4 Plants vs. Animals-Low

Plants vs. Animals FOCUS Question How do plants defend themselves against herbivores?

植物与动物焦点问题植物如何抵御食草动物?

Plants Feed the World For plants, the world is a dangerous place. Plants get energy from the Sun, and billions of hungry plant-eating creatures or herbivores, get energy by eating plants. Like other producers, plants are at the bottom of many food chains. Everything from tiny mites to huge elephants eats plants. How do plant species survive? Plants are rooted in one place, so they can't run away and hide. Instead, they have other ways of defending themselves against herbivores. Plants have direct forms of protection. These forms include physical structures and chemicals that deter herbivores. Plants also defend themselves in indirect ways. They get help from the natural enemies of herbivores. Wowser! There are more than 300,000 species of plants on Earth!

对于植物来说，世界是一个危险的地方。 植物从太阳获取能量，数十亿饥饿的食草动物通过吃植物获得能量。 和其他生产者一样，植物处于许多食物链的底部。 从微小的螨虫到巨大的大象，所有的生物都吃植物。 植物物种如何生存? 植物都扎根在一个地方，所以它们无法逃跑和躲藏。 相反，它们有其他方法来抵御食草动物。 植物有直接的保护方式。 这些形式包括阻止食草动物的物理结构和化学物质。 植物也会以间接的方式保护自己。 它们从食草动物的天敌那里得到帮助。 老古板!地球上有超过30万种植物!

Physical Defenses Anyone who has walked in the woods knows about the many thorns and prickles found on plants. These are direct forms of protection. Rose plants and cacti have large thorns to repel large herbivores such as deer. Tomato plants have thin hairs or trichomes (TRY-combs), that make it hard for smaller herbivores to eat them. Sharp trichomes on bean plants can trap insect herbivores by stabbing their feet Other trichomes are poisonous, such as those of stinging nettle plants. Raphides (RAY-fides) are needle-shaped crystals found inside the leaves of many plants. Raphides can irritate an herbivore's skin. These small crystals can also scratch the herbivore's throat, resulting in painful stinging. Kiwi fruit plants and agaves have raphides for defense.

任何在森林里行走过的人都知道植物上有许多刺和刺。 这些都是直接的保护形式。 玫瑰和仙人掌有很大的刺，以击退大型食草动物，如鹿。 番茄植株有薄薄的毛发或毛状体(TRY-combs)，这使得较小的食草动物很难吃到它们。 豆科植物上锋利的毛状体可以刺穿食草昆虫的脚来诱捕它们。其他毛状体是有毒的，比如荨麻植物的毛状体。 Raphides (ray -fide)是在许多植物的叶子中发现的针状晶体。 Raphides Raphides Raphides Raphides Raphides 这些小晶体也会划伤食草动物的喉咙，导致疼痛。 猕猴桃和龙舌兰都有防身用的raphides。

Other plants use waxy leaves as a defense. Slippery wax makes it difficult for caterpillars and other climbing insects to keep a foothold on the leaves. Magnolia and eucalyptus trees have waxy leaves to keep hungry plant eaters away. Some plants, such as passionflowers, have small structures that look like insect eggs. Female butterflies are less likely to lay eggs on leaves that already appear to have eggs. They know that eggs hatch and turn into hungry herbivores. If there are already eggs and caterpillars on a plant, there may not be enough food to feed their own young. They lay their eggs elsewhere.

其他植物用蜡状叶子作为防御。 光滑的蜡使毛毛虫和其他攀缘昆虫难以在树叶上立足。 玉兰花和桉树的叶子是蜡质的，可以赶走饥饿的食草动物。 有些植物，比如西番莲，有看起来像虫卵的小结构。 雌性蝴蝶不太可能在已经产卵的叶子上产卵。 它们知道卵孵化后会变成饥饿的食草动物。 如果植物上已经有了卵和毛虫，可能就没有足够的食物来喂养它们的后代。 它们在别处产卵。

Chemical Defenses Chemical defenses are another form of direct protection. Many plants make chemicals to help repair injuries caused by munching herbivores. Some plants also make chemicals that taste bad to a plant eater. Herbivores remember the bad taste of the chemicals and may avoid eating the plant in the future. Some plants have special cells called idioblasts in their leaves. These cells produce chemicals for defense and also contain needle-sharp raphides. The prick from the raphides causes pain Then the chemicals cause even more pain. This defense keeps herbivores from eating too much of the plant! Poison ivy and sedum are two of the many plant species that contain idioblasts. Do You Know? Caffeine is a chemical called an alkaloid. It is made in nature by coffee and tea plants to repel herbivore attacks.

化学防御是另一种形式的直接保护。 许多植物产生化学物质来帮助修复由食草动物引起的损伤。 一些植物也会产生对食草动物来说味道不好的化学物质。 食草动物会记住化学物质的难闻味道，将来可能会避免食用这种植物。 有些植物的叶子上有一种特殊的细胞，叫做异细胞。 这些细胞产生化学物质用于防御，也含有针尖的raphide。 莴苣的刺痛会引起疼痛然后化学物质会引起更大的疼痛。 这种防御可以防止食草动物吃太多的植物!毒葛和景天是许多含有异细胞的植物物种中的两种。 你知道吗?咖啡因是一种叫做生物碱的化学物质。 它是由咖啡和茶树在自然界中制成的，用来抵御食草动物的攻击。

Plants such as citrus trees and mint make oils that repel insects. You may enjoy these smells. But the fresh scent of mint as well as lemons oranges, and other citrus fruits keeps many insects away. In Africa, some antelopes eat the leaves of acacia trees. As soon as an antelope starts eating these leaves, the tree produces a bad-tasting chemical called tannin k. This chemical also makes the antelope sick by interfering with its digestion. Just fifteen minutes after an herbivore starts eating acacia leaves, the amount of tannin doubles! You can bet that the antelope will eat something else next time.

柑橘树和薄荷等植物可以产生驱虫油。 你会喜欢这些气味的。 但是薄荷、柠檬、橙子和其他柑橘类水果的新鲜气味可以赶走许多昆虫。 在非洲，一些羚羊吃金合欢树的叶子。 一旦羚羊开始吃这些叶子，树木就会产生一种味道很差的化学物质，叫做单宁酸k。 这种化学物质还会干扰羚羊的消化，使其生病。 食草动物开始吃金合欢树叶15分钟后，单宁酸的量就翻倍了!你可以打赌羚羊下次会吃别的东西。