Question

When the chloroplasts will be aligned with their flat surfaces parallel to the walls? When would they be perpendicular to the incident light?

Answer 1

Part 1: Chloroplasts
A cell organelle which contains the chlorophyll pigment and acts as the site of photosynthesis in green plants are called chloroplasts. These chloroplasts are found in the mesophyll cells of the green plants. The chlorophyll molecules require light for photosynthesis. But the intensity of the light is also important.

Part 2: Arrangement of chloroplast at low light intensity
The chloroplasts are arranged within the mesophyll cells according to their light intensity. When the light intensity is low, the chloroplasts are arranged in such a way that they get the maximum exposure to the sunlight. Thus when the light intensity is low, the chloroplasts will be aligned with their flat surfaces parallel to the walls. This type of arrangement is called epistrophe.

Part 3: Arrangement of chloroplast at high light intensity
The degradation of chlorophyll molecules due to high intensity light is called photooxidation. In order to prevent photooxidation, at high intensity the chloroplast are arranged perpendicular to the incident light.This type of arrangement is called parastrophe.