PLANTS – LIVING & GROWING
Plants grow almost everywhere in the world around us in all size and shapes. Some are so small that they can be seen only with a microscope. Others like the redwood tree in California tower high in the sky. Plants grow not only well watered soil, but in oceans, rivers, lakes and swamps, in deserts, on rock, far above the ground on branches of trees, on old pieces of wood, even on such unlikely things as crusts of bread, old shoes, or on top of arctic snow. Some strange plants eat insects, and other steal food from their neighbors.
Plants and animals are the living, growing things of the earth. Most animals’ move around, and many of them have sound apparatuses for making noises. Most plants making their whole lives silently in one place. Because they live so quietly, we sometimes forget that during their growing seasons they work hard all day long. For plants are just as alive as animals, and they have the same problems finding and keeping a place to live, getting food, fighting animal enemies and plant rivals, and having young, so that new plants will grow each year.
Scientists, taking hourly moving pictures of plants, then running them off quickly, have shown how active plants really are always twisting their stems and running their leaves towards the sun, stretching out longer, growing new buds, then flowers and finally seeds. Watch a sunflower as the sun moves across the sky and see for yourself what happens.
People often think of plants’ leaves and flowers as only decorative and of their fruits as solely for human beings and animals to eat. But for plants themselves their green leaves their many coloured flowers their great variety of fruits all the things about them are strictly business part of the job of keeping alive and providing for new plants.
Plants are fierce rivals. Anyone who has ever weeded a garden knows that often several different kinds of plants are fighting for quarters on the same piece of ground. Each plant has its own special equipment to help it in the hard business of living. Part of the fun of knowing plants is discovering each kinds way of getting along in the world.
WHY PLANTS ARE IMPORTANT
Getting food is one of the most important jobs of both plants and animals. Most animals can find food best by moving around after the plants or other animal they eat. Thai is the way they keep alive.
Plants have a different way of getting food. They can stay in one place and still eat. They do not need to dash around.
A green plants way of getting its food is just as important to every person on the earth as it is to the plant itself. For green plants do not eat other plants or animas as food. So far green plants are the are only things in the world that can make food from its raw materials –water a few minerals and a gas called carbon dioxide, which is all around us in the air. No animal can do this food making. And no animal can live without plant for food.
To be sure, some animals eat only other animals. But those other animals probably eat plants, or else they feed in turn, upon still other creatures who do. Without plants there would be no animals and no meat. Green plants are the wonderfully designed, self-running machines upon which every living things in the world really depend for food.
HOW PLANTS ARE MAKING FOODS
Only green plants can make food. This is because they have an important, almost magic, green substance called chlorophyll from two Greek words meaning leaf and green. Place a green leaf in a small jar and cover it with alcohol. After some hours the leaf will be yellowish, but the alcohol will be green. This green is chlorophyll, the plant’s green colouring matter that the alcohol has taken from the leaf.
Green plants can make food only if they can get the raw materials, carbon dioxide and water.
Green plants do not make chlorophyll unless they have light. And without chlorophyll they do not make food. Plants growing in nature depend on sunlight.
Carbon dioxide and water are both made of simple chemicals, put together in special ways. Green plants act as chemical laboratories, separating carbon dioxide and water into blocks of the simple chemical of which the gas and water are made. Then the plants rebuilt the blocks in another way so that they make sugars. The plants use this sugar as food.
The chlorophyll in green plants acts somehow as a screen to trap this energy, sunlight and use it making food. The process of food making by plants is called photosynthesis, which comes from two Greek words and means “putting together with the help of light”.
Besides furnishing food, plants do another thing for animals. Carbon dioxide and water both have oxygen in them. In separating carbon dioxide and water in to simple chemicals, plants are left with more oxygen than they need for staying alive. They return this extra oxygen to the air. Air contains oxen, nitrogen and other gases. But oxygen is the part of air, which all living things need. Plants help keep animals supplied with oxygen. If they did not do this, our supply of oxygen would soon run short.
