate?
Transpiration pull generates negative pressure in the xylem
Root pressure generates positive hydrostatic pressure in the xylem
Cohesion-tension theory is the primary driver of xylem sap movement
Xylem sap movement ceases entirely at night
