Sycamore seedlings (Acer pseudoplatanus). These three seedlings are at different stages of growth. At left, the first simple root (radicle) and first two leaves (cotyledons) are seen. At centre, the first two proper leaves are seen growing between the two cotyledons. These are more developed at right, where the root is now branching, increasing its surface area for the absorption of water and nutrients. The direction of the growth of the radicle is governed by gravity so that it always heads downwards. The shoot emerges later and grows in the opposite direction.