you would recollect from previous unit that the mesophyll cells in the fich, have a large number of chloroplasts. Usually the chloroplasts align jeduselves along the walls of the mesophyll cells, such that they get the p pimum quantity of the incident light. When do you think the theroplasts will they be perpendicular to the incident light? Parastrophe You have studied the structure of chloroplast in Chapter 8. Within (Parallel) the chloroplast there is membranous system consisting of grana, the stroma lamellae, and the matrix stroma (Figure 13.2). There is a clear division of labour within the chloroplast. The membrane system is responsible for trapping the light energy and also for the synthesis of ATP and NADPH. In stroma, enzymatic reactions synthesise sugar, which in tum forms starch. The former set of reactions, since they are directly light diven are called light reactions (photochemical reactions). The latter are not directly light driven but are dependent on the products of light eactions (ATP and NADPH). Hence, to distinguish the latter they are called, y convention, as dark reactions (carbon reactions). However, this should ot be construed to mean that they occur in darkness or that they are not ht-dependent.