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Plant Hormones
How can plants turn or move without nerves and muscles?
“Plant moves” are caused by chemical substances called hormones.
These chemicals are produced by the plant. They work alone or together
to help plants move in response to a stimulus.
Certain hormones are released by plants to promote
the growth of their cells, or to help them produce flowers or fruits.
Other hormones help to protect plants from stress and diseases.
Scientists have studied five major groups of plant
hormones, listed below. You’ll learn more about each group on the
next screens.
| Hormone |
Major Function |
| auxins |
cause plant growth and allow tropic
responses |
| cytokinins |
promote growth and cell division |
| gibberellins |
control stem and fruit growth |
| ethylene |
involved in fruit ripening and aging |
| abscicic acid |
causes leaves and fruits to fall |
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Ripened tomatoes on a vine show the effects of
the plant hormone ethylene.
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