Plant Hormones and Photoperiod

Review questions

• Define hormone
• List the five plant hormones found in plants
• Describe the major functions of each of the plant hormones
• Describe the role of IAA (auxin) in phototropism and gravitropism
• Explain the role of GA in seed germination
• Describe the role of ethylene in fruit ripening
• What is a climacteric fruit
• Why is ABA considered a stress hormone
• Know examples of turgor movements

Photoperiod

• What is a circadian rhythm and what type of cycle does it control
• Define photoperiod.
• Compare the type of plant responses controlled by circadian rhythms and photoperiod
• Define a long day, short day and day-neutral plant
• What is meant by critical night length
• What is phytochrome
• What wavelengths of light does phytochrome absorb
• What is the active form of phytochrome
• Explain night interruption experiments