Pollination and Its Agents
Pollination is the transfer of pollen grains from the anther to the stigma of a flower, enabling pollen-pistil interaction and later fertilisation.
In one line: Auto is same flower, geito is neighbour flower, xeno is another plant.
Concept Practice Coming SoonUnderstand it
- Pollination may occur within the same flower, between flowers of the same plant, or between flowers of different plants of the same species.
- Autogamy maintains genetic similarity, geitonogamy involves two flowers on the same plant, and xenogamy introduces genetic variation because pollen comes from a different plant.
- Agents may be abiotic, such as wind and water, or biotic, such as insects, birds, and bats.
- Flowers show adaptations suited to their agents: wind-pollinated flowers often produce abundant light pollen, while insect-pollinated flowers may have colour, scent, nectar, and sticky pollen.
- Exams often test outbreeding devices and pollen-pistil compatibility.
Example
Rule to remember
Classification rule: autogamy means same flower, geitonogamy means different flower on the same plant, and xenogamy means different plant of the same species.
See it worked out
Follow the example line by line, then use the same method on new questions.
Worked example
- 1If pollen moves from one flower of a plant to another flower on the same plant, classify it as geitonogamy.
- 2It is functionally cross-transfer but genetically close to self-pollination.
Method you can reuse
- 1Identify the source flower of pollen.
- 2Check whether the stigma belongs to the same flower, another flower on the same plant, or another plant.
- 3Classify as autogamy, geitonogamy, or xenogamy.
- 4Name the likely agent if adaptations are given.
- 5Add genetic consequence and compatibility if the question asks for significance.
Visual tip
A flow chart can show pollen transfer paths for autogamy, geitonogamy, and xenogamy. For adaptations, note feathery stigma in wind pollination and sticky pollen in insect pollination.
Check yourself
Answer the question in your head before opening the answer.
Try it yourself
Why does xenogamy usually increase genetic variation?
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Common wrong answer
A common wrong answer is calling every transfer between two flowers cross-pollination with variation. Geitonogamy does not introduce the same level of variation as xenogamy.
Don't mix this up
Exam tip
Write it in the exam
Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.
How CBSE asks it
Answer plan
- 1
Enough for 1 mark
Pollination is the transfer of pollen grains from the anther to the stigma of a flower, enabling pollen-pistil interaction and later fertilisation.
- 2
Add for 2 marks
Example: Maize is wind-pollinated and produces large quantities of pollen, while many insect-pollinated flowers have bright petals and nectar to attract visitors that carry pollen.
- 3
Add for 3 marks
Pollination may occur within the same flower, between flowers of the same plant, or between flowers of different plants of the same species.
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