Bio Prac 1, 29 Apr.pdf

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 ofthe 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 unisexualflowers. The male flowers are born in terminal 1
inflorescence while thefemale flowers areborn 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. 6
7. The pollen grains are produced in very large numbers.

2. Core Experiments
59
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 landing platform
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
7
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. Flower with
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. Core Experiments 61
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 by pollination ?
Ans.
The process
ot transterence of pollen grains
from anther to the stigma
is called pollination.
Q.2.
Nane the types of pollination
found in flowering plants.
Ans. Self-pollination
and cross pollination.
Q.3. What is 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 allogamy or xenogamy
?
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.