Course Content
Biology Form 3
About Lesson

Features and Mechanisms that Hinder Self-pollination and Self-fertilisation

(a) Hermaphrodites and Monoecious Plants

(b) Protandry and Protogyny

(c) Self-sterility or incompatibility

(d) Heterostyly


Dioecism and Monoecism

Monoecism – where male and female flowers are on the same plant but in different parts.

Dioecism – where male and female flowers are on different plants.

The flowers have features that attract insects.


Protandry and Protogyny

Protandry – stamens mature first.

Stamens mature and pollen grains are shed off before the stigma matures.

Protogyny – pistils mature first.

Stigma matures earlier before the stamens ripen to release the pollen grains. 


Self-sterility or incompatibility

Pollen grains from the anthers cannot grow on the stigma of the same flower or plant.



The diagram below represents an experimental set-up used by students to investigate a certain process.

Flower Q produced seeds while Flower P did not. Account for these results. (2 marks)

  • Due to self-sterility/incompatibility;
  • Flower Q undergoes cross-pollination;



Different lengths of style in flowers.

Styles at different heights with the filaments. Hence, the pollen grains cannot land on the same stigma.

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