Question

Circinate ptyxis present in fern leaves is due to
A) Epinasty
B) Hyponasty
C) Nutation
D) Movement of variation.

Answer 1

Hint: Many leaves plant parts show nastic movement and involve differentiable development. This form of movement is permanent or irreversible and is known as ephemeral movement form. It is an example of growth motion caused by uneven development of plant organs.

Complete answer:
To solve this question, first we should know about the nastic movement in plants. The movement of a plant component in response to an external stimulus in which the reaction direction is not defined by the stimuli direction is recognized as nastic movement.
Let us find the solution from the given options-
Epinasty is the downward folding of a leaf, arising from stronger upper-side growth than lower-side growth. The flower will open as a result of epinasty, leading to further development on the upper side.
So, option A is an incorrect option. Thus, epinasty is an incorrect answer.
The hyponasty is an upward folding or untwisting of leaves that result from greater lower-side growth. Because of hyponasty, Circinate ptyxis is present only in fern leaves. So, Hyponasty is the correct answer.
Nutation is the bending motions exhibited by certain parts of the plant due to the uneven growth rate of certain parts of the plant. So, option C cannot be the correct option. Nutation is an incorrect answer.

Thus, the right option is option B i.e. Hyponasty.

Note: The movements that take place without outside stimulus effect are termed autonomic movements. While random movements are brought on by definite internal stimuli, and if the movements are created in response to external stimulation, they are called paratonic movements.