Study of flowers adapted to pollination by different pollinating agencies (Wind Insects)
Practical Notebook Biology Standard XII
Study of flowers
Biology
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Practical Notebook
Standard XII
Class-12th
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4. Study of flowers adapted to pollination by different pollinating agencies (Wind and Insects)
Aim:
To study different adaptations shown by flower Requirements: Flowers of grass, maize, Salvia, Ocimum, Brassica, etc, forceps, hand lens, slide, etc. Observe the given flower with the help of a hand lens and note down different adaptations for pollination.
Maize flour (wind pollination):
The flowers are unisexual and the plant is monoecious inflorescence terminal (panicle of spikelets) while the female inflorescence is compound spadix, borne axillary. Flowers are small inconspicuous, non - attractive without color, odor, and nectar. The perianth is reduced to two lodicules. Stamens are extrorse and exserted. Anthers are versatile and produce a large number of tiny, lightweight, dry, dust-like pollen grains with smooth exits. Gynoecium shows a 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 the wind flows in the 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: Fig. Anemophily in maize Maize plant, B: paired spikelet, C:
open spikelet b. Salvia (Insect Pollination):
Flowers are bisexual and attractive and have bright-colored petals. The nectar and the nectar glands are present in the flower and they are situated in such a way that when the insect tries to reach the nectar glands, their wings and body parts will definitely touch the anther and stigma. in spadix of maize. V •
• Salvia shows blipped corolla. The larger lip-style stigma. There are two stamens located at the mouth of the corolla tube. Stamens of Salvia show short filaments and elongated divaricate connectives. The fertile lobe is at the tip of the long arm. The sterile anther lobe is situated at the tip of the shorter arm of the connective. When the insect enters the flower it lodges on the lower sterile lobe, pushes it and as a result, the upper fertile lobe bends down. Nectar glands are located at the base of the corolla tube The gynoecium is made up of two carpels fused together, showing a long style with a bifid, hary stigma. The stamens mature earlier than the carpels i.e. protandrous.
The visitor insect lands on the lower lip of the 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 insects with pollen grains ornamented. When gynecium matures, style elongates and the stigma bends down and thus gets positioned across the path of visitor insect.
When a pollen-laden insect visits a flower, the drooping stigma brushes the body of the insect and thus affects pollination. The pollination in Salvia is cross-pollination and affected by insects (i.e. entomophilous) The pollination mechanism in Salvia is called the lever mechanism because the divaricate connective swings like a lever help in pollination.
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