DP Biology (last assessment 2024)
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9.4 Reproduction in plants

Description

Nature of science:
Paradigm shift—more than 85% of the world’s 250,000 species of flowering plant depend on pollinators for reproduction. This knowledge has led to protecting entire ecosystems rather than individual species. (2.3)Understandings:

  • Flowering involves a change in gene expression in the shoot apex.
  • The switch to flowering is a response to the length of light and dark periods in many plants.
  • Success in plant reproduction depends on pollination, fertilization and seed dispersal.
  • Most flowering plants use mutualistic relationships with pollinators in sexual reproduction.

Applications and skills:

  • Application: Methods used to induce short-day plants to flower out of season.
  • Skill: Drawing internal structure of seeds.
  • Skill: Drawing of half-views of animal-pollinated flowers.
  • Skill: Design of experiments to test hypotheses about factors affecting germination.

Guidance:

  • Students should understand the differences between pollination, fertilization and seed dispersal but are not required to know the details of each process.
  • Flowering in so-called short-day plants such as chrysanthemums, is stimulated by long nights rather than short days.

Utilization:

  • The University of Göttingen, in Germany, conducted an extensive review of scientific studies from 200 countries for 115 of the leading global crops in 2005. They found that 87 of the crop plants depend to some degree upon animal pollination, including bees. This accounts for one-third of crop production globally.

 

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