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Rooting Out Better Yields

Root discovery may lead to crops that thrive in nutrient-poor soil.
The left panel shows a root cross-section from a plant grown under nonstress conditions. The right panel shows a comparable root from a plant grown under phosphorus-depleted conditions, highlighting how secondary growth of roots is suppressed under phosph

The left panel shows a root cross-section from a plant grown under nonstress conditions. The right panel shows a comparable root from a plant grown under phosphorus-depleted conditions, highlighting how secondary growth of roots is suppressed under phosph

In a discovery that is likely to lead to increased crop productivity in nutrient-poor soils, researchers in the college found that bean plants that suppress secondary root growth in favor of boosting primary root growth forage greater soil volume to acquire phosphorus.

The increase in the length of the root is referred to as primary growth, while secondary growth is the increase in thickness or girth of the root. Because root growth confers a metabolic cost to the plant, bean plants growing in phosphorus-depleted soils that send out longer, thinner roots have an advantage in exploring a greater volume of soil and acquiring more phosphorus.

"As a natural strategy for plants to deal with phosphorus stress, it's a winner," said lead researcher Christopher Strock, a plant biology doctoral student. "That's important because most soils throughout the world are phosphorus deficient, and root traits that improve phosphorus acquisition benefit farmers in developing countries who do not have access to phosphate fertilizers."

Researchers used the common bean as a model for this research because it is one of the most fundamental crops contributing to food security, with greater volume for direct human consumption than any other grain legume. It is especially important throughout the developing world in sub-Saharan Africa and Central and South America, where people don't have wide access to animal protein.

Despite the significance of this crop, yields throughout much of the world are constrained by soils that are acidic and extremely depleted in phosphate, one of the main nutrients that plants need to grow.

"If we can identify root traits that improve foraging efficiency, we can develop new cultivars that have greater ability to take up phosphorus, and have improved yields in these environments," said Strock. He was advised by University Distinguished Professor of Plant Science Jonathan Lynch, whose research group collaborates directly with plant breeders at the U.S. Department of Agriculture and agricultural centers in Colombia, Honduras, Mozambique, Zambia, and Malawi.

In conducting the study, which was published in Plant Physiology, plants were grown in both greenhouse conditions--at Penn State's University Park campus--and in select fields at the University's Russell E. Larson Agricultural Research Center at Rock Springs.

--Jeff Mulhollem