Maturation is generally terminated by some degree of drying, which results in a gradual reduction in metabolism as water is lost from the seed tissues and the embryo passes into a metabolically inactive, or quiescent, state. Seed development and germination are distinct physiological stages of the plant life cycle, in which key metabolic events related to the status of stored reserves contrast markedly. Metabolism during seed development is largely anabolic, being characterized by the massive synthesis and deposition of polymeric reserves within the storage tissues. Studies have also been undertaken to understand more about how sensitivity to abscisic acid (ABA) changes during embryo development, particularly during later maturation and desiccation. A large component of growth or maturation of the developing embryo is associated with the laying down of reserves; a role for ABA in this respect has been suggested, particularly in promoting the synthesis of storage proteins.