Pre-fertilisation — Part 2: Pollination, outbreeding devices and artificial hybridisation: visual lesson, ISC Class 12 Biology

Lesson

Pollination

Part 2 — getting the pollen to the stigma, and the controls that decide which pollen succeeds.

In this lesson you will

Distinguish autogamy, chasmogamy, cleistogamy, geitonogamy and xenogamy
Relate floral adaptations to wind, water and insect pollination
Explain outbreeding devices and pollen–pistil interaction
Describe emasculation and bagging in artificial hybridisation

Diagram

Kinds of pollination

Autogamy: pollen to the stigma of the same flower. Geitonogamy: to another flower of the same plant (functionally cross-pollination, but genetically like autogamy). Xenogamy: to the stigma of a different plant, bringing genetically different pollen.

Concept

Chasmogamy and cleistogamy

Chasmogamous flowers open, exposing anthers and stigma. Cleistogamous flowers never open; anthers and stigma lie close together, so pollen sheds directly on the stigma.

Table comparing chasmogamous and cleistogamous flowers
Feature	Chasmogamous	Cleistogamous
Flower opens?	Yes	No
Pollination	Self or cross	Autogamy only
Seed set	Depends on agents	Assured, even without pollinators
Examples	Most flowers	Viola (pansy), Oxalis, Commelina (which also bear chasmogamous flowers)

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