Which of the following correctly identifies a source and a sink in a plant?
|
Source |
Sink |
|
| A |
Sprouting potato tubers |
Growing apples |
| B |
Growing apples |
Sprouting potato tubers |
| C |
Young, growing potato tubers |
Mature leaves |
| D |
Growing apples |
Young, growing potato tubers |
The following steps describe the process of translocation.
What is the correct order of the steps?
III → II → IV → I
III → I → IV → II
I → III → IV → II
I → IV → III → II
Which of the following statements apply to phloem sieve tubes?
I only
II and III only
I, II and IV
III and IV only
Why can the symplastic pathway for loading sucrose be considered a passive process?
Sucrose moves from the companion cell into the sieve tube through plasmodesmata
Sucrose is carried against its concentration gradient into the companion cell through a co-transporter protein
H+ ions are pumped out of companion cells by proton pumps
Transfer cells contain many mitochondria to provide energy for the proton pumps to work
Which of the following describes the apoplast route along which sucrose is loaded into phloem sieve tubes?
I only
I and II only
I, II and IV
I, III and IV
Which of the following does not contribute to generating a high hydrostatic pressure at the source?
A high solute concentration in phloem sieve tubes due to the loading of sucrose
The incompressibility of water molecules
The rate at which sucrose is converted to starch in storage tissue
Rigid plant cell walls made of cellulose
Girdling, or ring-barking, involves the removal of a strip of bark around the entire circumference of a tree trunk. This removes the outer part of the vascular bundles which results in the death of the entire tree over time.
What could be a possible explanation for this?
Xylem is removed from the vascular bundles, so water and mineral salts cannot be transported to the leaves
Phloem is removed from the vascular bundles, so sugars cannot be transported to the roots
Xylem is removed from the vascular bundles, so sugars cannot be transported to the roots
Phloem is removed from the vascular bundles, so water and mineral salts cannot be transported to the leaves
The following photomicrograph shows the vascular bundle in a root.
Which letter identifies the phloem?
Aphid stylets can be used to measure phloem transport rates in plants. It was found that the transport rate in stylets located close to a source was much higher compared to those located close to a sink.
What could be a possible explanation for this?
The hydrostatic pressure at a sink is low due to the buildup of sucrose in the phloem sieve elements
The hydrostatic pressure at a sink is high due to water moving into phloem sieve elements by osmosis
There is a high hydrostatic pressure at the source due to the incompressibility of water
There is a low hydrostatic pressure at the source due to a low solute concentration in the sieve tube elements
Why are radioisotopes considered to be such important tools in studying translocation?
It provides a way to track the distribution of molecules between sources and sinks in a plant
To determine the order in which carbon compounds are generated
It provides a way to determine the rate of carbon fixation in a plant
Radioactive molecules contribute to the hydrostatic pressure in xylem vessels
