Are you what you eat? Physiological constraints on organismal stoichiometry in an elementally imbalanced world

The relative supply of energy and elements available to organisms in the environment has strong effects on their physiology, which, in turn, can alter important ecological processes. Here we consider how resource imbalances affect three basic physiological processes common to all organisms: elemental uptake, incorporation, and release. We review recent research that addresses these core issues (uptake, incorporation, and release) as they relate to elemental homeostasis in autotrophs and heterotrophs. Our review shows the importance that organism elemental homeostasis plays in determining the types of physiological processes used to acquire, assemble, store, and release biogenic elements, which are found in widely varying ratios in the environment. Future research should examine the degree to which organisms assess their internal nutritional composition and that of their food sources within a multiple elemental and biochemical context. Also, scientists should explore if and how the stoichiometry of cellular and molecular responses underlying nutrient (elemental and biochemical) acquisition, incorporation, and release depends on the nutritional composition of food resources. These types of queries will further improve our understanding of the physiological processing of primary elements involved in growth, reproduction, and maintenance of organisms.