HOW PLANTS ARE BUILT
Green plants are built so that they can be sure of having a steady supply of raw materials for food making. Every plant and every animal is made up of very tiny units or parts like building blocks. These units called cells can be seen only with a powerful microscope. Each plant cell has thin walls surrounding a living jelly like substance and some liquid cell sap. Some of the cells also have little spots of the green colouring matters called chlorophyll.
A very simple green plants may be only one single cell large. It has no trouble in making food from the water and carbon dioxide that come to it directly through its cell walls. A more complicated plant has many cells of different kinds. The plants work is divided among these cells, which from roots, stems, leaves, flowers and seeds. Getting raw materials is not as simple for a plant like this as for one-celled plants. Plants with roots, stems, leaves, flowers and seed use their leaves as food making laboratories.
Leaves are well fitted for their jobs. Look at the houseplant that has been sitting in the same position in a sunny window for a week or so. Its stems have spread the leaves out to face the sunlight. So that each gets as much sun as a possible. Turn the plants around so that the leaves are away from the light. After several days you can see that the stems are turning the leaves back to face the sunlight notice an out door plant. The stems are doing the same thing there spreading the leaves out to get sunlight.
Leaves are thin that the sunlight can reach as many of their cells as possible. If leaves were thick as branches, sunlight could reach only their top most layers and inner cells would be useless.
Many leaves are waxy coating on the outside especially on the side nearest the sun. This coating is waterproof but it’s waterproof to keep the moisture inside the leaf from escaping too much into the air outside, and so allowing the leaf to dry out. At the same time, this waxy coating is transparent the sunlight shine right through it.
The lines on a leaf are its veins and midrib. They help to strengthen the whole leaf and are part of its supply line in food making. For the leaf would be useless if it could not get its’ work supplies, carbon dioxide and water.
How plants are get carbon dioxide
Leaves get carbon dioxide from the air around them. They are full of tiny openings, so small that an average leaf has 125000 of them in each square inch of its surface. These openings are called stomata from a Greek word meaning mouth. Though these stomata gases come in and go out of the leaves. Inside the leaves are air spaces like little hallways, though which carbon dioxide goes to the food making cells and extra oxygen comes away.
How plants are get water
The water, it has come into plants from farther away and its supplying by the roots. Their tips are always reaching out to tap new moisture in the soil for it is the root tips that count in water collecting.
Roots tips are built like very end of each tiny root is a tough little cap. This is a roots protective armor as it pushes between the small bits of soil that are as rough as sand paper. Often the cap has a slippery coating to help it slide through the round. In back of armored points is the growing part the tiny section where the roots whole business of stretching longer is carried on for roots grow longer only at their tips.
Directly behind this lengthening part is the small root-hair section, covered with tiny hair like growths. These reach out firmly grasp bits of soil and soak up moisture through their thin walls. These roots hair live only a few weeks or months. As the root tips moves forward in to new territory, new root hairs keep growing and the older ones die. The bigger parts of the roots nearer the stem become thicker and covered with a layer through which water cannot pass. But the growing tips keep collecting moisture steadily.
If you pull up a plant you probably will not see the entire root tips. They are so delicate and grasp the bits of soil so firmly that many of them break off and remain in the ground when the plant is yanked up. You can see exactly what root tips looks like though by growing some yourself.
Put layers of blotting paper between two panes of glass. Place green gram seeds between the blotting paper and the glass so that you can see the seeds. Now fasten the panes together with rubber bands and stand them upright in a shallow tray of water. In a few days the seeds will sprout.
Now have a showcase view of some root tips. Imagine a full-grown plant with its hundreds of thousands of roots tips with their root hairs all-soaking up moisture. Roots tips are tiny, but all of them working together, keep a plant well supplied with the water it must have to stay alive.
PLANT PIPELINES
Even after water has soaked in to the roots of a plant, it still has to get to the leaves. Plants have pipelines, made of rows of long, slender cells. These stretch from every root tip, along the roots, through the stalks and stems, out through the veins, to every part of every leaf. Water coming into the root passes steadily through the plant, until it comes out into the food making cells of the leaves.
Usually these cells are so soaked with water that some of it escapes from their moist walls as a gas called water vapor, and goes out in to the air passages of the leaves. From there, it passes through the open stomata into the air around the plants.
