What makes plants lean toward the light? Even though plants are firmly rooted in the ground, they can still move as they respond to changes in their environment. Light is so important for plant growth that they actually "bend over backwards" to get their share!
about it this way. The plant cells that are on the "shady" side
of the plant actually grow longer than the cells on the "sunny"
side. These longer cells grow this way because of a chemical in them called
an auxin. An auxin, is a plant growth hormone that helps regulate
shoot growth. Under normal light conditions auxins are spread out in the
plant. But when sunlight varies, auxin is broken down on the sunnier side
of the stem. The higher concentration of auxin on the shady side causes
the plant cells on that side to grow more so it bends toward the light.
This bending toward light is called phototropism. Phototrophism is a response that causes house plants to lean towards the window and trees to branch over the road. Take a walk in the woods and look for fallen trees. Auxins cause fallen trees to turn at their tips and grow upright again.
Plants in Motion
National Science Education Standards
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