Germinated seed. Image 4 of 4. Coloured scanning electron micrograph (SEM) of the final stage in the germination of a plant seed. The seed coat (testa) has been lost. The embryonic plant that emerged has two main parts. The radicle (white), the embryonic root, is growing downwards in a response to gravity that is called geotropism. The root 'hairs' increase the ability of the root to obtain water and nutrients from its surroundings. The embryonic shoot (plumule) will grow upwards against gravity to the light, and its seed leaves (cotyledons, green) will photosynthesise. This is a swede (Brassica napus) seedling. For images of seed germination, see B787/394-397 and B787/398.