Plants – The essence of life
Introduction
From the colourful displays of spring to the vibrant colours of autumn, the beauty and variety of plants throughout the world is amazing. What is more amazing is how important plants are to all life on Earth, both as food and part of the cycle of atmospheric gas exchange.
I look forward to having you all join me on this journey of writing on this essential part of our lives.
What were the first plants?
Plants have been around a lot longer than animals. For millions of years the only living things on the planet were vast colonies of cyanobacteria (which still survive today). Like animals, early plants also moved from the sea onto the land, but unlike animals, many of these primitive plant forms survive today. Examples of these primitive plants are the ferns and the cycads. Of course the species alive today are different from their prehistoric ancestors as they have been evolving for tens of millions of years. Fossil records show that ferns existed as long ago as 360 million years, pre-dating all known land animals, while cycads were so prevalent during the Jurassic era that this period is also known as:
“The Age of the Cycads”.
Today cycads are an endangered species while ferns continue to thrive.
Ferns and cycads are today known as primitive plants. The flowering plants are known as higher plants.
Where on the Earth would you find the most plant life?
The tropical rainforests of Africa, South-East Asia, Central and South America contain the most rich and diverse plant life on the Earth. In the rainforests, there are hardly any changes in the seasons and there is constant supply of rain, sunlight and warmth. This means that flowers and fruits appear all year round.
There are different layers of plants in a rainforest. At the ground level fungi, mosses and ferns grow. Then there is a shrub layer, above which is the lower canopy of young trees. The thick canopy of mature trees comes next and rising above the canopy are a few tall trees.
How does a seed become a plant?
A seed needs water before it can start to grow or germinate. When the seed lands on the ground it takes in water through the seed case and starts to swell. It then sprouts a root, known as a radicle, which heads downwards and starts to absorb water. Then the young stem appears, known as a plumule, which grows up through the soil. The cotyledons are the seed leaves, which provide a source of food for germination to happen.
Above the ground, the leaves can start to make their own food through photosynthesis. Sometimes the stem pulls the cotyledons to the surface with it, where they turn into proper leaves, but other plants leave the cotyledons underground.
How do plants collect water?
Plants collect water from the soil which is carried up the plant from the roots. Water is taken in by root hairs, then it is drawn into the inner cells of the root. It is taken up to the leaves by the xylem. These cells join together to create tubes that stretch all the way up the plant. These are arranged together in bundles called vascular bundles. The heat of the Sun causes water in leaves to evaporate. Water that has travelled up the xylem from the ground then moves into the leaves to take its place.
Why are plants brightly coloured?
Plants have bright flowers to attract insects, birds and small animals. This is necessary for transferring pollen between plants in order to make seeds. When an insect visits a plant to eat its nectar, it touches the anthers. The anthers are part of the male section of a plant and they contain pollen. The pollen sticks to the insect. When the insect visits another flower the pollen is left on the stigma, part of the female organs. This plant is then able to make seeds that will eventually grow into new plants. This transfer of pollen is called cross-pollination.
Sunflowers are amongst the most striking of plants. They provide a useful oil for cooking,
Carnivorous plants
There are some carnivorous plants that catch and eat insects. Most of these kinds of plants live in swamps and bogs and may not be able to get the nitrogen they need from the soil. Instead, they get the minerals from insect bodies. The Venus flytrap has two lobes, each with three trigger hairs. If an insect lands on a lobe and touches two trigger hairs, or the same one twice, the lobes snap shut, keeping the insect inside. Its body is broken down by acid and the plant absorbs the liquid. Pitcher plants attract insects into its pitchers, where they fall in and drown. The plant then digests its prey.
How do plants distribute their seeds?
Plants have to spread their seeds to ensure that more plants will grow from them. There are various clever ways of doing this that nature has developed. Some seeds have wings or parachutes that are picked up and carried by the wind, or they might float on the waters of rivers and lakes. Other seeds are carried by animals, either by sticking in their fur or by tempting them with tasty fruits. When an animal or bird eats a berry, the tough outer layer isn’t digested and a new plant can germinate from their droppings. Animals such as squirrels bury nuts and acorns during the autumn months, often carrying them far from the parent tree. Those that remain uneaten may eventually grow into trees.
How do plants make food?
Chlorophyll is a chemical found in the green leaves of plants, stored in tiny packages called chloroplasts. It absorbs energy from the Sun to drive a process called photosynthesis, which means ‘building with light’. This system turns carbon dioxide from the air and water from the ground into sugar, which is stored into starch. This food is used to give plants energy to grow. Some energy will be stored so it can be used during the months when there is little sunlight. During photosynthesis, plants release oxygen into the atmosphere.
Plants are the only living things that can make their own food!
How do plants reproduce?
