Environmental Engineering Reference
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them with the other fungi in a monophyletic
group. This confl ict can only be resolved (while
retaining the reference to oömycetes as fungi) if
mycologists can agree to maintain two distinct
meanings of the term fungus: (i) the strict taxo-
nomic epithet covering members of the Kingdom
Fungi and (ii) a practical reference to microorgan-
isms studied by mycologists that share the charac-
teristics outlined above. So, oömycetes qualify as
fungi, just as euglenoids and red algae are algae
despite the fact that their origins are remote from
those of the green algae from which the land plants
evolved. If justifi cation for mycological research
on oömycetes is necessary, then one has only to
look at the literature on tip growth to understand
that oömycetes like Saprolegnia ferax represent
superb experimental subjects because their
hyphae grow faster and larger than those of most
fungi with chitinous walls (Money 1997 ) and to
consider the way in which research on steroid
hormones in oömycetes has shaped our view of the
physiological sophistication of the fungi (Mullins
1994 ). It is also worth remembering that the entire
fi eld of plant pathology might be said to have
originated with Berkeley's study of the oömycete
Phytophthora infestans . It is, of course, important
to think carefully about the relevance of informa-
tion gleaned from experiments on oömycetes to
other fungi and vice versa, and authors should ensure
that such caveats are included in their discussion
of data. But if mycologists can agree on a practi-
cal defi nition of the fungi, research on oömycetes
will continue to enrich our understanding of all
organisms and all of the fungi that absorb their
food, ramify through their surroundings in the
form of tip-growing hyphae and produce clouds
of spores in air and in water (Money 1998 ).
and female (oögonia) gametangia producing
respective gametes under unfavourable conditions
(DeBary 1860 ). Investigations carried out by a vast
array of aquatic mycologists from mid-nineteenth
to the early twenty-fi rst century and the Klebsian
Principles have led us to enunciate certain
general concepts regarding sexual reproduction
in Saprolegniaceae (Hawksworth 1991 ). These
are as follows:
1. Particular inorganic salts in a growth medium
favour the development of sexual apparatus.
2. A distinct correlation does exist between the
mass (weight) of the vegetative growth and
abundance of male and female gametangial
production.
3. Carbon-nitrogen ratio (C/N ratio) and certain
combination of its sources (Pieters 1915 ) stimu-
late production of male gametangia in excess pro-
duction of female gametangia while others are
antagonistic to the male gametangial production.
4. The variation in the concentration of constitu-
ents in a medium affects (Horn 1904 ) the
structural changes in the sexual apparatus.
5. The production of female gametangia may not
be stimulated by addition of inorganic salts to
a nutrient-rich medium (Obel 1910 ).
6. The sexual apparatus appears more frequently
to develop on older hyphae than on younger
hyphae, which indicates towards the effect of
age factor of vegetative phase on the produc-
tion of gametangia (Klebs 1899 ; Obel 1910 ).
However, it does not necessarily mean that
sexual reproductive process starts only when
the asexual sporulation ceases (Gow and Gadd
1995 ; Moore 1997 ) .
The family Saprolegniaceae is, at present, hav-
ing 17 genera (Johnson et al. 2002 ). These are
Achlya Nees von Esenbeck, Aphanodictyon
Huneycutt ex Dick, Aphanomyces deBary,
Aplanopsis Höhnk, Brevilegnia Coker and Couch,
Calyptralegnia Coker, Couchia W.W. Martin,
Dictyuchus Leitgeb, Geolegnia Coker, Leptolegnia
deBary, Phragmospor angium Seymour,
Plectospira Drechsler, Protoachlya Coker,
Pythiopsis deBary, Saprolegnia Nees von
Esenbeck, Sommerstorffi a Arnaudow and
Thraustotheca Humphrey. Prabhuji et al. ( 2010 )
has recorded the occurrence of the eighteenth genus.
Biodiversity and Taxonomic Studies
The members of saprolegniaceae typically
exhibit the complete life cycle, i.e. the pres-
ence of vegetative reproduction by production
of gemmae, asexual reproduction by formation
of zoosporangia producing bifl agellate zoo-
spores under favourable conditions and sexual
reproduction by formation of male (antheridia)
 
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