Topic 9.3: Growth in Plants

Essential Idea:  Plants adapt their growth to environmental conditions.
At SHS, Topic 9.3 is taught in the following class unit(s):

Statements & Objectives:

9.3.U1  Undifferentiated cells in the meristems of plants allow indeterminate growth.
  • Define indeterminate growth and totipotent.
  • State that most plants have indeterminate growth and have totipotent cells.
  • Define meristem.
  • Compare apical and lateral meristems.
9.3.U2  Mitosis and cell division in the shoot apex provide cells needed for extension of the stem and development of leaves.
  • Outline role of mitosis in the growth of stem and leaves while maintaining a meristem.
9.3.U3  Plant hormones control growth in the shot apex.
  • State the generic function of plant hormones.
  • Outline how auxin concentrations regulate plant growth in the root and stem.
  • Outline the role of auxin in apical dominance.
9.3.U4  Plant shoots response to the environment by tropisms.
  • State two external factors that control the growth of roots and stems.
  • Define tropism, phototropism and gravitropism.
9.3.U5  Auxin efflux pumps can set up concentration gradients of auxin in plants tissue.
  • Outline how PIN-transport proteins can direct direction of auxin flow.
  • Explain how auxin concentrations allow for phototropism in the stem.
  • Explain how auxin concentrations allow for gravitropism in the root.
9.3.U6  Auxin influences of cell growth rates by changing the pattern of gene expression.
  • State that auxin influences cell growth rates by changing gene expression.
9.3.A1  Micropropagation of plants using tissue from the shoot apex nutrient agar gels and growth hormones.
  • Define micropropagation.
  • Outline how changing auxin and cytokinin ratios can lead to development of roots or shoots from the same explant tissue.
9.3.A2  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.
  • Outline three roles of micropropagation of plant species. ​
9.3.NOS  Developments in scientific research follow improvements in analysis and eduction-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.
  • Outline role of microarrays in understanding role of plant hormones.
"When we try to pick out anything by itself, we find it hitched to everything else in the Universe." 
 John Muir,   1911