नमस्कार मित्रांनो इयत्ता बारावी Biology या Subject च्या Practical मध्ये PART - B: Demonstration Experiments (Spotting) हा भाग Practical Exam च्या दृष्टीने फार महत्त्वाचा आहे. या Blog Post मध्ये आपण Spotting Practical Number 4: Study of flower adapted to pollination by different pollinating agencies ह्या Practical Experiment चे Answer पाहणार आहोत. खाली दिलेल्या उत्तरांमध्ये काही अडचण असल्यास आम्हाला comment करा किंवा तुमच्या संबंधीत विषय शिक्षकांशी चर्चा करा.
B. DEMONSTRATION EXPERIMENTS (Spotting)
4. Study of flower adapted to pollination by different pollinating agencies.
Aim :- To study different adaptations shown by flower for pollination.
Requirements :- Flowers of grass, maize, Salvia, Ocimum, Brassica, etc, forceps, hand lens, slide, etc.\
Observe the given flower with the help of hand lens and note down different adaptations for pollination.
a. Maize flower (wind pollination) :-
• The flowers are unisexual and plant is monoecious. Male inflorescence is terminal tassel (panicle of spikeletes) while female inflorescence is compound spadix, borne axillary.
• Flowers are small inconspicuous, non-attractive without colour, odour and nectar. Perianth is reduced to two lodicules.
• Stamens are extrorse and exserted. Anthers are versatile which produce large number of tiny, light-weight, dry, dust like pollen grains with smooth exine.
• Gynoecium shows feathery or brush like stigma supported on a long style, coming out of the Perianth. The stigma is bifurcated. Styles and stigmas are bushy. Hence, in a single breeze, many flowers get pollinated if wind flows in a desired direction.
• In maize, flowers are unisexual and protandrous (stamens mature early), therefore, it is cross pollinated by the agency of wind (i.e. anemophilous).
Figure :-
b. Salvia (Insect pollination) :-
• Flowers are bisexual attractive and have bright coloured petals.
• The nectar and the nectar glands are present in flower and they are situated in such a way that when insect tries to reach the nectar glands, its wings and body parts will definitely touch the anther and stigma.
• Salvia shows bilipped corolla. The larger lip encloses style and stigma. There are two stamens located at the mouth of corolla tube.
• Stamens of Salvia show short filaments and elongated divaricate connective. The fertile anther lobe is at the tip of longer arm. The sterile anther lobe is situated at the tip of shorter arm of connective. When insect enters the flower it lodges on the lower sterile lobe, pushes it and as a result upper fertile lobe bends down. Nectar glands are located at the base of corolla tube.
• The gynoecium is made up of two carpels fused together, showing long style with bifid, hairy stigma. The stamens mature earlier than the carpels i.e. protandrous.
• Visitor insect lands on the lower lip of corolla and then pierces its proboscis right up to the nectar gland. In doing so, sterile anther lobes are pushed and fertile anther lobes bend down. dusting the body of insect with pollen grains are ornamented.
• When gynecium matures, style elongates and stigma bend down and thus gets positioned across the path of visitor insect.
• When pollen-laiden insect visits flower, the drooping stigma brushes the body of the insect and thus effects the pollination.
• The pollination in Salvia is cross pollination and effected by insects (i.e. entomophilous).
• The pollination mechanism in Salvia is called lever mechanism because the divaricate connective swings like a lever helping in pollination.
Figure :-
Figure and photographs :-
Questions
1. What is pollination?
Ans :- Transfer of pollen grains from anthers to stigma of a flower is called pollination.
2. Differentiate between self and cross pollination.
Ans :- Self-pollination occurs when pollen from a flower's own anthers fertilizes its own stigma. This often happens in flowers with both male and female reproductive parts. In contrast, cross-pollination involves pollen from one flower being transferred to the stigma of a different flower, typically of the same species. This process often requires external agents like insects or wind to facilitate the transfer.
3. Give reason as to why do maize as well as Saliva plants show cross pollination?
Ans :- Maize exhibits cross-pollination because it has unisexual flowers located on separate parts of the same plant, leading to cross-pollination between these parts. Salvia plants are cross-pollinated due to their dichogamous nature, with anthers maturing before the stigma, making cross-pollination necessary for fertilization.
4. Explain the term: a. Autogamy b. Allogamy c. Geitonogamy
Ans :- a. Autogamy refers to self-pollination, where pollen from a flower's own anthers fertilizes its own stigma.
b. Allogamy is cross-pollination, where pollen from one plant fertilizes the stigma of a different plant.
c. Geitonogamy occurs when pollen is transferred from one flower to the stigma of another flower on the same plant.
5. 'Pollination is pre-requisite for fertilization in flowering plants' - Explain/comment.
Ans :- In flowering plants (angiosperms), the male and female gametes are non-motile and are produced in different locations. Therefore, fertilization can only occur after pollination has transferred the pollen to the stigma, allowing the sperm to reach the ovule.
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