Science Fair Project Encyclopedia
This article is about biological spores. For the video game, see Spore (game).
The term spore has several different meanings in biology.
Categorization by function:
- Diaspores are dispersal units of fungi, as well as mosses, ferns, fern allies, and a few other plants.
- resting stage in the life cycle of some bacteria (see endospore) and loosely applied to some animal resting stages
- Chlamydospores (chlamydia) are thick-walled resting spores in fungi.
- Zygospores are thick-walled resting spores (hypnozygotes) of zygomycota fungi which are produced by sexual gametocystogamy and can give rise to a conidiophore ("zygosporangium") with asexual conidiospores.
Categorization by origin during life cycle:
- Meiospore is a product of meiosis (the critical cytogenetic stage of sexual reproduction), meaning it is haploid and will give rise to a haploid daught cell(s) or a haploid individual. An example is the parent of gametophytes of the higher vascular plants (angiosperms and gymnosperms)—the microspores (give rise to pollen) and megaspores (give rise to ovules) found in flowers and cones; these plants accomplish dispersal by means of seeds.
- Mitospore (conidium , conidiospore) is an asexually produced propagule, the result of mitosis. Most fungi produce mitospores. Mitosporic fungi are also known as anamophic fungi (compare teleomorph or deuteromycetes).
Categorization by motility - spores can be differentiated by whether they can move or not:
- Aplanospore cannot move, but could potentially grow flagella.
- Autospore cannot move and does not have the potential to ever develop any flagella.
- Ballistospore is actively discharged from fungal fruit body (mushroom).
- Statismospore is not actively discharged from fungal fruit body (see puffball).
Spores can be formed sexually or asexually, and therefore many different kinds of spores exist. In common parlance, the difference between "spore" and "gamete" (both together called gonites) is that a spore will germinate and develop into a Thallus (tissue) of some sort, whereas a gamete needs to combine with another gamete before developing further. However, the terms are somewhat interchangeable when referring to gametes, as indicated by the technical terminology given in the second definition above.
A chief difference between spores and seeds as dispersal units is that spores have very little stored food resources compared with seeds, and thus require more favorable conditions in order to successfully germinate. In their favor, spores are very hardy and require much less energy to produce. The strategy employed in producing spores, is to reach all the favorable locations by producing and dispersing very large numbers.
In the case of spore-shedding vascular plants such as ferns, wind distribution of very light spores provides great capacity for dispersal. Also, spores are less subject to animal predation than seeds because they contain almost no food reserve, however they are more subject to fungal and bacterial predation. Their chief advantage is that, of all forms of progeny, spores require the least energy and materials to produce.
Vascular plant spores are always haploid and vascular plants are either homosporous or heterosporous. Plants that are homosporous produce spores of the same size and type. Heterosporous plants, such as spikemosses, quillworts, and some aquatic ferns produce spores of two different sizes: the larger spore in effect functioning as a "female" spore and the smaller functioning as a "male".
Under high magnification, spores can be categorized as either monolete spores or trilete spores. In monolete spores, there is a single line on the spore indicating the axis on which the mother spore was split into four along a vertical axis. In trilete spores, all four spores share a common origin and are in contact with each other, so when they separate each spore shows three lines radiating from a center.
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