Everything about Water Mold totally explained
== ==
Oomycetes also known as
Water molds (or
water moulds: see
spelling differences) are a group of filamentous, unicellular
Heterokonts, physically resembling
fungi. They are microscopic, absorptive organisms that reproduce both sexually and asexually and are composed of
mycelia, or a tube-like vegetative body (all of an organism's mycelia are called its
thallus). The name "water mold" refers to their earlier classification as fungi, which stemmed from their preference for conditions of high humidity and running surface water, although they're now known to have evolved separately and show a number of differences. For instance, their
cell walls are composed of
cellulose rather than
chitin and generally don't have
septations. Also, in the vegetative state they've
diploid nuclei, whereas fungi have
haploid nuclei.
Instead, water molds are related to organisms such as
brown algae and
diatoms, making up a group called the
heterokonts. The name comes from the common arrangement and structure of motile cells, which typically have two unequal
flagella. Among the water molds, these are produced as asexual
spores called
zoospores, which capitalize on surface water (including precipitation on plant surfaces) for movement. They also produce sexual spores, called
oospores, that are translucent double-walled spherical structures used to survive adverse environmental conditions. A few produce aerial asexual spores that are distributed by wind.
The water molds are economically and scientifically important because they're aggressive plant pathogens (see
plant pathology). Some species can cause disease in fish. The majority can be broken down into three groups, although more exist.
The Pythium group is even more prevalent than Phytophythora and individual species have larger host ranges, usually causing less damage. Pythium damping off is a very common problem in greenhouses where the organism kills newly emerged seedlings. Mycoparasitic members of this group (for example P. oligandrum) parasitize other oomycetes and fungi, and have been employed as biocontrol agents. One Pythium species, Pythium insidiosum is also known to infect mammals.
The third group are the downy mildews, which are easily identifiable by the appearance of white "mildew" on leaf surfaces (although this group can be confused with the unrelated powdery mildews).
Classification of Oomycetes
Traditionally, this group was thought to include types of fungi, and indeed fungi themselves were once believed to be closely related to plants. However, further research has concluded that this isn't true and that fungi are more closely related to animals. Many species of Oomycetes are still described or listed as types of fungi and may sometimes be referred to as pseudofungi, or lower fungi. Oomycetes are actually members of the chromistans, which are in turn part of the larger Kingdom Protoctista.
Further Information
Get more info on 'Water Mold'.
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