My Science School

The Coast Redwoods (Sequoia sempervirens) are the tallest trees on Earth. They are found along the coastline of the Redwood National Park in Northern California. Apart from being the tallest trees on the planet, they are also some of the oldest living things on Earth. They have a life of up to 2,000 years. Even though it is not clear exactly why these trees can live to be so ancient, we do know that climatic conditions play a key role in this. They are also some of the most resilient trees on Earth. Their tannin-rich bark seems to be impenetrable to the fungus and diseases that affect other trees.

According to the Guinness Book of World Records, the king of these giants is a tree known as Hyperion. When it was last measured in 2019, it stood 116.07 metres tall from top to base, taller than a 35-storey building. Hyperion's exact location is a closely held secret, but it is known to be found in a hillside in which most of the old-growth coastal redwoods have been logged. Hyperion is estimated to be between 600 and 800 years old.

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Rafflesia Arnoldii, or the corpse flower, is the largest individual flower on Earth. It is a species of flowering plant in the parasitic genus Rafflesia found in the rain-forests of Sumatra and Borneo. With a strong and unpleasant odour of decaying flesh, it grows to a diameter of around one metre and weighs up to 11 kilograms. The buds of these flowers are about 30 cm wide and are very large and cabbage- like, in maroon or dark brown colour.

The flower is in fact a pot with five petals with striking red-brick and spotted cream colours, which warmly welcome carrion flies that are hungry for detritus. But the plant is now facing the threat of extinction and its existence is limited to places like Sumatra, Borneo, Thailand and the Philippines, because of depredations caused by humans and its own internal biology.

In terms of survival, everything seems to be against Rafflesia. Firstly, its seeds are difficult to germinate. As a result, it sustains entirely as a parasite on just one type of vine. This is dangerous as it can't survive without the vine. Apart from this, once it has acquired its nutrition by being a parasite, the plant breaks out as a flower bud, swells up over several months, and then bursts into flower. But even after this arduous growth phase, most of the flower buds perish before blooming. Even after blooming, Rafflesia can last only a few days, and is forced to pollinate in this short period of time. But the chances of pollination are very rare as the numbers of plants are decreasing steadily.

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A butte is an isolated hill with steep sides and a flat top created by the gradual erosion of the earth around by water, wind or ice. The Enchanted Mesa is a sandstone butte in New Mexico where the Acoma tribe lived, until a heavy storm and a landslide destroyed the only access to the peak, forcing them to move elsewhere.

Enchanted Mesa is a sandstone butte in Cibola County, New Mexico, United States, about 2.5 miles (4.0 km) northeast of the pueblo of Acoma. It is called Mesa Encantada in Spanish and Katzimo or Kadzima in Keresan. Acoma tradition says that Enchanted Mesa was the home of the Acoma people until a severe storm and landslide destroyed the only approach. There are no longer any ruins on the flat top. The butte is 430 ft (130 m) high, 1,250 ft (380 m) long and only 400 ft (120 m) ft wide, at its widest. The elevation at the top is 6,643 ft (2,025 m).

In 1892, when Charles F. Lummis was visiting Acoma he listened to the old Indian governor, Martín Valle, who told the story of how the Acoma people used to live on Enchanted Mesa. Their access to the top was on the southern side where a large piece of the butte was said to have spalled off and formed a ramp, a "stone ladder", up to the top. In reality, access was by climbing a ladder in a narrow fissure. Evidence of holes carved into the sandstone on either side of the fissure can be seen, located in the horseshoe shaped bowl at the southern end. The early inhabitants had a precipitous climb up the fissure, but it assured their safety. Into these holes were placed stout lengths of wood, the 'rungs' of the ladder. Today, this is still the only means of climbing access to the top of the mesa. Their fields, and the springs that were their water source, were in the valley. In the summer, the entire village would descend into the valley to tend the crops. One afternoon a severe thunderstorm washed away the "stone ladder", leaving only sheer rock faces all the way around the butte. Legend has it that three old women and a young boy had been left in the village, but they could not get down, nor could anyone else get back to the village. A giant thunderbird swooped down and scooped up the four and carried them to the valley floor. The Acoma people abandoned Enchanted Mesa and moved to White Rock Mesa, now called Acoma.

