Biology Posted: April 12th, 2014
For signaling pathways in particular examples discussed in your answers, describe the roles of receptors, kinases, repressors, and ubiquitination and proteolysis that are involved in the response.
1. What is the distinction between primary metabolism and secondary chemicals? Why is there such high diversity among different groups of plants for secondary chemicals?
2. For each major category of secondary chemicals- terpenes, phenolics, and alkaloids- describe the chemical structures common to each (include drawings), and describe examples for each category and their functions.
3. A plant biologist observed a pattern when a tropical plant was attacked by caterpillars. After a caterpillar ate a leaf, it would skip nearby leaves and attack a leaf some distance away. Simply removing a leaf did not deter the caterpillar from eating nearby leaves. The biologist suspected that the insect-damaged leaf sent out a chemical that signaled nearby leaves. How could the researcher test this hypothesis? Describe the known pathways of signaling and responses that might be involved.
4. One important aspect in flowering plant biology is the successful attraction of pollinators to ensure reproduction of the next generation. Describe the different categories of secondary chemicals in flowers that attract pollinators (consider color and odors).
5. A seed germinated in deep shade under a porch and the plant then grew towards the light and out of a crack into the sun. Describe the major events at each stage of growth in terms of perception of light involved in germinating, bending to the light, and the changes in the leaves and stem that occurred when full sun was experienced. Your answer should include phytochrome, blue light sensors, auxin, signaling pathways involved in growth response, and phenotypic responses in leaves and stem.
6. The flowers of certain plants open in the day and close at night. Design and describe an experiment that would determine whether these circadian rhythms are controlled by the plant’s circadian clock or by the presence or absence of light.
7. How can you make a summer flowering plant in the greenhouse flower during the short days of winter? Assume that your budget is extremely limited and you can only afford to use light for a short time each day. Describe the physiological mechanism of your answer.
8. Gardeners often pinch off shoot tips to promote a fuller and bushier growth. Describe the hormonal mechanism and response involved in promoting this growth.
