The body of a fungus (Fig. 11-1) is referred to as either a soma (meaning "body"), which is equal to the term "vegetative" in plants, or thallus, which is also applied to algae and bryophytes (nonflowering plants comprised of mosses and liverworts). The body of a mold or fleshy fungus consists of long, loosely packed filaments called hyphae.
Hyphae are divided by cell walls called septa (the singular form is septum). In most molds the hyphae are divided into one cell units called septate hyphae. In some fungi, the hyphae have no septa and look like long multinucleated cells called coenocytic hyphae. Cytoplasm flows or streams throughout the hyphae through pores in the septa. Under the right environmental conditions the hyphae grow to form a filamentous mass known as a mycelium. A fungus can
have a thallus many meters and penetrate its surroundings. In the hyphae of fungi there is a portion called the vegetative hyphae. Vegetative hyphae are where nutrients are obtained. The part of the hyphae responsible for reproduction is called reproductive or aerial hyphae.
Fungi can reproduce both sexually and asexually. Reproduction occurs with the formation of spores. Spores are always nonmotile and are a common means of reproduction among fungi. Do not confuse bacterial endospores with fungal spores; they are different. Bacterial endospores are formed so that the bacterial cell can survive in harsh environments. Once there is a less threatening environment, the bacterium leaves the endospore state and becomes active. The endospore germinates into a single bacterial cell. Asexual reproduction occurs when asexual spores are formed by the hyphae of one organism. When these spores germinate, they are identical to the parent. Sexual reproduction happens when the nuclei of sexual spores from two opposite mating strains of the same fungus species fuse. Fungi that grow from sexual spores have genetic characteristics of both parents.
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