Figure 10.33: Leaves changing color is a response to the shortened length of the day in
autumn. ( 19 )
school the next morning. But in the summer it will be bright early in the morning and the
sun may not set until late that night. Plants can detect the differences in day length and
respond accordingly. For example, in the fall when the days start to get shorter, the trees
sense it is time to begin the process of shedding their leaves.
Lesson Summary
- Plant hormones are chemical signals that regulate a variety of processes in plants.
- A plant tropism is growth towards or away from a stimulus such as light or gravity.
- Many plants undergo seasonal changes after detecting differences in day length.
Review Questions
- What is the term for dropping fruits, flowers, or leaves?
- What hormone is involved with fruit ripening?
- How are hormones involved in seed germination?
- What hormone is involved in tropisms?
- What hormones promote cell division?
- What hormone causes stems to elongate?
- What is phototropism?
- How does a tendril wind around a pole?
- How do plants detect the change in seasons?