XII BIOLOGY
CH-1 Reproduction in lower and higher plants
PART- Pollinating agents
Pollinating agents are of two types :-
A. Abiotic Agents:
1)Pollination by wind (Anemophily)
2)Pollination by water [Hydrophily] are two type-
B. Biotic Agents:
1)Pollination by insects (Entomophily)
2) Pollination by birds (Ornithophily)
3)Pollination by Bats (Chiropteryphily)
A. Abiotic Agents:
These
are non-living agents which include wind and water.
1)Pollination by wind (Anemophily)=
polination
take place by wind is called wind polination
Most of the important crop plants are wind
pollinated.
These includes wheat, rice, corn, rye, barley and
oats. Palms are also wind pollinated.
Adaptations in anemophilous flowers:
i)The flowers are small,
inconspicuous, colourless, without nectar and fragrance (odour).
ii)The pollen grains are light
weight, dry and produced in large numbers to increase chances to wastage.
iii)Stigma is feathery to trap
pollens carried by wind.
iii)Stamens are exserted with
long filaments and versatile anthers.
pollination
take place by water is called
pollination. are
two type
i)Hypohydrophily:.
Pollination occurs
below the surface of water Here the pollen grains have same
specific gravity as
water so they can swim in water.
e.g. In Zostera (sea grass) the pollen
grains are long, ribbon like and without exine.
ii) Epihydrophily-
The pollen grains float on the water Surface and
reach the stigma of female flower. e.g. Vallisneria is a submerged dioecious,
in which female flowers reach the water surface temporarily to ensure
pollination and male flowers float on the surface of water .
Specific gravity of pollen grain is equal to that water. why they float on surface of water Anemophilous plant e.g. Potamogeton, Halogaris, etc. entomophilous plant e.g. Lotus, Water hyacinth, Waterlily, etc
Adaptations
in hydrophilous flowers:
1. Flowers
are small and inconspicuous.
2. Perianth
and other floral parts are unwettable.
3. Pollen
grains are long and unwettable due to presence of mucilage.
4. Nectar
and fragrance are lacking in flowers. Male & female plant Vallisneria
Adaptations
in hydrophilous flowers
Male & female plant Vallisneria
Adaptations in
entomophilous flowers:
i)They are large, showy and often
brightly coloured.
ii)The flowers produce sweet
odour (smell) and have nectar glands.
iii)The stigma is rough due to
presence of hair or is sticky due to mucilaginous secretion.
iv)The pollen grains are spiny
and surrounded by a yellow sticky substance called pollen kit.
v)Some plants have special adaptations for the insect visitor to help in cross pollination, e.g. Jasmine, Rose, Salvia, (estrum, etc.
2)Pollination by birds (Ornithophily)
Only a few types of birds are specialised for pollination. e.g. Sun birds And humming birds.
Pollination by birds (Ornithophily)
e.g. - Bombax, Callistemon (Bottle Brush), Butea,
Bignonia etc.
Adaptations
in ornithophilous flowers:
i)Flowers are
usually brightly coloured, large .
ii)They secrete profuse, dilute nectar.
iii)Pollen grains are sticky and spiny.
iv)Flowers are generally without fragrance, as birds
have poor sense of smell.
Adaptations in Chiropterphilous flowers:
i)Flowers are dull coloured with strong fragrance.
ii)Flowers are large and strong.
iii)Flowers open at night time .
iv)Flower produce abundant nectar.
v)Flowers produce large amount of edible pollen
grains.
vi)e.g. Anthocephalous (kadamb tree), Adansonia (Baobab tree), Kigelia (Sausage tree) .