Midterm 2 Practice Questions Flashcards
Describe the ecological function of volatile terpenes in wild plants
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.
What is the 2nd most abundant molecule in plants?
Lignin, a phenolic
Name 3 physiological roles of flavanoids
structural stability, astringent taste deterrent, fragrance and coloration
What are the 3 main groups of secondary metabolites?
Terpenes, N-containing compounds, and Phenolics
The force that moves water across biological membranes
Water potential
What do aquaporins do?
They increase the rate of osmosis
What happens to transpiration rate as light intensity increases?
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)
What happens to transpiration as temperature increases?
Increases until stomata close- More water is lost when its hot, but photosynthesis doesn’t increase
What happens to transpiration as wind increases?
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
What happens to transpiration as humidity increases?
Decreases and stomata are open- [H20] is high outside the lead, reducing evaporation. Plant can still get CO2 without losing H20
What drives the flow of water through the xylem?
The evaporation of water from the leaves
If water potential drops in the soil, what happens to the stomata?
The stomata are likely to close to make the water potential lower in the leaves to draw up water and prevent even more loss
What is the function of guard cells?
Guard cells regulate the openings and closures of the stomata to ensure a balanced photosynthesis transpiration compromise
Where is the water potential most negative?
mesophyll cells of the leaf
Are sieve elements living or dead and do they have a nucleus?
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
What would happen to a plant without P-proteins or callose?
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.
Is phloem translocation always from shoot to root?
No. Translocation is from source to sink. Sources like mature leaves transport their excess photosynthate to sinks like juvenile leaves, roots, flowers and fruit.
Name 3 characteristics of model organisms
fast generation time, many offspring and cheap
What is the role of jasmonic acid in plants?
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.
What are 3 pieces of evidence that would demonstrate the proof of symplastic polymer trapping?
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
What is allelopathy?
The growth inhibition of plant growth under the canopy of the plant via the production of a secondary metabolite
What would produce dark blue fruit?
Anthocyanins- a phenolic
How are Phenolics produced?
They use the Shikimic pathway to produce tannins, simple phenolics and lignin. This pathway combined with the malonic pathway produces flavanoids and condensed tannins.
What is the purpose of anthocyanins?
They have UV absorptivity, and can attract pollinators or seed dispersers (unique colour also makes them recognizable)
What is the purpose of tannins?
They produce an astringent taste, thus deterring herbivory
Why are alkaloids dangerous?
Alkaloids are structurally diverse and have structures that resemble key molecules common in vertebrates. (ex. Non-protein amino acids)
