Coordination and Response in Plants

Tropic Responses

• Sensitivity is the ability to respond to stimuli.

• Plants exhibit tropic responses where parts of the body respond to stimuli.

Tropisms

• Growth movements related to directional stimuli.

• Examples include phototropism (response to light) and gravitropism (response to gravity).

• Positive tropism is growth towards the stimulus, negative tropism is growth away from it.

Phototropism and Gravitropism

• Shoots exhibit positive phototropism by growing towards light.

• Roots show positive gravitropism by growing towards gravity.

• Shoots are negatively gravitropic, growing away from gravity.

Advantages of Tropisms

• Positive phototropism helps in faster photosynthesis and pollination.

• Negative gravitropism in shoots lifts leaves for better light exposure.

• Positive gravitropism in roots aids in anchorage and water absorption.

Plant Growth Substances and Tropisms

• Growth in plants is controlled by growth substances like auxin.

• Auxin influences responses to light and gravity in shoots and roots.

• Auxin distribution causes uneven growth leading to tropic responses.

Auxin and Plant Growth

• Auxin is produced in growing roots and shoots, stimulating cell enlargement.

• Auxin influences the growth of shoots towards light in phototropism.

• In the absence of light, auxins accumulate on the lower side causing negative gravitropism.

Note

This transcript discusses coordination and responses in plants, focusing on tropic responses like phototropism and gravitropism. It explains how plants exhibit positive and negative tropisms towards stimuli, and the role of auxin in influencing growth patterns. Tropisms provide advantages such as better light exposure, pollination, and water absorption.