Stress and the Coarse Control of Growth and Root-Shoot Partitioning in Herbaceous Plants

From a priori reasoning and the integration of many experimental observations, a new, ecologically hased scheme is derived to explain the way in which plant growth and resource partitioning is broadly controlled by external environmental conditions. We suggest that the partitioning of resources between belowand above-ground plant parts is jointly controlled by the absolute amounts of belowand above-ground environmental stress, by the below-/above-ground environmental stress ratio, and by the growth potential of the species itself. Under particular conditions, any shortfall from the species's innate growth potential may be explained in terms of the total of, and ratio between, belowand above-ground stress. Hyperbolic relationships link the variables under consideration. Though the equations ultimately derived are not open to straightforward experimental validation, they are likely to be of value in predicting 'perceived stress' both aboveand below-ground, as an experiment involving three contrasted species indicates.