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9.3 Growth in plants

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Description

Nature of science:
Developments in scientific research follow improvements in analysis and deduction—improvements in analytical techniques allowing the detection of trace amounts of substances has led to advances in the understanding of plant hormones and their effect on gene expression. (1.8)
Understandings:
  • Undifferentiated cells in the meristems of plants allow indeterminate growth.
  • Mitosis and cell division in the shoot apex provide cells needed for extension of the stem and development of leaves.
  • Plant hormones control growth in the shoot apex.
  • Plant shoots respond to the environment by tropisms.
  • Auxin efflux pumps can set up concentration gradients of auxin in plant tissue.
  • Auxin influences cell growth rates by changing the pattern of gene expression.
Applications and skills:
  • Application: Micropropagation of plants using tissue from the shoot apex, nutrient agar gels and growth hormones.
  • Application: Use of micropropagation for rapid bulking up of new varieties, production of virus-free strains of existing varieties and propagation of orchids and other rare species.
Guidance:
  • Auxin is the only named hormone that is expected.
 Theory of knowledge:
  • Plants communicate chemically both internally and externally. To what extent can plants be said to have language?
Utilization:
  • Micropropagation is used for rapid bulking up of new varieties of plant.
Syllabus and cross-curricular links:
Biology
Topic 3.5 Genetic modification and biotechnology

Aims:
  • Aim 6: Investigations into tropisms could be carried out.

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