Plants 'r' us;Science

24th September 1999 at 01:00
Now the harvest festival season is here, Sue Dale-Tunnicliffe looks at the vital role that nature plays in all our lives

One of my favourite hymns contains the lines "Think of a world without any flowers, think of a world without any trees". Well, just think of it. There wouldn't be a world as we know it, because animals, including us, could not exist.

We need plants because through the process of respiration they make oxygen, which all living things need to live. Apart from performing this vital function, plants are an integral part of our lives. Everything in the picture is linked to plants - we eat, wear and carry things in them, use them for books, for writing materials and for all kinds of sport and entertainment (think of the things we hit balls with and bicycle tyres). A plant audit of your classroom will reveal many things connected to plants in some way. Some of them will still look like the plants they were made from, while others will have been changed by the manufacturing process.

Root it out

We eat plants raw and cooked. We rarely eat all of a plant, just particular parts of them. Many plant parts are still recognisable on our plates, but others (soya, for example) are altered so much during processing that you could easily fail to notice that they had ever been plants at all.

Fruits and vegetables are obvious plant parts. Fruits contain seeds (such as orange and apple pips) which we don't eat. But sometimes the seeds are the only part of a plant we do eat: peas and beans, for example (in mangetout - which means "eat all" in French - we eat both the fruit and the pea seeds, which are very little at this stage).

Leaves are tasty, too: cabbages and lettuces, both cooked and raw. Flowers? Well, we eat those too - cauliflowers and broccoli. Then there are stems, such as celery, and shoots, such as asparagus. Onions are the swollen leaf bases of the onion plant. Leeks and spring onions are stems made of leaves, and if you like Brussels sprouts, you are eating buds. We also eat roots - swedes, turnips, beetroots, carrots and radishes - while chips and crisps come from the swollen underground stem of the potato.

Do you spread margarine on your bread? Many of the spreads we put on our toast and sandwiches are made from oils taken from plant seeds (sunflower seeds, for example) and we also use plant oils for cooking.

Bread is made from the ground up seed of a special kind of grass called a cereal. Bread comes in many different forms, depending on how much of the seed has been removed and how the grain was ground. Cereals also provide us with breakfast foods. Puffed wheat still looks like wheat, but most breakfast cereals are so processed you can't recognise their origins. Another cereal, rice, is the most widely eaten plant in the world.

We even use plants to make our food taste nicer - dried berries of the pepper plant, ginger from a plant root and vanilla, the pod of a tropical orchid, for ice- cream.

Feeling thirsty? Then why not have a sip of something long, cool and refreshing. Drinks are often made from fruit and vegetable juices, but tea is made from the leaves of the tea bush and coffee from the beans (seeds) of the coffee plant. Chocolate is made from cocoa beans and cola drinks from the cola nut. In warmer parts of the world, such as Mauritius and the Caribbean, sugar cane is grown. You can chew the stem of this large, very sweet grass, from which the crystals we use to sweeten our drinks or sprinkle on our cereals are made.

Natural beauty

In between meals you might chew gum made from the latex (or fluid) of a tree from Guatemala and flavoured with mint from mint plants. After you have eaten you clean your teeth, and your toothpaste may also be flavoured with mint, as may the mouthwash in the bathroom.

We use many plant materials for keeping clean - and staying beautiful! The bathroom loofah is the bleached skeleton of the fruit of a gourd plant. Soaps are often derived from certain types of palm tree. Many toiletries and perfumes contain plant oils, either for their scent (lavender has long been used for this purpose) or for their therapeutic properties. The henna plant provides a widely used hair and body dye. The oil of the jojoba, a Mexican desert shrub, is used to make shampoos and cosmetics. Soothing lotions (such as after-sun cream) are often made from the aloe vera plant, which comes from central America.

Once washed, we use cotton towels to dry ourselves, and may even dust ourselves with talcum powder, often made from ground, dried cellulose, which is the substance plant-cell walls are made of. Babies' nappies are made from cotton if they are washable and from trees - wood pulp - if they are disposable.

Cotton on

And of course we wear plants as well. The frames for spectacles are moulded from plant cellulose and jeans are woven from cotton. The parts of the cotton plant used to make the material in our trousers are the fine hairs attached to the seeds, and there are about 10 seeds in each fruit, or cotton boll. One kilo of cotton, baled up ready for market, contains about 200 million of these seed hairs! Plants have also been used for centuries to colour our clothes. The traditional blue colour of jeans comes from the blue dye obtained from the indigo plant.

Clothes are also made from flax, a plant that has been used since prehistoric times to make fabric, or raffia (from a palm tree native to Madagascar). Flax is expensive, however, and fibres of the stinging nettle have been used in Europe as a cheap alternative. Other plants whose fibres have been used to make garments include the pineapple and an EastAsian plant called ramie (often mixed with wool to make pullovers).

We walk on plants all the time - many of our shoes have rubber soles and some footwear is made of rubber (Wellingtons) or cotton (tennis shoes). Even shoe leather is prepared using many plant extracts in the tanning process.

Green healing

Plants provide many medicines. The widely used drug aspirin was first extracted from the bark of a type of willow tree (though nowadays it is synthesised) and the rosy periwinkle (another Madagascan native) is used in some cancer cures. Even sticking plasters incorporate plant parts: cotton for the pad, and latex (sticky sap from the rubber tree) for the adhesive.

But besides being indispensable in so many ways, plants provide us with a lot of fun. Books are made from wood pulp. Toys of all kinds are made from wood, and soft toys are sometimes filled with seeds. From cricket bats (made from willow wood and rubbed with linseed oil, squeezed from flax seeds) to chess pieces and dice, we play with plants all the time. And what about guitars, recorders, maracas and drums? All can be made from wood.

So the next time you listen to some music, put on your shoes, read a book or wash your hair, remember that you are a lot closer to nature than you think.

RESOURCES * The Royal Botanical Garden at Kew has a display called People and Plants which can be visited as part of a trip to the gardens. Contact 0181 332 5632.

* There are many local botanical gardens and arboreta which you can visit. Look in the phone book or contact your local authority science adviser.

* Visit your local museum to find out what it has on display that is associated with plants.

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