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Udderly Fantastic: Mutant Plants a High Source of Calcium

By Lupe Chavez
September 14, 2001

A mutant plant that could provide more calcium to daily meals has been identified by an Agricultural Research Service scientist in Houston. This breakthrough will help scientists unlock more nutrients stored in plants.

Some commonly consumed plant leaves, like spinach, have high amounts of calcium stored in cellular crystals as calcium oxalate. But humans are unable to break down the crystals, and the calcium goes to waste. However, Paul Nakata, a plant physiologist with the ARS Children's Nutrition Research Center at the Baylor College of Medicine, has made major discoveries about the formation of calcium oxalate crystals. Nakata is continuing research on his findings published in the journal Plant Physiology.

In his ARS-funded study, Nakata isolated mutants of Medicago truncatula, a legume similar to alfalfa. In the laboratory, various M. truncatula plants displayed different amounts of crystal formation. Nakata compared the plants to each other in an effort to find which mutations would yield the most "free" calcium. One plant formed very minute levels of crystals, leaving calcium in a potentially usable state.

Understanding the mechanisms that form these crystals could improve human nutrition. Plants that take up calcium from the soil could potentially provide consumers with more usable calcium, the key ingredient for bone growth and development in children and adults.

The calcium-yielding mutant is undergoing further tests to determine if it is a viable crop plant. Nakata is currently cataloging its characteristics. He is checking to see if the mutation affected the plant's growth, and its vulnerability to pathogens, fungi, insects, temperature and other environmental conditions.

ARS researchers also made another discovery while analyzing the mutated plants. They were able to find mutations that created different crystalline shapes, something that may have occurred naturally in the evolution of plant cells. The calcium oxalate crystal has a coffin-shaped configuration; however, scientists saw that some mutant plants had square, rectangular, or diamond-shaped crystals. Some of these crystal shapes match those present in other legumes.

ARS is the U.S. Department of Agriculture's chief scientific research agency.