So, during the business of food –making, plants do air –conditioning, too. They help keep the atmosphere moist with escaping water vapor, and fresh with the extra oxygen they give off.
And roots do much more than merely collect water. They anchor the plants to the ground.
The hundreds of thousands of roots, branching through the soil and clinging to it, help bind it together so that it does not wash away. Roots help break apart the soil and keep it full of air spaces, too, so that rain soaks in to it, instead of running off quickly and causing floods.
USING THE FOOD
All day long, while the sun is shining, leaves make sugars from carbon dioxide and water.
They must have a way of distributing the food they make .So plants have another set of pipelines, leading away from the leaves and carrying the dissolved food all over the plant, to wherever it is needed.
Of course, some of the food is used at once, to keep the plants alive and growing. And just as some of an animal’s food is turned in to flesh and bone, so some of a plant’s food is turned in to stems and leaves and leaves and all its other parts.
From the first simple sugars that a plant makes, it goes on to make fats, starches and more complicated things .To do this, and it must have minerals. Roots soak up these with water, and the pipelines carry them to where they are needed.
Most plants make more food than they need at the time, so they store it in their roots, stems and seeds. People and animals use this stored food. Potatoes, carrots turnips and onions are only a few of the stored plant supplies.
GETTING ENERGY
In order to keep alive, all plants and animals need energy .The sun is the Number one maker of energy, but only plants can capture the energy in sunlight and keep it for future use. While plants are making food, they are also storing the sun’s energy inside themselves. Food has sun energy locked up in it. Every living thing in the world uses this energy. Animals and people use the sun energy in their food for heat, and to help them move around. Plants also use sun energy for their activities.
But to use energy, plants and animals must first set it free from the food where it is locked.
Every living thing does this in the same way-by taking in oxygen. This is what happens: The oxygen joins together with food stored in the plants’ or animals’ cells and changes it, so that it gradually stops being food and turns back to carbon dioxide and water. When it changes to gas and water, the energy locked up in it is let loose to be used by the plants and animals.
The business of setting energy free by joining food and oxygen is called respiration. Respiration is just the opposite of photosynthesis. Photosynthesis is using the sun’s energy for putting together carbon dioxide and water to make food. Respiration is taking apart food to make carbon dioxide and water and set free energy. Respiration goes on all the time in all living things .A certain amount of food is always being used to set free energy.
Plants need to take in oxygen just as animals do, in order to get energy. But they use this oxygen very slowly. Plants do not walk around from place to place, so they do not need nearly as much energy as animals do.
MAKING NEW PLANTS
Roots, leaves and stems are the plants’ food –making equipment. But besides making food,
Plants must grow new young ones, so that their very special kind, called their species, will not die out .The greatest number of land plants grow their young by means of seeds.
Flowers are plants’ seed-making machines. A simple flower is built like this: Green, leaf like parts, called sepals, are like a cup, holding the rest of the flower. Inside this cup is a colored ring of petals. These enclose a ring of petals. These enclose of often club-shaped growths called stamens. And, in the very center of the flower, is another part called a pistil.
The stamens and the pistil are very important in seed making, for the stamen is the male part of the flower and the pistil is the female part. Unless these two parts work together, seeds cannot be made. Each plant seed must have two parents, just as each animal must.
The female pistil broadens out at its base into a sort of chamber, called an ovary .In this are tiny pockets containing eggs. These will develop in to seeds if they join with little dust like particles grown by the male stamens.
But the eggs cannot move from the ovaries and the stamens cannot move from their place on the flower to take the particles to the ovaries. This is what happens: Stamens grow a yellow powder called pollen. When the pollen is ripe it is carried to the tops of the pistils by the wind or by insects or birds. From there, the pollen grains grow tubes down the pistils into the ovaries these tubes carry the male cells, join them with the eggs, and so start seeds.
Plants cannot make seeds unless pollen from the stamens reaches the pistils and grows tubes down into the ovaries.
BEES HELP TO PLANTS
Not all flowers are simply made. Some are very complicated. Some have stamens and pistils in one flower. Some have stamens and pistils in different flowers on the same plant, and some even have female flowers on one plant and male flowers on other.
