Some representative examples of seeds from eudicots and monocots are shown in Figure 18.1. (...) Instead, the perisperm and storage cotyledons serve as the main sources of nutrients during germination (see Figure 18.1). (...) Specialized embryonic structures peculiar to the grass family include the following (see Figure 18.1):
The single cotyledon has been modified by evolution to form an absorptive organ, the scutellum, which forms the interface between the embryo and the starchy endosperm tissue.
The basal sheath of the scutellum has elongated to form a coleoptile that covers and protects the first leaves while buried beneath the soil.
The base of the hypocotyl has elongated to form a protective sheath around the radicle called the coleorhiza.
In some species, such as maize, the upper hypocotyl has been modified to form a mesocotyl. During seedling development, the growth of the mesocotyl helps raise the leaves to the soil surface, especially in the case of deeply planted seeds.
"Plant Physiology and Development" int'l 6e - Taiz, L., Zeiger, E., Møller, I.M., Murphy, A.
