Prepare for NEET Biology Transport in Plants with MCQs & PYQs on NEET.GUIDE. Access free practice, previous year questions, and expert guidance to understand xylem, phloem, and movement of water.
A researcher is studying long-distance transport in a plant. They introduce a radioactive tracer into the phloem sap of a source leaf. Which of the following would LEAST likely be observed after a period of time?
Movement of the tracer towards a developing fruit
Presence of the tracer in the root tips
Detection of the tracer in a sink leaf
Significant accumulation of the tracer in mature xylem vessels of the source leaf
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.
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
The primary mechanism for xylem sap ascent in tall trees is transpiration pull. However, root pressure plays a minor role. Which statement BEST describes the limited contribution of root pressure to overall xylem sap ascent in tall trees?
Root pressure generates excessive pressure that could damage the delicate xylem tissues in tall trees.
Root pressure is only active during the night and therefore cannot contribute to daytime transpiration.
Tall trees have a significantly lower root surface area to volume ratio, minimizing the contribution of root pressure.
Root pressure can only push water a limited height due to the opposing force of gravity and the relatively low pressure generated.
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
The cohesion-tension theory explains the upward movement of water in plants. Which of the following is NOT a critical component of this theory?
Cohesion of water molecules
Adhesion of water molecules to xylem walls
Transpiration pull creating negative pressure
Active transport of water into xylem by root cells
A plant exposed to a fungal toxin exhibits significantly reduced translocation of potassium ions () despite normal transpiration rates. The toxin MOST likely affects which process?
Stomatal opening and closing
Water potential gradient in the xylem
Activity of membrane transport proteins involved in uptake into xylem
Root pressure generation
Transport of water and minerals in xylem is essentially
Multidirectional
Bidirectional
Unidirectional
Bidirectional but occasionally multidirectional
    Choose correct statements regarding the flow of sap in xylem?
I.    Flow is driven by higher concentration of sugar in the vessel elements
II.    Flow from root to twigs and leaves would be reduced if leaves are removed
III.    In the morning, sap begins to flow first in the twig then in trunk
IV.    Rapid flow of water put tissues under pressure much more than atmospheric pressure
    I and IV
II and III
I, II, III and IV
No one is correct
    The direction of movement in phloem is …A… and that of xylem is …B… .
Choose the correct pair of options
    A-downwards; B-downwards
A-only upwards; B-only downward
A-unidirectional; B-bidirectional
A-bidirectional; B-unidirectional
