Question 28 – Plant and animal responses - Questions

Plants respond to their environments and to pests in various ways.

Describe the meaning of the term positive gravitropism.

State the role of auxin (indole-3-acetic acid / IAA) in positive gravitropism of plant roots.

Plants can produce chemical defenses in response to herbivory (a biotic stress). Give one example of such a chemical and state how it defends the plant.

Plants can communicate warning signals to neighboring plants through several pathways, including airborne volatile organic compounds (VOCs) and soluble root exudates diffusing through the soil.

Scientists investigated this communication using pairs of potato plants ( $tuberosum\textit{Solanum tuberosum}$ ) exposed to attack by Colorado potato beetle larvae.

This is the method that they used:

Grow a 'donor' plant and a 'recipient' plant together in the same split-compartment pot.
Repeat to create 60 pairs of plants, divided into four treatment groups (15 pairs per group).
Separate the root systems of the two plants with either a solid plastic sheet or a perforated membrane.
Infest the 'donor' plants with beetle larvae in half of the groups.

The treatment groups are summarized in the table below:

Group	Donor plant infested with beetle larvae	Soil barrier between root systems
1	No	Solid plastic sheet (blocks both root contact and diffusion of soluble molecules)
2	Yes	Solid plastic sheet (blocks both root contact and diffusion of soluble molecules)
3	No	Perforated membrane (blocks direct root contact but allows diffusion of soluble molecules)
4	Yes	Perforated membrane (blocks direct root contact but allows diffusion of soluble molecules)

The scientists measured the concentration of a protease inhibitor (in $g−1\mu\text{g}\text{ g}^{-1}$ of leaf tissue) in the recipient plants at the start of the experiment and after 72 hours.

Suggest how the scientists could ensure that airborne volatile chemicals did not contribute to communication between plants in this investigation.

The results are shown in the table below:

Group	Mean protease inhibitor concentration $±\pm$ standard deviation ( $g−1\mu\text{g}\text{ g}^{-1}$ ) at start	Mean protease inhibitor concentration $±\pm$ standard deviation ( $g−1\mu\text{g}\text{ g}^{-1}$ ) after 72 h
1	$3.2 \pm 0.4$	$3.5 \pm 0.5$
2	$3.4 \pm 0.5$	$14.8 \pm 1.6$
3	$3.1 \pm 0.3$	$3.3 \pm 0.4$
4	$3.3 \pm 0.5$	$42.6 \pm 4.1$

The scientists conclude:

Beetle larvae attack on the donor plants leads to a defense response (increased protease inhibitor production) in the recipient plants.
This signaling is mediated by soluble root exudates diffusing through the soil.

Evaluate the support given by the results to the scientists' conclusions. You should comment on the quality of the scientists' data in your answer.

Plants respond to their environments and to pests in various ways.

Describe the meaning of the term positive gravitropism.

State the role of auxin (indole-3-acetic acid / IAA) in positive gravitropism of plant roots.

Plants can produce chemical defenses in response to herbivory (a biotic stress). Give one example of such a chemical and state how it defends the plant.

Plants can communicate warning signals to neighboring plants through several pathways, including airborne volatile organic compounds (VOCs) and soluble root exudates diffusing through the soil.

Scientists investigated this communication using pairs of potato plants ( $tuberosum\textit{Solanum tuberosum}$ ) exposed to attack by Colorado potato beetle larvae.

This is the method that they used:

Grow a 'donor' plant and a 'recipient' plant together in the same split-compartment pot.
Repeat to create 60 pairs of plants, divided into four treatment groups (15 pairs per group).
Separate the root systems of the two plants with either a solid plastic sheet or a perforated membrane.
Infest the 'donor' plants with beetle larvae in half of the groups.

The treatment groups are summarized in the table below:

Group	Donor plant infested with beetle larvae	Soil barrier between root systems
1	No	Solid plastic sheet (blocks both root contact and diffusion of soluble molecules)
2	Yes	Solid plastic sheet (blocks both root contact and diffusion of soluble molecules)
3	No	Perforated membrane (blocks direct root contact but allows diffusion of soluble molecules)
4	Yes	Perforated membrane (blocks direct root contact but allows diffusion of soluble molecules)

The scientists measured the concentration of a protease inhibitor (in $g−1\mu\text{g}\text{ g}^{-1}$ of leaf tissue) in the recipient plants at the start of the experiment and after 72 hours.

Suggest how the scientists could ensure that airborne volatile chemicals did not contribute to communication between plants in this investigation.

The results are shown in the table below:

Group	Mean protease inhibitor concentration $±\pm$ standard deviation ( $g−1\mu\text{g}\text{ g}^{-1}$ ) at start	Mean protease inhibitor concentration $±\pm$ standard deviation ( $g−1\mu\text{g}\text{ g}^{-1}$ ) after 72 h
1	$3.2 \pm 0.4$	$3.5 \pm 0.5$
2	$3.4 \pm 0.5$	$14.8 \pm 1.6$
3	$3.1 \pm 0.3$	$3.3 \pm 0.4$
4	$3.3 \pm 0.5$	$42.6 \pm 4.1$

The scientists conclude:

Beetle larvae attack on the donor plants leads to a defense response (increased protease inhibitor production) in the recipient plants.
This signaling is mediated by soluble root exudates diffusing through the soil.

Evaluate the support given by the results to the scientists' conclusions. You should comment on the quality of the scientists' data in your answer.

Plant and animal responses

Question 1

Plant and animal responses

Question 1

Plant and animal responses

Question 1

Plant and animal responses Questions

Plant and animal responses

Question 1

Plant and animal responses Questions