Chapter 25, Problem 5STP

Summary Introduction

Introduction :

The nastic movement is the non-directional movement that can be described as the response of plants towards a stimuli such as light, temperature, etc. The nastic movements are reversible and it does not represent growth in a direction. However, the other type of movement that is tropic movement involves growth in the direction of the stimuli.

Answer to Problem 5STP

Correct answer :

Option (C).

Explanation of Solution

Explanation/justification for the correct answer :

Option (C) Sunflower tracks the Sun. The tracking of the direction of the sun and facing towards its light is a typic of nastic response shown by the sunflower. As there is only variation in the position of the plant and not the growth, it is a nastic response. Hence, the correct answer is option (C).

Explanation for incorrect answer :

Option (A)bamboo plant growing towards the light source. The growth of the plant towards the direction of the life source is known as the phototropism, it is not a nastic response. Hence, it is an incorrect answer.

Option (B) corn plant roots growing downwards. The growth of the root in the downwards direction is also a type of tropism, which is gravitropism or geotropism. Hence, it is an incorrect answer.

Option (D) Vines grow up a tree. The growth of shoot in the opposite direction to the earth is also a type of geotropism, which is observed in the growth of the vines too. Hence, it is an incorrect answer.