FAMILY OF THE WEEK : NYMPHACEAEThe
family is represented by 8 genera and about 90 species most abundant in
tropics. In India there are 4 genera and 7 species occurring throughout
India.
Vegetative characters :They are perennial aquatic herbs with a creeping or erect sympodial
rhizome. There is a scattered arrangement of vascular bundles.
The
leaves are usually large, simple and long petioled, arising from the root stalk or from the slender floating stem (
Cabomba). They are usually floating or sometimes emerged as in
Nelumbo. often peltate.
Inflorescence and flowers :The
flowers are
axillary, solitary, long peduncled, and float on the surface or raised
much above the water(Nelumbo) or partially submerged. The flowers are
large showy, often sweet scented, bisexual, actinomorphic, hypogynous
or more or less epigynous and acyclic to cyclic.
The
calyx and
corolla are poorly differentiated. The calyx is composed of 3-5 sepals.
The sepals are distinct and green or coloured and petioled.
The
corolla is
polypetalous with three to indefinite and variously coloured or white
showy petals. In Nymphea numerous spirally arranged petals gradually
pass into stamens.
The androecium is composed of three to indefinite
distinct stamens. The gynoecium is of two to three to numeruos carpels.
In Nelumboideae there are a large number of carpels which are embedded
separately in round pits which are on the flat upper surface of of a
swollen spongy and obconical receptacle.
Fruits and seeds :In
Cabomboideae the fruit is a closed indehiscent follicle with one to
three pendulous seeds. In Nelumboideae the fruit is indehiscent one
seeded nutlet. The seeds are with a large embryo and with no endo ro
perisperm. In Nymphaeoideae the fruit is a spongy berry with numerous
seeds and it dehisces by swelling of mucilage. The seeds have small
embryo and endosperm and abundant perisperm.
Pollination and seed dispersal :Bright
and showy fragrant flowers favour pollination by insect, flies and
small beetles.Seed dispersal is mostly by water. Somespecies of Nuphar,
Brasenia, and Cabomba are dispersed by ducks which eat the pulp of
these fruits greedily.
Examples :
Nelumbo nucifera (Lotus) Kamal
Nymphaea nauchali(Indian red water Lily)
Nymphaea stellata(Indian blue water Lily)
Nymphaea alba (European white water Lily)
Victoria amazonica(Royal water Lily)
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