Download VISHAL ORCHIDACEAE

E-content generation of undergraduate classes with
special reference to the Orchidaceae
VISHAL SHARMA
P.G.GOVT.COLLEGE FOR GIRLS,
SECTOR 11,
CHANDIGARH-INDIA
The
flowering
plants
satisfy
man’s
requirements for food, shelter, clothing and
drugs, besides adding to his aesthetic values.
Their latter utility accounts for a highly
lucrative trade in floriculture. Plants worth 800
billion US $ (dollars) were traded last year. Till
very recently, the trade primarily revolve
around
roses,
lilies,
carnation,
chrysanthemums, tulips etc. but the trend is
now fast shifting in favour of orchids for their
long -lasting flowers of myraid shapes, sizes
and colours.
Inflorescence: Usually a spike (Orchis) , sometimes
raceme(Dendrobium) or solitary terminal(Cypripedium)
• Flower:Bracteate,sessile,complete,zygomorphic,most
ly bisexual,epigynous and are mostly trimerous
• Perianth:Usually six;in two whorls of three
each,outer one free whereas posterior tepal of inner
whorl is modified into lip or labium and acts as
landlig place for insects.The labium adnate to base of
column.The perianth lobes are variously coloured
and bear diverse and variegated patterns.
Androecium:The androecium is representedby one or two or
three stamens .In Orchis the single fertile stamen lies in outer
whorl and the inner whorl has only staminodes.The stamens and
styles fused to form a column like structure called columnor
gynandriumor gynastemium.The column is usually present
opposite the labellum.The anthers are bithecous,dehiscence
longitudinal
Gynaecium: Tricarpellary, syncarpous, Inferior, unilocular,
Placentation parietal,stigmas three with two fertile lobes and
modifi cation of third sterile lobe into a structure called the
rostellum and usually positioned in the centre of column
• Fruit:Capsule
• Seed: Non-endospermic
Pollination:The flower has a nectary concealed in the spur of
labellum or at the base of column.The insects land land on the
labellum and tries to reach the nectary and bite itor drill its
tissue to suck the juice contained in it.While entering the the
flower the insect displaces the the rostellumor some parts.In
doing so it exposes the sticky mass of pollinia and comes in
contact with it.This sticky mass of pollinia becomes cemented
to the insect while it is drilling the honey and when the insect
enters the next flower ,pollinia come in contact with the
stigma.
A very interesting pollination mechanism in Ophrys where
flower resemble to female species of bees and male insects
attracted by flowers of Ophrys due to female like appearance
and on reaching male insects get excited,carry out matting
movements and in so attach pollinia to their bodies.