1). If you were a plant pathogen, what would be the first obstacle to invading a host plant that you would have to overcome?
a). chemical toxins on the surface of a plant
b). physical barriers on the exterior of a plant
c). animal guardians of the host plant
d). immune proteins in the plant tissue
2). Some plants are recognized by fungal pathogens on the basis of their stomatal pores. Which of the following would provide these plants immunity from fungal infection?
a). removing all of the stomata from the plant
b). changing the spacing of stomatal pores in these plants
c). reinforcing the cell wall in the guard cells of stomatal pores
d). increasing the number of trichomes on the surfaces of these plants
3). Eating unscrubbed cassava root would likely
a). lead to indigestion because the skin of the cassava plant is very difficult to digest.
b). make you sick because the soil on the surface may contain harmful microbes.
c). make you sick because the skin contains cyanogenic glycosides that would produce cyanide in the digestive track.
d). harm your teeth because of the small stones that would be on the surface of the root.
4). You decide to plant a garden in which a beautiful black walnut tree is the centerpiece. You are quite disappointed, however, when none of the seeds you plant around the tree grow. What might explain this observation?
a). the tree filters out too much light, so the seeds fail to germinate
b). the roots of the tree deplete all of the nutrients from the soil, so the new seedlings starve
c). the tree produces chemical toxins that prevent seed germination
d). the roots deplete all of the water from the soil and thereby prevent seed germination
5). Vegetarians whose diet consists largely of soy are less likely to develop prostate cancer because
a). soy contains the anticancer drug taxol.
b). eating meat increases the probability of developing prostate cancer, so eliminating it from your diet reduces the chances of developing the disease.
c). soy protein prevents accumulation of the prostate-specific antigen (PSA) associated with prostate cancer.
d). soy contains a phytoestrogen that may down-regulate estrogen and androgen receptors in males who consume high soy diets.
6). The drink gin and tonic was created by British soldiers in India as a means of
a). dealing with boredom during the long hours between battles.
b). increasing revenue by selling the drink in the officer's club.
c). fighting malaria with the quinine in tonic water.
d). fighting scurvy with the juniper extract in gin.
7). Tomato plants are not good to eat because
a). when their tissue is damaged, it generates a foul odor that makes people sick.
b). they do not contain any useful nutrients for animals.
c). they contain chemical toxins that will make animals sick.
d). when their tissue is damaged, they produce proteinase inhibitors that will prevent digestive enzyme function in animals.
8). A plant lacking R genes would likely
a). be unable to carry out photosynthesis.
b). be susceptible to infection by pathogens.
c). be susceptible to predation by herbivores.
d). paralyze animals who ingested it.
9). Both plant and animal immune systems can
a). develop memory of past pathogens to more effectively deal with subsequent infections.
b). establish physical barriers to infection.
c). initiate expression of proteins to help fight the infection.
d). kill their own cells to prevent spread of the infection.
e). All of these are true.
Test Your Visual Understanding
1). Label structures a–e with the plant from which each comes and the effect each has on humans.
Morphine – a narcotic pain killer
Quinine – effective in treating malaria
Taxol – effective in treating some forms of cancer
Genistein – can mimic the effects of the human hormone estrogen
Manihotoxin – can be lethal because it releases cyanide when metabolized. Cyanide inhibits cellular respiration.
Apply Your Knowledge
1). Herbal medicine has long relied on plant extracts to cure human disease. Find three examples of herbal remedies that have been exploited by the pharmaceutical industry in modern drug production.
Answer: Quinine has been isolated from the bark of Cinchona trees for hundreds of years to treat malaria.
The pharmaceutical industry found a way to make several synthetic forms of quinine that are effective in treating some forms of malaria.
Breast cancer can be treated with taxol that is extracted from the Pacific yew. When the Pacific yew population faced possible extinction, the pharmaceutical industry found a way to synthesize taxol.
Opium poppies have long been used for their narcotic effect, both legally and illegally. The active ingredient is morphine. Understanding the biochemical structure of morphine and its affects on the human nervous system has lead to the synthesis of pain killers for medicinal use.
2). Diagram the events surrounding infection of a plant by a fungal pathogen. Include strategies used both by the pathogen and by the host plant.
Answer: Use figure 39.5 as a sample diagram. Add the following information to these labels which already occur on the diagram:
Plant epidermal cell – Layers of cutin make it difficult for fungi to get past the plant's surface.
Fungus entering stoma – Although essential for gas exchange and transpiration, stoma are the weak link in the plant's first line of defense. Fungi locate stoma and enter through that opening.
Plant cell – Plant cells can sometimes recognize the fungus by proteins it releases. This can trigger a hypersensitive response which kills the fungus and prevents further spread of the infection.
3). If you wanted to find new phytopharmaceuticals that could fight cancer, how would you go about identifying new compounds?
Answer: If you were looking for a new phytopharmaceutical to fight cancer, you could start by studying cultures that have reduced cancer rates. Try to find a correlation between diet or herbal medicines that are used. If you find a very promising species of plant and find out how it is prepared as a food or remedy. Use this information to begin isolating compounds from the plant and testing them in cultured cell lines. This is the approach that an ethnobotanist would use. Ethnobotanists are trained in plant biology, biochemistry, sociology and anthropology.