Pollen from the stamens of all these flowers must reach the pistils of other flowers of the same kind. Since they are anchored in one place, flowers must have outside help with this.
Many plants depend on insects to carry their pollen. Of these, bees are the greatest helpers. For bees, to make honey, need the sweet liquid called nectar, which many flowers have. Bees also mix some pollen with nectar to make “bee bread” as food for young bees.
But flowers don’t furnish these things free. Bees must work for what they get, although of course they don’t furnish these things free. Bees must work for what they get although of course they don’t thing this out. There are merely collecting nectar for food. But the nectar of flowers is always placed so that bees must crowd by the pistil and stamens onto their hairy bodies and legs. As they fly from blossom some of the pollen from one flowers stamens brushes off onto the pistil of the next flower they visit. In this way bees help spread pollen while they are collecting nectar.
Beside their nectar flowers have other ways of drawing bees to them. Their coloured petals are like advertising signs hung out to attract the bees’ attention. Many flowers even have little lines of their petals like guidelines. They help lead the bees to the nectar.
Flowers advertise another way by their smells, which attract bees to them. And many flowers have petals arranged like landing fields for the bees. A few pistils receive pollen from the stamens in the very same blossom but most of them get their pollen from other flowers of the same kind some in complicated ways. OTHER HELPER.
Files, gnats, butterflies or moths carry the pollen of some plants. Flowers like evening primroses, which are pollinated by night flying moths, have light coloured petals that the insects can see in the dark.
Hummingbirds’ speed the pollen of some flowers. These flowers have their nectar in long tube like blossoms. Bees cannot reach into these, but hummingbirds have no landing fields or nectar guides. Hummingbirds do not land as they sip nectar. They stay still in one place in the air, beating their wings to keep themselves up. The stamens grow so that they tough the birds as they hover. Many of the hummingbirds’ flowers are red. This seems to be a favorite colour with these birds.
Many flowers, which depend on flying insects, protect themselves from those that might crawl up from the ground and steal nectar without carrying pollen to other flowers. These plants have stems that trap insects with sticky flypaper juices, or hairs like barbed wire. Or they have growths that detour the invaders on to the leaves, away from the flowers.
THE WIND HELP TO PLANTS
The flowers of grasses and many trees depend on the wind to spread their pollen. These blossoms are likely to be feathery or plume like so that they spread nets to catch the pollen drifting through the air. Wind-pollinated flowers do not have odors or bright petals, as they do not need to attract insects. They are usually small and inconspicuous, like the flowers of grasses.
PACKEAGED PLANTS
After pollen has reached the ovary of a flower, the petals and the outer part of the pistil and stamens usually wither and die. They have finished their work.
Now seeds start to form. This is what happens: Within the ovary of the flower, very, very tiny plants, with roots, stems and leaves, begin to develop. They are so small and young that they cannot yet shift for them selves. They will need food to keep them selves. They will need food to keep them alive from the time they first start growing in the earth until their leaves are big enough to make sugars. So the Parent plant helps them by making seeds.
A seed is a package made up of a little plant with enough food packed around it, or in it, to last the plant through its early days. This package is done up in a heavy outside wrapper-the seed coat .If you split open a soaked lima bean you can see a tiny plant .The “halves” are the parts of this plant that contain the food.
Seeds grow inside an ovary only until the little plants have reached a certain size and until their food supply is provided. Then the seeds stop growing and often go in to a resting period before they are ready to sprout.
While seeds are forming, a pod, berry, fleshy fruit, or some way of setting out on their own If they all dropped to the ground under their parent plants, there would be too amount of sunlight, water and soil plants for these things would be so great that most of the plants would be so great that most of the plants would die. TRAVELERS
Seeds have many ways of traveling. Some drift with the wind. Two short wings help maple seeds. Instead of falling from the maple branches directly to the ground, the seeds spiral slowly on their wings through the air, and the slightest breeze carries them away to a new spot. Elms, ashes and pines also have winged seeds.
Dandelion seeds have silky parachutes, for drifting away. Milkweed, cottonwood and clematis seeds also sail through the air on tufts of down.
