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D3.1.10—Promoting cross-pollination

Cross-pollination is promoted by timing differences, separation of sex organs, pollinator movement, wind transfer and self-incompatibility mechanisms in flowering plants.

Syllabus
First assessment 2025
Objective
D3.1.10
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1A
Typical marks1

Common command terms

  • Outline

Recent exam appearances

November 2025Paper1A ["HL"] · TZ329[ 1 ]D3.1.10—Promoting cross-pollination

Coverage 2025–2025 · Updated 16 Jul 2026

Plants Promote Cross-Pollination before Pollen Reaches the Stigma

Cross-pollination transfers pollen from an anther on one plant to a stigma on a different plant of the same species, increasing opportunities to combine different parental alleles.

Mechanism How self-pollination is reduced
anthers and stigma mature at different times self-pollen is absent when the stigma is receptive
anthers and stigma are at different heights a visitor contacts them on different body regions
separate male and female flowers or plants one flower or plant cannot supply both gametes
pollinator movement or wind carries pollen between individuals

Cross-pollination can increase genetic variation, but it also depends on pollen reaching a compatible plant. The mechanism reduces selfing; it does not ensure successful fertilization.

Flowering-Plant Reproduction Links Transfer, Recognition and Establishment

pollen production → transfer to stigma → compatibility check → pollen-tube delivery → gamete fusion in ovule → seed and fruit formation → dispersal → dormancy release → germination and reserve mobilization

Transition problem Adaptation
pollen must reach a conspecific stigma pollinator attraction, wind transfer and flower geometry
selfing can reduce variation timing, spatial separation, separate sexes and self-incompatibility
offspring compete with parent seed dispersal
growth begins in poor conditions dormancy and environmental germination requirements

Pollination is gamete delivery, fertilization is nuclear fusion, and dispersal moves the resulting seed. Keep those transitions separate while explaining how each supports successful outcrossing and establishment.

Promoting cross-pollination

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Outline how cross-pollination can be promoted by flowering plants.

Concept essentials

  • Different maturation times of anthers and stigmas can reduce self-pollination.
  • Separate male and female plants strongly promote cross-pollination.
  • Self-incompatibility prevents successful fertilization by self pollen.