Nutrient Foraging in Plants

by

Angela Hodge

• LAST REVIEWED: 12 August 2022
• LAST MODIFIED: 24 July 2013
• DOI: 10.1093/obo/9780199830060-0114

Introduction

Soils are physically the most complex of all environments, comprising solid, liquid, and gas phases, and vary considerably in their ability to supply nutrients. Plant roots acquire nutrients from the solution (liquid) phase but the equilibrium among these different phases controls the nutrients available, which also depends on the nutrient in question. Consequently, nutrients in soil are distributed in a non-uniform or heterogeneous manner. This heterogeneity occurs at a range of scales including those relevant to plant roots. Roots therefore have to respond to this heterogeneity or “patchiness” in resource supply in order to acquire nutrients essential for growth and normal metabolic function. This is aided by the modular structure of the root system, which enables flexibility in the spatial configuration of the root system (i.e., root system architecture) and plasticity in physiological and morphological responses. Most early studies focused on measuring the type and size of the observed response to nutrient heterogeneity with little consideration as to what this meant in terms of actual nutrient acquisition. Consequently, there is a vast literature on the various root responses by different plant species conducted under a wide range of environmental conditions but from which comparisons are difficult to make and the importance of the response obscure. More recently, investigative studies have moved toward more emphasis being placed upon the functional importance of the root response in terms of nutrient acquisition and, importantly, the environmental context in which that response is produced. This is an important shift in emphasis, as responses observed under ideal and often controlled conditions may not necessarily relate to those that actually occur in the natural environment. The majority of plant species also have additional means to forage their environment for resources including the formation of mycorrhizal symbiotic associations, while a smaller number of plant species can form symbiotic associations with nitrogen-fixing prokaryotes. Roots can also release substances into the soil that have a specific role to play in nutrient acquisition. Although plants can also forage for resources aboveground, resulting in plasticity in aboveground structures, the majority of plants acquire their nutrients from the soil environment: hence, this is the main focus of the text and resulting bibliography.

General Overviews

Nutrient foraging in plants is a multidisciplinary field drawing on ecology, biology, and more recently, molecular biology. There are, however, few books (other than edited special volumes) devoted solely to this topic but, rather, the subject matter tends to be covered in the majority of plant science textbooks in a general manner. A more comprehensive coverage of the topic is provided in Fitter and Hay 2002 and Lambers, et al. 2008. Fitter and Hay 2002 is an inexpensive textbook that includes a chapter on mineral nutrients under which the causes of soil heterogeneity, various roots responses, and symbiotic associations are all introduced, and is designed as a companion for undergraduate teaching; Lambers, et al. 2008 similarly covers these areas in a more expansive way with specific chapters devoted to these topics. A number of reviews in specialized journals or as chapters in books have been published on this topic, including: how roots respond to heterogeneity in nutrient supply (Hodge 2004) or nutrients and water (Huang and Eissenstat 2000), while Cahill and McNickle 2011 considers the behavioral ecology of nutrient foraging by plants. Caldwell and Pearcy 1994 is an edited special volume of chapters by notable ecologists that provides a more in-depth analysis of the impact of environmental heterogeneity both above and belowground on plants. Hutchings, et al. 2000 is also an edited special volume produced from the 40th Symposium of the British Ecological Society on environmental heterogeneity but is broader in its scope, while de Kroon, et al. 2009 considers plant foraging behavior both above and belowground.

• Cahill, James F., and Gordon G. McNickle. 2011. The behavioural ecology of nutrient foraging by plants. Annual Review of Ecology, Evolution, and Systematics 42:289–311.

  DOI: 10.1146/annurev-ecolsys-102710-145006

  Considers how nutrient and non-nutrient cues in soil may influence root responses to their environment and differences that occur among plant species. The article also suggests methods used to model animal behavior may prove fruitful to explain behavioral responses by plants.

• Caldwell, Martyn M., and Robert W. Pearcy, eds. 1994. Exploitation of environmental heterogeneity of plants: Ecophysiological processes above- and belowground. San Diego, CA: Academic Press.

  Comprises chapters written by notable ecologists and provides an excellent overview of environmental heterogeneity, both above- and belowground, and its impact upon plants. Topics include patterns and scale of heterogeneity, plant plasticity, and root architecture.

• de Kroon, Hans, Eric J. Visser, Heidrun Humber, Liesje Mommer, and Michael J. Hutchings. 2009. A modular concept of plant foraging behaviour: The interplay between local responses and systemic control. Plant, Cell and Environment 32:704–712.

  DOI: 10.1111/j.1365-3040.2009.01936.x

  Considers plant foraging to heterogeneous environments from signal perception through to the plant response using examples from both above- and belowground.

• Fitter, Alastair H., and Robert K. M. Hay. 2002. Environmental physiology of plants. 3d ed. London: Academic Press.

  An introductory text to the topic, aimed at an undergraduate audience. Considers the acquisition of resources by plants, including light and water as well as nutrients in the context of differing environmental conditions. An essential read for those new to the field.

• Hodge, Angela. 2004. The plastic plant: Root responses to heterogeneous supplies of nutrients. New Phytologist 162:9–24.

  DOI: 10.1111/j.1469-8137.2004.01015.x

  Review of the literature on how plants respond to nutrient heterogeneity: including morphological and physiological plasticity, root demography, and associations with microorganisms. Emphasis is placed on understanding the observed response in the context in which the response is observed.

• Huang, Bingru, and David M. Eissenstat. 2000. Root plasticity in exploiting water and nutrient heterogeneity. In Plant-environment interactions. 2d ed. Edited by Robert E. Wilkinson, 111–132. New York: Marcel Dekker.

  DOI: 10.1201/9780824746568

  Extensive review of the literature on how roots respond to heterogeneity in both nutrient and water supply.

• Hutchings, Michael J., Elizabeth A. John, and Alan J. A. Stewart, eds. 2000. The ecological consequences of environmental heterogeneity. Oxford: Blackwell.

  A collection of nineteen papers by invited authors from the 40th Symposium of the British Ecological Society held at the University of Sussex, 23–25 March 1999. Most of the chapters have a plant-related aspect, although animals and insect interactions are also included.

• Lambers, Hans, F. Stuart Chapin III, and Thijs L. Pons. 2008. Plant physiological ecology. 2d ed. New York: Springer.

  DOI: 10.1007/978-0-387-78341-3

  Introductory text containing several chapters devoted to various nutrient-acquisition mechanisms by plants including mineral nutrition, symbiotic associations, and interactions among plants. An ideal text for both undergraduate and graduate level.