Plastic plants and patchy soils.

Abstract

Soil nutrients are distributed in a non-uniform or 'patchy' manner. It is well established that the modular nature of root systems allows them to show both morphological and/or physiological plasticity upon encountering nutrient-rich patches. These plastic responses are widely believed to be foraging mechanisms by the plant to enhance nutrient resource capture. Although morphological plasticity has traditionally been viewed as the more expensive option as it requires new root construction, more recent evidence suggests this may not necessarily be the case. Moreover, plants may be able to recapture most of the initial outlay involved in new root construction, again lowering the overall cost to the plant. Under natural conditions the roots of most plant species have an additional nutrient acquisition mechanism namely mycorrhizal symbiosis. However, the impact of these important symbiotic associations upon the host plant's response to nutrient patches has received relatively little attention. The mycorrhizal fungal symbiont should, in theory, be better able to compete directly with the rest of the microbial community for the nutrients in the patch. This could potentially be important to the host plant, as generally, root proliferation responses are more important for interspecific plant, than plant-microbial, competition.