Other seeds are hitchhikers. Beggar ticks and burdocks hook themselves firmly to passers by animals or people –and ride as far as they are allowed. Mistletoe seeds are sticky and cling to the claws of birds, to be wiped off some distance from their starting point.
Animals are great seed spreaders Squirrels, preparing for winter, hide great quantities of nuts-often more than they use. Some of these sprout and grow. Birds and animals eat berries of fruits. The seeds unharmed by digestive juices, finally drop to the ground. Many of them grow.
Many seeds of wild plants never reach spots where conditions are right for growing. Or, if they do, other plants or dies for one reason or another crowds them out. Wild plants, to be sure of new young plants each year, form and spread millions more seeds than will ever take root.
SPRING TIME
Even before seeds go traveling, the tiny plants inside them have begun their resting periods. Several months may pass before they start growing again. Then they can start only if they have water, air and the right temperature. In northern climates this is usually in the spring.
Seeds are dry, tightly crammed packages until the moisture of the damp earth soaks through their heavy wrappings. Then the little plants and their food swell and burst the seed coats, which water has softened.
The little plants start growing and making special digestive juices. These juices change the food stored in the cells from dry starches, fats and proteins to dissolved form. Water carries this dissolved food to the important growing points of the young plants-the tip of the root and the tip of the stem. There the food is made in to new living cells that build up the plant.
At the same time, oxygen from the air, taken in by the plant, helps let loose the energy of some of the food. This energy is used in the work of some of food. This energy is used in the work of building cells. Young plants have tremendous force. Water added to a jar packed full of seeds makes them swell and sprout. Enough energy is let loose so that they can break a closed jar.
ROOTS DOWN, STEMS UP
When the plant has water, air and its favorite temperature, its root starts reaching down in to earth and its stem starts growing upward. Young roots grow down and stems up, no matter in what position the seeds are planted .An experiment will show this:
Put green gram seeds between blotting paper and panes of glass, and place the glass in a shallow dish of water. When the roots start growing downward, give the glass quarter turn, so that the roots and stems are reaching outside ways. Wait and watch –soon they will begin pointing up and down again. Each time they do this turn the glass. Each time, the roots and stems will turn, to grow up and down.
YOUNG PLANTS
While plants are still pushing upward through the earth to reach the light, they are unable to make food. They depend entirely on the food stored in the seed. If they are planted too deeply and use up their food before they break through the ground, they die.
The plants temporary seed help in feeding them. Some plants like common beans have their seeds food stored in their two fleshy temporary leaves. These grow with the plants up to the light. They even become green and do some food making for a while. But as the food stored in them is used up they shrivel. By this time however, the bean plants has grown their green leaves, and roots that spread out through the earth. It has become an independent plant able to feed itself.
Other plants, like corn have single temporary seed leaves that stay within the seeds, underground. There they act as the plants supply line, sending food to the root and stem tips, until the plants grow green leave, are fully rooted and are able to shift for themselves.
SEEDS ARE IMPORTANT
Each green seed producing plant’s whole life, from the moment its first little root plunges into the ground is aimed at making seeds and more seeds so that new young plants will keep growing each year.
We are fortunate that this is so, for seeds are very important to us. Not only do we use them in growing new crops each year, but wheat and rice seeds are the principal foods for hundred of millions of people all over the world. Oil from cotton, coconut and peanut seeds is used in making food products and many other things.
FRUITS OF PLANTS
The fruits are containers with the enclosed seeds of plants.
Some seeds surrounded by a soft, fleshy wall are called berries.
Ex: Tomatoes, Grapes
Some fruits are berries with a hard rind.
Ex: Cucumber
Some fruits are containing many tiny fruitlets joined together to make a larger fruit.
Ex: Blackberry
Some seeds are hard and one seeded fruits.
Ex: Nut
Some fruits are fleshy fruits called pomes.
Ex: Apple, Pears, quinces
Some fruits are capsules, which split to sprinkle their seeds on the ground when the wind shakes them.
Ex: Poppy
Some fruits are berries with a leathery rind.
Ex: Orange, Lime and Mandarin
OTHER WAYS OF GROWING NEW PLANTS
Sprouting Leaf
Tuber
Bulbs
Corms
Rhizome
Runners
