Chapter 22, Problem 31A

Summary Introduction

Introduction :

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

Answer to Problem 31A

Correct answer :

The correct answer is option (B) The plant grows toward the light

Explanation of Solution

Explanation/justification for the correct answer :

Option(B) The plant grows toward the light. Phototropism is the growth of plants to light caused by unequal auxin distribution. When the growth of the plant happens towards the light. Then, the phototropism is said to be positive. So, the correct answer is option (B).

Explanation for incorrect answer :

Option (A) The plant grows away from the light. When the growth of the plant happens away from light. Then, the phototropism is assumed to be negative. So, this is an incorrect answer.

Option (C) The plant grows toward the gravity. Gravitropism is a response to gravity on plant growth. Roots typically exhibit a positive gravitropism. The growth of plants towards gravity is called positive gravitropism. So, this is an incorrect answer.

Option (D)The plant grows away from the gravity. The growth of the plants away from the gravity is assumed to be negative gravitropism. So, this is an incorrect answer.