How plants tell time

What was the flower clock?

• 
  The only way people in the 18th century could tell time

• An experiment Linnaeus used to discover phytochromes

• An experiment Linnaeus used to discover that the day has 24 hours

• A way Linnaeus organized flowers so that their blooming could predict the time of day

What is circadian rhythms?

• A fun dance

• When the seasons change

• Your body's internal timekeeper

• Your bedtime

Phytochrome molecules detect:

• Light

• Temperature

• Gravity

• Time

How do plants know the difference between morning light and afternoon light?

• A difference in the total amount of light

• A difference in the ratio of light wavelengths

• A difference in the speed of light

• A difference in the size of the light molecules (photons)

What is starch?

• A polymer plants use to store protein

• 
  A network of triglycerides

• A collection of unlinked glucose molecules stored in plant vacuoles

• A polymer of glucose

How do phytochromes work within the plant cell?

What is more important when a plant is deciding when to create blooming flowers: the time of day or the season of the year? Why?

Circadian rhythms are especially important in the beginning of a plant's life. Until their phytochromes perceive the presence of light, seed sprouts grow tall and long, and do not produce any green pigment. As soon as they reach light, they begin to produce green pigment and broader leaves. What are the advantages of producing green pigment only after the presence of light?