Patience with Peas

Archaeological folklore is enhanced by fanciful yarns about an ancient Pharaoh's tomb containing dried seeds that sprouted when planted and watered--thousands of years after they were first interred. The truth of the tale has yet to be proved, but common chickweed seeds have germinated after lying dormant for more than three decades; Oriental lotus seeds, after about 1,000 years. Such long survival, despite heat, cold or even radiation, is managed by the seed when it enters anabiosis --a state of suspended animation in which its metabolism stops, its skin hardens and thickens, and its water content falls to about 10% of normal.

Fascinated by the dormant seed, botanists have long been frustrated in their efforts to see or photograph it clearly. Preparing slides for microscopic inspection usually necessitated the use of liquid solutions that immediately revived anabiotic cells, altering the dormant structures. Now, because of the perseverance of German Botanist Ernst Perner, several theories about anabiosis have finally been confirmed. By using dry osmic-acid vapors to fix and stain his slides, Perner has successfully photographed anabiotic pea cells with an electron microscope.

Strength & Insulation. One of his remarkable pictures clearly shows that protein molecules eventually used by the developing plant are rearranged during anabiosis into physiologically inactive crystals--a structure that scientists had suspected but never observed. Other photographs reveal the protective shift of tiny sacs of fluid called vacuoles, which are distributed through the cytoplasm of a young, active cell. During anabiosis, they line up in rows against the inner cell wall, probably to strengthen and insulate it against long periods of heat or cold, and to facilitate the rapid absorption of water when it becomes available.

Perner's work disposes of a theory that the high stresses of shrinkage damage some cell membranes, which are somehow repaired when the cell returns to normal activity. His photographs show that during anabiosis membranes contract in intricate folds within the shrunken cell.

Perner was not the first to use osmic-acid vapor. Others had tried it without success. Undismayed when exposing pea cells to the vapor for two months failed to produce results, Perner doggedly lengthened the experiment to nine months and finally got his pictures. "My greatest achievement," he says, "was that I was patient."

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