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The first land plants appeared during the Silurian period, around 440 million years ago. These simple plants reproduced by releasing spores. Plants produced oxygen and provided food for the first land animals - amphibians. Amphibians first developed in the Devonian period, 420 million years ago, from fish whose fins evolved into limbs.

Botanists now believe that plants evolved from the algae; the development of the plant kingdom may have resulted from evolutionary changes that occurred when photosynthetic multicellular organisms invaded the continents. The earliest fossil evidence for land plants consists of isolated spores, tracheid-like tubes, and sheets of cells found in Ordovician rocks. The abundance and diversity of these fossils increase into the Silurian Period (about 443.8 million to 419.2 million years ago), where the first macroscopic (megafossil) evidence for land plants has been found. These megafossils consist of slender forking axes that are only a few centimetres long. Some of the axes terminate in sporangia that bear trilete spores (i.e., spores that divide meiotically to form a tetrad). Because a trilete mark indicates that the spores are the product of meiosis, the fertile axes may be interpreted as the sporophyte phase of the life cycle.

Fossils of this type could represent either vascular plants or bryophytes. Another possibility is that they are neither but include ancestors of vascular plants, bryophytes, or both. The earliest fossils also include at least one or more additional plant groups that became extinct early in the colonization of the land and therefore have no living descendants. By the early Devonian Period (about 419.2 million to 393.3 million years ago), some of the fossils that consist of forking axes with terminal sporangia also produced a central strand of tracheids, the specialized water-conducting cells of the xylem. Tracheids are a diagnostic feature of vascular plants and are the basis for the division name, Tracheophyta.

Credit: Britannica

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FRUITS

All plants produce fruits that contain their seeds. Some fruits are dry husks, but others are juicy and tasty. These attract animals, which eat them and carry the seeds in their stomachs. The tough-skinned seeds are not digested, but are scattered far away from the parent plant in the animals’ droppings, and grow into new plants. The fruits are cultivated types that have been specially bred for their size and flavour.

1. ORANGE An orange has very soft juicy flesh contained in many segments, which are enclosed by a hard rind. Each segment usually contains a seed, or pip. An orange is technically a type of berry, which develops over the winter from the single ovary of an orange flower. Green at first, it turns orange as it swells to full size.


2. BANANA The bananas that are cultivated in the tropics have been bred to be seedless, but the wild bananas of Southeast Asia have small fruits containing many big, hard seeds. They grow in bunches on large plants with huge leaves that sprout straight from the ground.


3. NUTS All nuts are large seeds, which the plant has equipped with a store of concentrated plant food. This ensures that the seedlings get a good start in life. The nut is surrounded by a hard shell, which is technically a fruit, but tough and fibrous rather than soft and juicy.


4. DURIAN To attract fruit-eating mammals, many fruits are fragrant. The Southeast Asian durian fruit is famous for its strong aroma, which some people like and others hate. Animals such as forest pigs and orang-utans seem to love both its smell and taste.


5. GRAPES Some fruits such as grapes grow as clusters of soft, edible, thin-skinned berries. Each berry has several seeds embedded in its flesh, although many cultivated varieties of grapes are seedless. Berries are often vividly coloured to attract birds, which have excellent colour vision.


6. PEACH The juicy flesh of a peach, plum, or cherry encloses a hard “stone” that contains a single seed. This type of fruit is called a drupe. The fleshy part is meant to be eaten, so animals spread the seeds, but some animals such as parrots can crack the stones and eat the seeds, too.


7. BROAD BEAN The edible part of a broad bean plant is its seeds, and its fruit is the entire pod. The wild ancestors of such beans do not attract animals. Instead, their pods dry up and split open with explosive force, so the seeds shoot out and are scattered on the ground.


8. TOMATO Not all fruits are edible. Some of the wild relatives of tomatoes are extremely poisonous. They include deadly nightshade, which is lethal to humans, although some animals can eat the berries without coming to harm. Tomatoes are also related to chilli peppers.

