发布时间 : 星期五 文章生物专业英语第三版蒋悟生编__课文翻译更新完毕开始阅读1ae07b0026284b73f242336c1eb91a37f0113217
根，具有根样的固定作用，或者他们成为饲喂结构称吸器。菌丝或有细胞隔膜或没有细胞隔膜，但至少有一个细胞核。低级真菌是多核体的，即，一大团细胞质含有多个细胞核。
Hyphae grow and branch to form a filamentous network called a mycelium. Food is digested and absorbed at the tip of each hyphae; more hyphae are generated as this process continues. As a result, fungi may grow very rapidly. Growth depends on mitosis and the rapid manufacture of cytoplasm; fungal mitosis is unique in that it occurs within the nucleus. Hyphae from genetically distinct individuals may fuse to form a heterokaryon-a single cytoplasm with dissimilar nuclei.
菌丝生长形成分支，进而形成网状结构称为菌丝体。在菌丝尖端，食物被消化并吸收；这个过程能持续产生更多菌丝。结果，真菌生长很快。生长靠有丝分裂和细胞质的快速产生。真菌的有丝分裂很独特，即它只发生在细胞核里。遗传学明显不同的菌丝个体融合形成异核体——同一个细胞质中含有不同的细胞核。
As nonmotile heterotrophs, fungi must eventually be able to find new sources of nutrients. This function is fulfilled by spores, the fungal reproductive bodies. Spores may be home on aerial hyphae, which discharge spores into the air, and depending on the species they may haploid or diploid. There are two main categories of spores: (1) dispersal spores, which are usually short-lived and are produced in large numbers during active fungal growth; and (2) survival spores, which are usually produced in smaller numbers and at a time in the life cycle when the fungus is under some kind of environmental stress.
作为不会移动的异养生物，真菌最终能够发现营养新资源的。这个过程由孢子来完成，即真菌的生殖体。孢子可能是在气生菌丝的中心，将孢子释放到空气中，依赖物种不同，可能是单倍体也可能是二倍体。有两种主要的孢子：（1）分散的孢子，通常生命期短，数量大，主要存在于活跃的菌丝生长阶
段；（2）存活孢子，通常产生很少的数量，在生存压力条件下的一种生命循环。 Classification of fungi
As with some of the other groups you have studied, it is difficult to group fungi according to actual evolutionary relationships. In general, they are classified according to morphology, methods of reproduction, and modes of spore
production. On the basis of these features, the single division of the kingdom Fungi, Mycota, is divided into six principal classes. 对真菌依据实际进化关系进行分类是很困难的。总体来说，它们是依据形态学，生殖方式，孢子产生的模式来分类。基于这些特性真菌界的门被分成6个基本纲。
The lower fungi comprise the groups Chytridiomycetes, Oomycetes, and Zygomycetes. All lack septate hyphae and are commonly coenocytic; spores are formed by asexual means. Of the six fungal classes, only the oomycetes usually have a diploid vegetative state. Oomycetes and chytrids (sometimes called water molds) produce motile, flagellated spores in sporangia. They also produce gametes in gametangia; oomycetes are distinguished by their large, immobile egg cells. In fact, both these groups have such distinctive features that some biologists prefer to classify them as protists rather than fungi. Zygomycetes resemble the other two classes in this group but have nonmotile spores. They are also completely terrestrial, and some form mycorrhizal associations with plant roots.
低级真菌包含壶菌，卵菌纲和接合菌。所有缺乏隔膜的菌丝是通用的多核细胞的；孢子通过非性方式产生。只有卵菌纲通常有二倍体的营养状态。卵菌纲和壶菌在孢子囊中产生能动的带鞭毛的孢子。在配子囊中产生配子；卵菌纲具有非寻常大的静止的卵细胞。实际上，这两大群具有不同的特征，生物学家宁愿把它们归为原生动物而不是真菌。接合菌与其它两纲相似，但它的孢子不会动。它们完全是陆生的，一些菌根与某些植物的根形成共生关系。
The higher fungi include the class Ascomycetes, the largest class of fungi. Most ascomycetes are either saprobes or parasites. Asexual reproduction produces spores called conidia, which develop on the tips of specialized aerial hyphae. In the ascomycete sexual cycle, hyphae of different mating strains fuse, giving rise to ascospores that form in a small, saclike ascus. Groups of asci form fruiting bodies. Ascomycetes of interest to humans include truffles, yeasts, and Penicillium species.
高级真菌包括子囊菌纲，最大的真菌纲。大多数子囊菌要么是腐生菌，要么是寄生菌。非性繁殖产生的孢子称分生孢子子实体，其依赖特化的气生菌丝尖。在子囊菌性循环过程中，不同的菌丝通过株融合进行匹配，产生的子囊菌存在于小类子囊中。子囊群形成果实体。对人类有利的子囊菌包括块菌，酵母和产青霉素菌。
Most members of the class Basidiomycetes—the second group of higher fungi form visible fruiting bodies. A prime characteristic distinguishing basidiomycetes from ascomycetes is the dense mass of dikaryotic hyphae called the basidiocarp-the \seen on damp lawns and the forest floor. Club-shaped basidia, each bearing four haploid basidiospores, line the surfaces of the gills on the underside of the mushroom cap. Members of this group undergo both sexual and asexual reproductive processes at different times in their life cycle, and in response to varying environmental influences.
纲中大多数菌为担子菌，第二大类高级真菌，能形成可见的果实体。担子菌与子囊菌相比，最基本不同是它具备浓密的双核菌丝，称担子果。棒形担子，每个都含有4个单倍体的担子孢子，线形地排列在蘑菇帽下的菌褶表面。大多数成员有性和非性繁殖两种，在不同生命循环中有不同形式，并依据环境变化而变化。
The class Deuteromycetes, or Fungi Imperfecti, includes a variety of fungi that lack modes of sexual reproduction. Most are
known to reproduce asexually by means of conidia. Deuteromycetes important to humans include those used to ferment soybeans and rice to make soy sauce and sake respectively, and those responsible for producing citric acid and the highly dangerous aflatoxin.
半知菌纲，包括大量无性繁殖的真菌。分生孢子完成非性繁殖。对人类很重要的半知菌纲包括发酵大豆成酱油和大米发酵成清酒的菌类，它们也产生柠檬酸和有毒的黄曲霉毒素。 Lichens: The Ultimate Symbionts
Lichens are composite organisms in which about 90 percent of the lichen mass consists of one species of fungus, while the remaining 10 percent is made up of one or two species of algae. The algal portion of the lichen provides the fungal portion with essential nutrients, while the presence of the fungal component may enable the alga to exploit an otherwise unavailable ecological niche. Lichen fungi are usually ascomycetes, although the other two higher fungi are sometimes found in lichens. Lichens have a number of remarkable features, including their ability to become almost completely desiccated without drying and their ability to absorb inorganic nutrients. Reproduction in lichens is not well understood.
地衣是复合生物，大概90%的地衣团由一种地衣组成，10%含有一两种藻类。藻类为真菌提供必要的营养，真菌为藻类提供了难得的小生态环境。地衣真菌通常是子囊菌，有时在地衣中也能发现其他两类真菌。地衣有大量的显著特征，包括在几乎脱水条件下仍能吸收无机养分。地衣繁殖方式还不清楚。 Fungal Evolution
The various fungi may have arisen independently from prokaryotes, since some evidence suggests that ascomycetes and basidiomycete did not evolve from known lower forms. However, all fungi do show the same dependence on nutrients produced by plants, animals, or algae.