8 Leaves change color

What is a plant? Plants are living things. They come in all shapes and sizes, from tiny waterweeds to towering trees. Plants are different from animals in one very important way—they can make food for themselves from sunlight. Animals can't do this. They depend on plants for their food. Where do plants grow? There are about 400,000 different kinds of plants on Earth, and they grow just about everywhere in fields and forests, deserts and mountains. Apart from air, the two things plants need are sunlight and water, so you won't find them in places that are completely dark or dry. Are plants really alive? Plants are just as alive as you are. They need air, food and water to grow, and they can make lots of new plants like themselves. This proves that they are alive. Things like stones and rocks don't feed, grow or have young because they are not alive. All the food in the world starts with plants. You may eat eggs, meat and cheese but, without plants, no chicken or cow could produce these foods! Corals and sea anemones may look like plants, but they are imposters, In fact, they are animals!

什么是植物？植物是生物。 它们有各种形状和大小，从微小的水草到参天大树。 植物在一个非常重要的方面与动物不同——它们可以利用阳光为自己制造食物。 动物做不到这一点。它们以植物为食。 植物生长在哪里？地球上大约有40万种不同的植物，它们生长在田野、森林、沙漠和山脉的任何地方。 除了空气，植物还需要阳光和水，所以你在完全黑暗或干燥的地方找不到它们。 植物真的有生命吗？植物和你一样是有生命的。 它们需要空气、食物和水来生长，它们可以产生许多像它们一样的新植物。 这证明他们还活着。 像石头和岩石这样的东西不会进食、生长或生育，因为它们不是活的。 世界上所有的食物都始于植物。 你可以吃鸡蛋、肉和奶酪，但如果没有植物，鸡或牛就不可能生产这些食物！珊瑚和海葵可能看起来像植物，但他们是骗子，事实上，他们是动物！

Why do trees have leaves? Like all plants, trees need their leaves to stay alive. Leaves are a tree's food factories. They contain a sticky green stuff called chlorophyll. The chlorophyll uses water, sunlight and carbon dioxide in the air to make a sugary food. The food is then carried to every part of the tree in a sweet and sticky juice called sap. Why do some trees lose their leaves in autumn? Big green leaves are useful in spring and summer. They make food while the Sun shines and the days are long. When the days get shorter, there's less time for making food and the tree must live off its food reserves. Rather than feed their leaves too, some trees shed their leaves in autumn. Why do leaves change colour? It's the chlorophyll in a plant's leaves that makes them look green. But in autumn, the chlorophyll breaks down. Once the green colouring has gone, the leaves' other colours show through beautiful shades of red, yellow and gold. If you have ever chewed a blade of grass you will know how sweet sap tastes. Hungry young caterpillars think so, too. That's why they eat leaves! The way plants make food in their leaves is called photosynthesis. During photosynthesis, plants take in carbon dioxide front the air. And they give out oxygen—the gas we all need to survive. We call plants that lose their leaves in the autumn deciduous. Evergreens have tough leaves that can survive the winter. The trees still lose their leaves, but not all at the same time.

为什么树有叶子？像所有的植物一样，树木需要树叶来维持生命。 树叶是树木的食物工厂。 它们含有一种叫做叶绿素的粘性绿色物质。 叶绿素利用水、阳光和空气中的二氧化碳来制造含糖食物。 然后，食物以一种又甜又粘的汁液的形式被带到树的各个部分，这种汁液被称为树液。 为什么有些树在秋天落叶？ 大的绿叶在春天和夏天是有用的。 他们在阳光明媚、白天漫长的时候做食物。 当白天变短的时候，制造食物的时间就变少了，树必须依靠它的食物储备来生存。 有些树在秋天落叶，而不是给叶子喂食。 树叶为什么会变色？ 是植物叶子中的叶绿素使它们看起来是绿色的。 但到了秋天，叶绿素就会分解。 一旦绿色褪去，树叶的其他颜色就会呈现出美丽的红色、黄色和金色。 如果你曾经咀嚼过一片草叶，你就会知道汁液的味道有多甜。 饥饿的小毛毛虫也这么认为。 这就是它们吃树叶的原因！植物在叶子中制造食物的方式被称为光合作用。 在光合作用过程中，植物从空气中吸收二氧化碳。 它们释放氧气——我们生存所需要的气体。 我们称秋天落叶的植物为落叶植物。 常青树长着坚韧的叶子，能挺过冬天。 树木仍然会掉叶子，但不是在同一时间。

why do roots grow so long? Long roots fix a plant firmly in the ground so that it won't fall over on windy days. But roots do another job, too. By spreading out far and wide, they can suck up water and goodness from all the soil around. Then the roots send the water up the stem or trunk and into the leaves. Why are stems so straight? A plant needs to hold its leaves up to the sunshine, which it uses to make its food. Many plants grow tall, straight stems, so that they can beat their neighbours to the sunlight. A wild fig tree in South Africa grew roots 120 metres down into the soil. If it was put on the roof of a 40-storey office block, its roots would reach down to the ground. In the strongest winds, a tree can sometimes be blown right over. Its roots are wrenched out of the ground as the tree falls down with a crash. At the ends of the roots are tiny hairs, which burrow into the spaces between the lumps of soil. Sunflowers not only grow up towards the light, but their flowers follow the Sun! As the Sun appears to move across the sky through the day, the flower-heads turn to face it. Not all plants have straight stems. Some have stems that bend and curl, clambering their way over nearby plants as they climb up to the light.