TREES

Trees are the tallest, heaviest, and oldest of all living things. The Californian giant sequoia known as General Sherman weighs approximately 6,000 tonnes - 30 times as much as the biggest animal, the blue whale. The oldest living bristlecone pine tree, which also grows in California, is nearly 5,000 years old. Yet even these ancient giants can still produce tiny seeds that grow into new trees.

LEAVES Like all green plants, trees absorb sunlight through their leaves and use its energy to turn air and water into sugar. A tree’s leaves are its food factories.

COMPOUND LEAVES Most trees have simple leaves of various shapes, but some have compound leaves, made up of many leaflets. These either sprout from a long stalk (pinnate) or fan out from a single point (palmate).

NEEDLES AND SCALES Thin leaves make food efficiently, but they are easily damaged by hot sunshine or frost. So many trees that grow in very hot or cold places have thicker, tougher needles or scales.

FRUIT The flowers of some trees turn into juicy fruits that contain seeds. If birds eat the fruit, the seeds pass through them unharmed and are scattered far away.

TREE RINGS Every year a tree adds a layer of new wood to its trunk. If the tree is cut down, each year’s growth shows as a visible ring, so the number of rings gives its age.

FLOWERS All trees produce flowers, but some may not be obvious because they do not have colourful petals. Other trees, however, such as apples, have showy flowers that attract insects.

SEEDS AND NUTS Some trees have tiny seeds, but others produce the bigger seeds we call nuts. Animals eat them, but also bury and forget them, so they grow into new trees.

CONES Coniferous trees such as pines have woody cones that contain small papery seeds. When the cones open up in the sun, the seeds fall out and blow way.

DECIDUOUS LEAVES Many trees lose their leaves in winter, and grow new ones in spring. Before they fall, the old leaves lose their green colour and turn yellow, brown or even red.

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FLOWERS

Many plants produce beautiful flowers, often vividly coloured and fragrant. These intricate structures form the reproductive parts of plants and have evolved so that they attract insects and birds to sip the sugary nectar at the flower’s centre. While feeding, the insect or bird is dusted with pollen, which is produced by the stamens and contains the male sex cells. The pollen is deposited on the sticky stigma of another flower. This is pollination. A pollen tube then grows down the style to the ovary and fertilizes an ovule. This is fertilization. Some plants, such as grasses and many types of trees, rely on the wind to carry their pollen and their flowers do not need showy petals or fragrant nectar to attract animals. Since this is a less efficient system, they must produce far more pollen, which can fill the air and cause hay fever.

1. Flower Structure A typical flower develops inside a bud at the end of a stalk. When the bud opens, it reveals a ring of petals, each of which secretes nectar from its base. At the centre of the flower lie the male structures that produce pollen. These surround the female structures that hold the ovules, or egg cells. An outer ring of green sepals may protect the flower when it is in bud.


2. Carpel An ovary, a style, and a stigma form the main parts of a carpel. At the heart of the flower lie the ovules, enclosed in a case called an ovary. The top of each ovary extends into a style that carries a sticky pad called a stigma. The flowers of some plants have man carpels, each with their own stigma, but this lily has just one.


3. Stamen The tiny, dust-like pollen grains that contain the male cells are produced by stamens. These usually form a ring around the central carpel or carpels. Each stamen has a long filament, which supports a club-like anther that produces the pollen.


4. Transferring Pollen Insects such as butterflies often drink nectar from one type of flower. Hummingbirds do the same, because their bills are the right shape to reach the nectar. The bird and the insect get dusted with pollen in the process, and carry it directly to another flower of the same type.


5. Fertilization If a hummingbird sips nectar from this lily, it will pickup pollen on its breast feathers. If the bird visits another lily, the sticky central stigma may pick up the pollen. Each pollen grain then sprouts a long tube that grows down through the carpel to reach an ovule. The male cell moves down the tube to fertilize the ovule so it can develop into a seed.

