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.