Quiz Lecture 9

How a plant cell responds to a hormone depends on the

• concentration of the hormone.

• amount of available sunlight.

• 
  

  presence of other plant cells nearby.

• 
  

  "shelf life" of the hormone.

• cell that secretes the hormone.

Venus flytraps catch insects in order to supplement their input of

• potassium

• magnesium

• meat

• phosphorus

• nitrogen

A plant scientist was hired by a greenhouse operator to devise a way to force iris plants to bloom in the short days of winter. Iris normally blooms as a long-day (short-night) plant. Which of the following treatments has the best chance of creating iris blooms in winter?

• 
  

  alternate 4 hours of darkness with 4 hours of light repeatedly over each 24-hour period

• 
  

  artificially increase the period of darkness in the greenhouse

• interrupt the long winter nights with a brief period of light

• 
  

  increase the temperature to more closely follow summer temperatures

After seeds were planted, some of the seedlings did not emerge from the soil. Is it possible that this is because some of the seeds were planted upside down?

• No; auxins in the shoots cause curvature away from gravity.

• Yes; after seeds are planted, water and settling of the soil may cause them to shift in their orientation.

• 
  

  No; gibberellins and abscisic acid, in balanced concentrations, cause shoots to grow away from gravity.

• 
  

  No; sunlight penetrates soil to the depth of seeds and shoots grow toward the sunlight.

• 
  

  Yes; if the seed was oriented so that the embryonic shoot pointed down, it would grow in that direction because sunlight doesn't reach it.

________ maintains seed dormancy, and ________ ends seed dormancy by stimulating enzymes that break down the food reserves of the seed to fuel seedling growth.

• 
  

  Abscisic acid; ethylene

• Abscisic acid; gibberellin

• 
  

  Auxin; cytokinin

• Cytokinin; auxin

• Gibberellin; abscisic acid

In the fall, the leaves of some trees change color. This happens because chlorophyll breaks down and the accessory pigments become visible. What hormone triggers this response in plants?

• phototropin

• ethylene

• 
  

  cytokinin

• abscisic acid

What are the sites of highest ethylene production in plants?

• roots

• seeds

• ripening fruits

• shoot apical meristem and young leaves

Which hormone prevents seeds from germinating until conditions are favorable for the growth of the plant?

• Zeaxanthin

• Gibberellin

• Abscisic acid

• Ethylene

Shoots can be characterized as which of the following?

• positive for phototropism and neutral for gravitropism

• neutral for phototropism and positive for gravitropism

• negative for phototropism and positive for gravitropism

• 
  

  positive for phototropism and negative for gravitropism

Mammalian eyes sense light because the photoreceptor cells have molecules called opsins that change structure when exposed to light. Which of the following plant molecules is most analogous to mammalian opsins in their light-sensing ability?

• phytochrome

• auxin

• cytokinin

• expansin