Sweet pea seed germination sequence. Sequence showing the germination of a sweet pea seed (Lathyrus odoratus). The seed itself remains below ground as it germinates (hypogeal germination). Initially the seedling root, called the radicle, emerges and grows downwards under the influence of gravity. A shoot emerges and grows upwards against gravity. This response to gravity is known as geotropism. The root system develops, taking up water and nutrients from the soil, and the shoot grows above ground and develops leaves for photosynthesis.