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  • 种子植物

    Leaves of a Ginkgo tree, known for its unique fan-shaped foliage.

    How old can a plant be?
    ::植物能有多老?

    This is obviously a seed plant. It is a Gingko tree, which is an unique in that there are no close living relatives. Gingkoes can live for a very long time. Some specimens of this are thought to be over 2,500 years old. The Ginkgo is also known as a living , with related to modern Ginkgo from the Permian period, dating back 270 million years.
    ::这显然是一种种子植物。 它是一个金科树, 其独特之处在于没有亲近的亲缘关系。 金科斯可以长寿。 据认为, 其中一些样本已经超过2500年了。 银歌也被称为一种生活, 与波尔米安时期的现代金戈有关, 追溯到2. 7亿年前。

    Seed Plants
    ::种子植物

    Seed plants are called spermatophytes . The evolution of seeds by was a very big deal. In fact, it was arguably as important as the evolution of . Seeds solved the problem of releasing offspring into a dry world. Once seeds evolved, vascular seed plants and their descendants diversified to fill niches everywhere. Today, vascular seed plants dominate Earth.
    ::种子植物被称为精子植物。种子的进化是一件非常大事。事实上,它与种子的进化同样重要。种子解决了将后代释放到干燥世界的问题。一旦种子进化,血管种子植物及其后代多样化,以填补各地的空隙。今天,血管种子植物主宰着地球。

    Parts of a Seed
    ::种子的一部分

    As shown in Figure , a seed consists of at least three basic parts: the embryo , seed coat , and stored food .
    ::如图所示,种子至少由三个基本部分组成:胚胎、种子外套和储存的食物。

    • The embryo develops from a fertilized egg . While still inside the seed, the embryo forms its first leaf ( cotyledon ) and starts to develop a (hypocotyl) and root (radicle).
      ::胚胎从受精卵中发芽。 虽然胚胎还在种子中,但胚胎形成第一个叶子(联苯酮),并开始形成一种(乙酰)和根()。
    • The tough seed coat protects the embryo and keeps it from drying out until conditions are favorable for germination .
      ::坚硬的种子大衣保护胚胎 防止它干涸 直到孕育的有利条件
    • The stored food in a seed is called endosperm . It nourishes the embryo until it can start making food on its own.
      ::种子中储存的食物叫做内分泌素,它孕育胚胎,直到它自己开始生产食物。
    Parts of an avocado seed: seed coat, embryo, hypocotyl, radicle, cotyledons.
    A typical plant seed, like this avocado seed, contains an embryo, seed coat, and endosperm. How does each part contribute to the successful development of the new plant?

    Many seeds have additional structures that help them disperse. Some examples are shown in Figure . Structures may help them travel in the wind or stick to . Dispersal of seeds away from parent plants helps reduce with the parents and increases the chance of offspring surviving.
    ::许多种子有额外的结构来帮助他们驱散,图中有一些例子。结构可以帮助他们在风中旅行或坚持。从母植物中分离出种子有助于减少父母,增加后代存活的机会。

    Dandelion, maple tree, and burdock seeds demonstrating various seed dispersal mechanisms.
    Dandelion seeds have tiny “parachutes.” Maple seeds have “wings” that act like little gliders. Burdock seeds are covered with tiny hooks that cling to animal fur.

    Classification of Seed Plants
    ::种子植物分类

    The two major types of seed plants are the gymnosperms (seeds in cones) and (seeds in ovaries of flowers). Figure shows how the seeds of gymnosperms and angiosperms differ. Do you see the main difference between the two seeds? The seed is surrounded by an ovary .
    ::两种主要类型的种子植物是体操植物(锥形种子)和(花卵型种子),图表显示体操植物和血管植物的种子如何不同。你看到这两种种子的主要区别吗?种子周围是卵巢。

    Comparison of gymnosperm and angiosperm seeds, highlighting their structural differences.
    In gymnosperms, a seed develops on the scale of a cone. Only an angiosperm seed develops inside an ovary.

