Midterm 2 Practice Questions

Question 1

Describe the ecological function of volatile terpenes in wild plants

Answer 1

Volatile terpenes can be used for SAR (systemic acquired resistance), where plants under predation can signal to nearby plants to increase their production of relevant defense chemicals.

Question 2

What is the 2nd most abundant molecule in plants?

Answer 2

Lignin, a phenolic

Question 3

Name 3 physiological roles of flavanoids

Answer 3

structural stability, astringent taste deterrent, fragrance and coloration

Question 4

What are the 3 main groups of secondary metabolites?

Answer 4

Terpenes, N-containing compounds, and Phenolics

Question 5

The force that moves water across biological membranes

Answer 5

Water potential

Question 6

What do aquaporins do?

Answer 6

They increase the rate of osmosis

Question 7

What happens to transpiration rate as light intensity increases?

Answer 7

Increases and stomata are open- light increases photosynthesis which will increase the need for CO2. The tradeoff is greater because the it gets more CO2 than it loses water (favourable if stomata have to be open)

Question 8

What happens to transpiration as temperature increases?

Answer 8

Increases until stomata close- More water is lost when its hot, but photosynthesis doesn’t increase

Question 9

What happens to transpiration as wind increases?

Answer 9

Increases until closed- More air flow by the lead will cause the CO2 in the air to move to low [CO2] in the leaf. The low [H20] outside the leaf will put more water out, but the greater compromise is from the CO2

Question 10

What happens to transpiration as humidity increases?

Answer 10

Decreases and stomata are open- [H20] is high outside the lead, reducing evaporation. Plant can still get CO2 without losing H20

Question 11

What drives the flow of water through the xylem?

Answer 11

The evaporation of water from the leaves

Question 12

If water potential drops in the soil, what happens to the stomata?

Answer 12

The stomata are likely to close to make the water potential lower in the leaves to draw up water and prevent even more loss

Question 13

What is the function of guard cells?

Answer 13

Guard cells regulate the openings and closures of the stomata to ensure a balanced photosynthesis transpiration compromise

Question 14

Where is the water potential most negative?

Answer 14

mesophyll cells of the leaf

Question 15

Are sieve elements living or dead and do they have a nucleus?

Answer 15

Sieve elements are alive because they are part of the phloem. They do not have a nucleus, as most of their biosynthetic processes are carried out by their companion cell

Question 16

What would happen to a plant without P-proteins or callose?

Answer 16

When wounded, the phloem would leak sap because of the pressure release. Without callose or p-proteins the plant would not be able to stop the sap from leaking out of the phloem and stop the flow.

Question 17

Is phloem translocation always from shoot to root?

Answer 17

No. Translocation is from source to sink. Sources like mature leaves transport their excess photosynthate to sinks like juvenile leaves, roots, flowers and fruit.

Question 18

Name 3 characteristics of model organisms

Answer 18

fast generation time, many offspring and cheap

Question 19

What is the role of jasmonic acid in plants?

Answer 19

Jasmonic acid is used as a signalling molecule in many plants. Upon wounding to the plant, the release of membrane lipids triggers the synthesis of jasmonic acid, which in turn activates the synthesis of various defence molecules. Jasmonic acid is transported to other parts of the plant that haven’t been attacked to create local protection.

Question 20

What are 3 pieces of evidence that would demonstrate the proof of symplastic polymer trapping?

Answer 20

1) Higher concentrations of sucrose must be found in the bundle sheath cells
2) The enzymes required for stachyose and raffinose synthesis are present in the companion cell
3) The plasmodesmata between the bundle sheath cell and the intermediary cell are smaller than the plasmodesmata between the companion and sieve element cell so the polymers can move back

Question 21

What is allelopathy?

Answer 21

The growth inhibition of plant growth under the canopy of the plant via the production of a secondary metabolite

Question 22

What would produce dark blue fruit?

Answer 22

Anthocyanins- a phenolic

Question 23

How are Phenolics produced?

Answer 23

They use the Shikimic pathway to produce tannins, simple phenolics and lignin. This pathway combined with the malonic pathway produces flavanoids and condensed tannins.

Question 24

What is the purpose of anthocyanins?

Answer 24

They have UV absorptivity, and can attract pollinators or seed dispersers (unique colour also makes them recognizable)

Question 25

What is the purpose of tannins?

Answer 25

They produce an astringent taste, thus deterring herbivory

Question 26

Why are alkaloids dangerous?

Answer 26

Alkaloids are structurally diverse and have structures that resemble key molecules common in vertebrates. (ex. Non-protein amino acids)