Stages of Development

• The globular stage is one of the earliest phases of embryonic development in plants, characterized by the formation of a spherical mass of cells. During this stage, the embryo is a simple, undifferentiated, three-dimensional structure that marks the beginning of cell division and differentiation. It sets the foundation for the establishment of the plant body plan, including the development of the apical-basal axis.
• The heart stage follows the globular stage and is named for the heart-like shape of the embryo as it begins to differentiate more clearly. During this stage, the cotyledons (embryonic leaves) start to form, and the shoot apical meristem becomes distinguishable between them. This stage is crucial for the establishment of the radial axis and further differentiation of the plant's shoot and root systems.
• The torpedo stage is characterized by the elongation of the embryo, which takes on a torpedo-like shape. Significant differentiation occurs during this stage, with further development of the cotyledons, shoot apical meristem, and root apical meristem. The primary tissues of the plant, including the vascular system, begin to form, setting the stage for the mature structure of the plant.
• The maturation stage is the final phase of embryogenesis, where the embryo grows to fill the seed, and the tissues differentiate into their mature forms. The embryo now has a fully developed shoot and root system, and the cotyledons are fully formed and may begin to store nutrients. This stage ends with the desiccation of the seed, preparing the embryo for dormancy and eventual germination.