    There are only about 1,000 living of gymnosperms, whereas there are hundreds of thousands of living species of angiosperms. Living gymnosperms are typically classified in the divisions described in the Table . Most modern gymnosperms are trees with woody trunks. The majority are conifers such as pine trees.
    ::健身房只有大约1,000人生活在健身房里,而有几十万活种血管。 健在的健身房一般按表中所述的分类。 现代健身房大多是树干木质的树,大部分是松树等细树。

      Division Description
    A large Ginkgo biloba tree with vibrant yellow leaves in an outdoor setting.
    		Ginkgoes There is only one living species (Ginkgo biloba); some living trees are more than 2000 years old; they originated in Asia but now are cultivated all over the world; they have been used for medicines for thousands of years.
    A large conifer tree with dense needle-like leaves in a forest setting.
    		Conifers There are more than 700 living species; most are trees such as pines with needle-like leaves; they are often the dominant plants in their habitats ; they are valuable to humans for paper and timber.
    Cycads with stout trunks, fern-like leaves, and large seed cones in a tropical setting.
    		Cycads There are about 300 living species; they are typically trees with stout trunks and fern-like leaves; they live only in and subtropical climates; they have large, brightly-colored seed cones to attract pollinators .
    Close-up view of green, woody vines with tightly clustered buds, typical of Gnetaceae.
    		Gnetae There are fewer than 100 living species; most are woody vines with evergreen leaves; they live mainly in tropical climates; they are the least well known gymnosperms but the most similar to angiosperms.

    Evolution of Seed Plants
    ::种子植物演变

    The earliest seed plants probably evolved close to 300 million years ago. They were similar to modern ginkgoes and reproduced with pollen and seeds in cones. Early seed plants quickly came to dominate forests during the , or Age of the Dinosaurs , about 250 to 65 million years ago.
    ::最早的种子植物或许在近3亿年前就已经发展了。 它们与现代的银洞相似,用花粉和锥形种子繁殖。 早期的种子植物在恐龙时代,也就是大约2.5亿到6500万年前迅速占据了森林的主导地位。

    As seed plants continued to evolve, Earth’s overall climate became drier, so early seed plants evolved adaptations to help them live with low levels of . Some also evolved adaptations to cold. They had woody trunks and needle-like, evergreen leaves covered with a thick coating of waxy cuticle to reduce loss. Some of the trees were huge, like today’s giant sequoia, a modern conifer (see Figure ).
    ::随着种子植物的不断发展,整个地球的气候变得更加干燥,因此早期的种子植物发展了适应性来帮助他们生活在低水平的温度下。 有些还演变了对寒冷的适应性。 它们有木干和像针一样的、绿色的叶子,上面覆盖着厚厚的蜡结层以减少损失。 有些树是巨大的,就像今天的巨型雪茄一样,是一个现代小精灵(见图 ) 。

    A person stands beside giant sequoia trees, showcasing their immense size.
    The person standing at the foot of this giant sequoia shows just how enormous the tree is. Some early seed plants also grew very large.

    Eventually, some gymnosperms started to evolve -like traits. For example, cycad ancestors were the first plants to use as pollinators. They also used and monkeys to disperse their brightly colored seeds. Of modern gymnosperms, Gnetae probably share the most recent common ancestor with angiosperms. Among other similarities, Gnetae produce nectar , a sweet, sugary that attracts insect pollinators. Most modern flowering plants also produce nectar.
    ::最终,一些体操动物开始进化 — — 类似特征。 比如,细胞祖先是最早用作授粉者的植物。它们还利用和猴子驱散其彩色种子。 在现代体操动物中,Gnetae可能与血管动物分享最新的常见祖先。除其他相似之处外,Gnetae生产蜜蜜,一种甜甜的糖,吸引昆虫授粉者。大多数现代花生植物也生产蜜。

    Summary
    ::摘要

    • Most are seed plants, or spermatophytes. They reproduce with seeds and pollen.
      ::多数是种子植物,或精子,它们用种子和花粉繁殖。
    • Some modern seed plants are gymnosperms that produce seeds in cones.
      ::有些现代种子植物是体操植物,产生锥形种子。

    Review
    ::回顾

    1. Identify the parts of a seed and the role of each part.
      ::确定种子的各个部分和每个部分的作用。
    2. Name and describe the divisions of gymnosperms.
      ::名称和描述体操场的分部。

    Resources
    ::资源