biology class 12 practical

1. EXPERIMENT 9.1
AIM: To study the flowers adapted to pollination by different agencies (wind, insect and birds).
REQUIREMENTS
Fresh fHowers of maize or any other cereal/grass, Salvia/Ocimum and Brassica (mustard) forceps,
hand lens, slide, needle etc.
PROCEDURE
Place the given flower on a slide and observe it with the help of hand lens. Note down the
adaptations of the flowers meant for pollination by the external agencies.
Maize Flowers (Anemophilous or Wind Pollinated Flowers)
The flowers of maize show following adaptations for pollination by wind.
The maize plant is monoecious and bears unisexual flowers. The male flowers are born in terminal
1
inflorescence while the female flowers are born in axillary inflorescence.
2. Flowers are small and inconscipicous.
3. The flowers are colourless, odourless and nectarless.
Flowers are produced above the foliage or placed in hanging position.
5. Both the stigmas and anthers are exerted (i.e., hang outside the perianth).
6. Anthers are versatile, and pollen grains are light, small and dusty.
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7. The pollen grains are produced in very large numbers.

2. C o r eE x p e r i m e n t s
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1a is hairy, feathery or
branched to catch wind born pollen grains.
8.
Male flowers
:
Tassel
Pollen grains
Cobl Versatile
anther
Elongated
styles Feathery
stigma
Pollen grains
of another plant Ovary
Stigmas
Fig. 9.2. Feathery stigmas and versatile
anthers in a flower of grass.
Fig. 9.1. Anemophily in maize.
Salvia Flovwers (Entomophilous or insect Pollinated Flowers)
The flowers of Saliva show following adaptations for pollination by insects.
1 The flowers are showy or brightly coloured for attracting pollinating insects.
Ihe lowers are born in verticellaster inforescence to become conspicuous.
2
Flowers secrete nectar to feed visiting insects. Nectar glands are placed in such a position that
B
an insect must touch both the anthers and stigmas.
ne flowers are protandrons with bilipped corolla and have turn pipe or lever mechanism.
5
The flowers have landingplatform for the insects.
ach stamen has long connective which bears a fertile anther lobe at the upper end and sterile
plate like anther lobe at the lower end. he two sterile anther plates block the path of insect.
9 tne insect moves inward a young
flower in search of nectar, its head pushes, the anther plates
As
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d rorces the fertile anther lobes to strike against its back.
8 Older flowers the style brings the stigma in such a position that it brushes against the back
In
insect and collect pollen grains brought by the insect from a young flower.

3. ogy
Comprehensive Laboratory Manual in Biolno.
60
Closed stigma Fertile
anthor lobo
Shesdeirngo
pollen grains
on the bak
of insoct
B
Stigma
receivingg
/pollen grains
from the back
Sterile
A anther lobe
Mature
Nectariferous
stigma
disc
of insect
D
C
Withering
anther
Fig. 9.3. Pollination in Salvia. A. Flowerwith mature anthers, enclosed stigma and short STe
B. Shedding of pollen grains on the back of entering insect. C. Flower with mature stigma and witrer
anthers. D. Stigma receiving pollen grains from the back of entering insect.
Bignonia/Callistemon (Bottle brush) Flowers (Ornithophilous or Bird Pollinata
Flowers)
The flowers of Bignonia show following adaptations for pollination by birds.
The flowers are usually brightly coloured-red, orange, yellow or blue.
The floral parts are commonly leathery.
Humming blrd
Fig. 9.4. Pollination in Bignonia. Humming bird collecting nectar from
Bignonia flower and thus pollinating it.

4. C o r e E x p e r i m e n t s
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In some cases, the corolla are leathery,
3.
The flowers secrete abundant watery nectar or have edible parts.
The nectar is secreted in such abundance that drops of it can be brought down by shaking
.
branches.
The flowers are generally odourless or without fragrance.
6.
VIVA VOCE
Q.1. What is meant bypollination?
Ans. The process ot transterence of pollen grains from anther to the stigma is called pollination.
Q.2. Nane the types ofpollination found in flowering plants.
Ans. Self-pollination and cross pollination.
Q.3. Whatis autogamy?
Ans. It is a type of self-pollination in which an intersexual flower is pollinated by its own pollen
Q.4. What is geitonogamy?
Ans. It is a type of pollination in which pollen grains of one flower are transferred to the stigma
of another flower belonging to either the same plant or genetically similar plant.
Q.5. What is allogamyorxenogamy ?
Ans. It is a type of pollination in which pollen grains from anther of one flower are transferred to
the stigma of a genetically different flower.