Exudation of metabolites from roots helps plants to adapt to a wide range of habitats by facilitating resource foraging and by promoting plant-organismal interactions. Most of these functions are facilitated by small molecules that vary in their biological activities. Hence a robust understanding about the changes in the composition of exudates and their rate of release from roots under different environmental stresses is vital to accurately define the processes operating at the plant-soil interface. Even though plants are known to exude an array of small molecules under environmental stress, the ability of plants to tailor the composition of metabolites in roots and exudates so as to increase the uptake of specific forms of nutrient is less known.
Results/Conclusions
We studied the changes in composition and rate of exudation of metabolites from roots of Andropogon spp. exposed to different forms of phosphorous (P) fertilization. Plants were initially grown with available forms of nutrients and were transferred to different nutrient treatments of varying P bioavailability. There were significant and consistent shifts in the metabolic profiles in roots within 36 hours after exposure to various nutrient treatments. Compared to the full-nutrient control, the root exudation was higher in plants that were exposed to lower phosphorous treatments. Within the P deficient treatments, a supply of lower bioavailable form of P facilitated a greater exudation of metabolites compared to treatments that completely lacked P. The exudate profile differed significantly between various P treatments with malic and citric acid more abundant with complete absence of P. The exudate profile from the lower-bioavailable P treatments were uniquely higher in metabolites that have higher chelation capacity, and were efficient in mobilizing P from the less bioavailable forms. Our study highlights the ability of roots to sense the bioavailability of nutrients, and tailor the exudate profile so to increase its resource foraging capacity.