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PLANTS

All green plants use the energy of sunlight to make sugary carbohydrate food from water and carbon dioxide in the air. This is why they grow well only in sunlit, moist places. The food fuels growth and is used to make cellulose — the tough, fibrous tissue that helps support all the various parts of the plant, from its stems and leaves to its flowers.

1. GERMINATION A bean plant begins life as a seed with two halves, called cotyledons. In spring when the weather is mild, the seed starts to absorb water through a minute hole in its outer coating (the testa). The seed swells and about three days later a root grows to hold the plant in place, and a shoot appears above the ground. This process is called germination.


2. ROOTS The plant’s roots absorb water from the soil. The water is used by the leaves to make food. The water also contains dissolved mineral salts, such as nitrates and phosphates, which are essential for growth.


3. STEM The strong stem of the plant supports its leaves in the sunlight. It also contains bundles of tubes or veins. These allow water containing dissolved nutrients to flow up from the roots to the leaves, and also carry sugary food from the leaves to other parts of the plant.


4. LEAVES The leaves are the plant’s food factories. They act like solar panels, as the green chlorophyll enables the plant to absorb the energy of sunlight and use it for photosynthesis - the process in which the plant takes carbon dioxide from the air, and combines it with water drawn up by the roots to make sugar. Oxygen is also produced in the process and released into the air.


5. TRANSPIRATION As sunlight warms a plant; water in the leaves is lost as water vapour, through pores called stomata. The leaves then take in water from the stem, which in turn draws more water up into the plant from the roots. The water carries nutrients from the soil with it.

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You may think there is not much you can do to help save plants. But there are lots of things you can do. When you go on a hike, stay on the path. Leaving the path harms the plants.

Sometimes you can help plants by not doing things. Do not pick or dig up wild flowers and other plants. Even though some are still plentiful, others are becoming rare. Enjoy wild flowers by taking pictures, or by drawing them. Buy seeds gathered in national parks or from seed companies. Then other people can enjoy the wild flowers, too.

Remind grown-ups to be very careful with campfires or outdoor cooking. Make sure that fires are out completely before you leave the area. If the weather has been very dry, don’t build fires at all. And when you leave camp, take all your rubbish with you to a litter bin.

Don’t break off limbs or peel bark from trees. The outside bark protects a tree from harmful insects and fungus. The inner bark moves food from the leaves to the roots. Peeling off a tree’s bark or breaking off its limbs can kill the tree.

You can help save trees by recycling. Many communities have recycling programmes. This means that used paper is picked up and taken to factories that use it to make new paper. Your family can recycle junk mail, old magazines, boxes, cereal boxes, toilet paper tubes, and even the tags from teabags.   

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People are working together in many ways to save the world’s plants.

Some people work directly with plants. Growers trade seeds with one another to help a species’ chances to survive. They also grow endangered plants in greenhouses. Then they replant the plants in the wild. Sometimes, people build fences around rare plants in the wild to keep away animals that may eat or trample them.

Many groups work to protect plants. These include the United Nations, the International Union for the Conservation of Nature and Natural Resources (IUCN), and the World Wide Fund for Nature (WWF). They inform governments and people about endangered plants and raise money to help save them.

Many governments have passed laws to protect plants. These laws protect endangered plants and animals from hunting, collecting, and other activities that could harm them or their communities. Many countries also have signed an agreement called CITES. By signing this agreement, they promise not to buy or sell endangered plants or animals, or products made from them.

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The forest rangers are worried. The weather is hot and there has been no rain for a long time. They know the forest is as dry as dust. It would take only a tiny spark or a lightning strike to turn the whole forest into a roaring, raging sea of fire.

From their watchtower high above the trees, the rangers see a thin spiral of smoke. Fire! There’s a fire in the forest!

A quick call for help goes out. Firefighters rush to the blaze, in trucks. Working quickly, they battle the blaze with streams of water and shovelfuls of soil. They chop down trees and dig up the ground to keep the fire from spreading.

Overhead, aeroplanes swoop over the fire, dropping water and chemicals on it. Other planes bring firefighters called smoke jumpers. They parachute into places that the firefighters on the ground can’t reach.

