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
Related Questions
Girdling experiments demonstrate the role of which tissue in the transport of sugars?
Phloem
Xylem
Cambium
Pith
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 apoplastic pathway of water transport in plants is interrupted at the endodermis by which structure?
Cell wall
Plasmodesmata
Casparian strip
Plasma membrane
The transpiration pull in plants can lift a column of water in xylem to a height of over 130 meters. This lift is primarily driven by:
Active transport of water by root cells
Capillary action in xylem vessels
Root pressure generated in the roots
Evaporation of water from leaves
What is the main form in which sugar is transported in phloem?
Glucose
Fructose
Sucrose
Starch
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.
The cohesion-tension theory explains the ascent of sap in the xylem primarily due to:
Root pressure
Capillary action
Active transport of water
The cohesive properties of water and transpiration pull
Which of the following is NOT a major driving force for long-distance transport in plants?
Transpiration pull
Root pressure
Active transport
Diffusion
The pressure-flow hypothesis explains the movement of:
Sugars in phloem
Water in xylem
Minerals in xylem
Water in phloem
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
