The primary parietal cells differentiate to epidermis, endothecium, middle layer, and tapetum (from outer to inner).
Strepsirrhines have a reflective layer, the tapetum lucidum, behind the retina, which increases the amount of light for night vision, while haplorrhines have no tapetum but, instead, an area of enhanced vision, the fovea.
Timely initiation of tapetal programmed cell death is essential for the regulated release of wall materials from the tapetum to the developing microspore including carbohydrate, lipid molecules, and other nutrients.
In addition, thick, protrudent, hair-like structures (probaculae) were observed outside the plasma membrane, which indicated that sporopollenin components were actively transported from the tapetum to the microspores.
Immunohistochemical localization of QRT3 suggests that the protein it encodes is secreted from the tapetum during the early stages of microspore development (Rhee et al. 2003).
This change was observed along with the starting of disruption of the tapetum associated with the formation of tetra structures.
Subsequently the PMC cellulosic wall disappeared completely and the tapetum degenerated as the microspores increased in size.
The tapetum edge facing the loculus also appeared densely stained.
The tapetum adjacent to the sporogenous cells plays a crucial role in supplying nutrients to microsporocytes and providing their release form tetrads. Therefore most mutations with defects in the tapetum cause male sterility.
Among the four somatic cell layers, the tapetum cells are of considerable physiological significance because all nutritional materials entering the sporogenous cells passes through or originates from the tapetum [ 4].
