part 14

130 The material which makes plants green (chlorophyll) is necessary if they are to use energy from light for healthy growth. Unlike animals, plants can take what they need straight from the air and earth and water in which they live. Through their green leaves and stems they separate H from H2O and unite it with CO2 to make carbohydrates. Structure of part of a carbohydrate, a sugar. This power of plants is named photosynthesis (from the Greek words for light and putting together). People and animals depend upon photosynthesis in plants to supply their food and energy. We and the animals either eat plants or eat plant-eating animals or both.

如果植物要利用光能健康生长，使植物变绿的物质（叶绿素）是必需的。 与动物不同，植物可以直接从它们赖以生存的空气、土壤和水中获取所需的物质。 它们通过绿色的叶子和茎将氢从水中分离出来，并与二氧化碳结合，生成碳水化合物。 碳水化合物的部分结构，如糖。 植物的这种能力被命名为光合作用（来自希腊语中的光和结合）。 人和动物依靠植物的光合作用来提供食物和能量。 我们和动物要么吃植物，要么吃食草动物，或者两者兼而有之。

131 When we think it out we can see that most of the energy we use comes from the sun by way of the materials which plants build up in photosynthesis. Scientists know only a little, so far, about photosynthesis. It is only a little more than a hundred years since the first account of it was given by the German scientist von Mayer. But with more experimenting being done every year, much more will certainly be known before very long. The rate at which scientific knowledge is increasing is going up all the time. In time (but we may have to wait a long time before this) it may even be possible to use the energy of light itself in industry to do in our factories something like what plants do in their green cells.

当我们想清楚了，我们可以看到，我们使用的大部分能量来自太阳，通过植物在光合作用中积累的物质。 到目前为止，科学家对光合作用知之甚少。 从德国科学家冯·迈耶第一次描述它到现在不过100多年。 但是，随着每年进行的实验越来越多，不久之后肯定会知道更多。 科学知识增长的速度一直在上升。 假以时日（但我们可能要等很长一段时间），甚至有可能在工业中利用光能本身在我们的工厂中发挥作用，就像植物在绿色细胞中发挥作用一样。

132 Before long, we may learn from working on photosynthesis how to make or grow more food. As we have seen (page 13 above) more than one billion people on this planet are short of food. As more and more people are born, the need for new food supplies will increase. It may be that we can find what we want in the sea. It is thought that as much as 90 per cent of the photosynthesis which takes place in the world goes on in microscopic water plants in the sea. Maybe much of the food people are going to need in the future will come out of the oceans. Or making food straight from complexes of carbon, hydrogen and oxygen may become a great new industry. At present we have to get most of the energy used in industry by burning coal and oil and other fuels.

不久，我们可能从光合作用的研究中了解到如何制造或种植更多的食物。 正如我们所看到的（上面第13页），这个星球上有超过10亿人缺乏食物。 随着越来越多的人出生，对新食物供应的需求将会增加。 也许我们能在海里找到我们想要的东西。 据认为，世界上90%的光合作用是在海洋中微小的水生植物中进行的。 也许未来人们需要的大部分食物将来自海洋。 或者直接从碳、氢和氧的复合物中制造食物可能会成为一个伟大的新产业。 目前，我们必须通过燃烧煤、石油和其他燃料来获得工业中使用的大部分能源。

133 This energy is the sun's energy stored up long ago by plants. Coal comes from the dead bodies of plants stored, away from the air and under pressure, through millions of years in great beds in the earth. The amount of coal and oil in the earth is, it is true, very great, but the amount we are using today is great too. A time may come before long when we will have used up all the coal and oil that is easy to get at. We have been taking oil out of the earth only since about 1860. Without oil there would be no cars and no airplanes. It is strange to think that airplanes depend on what plants were doing millions of years ago.

这种能量是植物很久以前储存起来的太阳能。 煤来自植物的尸体，这些植物在远离空气和压力的情况下，在地球的大床中储存了数百万年。 诚然，地球上的煤和石油储量非常大，但我们今天使用的量也很大。 不久以后，我们就会用完所有容易得到的煤和石油。 我们从1860年左右才开始开采石油。 没有石油就没有汽车和飞机。 飞机依赖于数百万年前植物的活动，这是一件很奇怪的事情。

134 Plants and animals all need air. Only about one fifth (1⁄5) of the air is oxygen. The other four fifths is another gas, without taste, smell or color, named nitrogen. Both plants and animals need nitrogen as well as oxygen but they cannot take it from the air themselves. How do they get their supply of nitrogen? There are very small organisms in soil and water which can take nitrogen out of the air and fix it in complex materials which plants and animals can use. These materials are taken up by plants through their roots in water from the soil. Animals get their nitrogen by eating plants. Some of this nitrogen comes away in animal waste and people have for many thousands of years known enough to put animal waste back into the soil to help plants grow.

植物和动物都需要空气。 只有大约五分之一（1 / 5）的空气是氧气。 另外的五分之四是另一种气体，没有味道，没有气味，也没有颜色，叫做氮。 植物和动物都需要氮和氧气，但它们自己不能从空气中获取。 它们如何获得氮的供应？ 土壤和水中有一种非常小的生物，它们可以从空气中吸收氮，并将其固定在动植物可以利用的复杂材料中。 这些物质通过植物的根从土壤中吸收水分。 动物通过吃植物来获取氮。 其中一些氮是通过动物粪便排出的，几千年来，人们已经足够了解将动物粪便放回土壤中以帮助植物生长。

135 Nitrogen, like carbon, oxygen and hydrogen, is used over and over again in support of life. Plants build nitrogen up into complex structures. Animals eat the plants. Then animal waste and dead plants and fallen leaves are broken down into simpler forms again. So the great round goes on without end, all made possible only by energy coming from the sun. Scientists say that all the oxygen and all the carbon dioxide now in the air have been put there after use by plants through photosynthesis.

135氮，像碳、氧和氢一样，被反复使用以维持生命。 植物将氮合成复杂的结构。 动物吃植物。然后动物粪便、死植物和落叶又被分解成更简单的形式。 所以这个巨大的循环没有尽头，这一切都是由于来自太阳的能量。 科学家们说，现在空气中所有的氧气和二氧化碳都是植物通过光合作用利用后排放到那里的。