Root Discovery May Lead to Crops That Need Less Fertilizer

Bean plants that suppress secondary root growth in favor of boosting primary root growth forage greater soil volume to acquire phosphorus, according to Penn State researchers, who say their recent findings have implications for plant breeders and improving crop productivity in nutrient-poor soils.

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 in the College of Agricultural Sciences. "That's important because most soils throughout the world are phosphorus deficient, and root traits that improve phosphorus acquisition not only can help to improve the efficiency of fertilizer uptake for farmers here in the U.S., but also 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. In those regions, beans are a primary source of protein and nutrition.

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Image: Research team members are shown here excavating common bean plant roots during the greenhouse experiment. Using laser ablation tomography, they were then able to section and measure root anatomy in hundreds of samples. (Credit: Jonathan Lynch Lab/Penn State)