Getting to the Root of Plant Biology
Written by: Gail Maiorana
Photographer: ASU Research Magazine

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CAT scan: computerized axial tomography; this process makes detailed pictures of cross-sections of the body that are 100 times clearer than a common x-ray... more

Fossilized: preserved in an identifiable form.

Petrified: converted into stone or stony substance.

fossilised acornsSome people gaze out at the landscape and see plants. Professor Kathleen Pigg of Arizona State University sees the latest chapter in a long story.

Human beings weren't around for the early episodes in this long story starring plants. So Pigg studies fossilized plants to learn more about the plants that grow today. She can find out what happened to one type of plant during millions or even hundreds of millions of years.

Plants became fossilized in different ways. Pigg knows that water with minerals in it covered some plants in the Triassic, Eocene and other eras. Volcanic lava provided some of the minerals. The minerals hardened like rock around each plant cell so that the cell pattern was "petrified." Usually only a piece of the plant, such as a cone, leaf or stem, got petrified.

Pigg has traveled to many places to collect petrified plant parts. Back in her laboratory at ASU, she uses a rock saw to cut through the hardened minerals at different angles . Some pieces get cut into very thin slices, like a loaf of bread, and then examined under a microscope. Pigg uses a computer to take a picture of each thin slice, and the computer puts the pictures of the pieces together. She says it's like doing a CAT scan in a hospital because it lets her see in 3D.

Other people collect preserved plants to make jewelry. Petrified wood, like the wood from the Petrified Forest in Arizona, is often made into jewelry. Fossil resin known as amber is popular, too. Fossilized plants also can help large companies find oil and coal.

Pigg really likes to study the petrified plants that changed a lot in later years or that didn't survive. She likes to imagine what the plants were like when they lived. She knows that if she pays close attention, Mother Nature will explain what happened in the plant story.


The Geological Time Scale:


PERIODS (and Epochs) AGE (Beginning)
    PLEISTOCENE 1.8 million years
  NEOGENE PLIOCENE 5 million years
    MIOCENE 24 million years
  PALEOGENE OLIGOCENE 34 million years
    EOCENE 55 million years
    PALEOCENE 65 million years
MESOZOIC CRETACEOUS   141 million years
  JURASSIC   205 million years
  TRIASSIC   215 million years
PALEOZOIC PERMIAN   298 million years
  CARBONIFEROUS   354 million years
  DEVONIAN   410 million years
  SILURIAN   434 million years
  ORDOVICIAN   490 million years
  CAMBRIAN   545 million years
PRECAMBRIAN PROTEROZOIC   ~2500 million years
  ARCHAEOZOIC   ~4600 million years


For further reading, Pigg recommends The Evolution of Plants and Flowers by BarryThomas (St. MartinĂ s Press: New York, 1991) or National Geographic magazine.

To view researchers at work in the field, click here.

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Bibliographic details:

  • Article: Getting to the Root of Plant Biology
  • Author(s): Gail Maiorana
  • Publisher: temp
  • Site name: ASU - Ask A Biologist
  • Date published: November 6, 2009
  • Date accessed: March 19, 2018
  • Link:

APA Style

Gail Maiorana. (2009, November 06). Getting to the Root of Plant Biology. ASU - Ask A Biologist. Retrieved March 19, 2018 from

American Psychological Association. For more info, see

Chicago Manual of Style

Gail Maiorana. "Getting to the Root of Plant Biology". ASU - Ask A Biologist. 06 November, 2009.

MLA 2017 Style

Gail Maiorana. "Getting to the Root of Plant Biology". ASU - Ask A Biologist. 06 Nov 2009. ASU - Ask A Biologist, Web. 19 Mar 2018.

Modern Language Association, 7th Ed. For more info, see
Kathleen Pigg Arizona State University

Kathleen Pigg with fossilized plant sample.

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