Spore（spore）It can develop into new individuals directly or indirectly after being separated from parentsgerm cell。It is the product of mitosis or meiosis;Most arehaploidAnd a few are diploid.Spores are usually unicellular or multicellular propagules.The diversity of spores is formed due to the difference of its characters, occurrence process and structure.[1]
Homospores have only one type of spore, and their prothalli areMonoeciousOf.However, heterospores have dimorphic spores with different sizes and male and female differentiation, and their prothalli are generallyDioeciousOf.Heterospores have differentiated in Selaginella of ferns;Chinese chive, apple, sophora andRhododendronThey also have heterospores.Gymnosperms and angiosperms are completely heterospores.[3]
From the point of view of spore structure, spores can be divided into two types: zoospore and acinospore.The number of zoospores produced by each sporangium varies according to plant species, but most algae generally produce 16-64 zoospores per sporangium.Such spores are usually pear shaped or spherical, and may have 2 or 4 flagella or several flagella depending on the species.After being released from the sporangium, zoospores can swim for a period of time, such as the green algae of the genus Panastraceae, which can swim for 4 minutes, and the filamentous algae can swim for 3 days.Then, the flagellum is removed, the cell wall is secreted, and new prothalli are formed.However, the spores of some algae fungi and higher cryptogamous plants have no flagella, are light, can float in the air, and have a protective layer, which can resist adverse growth conditions.Most of the Rhodophyta plants produce acinetospores, which are cut from the end of the filamentous body formed by zygote germination.[3]
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There are two ways to form spores: one is the spores formed after mitosis, called mitospores;The other is the spore produced by meiosis, called meiosis spore.
The plant body of lower plants produces spores through mitosis, and can directly germinate to produce new plant individuals. The genotype of its offspring is completely consistent with that of its parent plants.This process belongs to asexual reproduction, so silk spores are also called asexual spores.If the parent is a haploid plant (such as Chlamydomonas), the chromosome ploidy of the filamentous spores is 1n;If the parent is a diploid plant (such as Hyalus of brown algae), its chromosome ploidy is 2n.There are two types of filamentous spores: one is flagellate zoospore;Another species, which does not have flagellum and cannot swim, is called acinetospore.Homospores have many different characteristics due to the different time and location of plant species and spores.[3]
