The embryo, endosperm and seed coat structure of developing Moringa oleifera seed

•Microscopical study of developing Moringa oleifera seed•Illustrating and describing embryo, endosperm and seed coat structure of developing Moringa oleifera seed•Commencement and completion of cotyledon development•Epidermal layer of the inner integument divides testa from the cotyledons.•Seed are non-endospermic.

In order to comprehend storage compound synthesis and accumulation throughout seed growth, the integral processes of embryogenesis and endosperm development need to be described. Micro-anatomical studies of developing Moringa oleifera seed have revealed the endosperm to be primarily nuclear, becoming cellular from the chalazal end towards the developing embryo at a fruit diameter of ± 6 mm. At a fruit diameter of ± 8 mm the cellular endosperm had covered the entire inner integument, which coincides with the developing embryo reaching the globular stage. Cotyledon development commenced at a fruit diameter of ± 12 mm and continued up until ± 24 mm. It was also during this phase that the majority of storage compounds were synthesized and stored, making it the most sensitive stage to environmental stresses. At the end of this phase the cotyledons had filled the entire space covered by the seed coat, while the unicellular epidermal layer of the inner integument remained distinctly visible between the cotyledons and the testa. The mature seed coat had layers of thickened as well as fibrous cells while being roughly triangular with three wings. Prior to studying the physiological and biochemical processes during seed growth and development, the post-fertilization anatomy of the endosperm and embryo needed to be understood.