Two parts of the leaf give it support. They are the midrib and the veins. The midrib runs down the centre of the leaf from the stalk to the tip. It contains tough fibres. The veins spread out from the midrib. They also contain tough fibres. The veins support the thin parts of the leaf which make up most of the leaf blade.

There are two sets of tiny pipes in the midrib and veins. The first set carry water from the stem and stalk to all parts of the leaf blade. The second set carry food made in the leaves and dissolved in water to the stalk. From here the food can either travel down to the roots or upwards to provide materials and energy for the growing shoot.

Most leaves are very thin and have two large faces. The size of the faces helps the plant in two ways. The leaf soaks up sunlight to make food on its upper surface. The lower face it covered in tiny holes. These 'leak' water to the air and cause new water to be drawn up from the roots.

As leaves have two vital tasks it is essential that they are allowed to perform them well. The plant makes sure of this by arranging the leaves along the stem so they do not overlap each other too much. Otherwise some leaves would not receive enough light to make food efficiently and also the air around the overlapping leaves would become filled with water vapour. This would then slow down or stop evaporation.

There are three common arrangements of leaves on stems to make the leaves work efficiently. They arrangements are growing the leaves in pairs along the stem, growing them alternately and growing them as whorls.

Most flowering trees have broad, flat leaves and this is why they are known as broadleaved trees. Some of these trees produce such large leaves, that they are divided up into smaller leaflets. The horse chestnut is an example of this kind of tree. Its leaves are divided into five, six or seven leaflets.

Coniferous trees such as the pines produce leaves which are very different from broadleaved trees. The conifer leaf is long, round and thin like a needle. It keeps in leaf all the year round so it can still make some food during the winter. Each needle has only a small area on its underside for losing water because, as many conifers grow in places where the ground is frozen in winter, they must not lose too much water before the ground thaws. Others grow in places with long, dry seasons.