Chapter 22, Problem 28A

Summary Introduction

To write:The difference between tropic response and nastic response and their relation

Introduction:The roots growing down in plants, the stems growing upward, the trees dropping their leaves and the leaves of some plants trapping an insect are due to plant responses to their environment.

Explanation of Solution

A tropism is the response to an external stimulus by growth of a plant. If the resulting plant growth is in the direction of stimulation it is called a positive tropism. If the resulting growth of plants is away from the stimulus, this is called a negative tropism.

A plant response which causes movement independent of stimulus direction is a nastic response. It is not a response to growth, is reversible and can be repeated several times. A nastic response is solar tracking exhibited by some plants, such as a sunflower.

The plant responses are nastic response and tropic response.

Conclusion

Thus,nastic response provides maximum light exposure while the tropic response plant growth towards the external stimulus.