Final answer:
In monocot seeds, the seminal roots form first, emerging as the radicle during seed germination. The primary shoot then emerges, and later, adventitious or crown roots form to establish a fibrous root system.
Step-by-step explanation:
The roots that form first are the seminal roots, which occur after a plant embryo emerges from the seed during germination. Specifically, in monocot seeds like grass, the primary root that emerges is termed a radicle. Following the radicle's emergence, the roots proliferate into a fibrous root system, primarily consisting of adventitious roots. These adventitious roots are roots that form from parts of the plant other than the radicle, such as the stem base, and they contribute significantly to the creation of a fibrous root system. Conversely, crown roots are produced later and typically originate from the crown at the base of the plant.
During the germination of monocot seeds, the seminal roots initially manifest followed by the primary shoot (coleoptile), and eventually, adventitious or crown roots emerge, providing the plant with a stable, fibrous root system. The seminal roots or primary roots thus play a vital role in the early stages of a plant's life, supporting the young seedling until the more robust and complex crown roots develop.