Question

When are the chloroplast aligned with the flat surfaces parallel to the walls ? When are they aligned perpendicular to the incident light?

Answer 1

(a) Chloroplasts of higher plants show phototectic movement, under strong light. Chloroplasts are aligned with the longitudinal walls of mesophyll ' cells with their edges only towards light. This position is called parastrophe.
(b) In moderate light, chloroplasts arrange themselves perpendicular to the incident light. The arrangement is called epistrophe.
(c)In poor light the chloroplasts are arranged variously. This position is called apostrophe.