Plant Control of Response

Plants growing in a partially dark environment will grow toward light in a response called phototropism. Which of the following statements is true regarding phototropism? 

• It is caused by an electrical signal.
• One chemical involved is ethylene. 
• Auxin causes a growth increase on one side of the stem.
• Auxin causes a decrease in growth on the side of the stem exposed to light. 

We know from the experiments of the past that plants bend toward light because 

• they need sunlight energy for photosynthesis. 
• cell expansion is greater on the dark side of the stem. 
• the sun stimulates stem growth. 
• auxin is inactive on the dark side of the stem. 

Tags

NGSS.HS-LS1-5

The ripening of fruit and the dropping of leaves and fruit are principally controlled by 

• auxins. 
• cytokinins.
• ethylene. 
• carbon dioxide concentration (in air).

Which of the following hormones would never be found in high concentrations in a dormant overwintering flower bud? 

• ethylene
• abscisic acid 
• cytokinins 
• auxin 

If you were shipping green bananas to a supermarket thousands of miles away, which of the following chemicals would you want to eliminate from the plants' environment? 

• CO₂ 
• cytokinins 
• ethylene 
• auxin 

Which of the following plant growth responses is primarily due to the action of auxins? 

• the detection of photoperiod 
• cell elongation
• fruit development 
• leaf abscission 

Experiments on the positive phototropic response of plants indicate that 

• auxin can move to the shady side of the stem. 
• auxin is synthesized in the area where the stem bends. 
• auxin moves down the plant apoplastically. 
• auxin is only of secondary importance in the process.

Incandescent light bulbs, which have high output of red light, are least effective in promoting - 

• entrainment of circadian rhythms.
• flowering. 
• phototropism. 
• photosynthesis.

Tags

NGSS.HS-LS1-5

Many plants flower in response to day-length cues. Which of the following statements best summarizes this phenomenon? 

• As a rule, short-day plants flower in the summer.
• As a rule, long-day plants flower in the spring or fall. 
• Flowering in day-neutral plants is only influenced by day length if there is an exceptionally warm spring. 
• Flowering in short-day and long-day plants is controlled by phytochrome.

If a short-day plant has a critical night length of 15 hours, then which of the following 24-hour cycles will prevent flowering? 

• 8 hours light
  16 hours dark 
• 8 hours light
  8 hours dark/light flash
  8 hours dark 
• 4 hours light
  20 hours dark 
• 6 hours light
  2 hours dark/light flash
  16 hours dark