为什么根会长得这么长？ 长长的根把植物牢牢地固定在地上，这样在刮风的日子里就不会倒下。 但根还有另一个作用。 通过向四面八方伸展，它们可以从周围的土壤中吸收水分和养分。 然后根把水输送到茎或树干上，进入树叶。 为什么茎这么直？ 植物需要让叶子保持在阳光下，用阳光来制造食物。 许多植物长着又高又直的茎，这样它们就能比周围的植物抢到阳光。 南非一棵野生无花果树的根深入土壤120米。 如果把它放在40层办公大楼的屋顶上，它的根部就会垂到地面。 在最强的风中，一棵树有时会被吹倒。 当树轰然倒下时，它的根被扭出了地面。 在根的末端有细小的毛，这些毛钻入土壤块之间的空间。 向日葵不仅向着光生长，而且它们的花也跟着太阳生长！当太阳在一天中划过天空时，花头转向面对它。 不是所有的植物都有直茎。 有些植物的茎会弯曲和卷曲，当它们向上爬时，会爬过附近的植物。

Which plants grow in water? The giant water lily grows in the lakes and rivers of South America. Its roots lie deep in the mud and its huge leaves float on the water's surface. This is the best place for catching the sun! Each leaf curls up at the rim so that it can push other leaves aside. Which are the smallest plants? Although some types of algae grow to be the most enormous plants, there are other algae so small you can only see them through a microscope. The very smallest float in lakes and oceans, and are called phytoplankton. They are so tiny that whales catch millions in every gulp! Which forests grow in the sea? Huge forests of kelp grow off the coast of California in the United States. Kelp is a kind of seaweed that grips on to rocks, and sends long, ribbon-like stems up through the water. Some of the stems can be 200 metres long-as long as eight swimming pools laid end to end. The giant water lily's leaves grow on long, strong stems. On the underside of each leaf is a web of supporting veins. This makes the leaves so strong that a toddler could sit on one without sinking! The leaves and roots of water plants give food and shelter to many animals. But they are also places where hunters can hide. Not all water plants are rooted in the mud. Some seaweeds float in the water, thanks to pockets of air in their leaves-rather like their very own rubber rings!

哪些植物生长在水中？ 巨大的睡莲生长在南美洲的湖泊和河流中。 它的根深埋在泥里，巨大的叶子浮在水面上。 这是晒太阳的好地方！每一片叶子在边缘卷曲起来，这样它就可以把其他叶子推到一边。 哪些是最小的植物？ 尽管有些类型的藻类长得非常巨大，但也有一些藻类很小，你只能通过显微镜才能看到它们。 最小的浮游生物漂浮在湖泊和海洋中，被称为浮游植物。 它们是如此之小，以至于鲸鱼每一口就能抓到数百万个！哪些森林生长在海里？ 巨大的海带森林生长在美国加利福尼亚海岸附近。 海带是一种海藻，可以附着在岩石上，并在水中发出长长的带状茎。 一些茎长可达200米——有8个游泳池首尾相连那么长。 巨大的睡莲叶子长在又长又壮的茎上。 在每片叶子的背面都有支撑叶脉的网。 这使得树叶非常坚固，一个蹒跚学步的孩子可以坐在上面而不会下沉！水生植物的叶子和根为许多动物提供食物和住所。 但它们也是猎人可以躲藏的地方。 并不是所有的水草都植根于泥里。 有些海藻可以漂浮在水中，这要归功于它们叶子里的空气袋——就像它们自己的橡胶环一样！

Which plant... traps a treat? When an insect lands on a Venus flytrap, it gets a nasty surprise! It only has to brush against one tiny hair on an open leaf tip, to make the leaf snap tightly shut. There's no escape for the poor insect. The flytrap changes it into a tasty soup, which it slowly soaks up. ...fools a fly? Pitcher plants have unusual vase-shaped leaves that tempt insects with a sugar-sweet smell. But the leaves are slippery traps. When a fly lands on them, it loses its footing, slips inside the 'vase', and drowns in a pool of juice. ...snares a snack? The sundew's leaves are covered in hairs, which sparkle with glue-like drops. When an insect lands on a leaf, it gets stuck fast. The more it struggles, the more it sticks. At last, the leaf folds over, traps the fly, and starts dissolving it into liquid food that it can drink up. The bladderwort is an underwater meat-eater. Along its leaves are bubble-shaped bags, which suck in tiny creatures as they paddle past. Did you know that flytraps can count? The first time an insect touches a hair on one of the leaf tips, the trap stays open. But if it touches it a second time, the trap snaps shut! Many meat-eating plants grow on wet. boggy ground where the soil is very poor. They need their juicy snacks for extra nourishment.

