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Germplasm
| Article
# : |
10918 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
7 / 1986 |
2,376 Words |
| Author
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Steven C. Witt
Steven C. Witt, biologist and science writer, is the author
of
two books, Biotechnology and Genetic Diversity and Genetic
Engineering of Plants, and numerous articles on agricultural
genetics. |
Ask most agricultural scientists to list our natural resources and they will probably answer "soil, water, and air." Yet there is a fourth resource that for many years has received scant attention. It is germplasm, the natural resource which makes Earth unique, insofar as we know, in our solar system.
Whether it's strictly the product of nature, the work of a skilled plant breeder, or the result of a molecular biologist's gene-splicing experiment sitting in a petri dish, if it contains "the stuff of life," it can be called germplasm.
Germplasm is one of those venerable terms that scientists have never clearly defined, yet can't replace. In essence, germplasm in the material that controls heredity: the sum of the qualities and potentialities genetically derived from one's ancestors. Germplasm controls the process of inheritance and genes are part of that process.
Germplasm consists of combinations of genes working in concert. Genes are microscopic chemical messages, written in a molecular alphabet called DNA, that contain the instructions for building every part and characteristic of every living thing--the smell of a geranium, the shape of a pig's nose, the blush of a peach.
So what, other than genes, does germplasm contain? Scientists don't exactly know. "Many of us [geneticists] would love to find out exactly what and where are the raw materials that 'cause' evolutionary changes," says Dr. Michael Freeling, University of California, Berkeley molecular geneticist. Until they do find out "exactly," the easiest way to remember the difference between genes and germplasm is this: genes are the blueprints of life and germplasm is the "stuff of life"--genes plus whatever additional materials control inheritance.
Because scientists cannot tell precisely what germplasm is, it is not surprising that no one knows quite how to measure it. It does not come in barrels, ounces, karats, tons or wheelbarrows; it has no standard unit of measurement. Most often it comes in seeds. But while a simple teaspoon can hold more than 100,000 petunia seeds, it only holds a few corn seeds or kernels.
Plant germplasm also comes in the form of cuttings--whole branches or shoots taken from a plant or tree; or small pieces of a plant leaf, stem, or root--pieces of plant tissue; or a slimy lump of plant cells the size of your thumbnail, called a "callus." Germplasm
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