Can you imagine growing taller than a ten-story building? How about living to be 4,000 years old? Ever grow 2 inches (5 centimeters) in one day? Such things are not likely to happen in your life. But life would be very different if you were a tree!
WHAT IS A TREE?
Trees are plants. They are usually tall and have a main stem called a trunk. They come in many colors and sizes. The tallest trees are the tallest plants on Earth. Some trees can grow as tall as a soccer field is long. Trees grow everywhere on Earth, except for deserts at the equator and the North and South poles.
WHY ARE TREES SO IMPORTANT?
Trees provide protection from the wind. Tree roots spread through the ground and keep wind and rain from washing soil away. Trees and forests store water during times of drought and suck up extra water when it rains a lot. Without forests, areas would flood more often. Trees provide places for animals and other plants to live. Trees help keep Earth the right temperature for life. Trees help create the air we breathe by turning the gas carbon dioxide into oxygen.
Aside from all that, many people rely on trees to earn their livings. Wood from trees builds houses. We eat fruits and nuts that grow on trees. Olive oil and coconut oil come from trees. Corks, spices, and maple syrup are tree products. Trees are even used to make some medicines that fight cancer and other diseases.
PARTS OF A TREE
The five major parts of a tree are roots, trunk, leaves, flowers, and seeds. All these parts work together to help a tree live, grow, and produce new trees.
What do all those roots do underground? Roots hold the tree in place. They also have tiny, little hairs that absorb water and minerals from the soil. The tree needs water and minerals to live and grow. Roots are always growing. In some trees, roots spread farther underground than the tree spreads up in the air!
How does the trunk help the tree? A tree’s trunk is covered by bark, which protects the tree. Openings in the bark let air get in and out of the trunk. Bark is made of mostly dead cells. Bark can be a different color and thickness on different trees. Scientists often use bark to help tell types of trees apart.
Under the bark, a tree’s trunk moves water and minerals around to parts of the tree that need them. As the tree grows, cells inside the trunk are continually dying and being replaced. The cells closer to the center of the trunk die. New cells grow around them and make the trunk thicker. This growth leaves behind rings in the tree trunk. You can tell how long a tree lived by cutting through the trunk and counting these rings!
Why are leaves green? Leaves contain a chemical called chlorophyll. Chlorophyll is green. Chlorophyll combines with carbon dioxide from the air, water in the leaf, and light from the Sun to make food for the tree. This food provides energy for the tree to grow.
Water constantly leaks out of a tree into the air through its leaves. This evaporating water keeps the tree cool on hot days just like evaporating sweat keeps you cool. The tree’s roots draw water from the ground to replace what is lost. The trunk carries the water to the leaves. It’s important that water keep moving through a tree to prevent it from overheating.
Some trees have large, colorful flowers. Others have flowers that are small, pale, and hard to notice. Still others, such as pine trees, make no flowers and instead have cones. These flowers and cones produce pollen, which helps the trees reproduce. Wind, birds, bats, mammals, and insects carry pollen from male flowers to female flowers. This fertilizes the trees and allows them to create seeds.
Once fertilized, seeds ripen on the tree. Once ripe, the seeds have many interesting means of spreading far and wide before hitting the ground. Water, wind, mammals, birds, ants, and people can all help to send tree seeds far from their parent trees.
Pine tree seeds have winglike shapes and float to the ground like little helicopters. Oak seeds are encased in hard acorn shells, which squirrels plant in the ground. The seeds of a willow tree have fluffy fibers, which let the winds carry them far and wide. Coconuts are seeds that can float across the ocean to find homes on distant shores!
Source: Microsoft ® Encarta