Gymnosperms are a group of plants that include conifers, cycads, and ginkgoes. They are characterized by the production of seeds, which are not enclosed in a fruit or ovary as they are in angiosperms. Instead, the seeds of gymnosperms are exposed on the surface of a cone or other structure, and are often protected by scales or bracts.
During the development of an embryo in a gymnosperm, the main source of nutrition is the seed itself. The seed contains a store of nutrients, including carbohydrates, proteins, and lipids, that are necessary for the growth and development of the embryo. These nutrients are provided by the parent plant, and are stored in the seed until it is ready to germinate.
The seed of a gymnosperm also contains a small structure called the cotyledon, which is responsible for providing additional nutrients to the developing embryo. The cotyledon is a leaf-like structure that is present in the seed of all vascular plants, including gymnosperms and angiosperms. It is responsible for absorbing nutrients from the seed and transferring them to the embryo as it grows and develops.
In some gymnosperms, the cotyledon is large and well-developed, and is able to provide a significant amount of nutrition to the developing embryo. In other gymnosperms, the cotyledon is smaller and less well-developed, and relies on the nutrients stored in the seed to support the growth and development of the embryo.
Once the seed germinates and the embryo begins to grow, it may also be able to absorb nutrients from the surrounding soil through its root system. However, the main source of nutrition for the developing embryo in gymnosperms is the seed itself, and the nutrients stored within it.
In summary, the main source of nutrition for the developing embryo in gymnosperms is the seed, which contains a store of nutrients that are necessary for growth and development. The cotyledon is also able to provide additional nutrition to the embryo as it grows. Once the seed germinates and the embryo begins to grow, it may also be able to absorb nutrients from the surrounding soil through its root system.