Mass transport

In an investigation into the transport mechanisms of soybean plants (Glycine max), scientists applied a localized metabolic respiratory inhibitor (sodium azide, which blocks ATP production) to a section of the stem using a treated collar. Control plants received a collar containing only distilled water. They then applied a solution of radioactively-labelled sucrose, containing $14C^{14}\text{C}$ , to a leaf situated above the treated collar.

After 6 hours, they:

Identified the distribution of the $14C^{14}\text{C}$ radiolabel in each plant.
Recorded the relative water content (RWC) of the leaves above the treated section.

The results showed:

In control plants, the $14C^{14}\text{C}$ radiolabel was distributed throughout the plant, including the roots and lower stem.
In inhibitor-treated plants, the $14C^{14}\text{C}$ radiolabel was only detected in the leaf that was supplied with $14C^{14}\text{C}$ -sucrose and did not pass below the treated collar.

The relative water content data are presented in the table below:

Plant group	Leaf relative water content / % of maximum ( $\pm 2\,$ standard deviations)
Inhibitor-treated	$(±6.8)78.4\ (\pm 6.8)$
Control	$(±5.9)82.1\ (\pm 5.9)$

Explain how the distribution of the radioactively-labelled sucrose supports the conclusion that translocation in the phloem requires metabolic energy.

Explain how the leaf relative water content results support the conclusion that water transport via the xylem is a passive process.

After 6 hours, they:

Identified the distribution of the $14C^{14}\text{C}$ radiolabel in each plant.
Recorded the relative water content (RWC) of the leaves above the treated section.

The results showed:

In control plants, the $14C^{14}\text{C}$ radiolabel was distributed throughout the plant, including the roots and lower stem.
In inhibitor-treated plants, the $14C^{14}\text{C}$ radiolabel was only detected in the leaf that was supplied with $14C^{14}\text{C}$ -sucrose and did not pass below the treated collar.

The relative water content data are presented in the table below:

Plant group	Leaf relative water content / % of maximum ( $\pm 2\,$ standard deviations)
Inhibitor-treated	$(±6.8)78.4\ (\pm 6.8)$
Control	$(±5.9)82.1\ (\pm 5.9)$

Explain how the distribution of the radioactively-labelled sucrose supports the conclusion that translocation in the phloem requires metabolic energy.

Explain how the leaf relative water content results support the conclusion that water transport via the xylem is a passive process.

Question 1

Mass transport

Question 1

Mass transport

Question 1

Mass transport Questions

Mass transport

Question 1

Mass transport Questions