School of Life Sciences | Ask A Biologist

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Getting to the Root of Plant Biology

By Gail Maiorana
Photography by 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. Associate 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:

ERAS PERIODS     (and Epochs) AGE (Beginning)
CENOZOIC QUATERNARY Holocene (Recent)
Pleistocene
10000 years
1.8 million years
CENOZOIC TERTIARY Pliocene
Miocene
Oligocene
Eocene
Palaeocene
5 million years
24 million years
34 million years
55 million years
65million years
MESOZOIC CRETACEOUS
JURASSIC
TRIASSIC
141 million years
205 million years
215 million years
PALEOZOIC PERMIAN
CARBONIFEROUS
DEVONIAN
SILURIAN
ORDOVICIAN
CAMBRIAN
298 million years
354 million years
410 million years
434 million years
490 million years
545 million years
PRECAMBRIAN PROTEROZOIC
ARCHAEOZOIC
~2500 million years
~4600 million years

 

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

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

Kathleen Pigg

Kathleen Pigg with fossilized plant sample.

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Kathleen Pigg

Kathleen Pigg with fossilized plant sample.

Share to Google Classroom

Be part of Ask A Biologist

by volunteering, or simply sending us feedback on the site. Scientists, teachers, writers, illustrators, and translators are all important to the program. If you are interested in helping with the website we have a Volunteer page to get the process started.