Download Concept Check Questions

Concept Check Questions
Chapter 39 – Plant Responses to External and Internal Signals
39.1
Signal transduction pathways link signal reception to response
1. The sexual dysfunction drug Viagra inhibits an enzyme that breaks down cyclic GMP. Assuming that
tomato leaf cells have a similar enzyme, would you predict that applying Viagra will cause a normal deetiolation of aurea tomato leaves?
2. Cyclohexamine is a drug that inhibits protein synthesis. Predict what effect cyclohexamine would have
on de-etiolation.
39.2
Plant hormones help coordinate growth, development, and response to stimuli
1. Predict the triple-response phenotype of a plant with the double mutation ctr and ein. Explain.
2. In the diseased state known as “witch’s broom,” branches grow and proliferate excessively. Suggest a
hypothesis to explain how a pathogen might induce this growth pattern.
3. Fusioccin is a fungal toxin that stimulates the plasma membrane H+ pump of plant cells. How might it
affect growth of isolated stem sections?
39.3
Responses to light are critical for plant success
1. A plant flowers in a controlled chamber with a daily cycle of 10 hours of light and 14 hours of darkness.
Is it a short day plant? Explain.
2. Assume that poinsettias grown in a greenhouse require at least 14 hours of darkness to flower. If work
has to be done at night, what light source would not disrupt the flowering schedule? Explain.
3. Upon germination, some vine seedlings grow toward darkness until they reach an upright structure.
This adaptation helps the vine “find” a shaded object to climb. Suggest an experiment to test whether
this negative phototropism is mediated by blue light photoreceptors or by phytochrome.
39.4
Plants respond to a wide variety of stimuli other than light
1. Thermal images are photographs of the heat emitted by an object. Researchers have used thermal
imaging of plants to isolate mutants that overproduce abscisic acid. Suggest a reason why these
mutations are warmer than wild-type plants under conditions that are normally nonstressful.
2. A worker in a commercial greenhouse finds that the potted chrysanthemums nearest to the aisles are
often shorter than those growing in the middle of the bench. Suggest an explanation.
39.4
Plants defend themselves against herbivores and pathogens
1. Chewing insects mechanically damage plants and lessen the surface area of leaves for photosynthesis.
In addition, these insects make plants more vulnerable to pathogen attack. Suggest a reason why.
2. A scientist finds that a population of plants growing in a breezy location is more prone to defoliation by
insects than a population of the same species growing in a sheltered area. Suggest a hypothesis to
account for this observation.