Pollen is the method by which flowering plants reproduce. These tiny grains contain the genetic material of the plant and are so small because they are designed to be carried by the wind to plants of the opposite sex. Some plants use insects, such as honey bees, in order to spread their pollen. The plants lure the bees with sweet sticky deposits called nectar. While trying to reach the nectar, the bees brush up against the plant’s stamen, which produce the pollen. When the bee visits a plant of the opposite sex, the pollen is transferred to sticky areas called anthers. Trees also produce pollen, as do the grasses. Airborne pollen can cause a violent reaction in some people as the tiny grains are mistake for invading bacteria when they land on the membranes inside the nose. This reaction is called hay fever. People are becoming more prone to this hay fever reaction, though scientists are not sure why this is.
What are evergreens?
Most plants shed their leaves in winter to survive the cold and avoid losing water. Evergreens are different, as they keep their leaves all year round. They lose and renew a few of their leaves throughout the year, but most leaves can survive for several years. The leaves tend to be tougher than those found on other plants. Some evergreens, such as conifers, have needle-like leaves that keep water loss to a minimum. These leaves are better able to cope with changes in temperature than wide, flat ones. Most tropical plants are evergreen and tend to be described as broadleaf evergreens as their leaves are not needle-shaped.
What is different about grasses?
Nearly all plants grow from the top. This means that if you cut the top off the plant, it stops growing. The plant will then put out new growth from the area surrounding the cut. Gardeners can use this feature to prune plants into shape and prevent them from growing too high. Grasses are different. The growing part of the grass is at the base. This simple fact means that when you cut your lawn you do not damage the growing part, which continues to grow upwards. This is the reason that it is possible to create smooth, ornamental lawns and even playing surfaces. More importantly, it allows the grass to survive grazing by animals, such as sheep, that crop the grass right down to ground level.
Purpose of roots
Most plants have roots. They are the portion of the plant that is underground. Roots have two main purposes. Firstly they provide an anchor that allows the plant to grow. Trees need very deep and strong roots to enable the tree to withstand the pressure of the wind as it grows. Often a tree’s roots will be extensive under the ground as the branches are above.
The root’s other purpose is to extract water and nutrients from the ground. They do this in a similar way to the lungs in an animal. The roots get progressively smaller and smaller, ending in tiny hair-like structures. These have a large surface area and absorb nutrients dissolved in water in the soil. The water is pumped up the root system and through the plant using a process called capillary action.
Which is the tallest tree in the world?
The world’s tallest trees are the coast redwoods of California. The tallest living one stands at about 112m in Humboldt Redwoods State Park, Northern California. These trees compete for sunlight, so they need to grow taller than their neighbours to survive. It is thought that water entering the base of a redwood could take up to 24 days to reach the top. The tallest tree that has ever been measured was a eucalyptus in Australia. It was 132m tall, but would probably have originally measured over 150m.
The redwood forests of California are one of the natural wonders of America. The trees dwarf all the plants around them.
Do plants get ill?
Plants are living organisms. This means that they are susceptible to attack by viruses, bacteria and other harmful agents, just like us. One look in any garden centre is enough to show the bewildering array of diseases that can befall plants and the wide range of treatments available and help them recover.
Dutch elm disease
This disease is carried by a beetle that loves to make its home in elm trees. The disease arrived in the UK in 1927 and has since destroyed nearly 100 percent of all the elm trees in the country. The beetle carries a fungus that attacks the tree by blocking its water-carrying vessels. Since its introduction into the UK, the disease has killed over 25 million trees. The English elm is particularly susceptible to the fungus. Every effort to re-introduce the tree into the wild has failed.
The benefits derived from plants:
Plants lay a crucial role in the ecosystem of the Earth. Unlike animals, which breathe out carbon dioxide, plants work the other way round, absorbing carbon dioxide and excreting oxygen. This has led to forests being described as the ‘lungs of the planet’. The carbon dioxide that plants absorb remains locked in the plant after it dies and over time becomes transformed into the fossil fuels we use so much of today. Burning these fuels releases the carbon dioxide into the air. As fossil fuels are used up, we may start to use the energy stored in plants directly by turning them into bio-fuels.
Plants also provide shelter for animals and insects to live in. They are also a vital part of the food chain. Rotting plants provide energy for the creatures in the soil, while higher animals consume vast amounts of plant matter and are, in turn, eaten by carnivores. Plants are also useful chemical factories. Many ancient remedies are based on plant extracts and drug companies are constantly exploring the world looking for plants that may provide new sources of drugs. Trees are also a valuable source of building materials. This has led to much of the world’s supply of hard woods being over-harvested.
Conclusion
It is difficult to imagine a world without plants. Certainly it would not be a world that could sustain life as we know it.
Looking after the plant species is just as important as conserving endangered animal species.
For more on my series on amazing life in the water, on land & astoundingly parading the air, please follow me.
Thank You!
References:
https://en.wikipedia.org/wiki/Plant
https://simple.wikipedia.org/wiki/Plant
https://www.britannica.com/topic/plant
www.encyclopedia.com › Plants and Animals › Botany › Botany: General
www.biology4kids.com/files/plants_man.html
www.mbgnet.net/bioplants/earth.html
All images linked to their sources
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