这植物……陷阱是一种享受？ 当一只昆虫落在捕蝇草上时，它会得到一个令人讨厌的惊喜！它只需要在打开的叶尖上刷一根细小的毛，就能让叶子紧紧地合上。 可怜的昆虫无处可逃。 捕蝇器把它变成了美味的汤，慢慢地吸收。 ．..傻瓜是苍蝇？猪笼草长着不同寻常的花瓶状叶子，散发着甜味，吸引着昆虫。 但树叶是很滑的陷阱。 当一只苍蝇落在它们上面时，它就会失去立足点，滑进“花瓶”里，淹死在果汁池里。 ．..诱捕零食？紫菜的叶子上覆盖着绒毛，上面有像胶水一样的水滴，闪闪发光。 当昆虫落在树叶上时，它会很快被粘住。 越是挣扎，越是坚持。 最后，叶子折叠起来，困住了苍蝇，并开始把苍蝇溶解成液体食物，让苍蝇喝掉。 狸藻是一种水下食肉动物。 它的叶子上有气泡状的袋子，当微小的生物游过时，它们会被吸进去。 你知道捕蝇器会数数吗？ 昆虫第一次接触到叶尖上的一根毛，陷阱就会保持打开状态。 但如果它第二次碰到它，陷阱就会自动关闭！许多食肉植物在湿地上生长。 土壤非常贫瘠的沼泽地。 它们需要多汁的零食来补充营养。

Why do plants have flowers? Many plants have colourful, perfumed flowers that attract insects and other animals. The visitors feed on drops of sweet nectar inside the flower. As they feed, they pick up a fine yellow dust called pollen, which they carry to another flower. When the pollen rubs off on the second flower, that flower can start to make seeds. Which flower fools a bee? A bee orchid's flowers look and smell just like female bees. Male bees zoom to the flowers wanting to mate with them but they have been tricked! The plant's just using them as postmen to deliver little packets of pollen to other orchids nearby. Which is the smelliest flower? The dead horse arum is well named it stinks of rotten meat! But blowflies love it. These plump flies usually lay their eggs inside the rotting bodies of dead animals. They are fooled by the plant's rotten smell, and crawl inside it to lay their eggs, picking up pollen on the way. This plant is called hotlips-and no wonder! The lipstick- red markings on its leaves are a wonderful way to attract visitors to its tiny flower. Many trees and grasses spread their pollen on the wind. They don't need animal visitors, so they don't grow bright flowers. Pollinators, such as this bat, don't mean to get pollen all over themselves. But a cactus flower is shaped in such a way that the bat just can't help it! During the summer, the air can be so full of pollen that it makes many people sneeze. Poor things they haven't got a cold, they've got hay fever.

植物为什么有花？ 许多植物都有色彩鲜艳、芬芳的花朵，吸引昆虫和其他动物。 来客以花蜜滴为食。 当它们进食时，它们会捡起一种叫做花粉的黄色细尘，并将其带到另一朵花上。 当花粉蹭到第二朵花上时，那朵花就可以开始结出种子了。 哪一朵花能愚弄蜜蜂？蜂兰的花朵看起来和闻起来就像雌蜂。 雄蜂嗡嗡地飞向花朵，想要与它们交配，但它们被欺骗了！这种植物只是把它们当作邮递员，把小袋花粉传递给附近的其他兰花。 哪一朵花最臭？ 死马魔芋的名字很好听，它散发着腐肉的臭味！但是苍蝇喜欢它。 这些胖乎乎的苍蝇通常在腐烂的动物尸体里产卵。 它们被植物的腐烂气味所迷惑，爬进里面产卵，在路上捡花粉。 这种植物被称为热唇——难怪！它的叶子上的口红红色的斑纹是吸引游客到它的小花上的一种奇妙的方式。 许多树木和草通过风传播花粉。 它们不需要动物游客，所以它们不会长出鲜艳的花朵。 传粉者，比如这只蝙蝠，并不是要把花粉弄得到处都是。 但是仙人掌花的形状是这样的，蝙蝠就是忍不住！在夏天，空气中充满了花粉，使许多人打喷嚏。 可怜的小家伙，他们不是感冒，是花粉热。