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
Which of the following manipulations would MOST directly inhibit the loading of sucrose into the sieve tube elements at the source?
Decreasing the hydrostatic pressure in the sieve tube elements
Blocking plasmodesmata between companion cells and sieve tube elements
Increasing the concentration of sucrose in the sink
Inhibition of apoplastic proton pumps in companion cells
The pressure-flow hypothesis explains the translocation of sugars in the phloem. Which of the following statements regarding this hypothesis is INCORRECT?
Active loading of sugars at the source creates a high solute concentration in the sieve tubes.
Water moves from the xylem to the phloem at the source, increasing turgor pressure.
Sugars are unloaded at the sink, lowering the solute concentration and water potential.
Water moves from the sink to the source via the phloem, driven by a pressure gradient.
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 combination of factors would MOST effectively enhance the rate of transpiration in a plant?
Low light intensity, high humidity, open stomata, and still air
High light intensity, high humidity, closed stomata, and strong wind
Low light intensity, low humidity, closed stomata, and still air
High light intensity, low humidity, open stomata, and strong wind
A plant is exposed to a chemical that specifically inhibits the activity of aquaporins in root cells. Which of the following would be the MOST direct consequence of this inhibition?
Increased rate of transpiration
Enhanced mineral absorption
Stimulation of phloem loading
Reduced water uptake by the roots
A xerophyte with a CAM pathway faces prolonged drought conditions. Which of the following physiological responses would be LEAST likely to occur?
Increased stomatal aperture during the day
Accumulation of organic acids at night
Reduced transpiration rates
Increased root-to-shoot ratio
The apoplast pathway in plants is interrupted by the Casparian strip. Which of the following statements about its impact on water movement is most accurate?
It forces water and dissolved minerals to enter the symplast before reaching the stele.
It facilitates the rapid movement of water through the cortex via plasmodesmata.
It prevents the passage of water into the root hair cells.
It increases the rate of transpiration by reducing the resistance to water flow.
Which of the following combinations of factors would result in the HIGHEST rate of transpiration in a mesophytic plant?
High temperature, low humidity, high wind speed, open stomata
Low temperature, high humidity, low wind speed, open stomata
High temperature, high humidity, high wind speed, closed stomata
Low temperature, low humidity, low wind speed, closed stomata
A plant cell with a water potential of -0.6 MPa is placed in a solution with a water potential of -0.8 MPa. Which of the following will occur?
Water will move out of the cell, causing plasmolysis.
Water will move into the cell, causing turgor pressure to increase.
There will be no net movement of water.
The cell will burst due to excessive water uptake.
