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Roots and growth of a palm tree.

Billions of years ago tiny single celled organisms lived in the oceans of the earth

From these humble beginnings, the whole plant kingdom as we know it today has evolved.

Many plants remain in water, but others colonised the land. To do this successfully, they needed some way to support themselves. Some plants eventually developed a material called lignin, which made there stems tough and woody so that they could grow taller. When cells divide they make the plant grow longer. Because all plants need light, the tall plants do better than the smaller ones which have to survive in the shade. Although most palm trees do not have to face harsh winters, their growth is affected by another factor - Rain. In some parts, rainfalls all year round. Palm trees that grow in dry areas often have tough leathery leaves to prevent hot winds drying them out.

Palm trees have fibrous roots and trunk. They all produce flowers, and after pollination these flowers develop seeds (if they have an ovary). The seeds are often enclosed in a hard nut or a fleshy fruit.

Palm trees have fibrous roots that people say plunge down deep into the earth. But this is often far from the truth. Instead of growing downwards, most of the trees roots grow outwards forming a criss-crossing net that anchors the tree in the ground. Over all in the ground, tiny root hairs collect water and minerals and channels them into rootlets. The precious water passes from the rootlets into the main roots and finally, after a long journey, into the trunk.

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Roots for waterlogged ground

Most trees are unable to grow in soil that is permanently waterlogged because the soil is unstable and moves around. It is also very low in oxygen which tree roots need. A few palm trees love these conditions in the mangroves on coastal mud flaps. There are two special kinds of roots. Stilt roots arch from the mangroves trunk and anchor the tree in mud. Breathing roots, or pneumatophores, grow up through the mud and are exposed to the air at low tide, enabling the collection of oxygen.

The roots draw minerals up from the ground and carry nutrients downwards from the leaves. The inner living cells are constantly dividing. Produced in their millions, these cells die when they become cut off from the supply of water and sap.

For any plant, growth is a demanding business. In Perth growth is slowed down or brought to a halt every year by the cold and darkness of winter for our palms.

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Leaves

Leaves are like miniature power-stations, but instead of burning fuel they generate it. They take in energy in the form of sunlight and use it to turn carbon-dioxide and water into sugars. These sugars can then be used as a fuel, Or they can form cellulose, the substance that forms the cells and on which the wood forming substance, Ligin, is laid down.

Leaves get their colour from the green pigment they contain called chlorophyll, which harness the energy in sunlight. To make the most of the sunlight falling on their leaves, plants often have "accessory" pigments as well. These absorb light of different wavelengths, and pass the energy on to the chlorophyll. The main accessory pigments are carotenoids, which can be orange, yellow or red, and xanthophylls, which are yellow and anthocyanins, which are purple, scarlet and blue. The balance of these pigments changes, and the result is often a brilliant burst of colour. E.G. Chamberyonia macrocarpa in the cooler weather changes brighter in colour. It may also contain more sugars.