At last, after many hours or sometimes many days, the fire is out. Thousands of trees have been saved. Thousands of trees have been destroyed.

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Imagine a world in which most of the trees are dead, where leaves and flowers are spotted with disease, and fruits can’t grow. It wouldn’t be a very nice world. But many scientists fear that’s what our world may be like someday - if we don’t do something now about air pollution.

Air pollution begins when gases from cars, factories, lawn mowers, and burning wood enter the air. Acid rain forms when certain chemicals from air pollution rise up and mix with the water in the clouds.

The rain or snow that falls from these polluted clouds harms the leaves of trees. The trees slowly lose their leaves and die. Acid rain also soaks into the soil and damages plants and crops. Many of the world’s forests - especially the pine forests of northern Europe - are suffering from the effects of acid rain.

Air pollution is a very serious problem. But scientists and many other people are working very hard to clean up the air and keep it clean, for the sake of all the world’s people and plants.

Vanishing Tropical Rain Forests

Everywhere in the world people are taking over more land. In tropical rain forests, parts of the forest are cut down and burned to make room for crops. After a time, the soil in these parts is no longer good for growing crops. Then the people move on to another place. It is hard for new plants to grow in the poor soil. Without plants and trees, the soil that is left washes away.

People also destroy tropical rain forests to get timber. The trees that grow in these forests provide valuable wood. Every day, in many countries, people are cutting down trees that have taken years and years to grow.

In the world’s biggest tropical rain forest, the Amazon rain forest in South America, people are building a giant motorway. Trees are being cut down to build the motorway. When the road is finished, more people will travel into the rain forest. This may lead to even more destruction.

The world’s tropical rain forests are home to many kinds of rare animals. They may have lived there for many thousands of years in the safety of the trees. But now the tropical rain forest is disappearing fast. Scientists believe that some rain forest animals will die out even before they have been discovered!

Threats from People

People are a plant’s worst enemies. This is mainly because people want or need things that can be made from plants.

Many kinds of plants are becoming rare because of their beauty. People often dig these plants up and take them home. The beautiful flowers of orchids and some cactuses have made them targets for collectors. The rare Cooktown orchid of Australia, though protected, is picked by collectors.

Great numbers of palm trees are destroyed for their stems, which are made into furniture, and for their fruit. Hundreds of types of palms are endangered today.

People kill many plants for use in medicines. The Pacific yew was once the source of a drug that doctors use to treat cancer. But getting the drug threatened these trees so much that researchers found other ways of making the drug.

People kill plants when they develop land. Lots of land is used for building. Even more is changed into farmland or grazing land for cattle and other animals. As the population increases, people build more roads, houses, factories, mines, shopping centres, and car parks.

But plants need their own special place to live in, too. They need the right kind of soil, the right temperature, and the right amount of rainfall. They need the right habitat. When habitats disappear, the animals that live there often disappear too. If we destroy too many natural habitats, we may lose many of the plants and animals in our lives.

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Threats from Animals

All over the world, plants are being destroyed by animals. Sometimes this is perfectly natural and is part of the balance of nature. Other times, it can be disastrous.

Insects such as caterpillars and grubs, which later become beetles, often eat leaves or burrow into the wood of trees. But sometimes, a nest of tent caterpillars eats all the buds or young leaves on a tree. When this happens, the tree will die.

Big problems also arise when people bring animals to areas where they don’t belong. Rabbits have destroyed valuable grazing land in Australia. They eat the grasses farmers need for their livestock. Rabbits were turned loose in 1859 by British settlers. But in Australia, rabbits have few natural enemies, so now there are too many rabbits.

In Hawaii, escaped pigs and goats have destroyed many rare plants. They trample the plants and eat the roots so the plants can’t grow back. Goats also may eat all the plants on a hillside. With no roots to hold the soil, rain can wash it down the hill. This loss of soil is called erosion and keeps plants from growing. Today, about half of Hawaii’s plants are either very rare, endangered, or already extinct.

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