They are an attractive structure for the study of the regulation of morphogenesis including primordium initiation, directional division and cell expansion, asymmetric growth, and cellular differentiation. Ovule development is considered to be those processes occurring prior to fertilization with further development constituting seed development. One example is that the suspensor cells may contribute GA to the developing embryo up to the heart stage, since lack of a suspensor in cultured embryos can be overcome by supplying GA in the culture medium. When this is done normal embryonic development occurs in culture. In general early embryogenesis is promoted by low concentrations of IAA and high amounts are inhibitory.
Cytokinins enhance the cycle cycle especially in endosperm tissue.
Mid-embryogenesis is characterized by high levels of IAA and GAs during cell expansion and fruit growth. Mutants suggest that GA levels can be very low and high levels are not required. Ethylene does not seem to be required during development of seed, but will be important in germination. Once dessication is complete, ABA levels decline rapidly and it will inhibit germination. The development of dicotyledon embryos may not involve ABA, and they seem to be different from monocotyledons.