CK-12 Foundation
Ck 12: Life Science: Plant Hormones
[Free Registration/Login may be required to access all resource tools.] Plants may not move, but that does not mean they don't respond to their environment. Plants can sense gravity, light, touch, and seasonal changes. Learn more about...
BBC
Bbc: Gcse Bitesize: Plant Hormones
Plants produce hormones and respond to external stimuli, growing towards sources of water and light, which they need to survive. Read about tropisms and auxins that are used to control growth in plants. There is a quiz at the end.