McGraw Hill
Mhhe: Plant Growth and Growth Regulators
A very good overview of the hormonal control of plant responses to different environmental cues. Good place to start research.
CK-12 Foundation
Ck 12: Biology: Plant Responses
[Free Registration/Login may be required to access all resource tools.] Describes ways that plants respond to environmental stimuli.
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.
McGraw Hill
Glencoe Biology: Plant Hormones and Responses: Self Check Quiz
This multiple-choice quiz on plant hormones and responses allows students to get hints for each question and check their answers after submitting.
CK-12 Foundation
Ck 12: Life Science: 7.13 Tropisms
Learn how plants respond to different environmental stimuli.