Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
, 166 (2), 509-17

Root Nutrient Foraging

Affiliations
Review

Root Nutrient Foraging

Ricardo F H Giehl et al. Plant Physiol.

Abstract

During a plant's lifecycle, the availability of nutrients in the soil is mostly heterogeneous in space and time. Plants are able to adapt to nutrient shortage or localized nutrient availability by altering their root system architecture to efficiently explore soil zones containing the limited nutrient. It has been shown that the deficiency of different nutrients induces root architectural and morphological changes that are, at least to some extent, nutrient specific. Here, we highlight what is known about the importance of individual root system components for nutrient acquisition and how developmental and physiological responses can be coupled to increase nutrient foraging by roots. In addition, we review prominent molecular mechanisms involved in altering the root system in response to local nutrient availability or to the plant's nutritional status.

Figures

Figure 1.
Figure 1.
Nutrient gradients and the formation of nutrient patches in soils. Many processes are involved in the formation of vertical gradients in soils, such as nutrient uptake, nutrient leaching, biological cycling, and movement of water. An increased nutrient uptake from the superficial soil strata decreases nutrient concentrations in this soil layer. In addition, concentrations of mobile nutrients may decrease as they move downward and become prone to leaching. Biological nutrient cycling acts in an opposite way to leaching, because it recovers nutrients from deeper soil profiles and brings them back to the surface in the form of litter deposits. In addition, the increased topsoil deposition of organic matter (O.M.) increases, for example, the availability of P and organic nitrogen (org. N) in this soil layer. Some nutrients, such as Ca and Mg, do not generally show strong vertical gradients in most soils. At a smaller scale, the intense uptake of immobile (purple) and mobile (green) nutrients can result in the formation of depletion zones for the immobile nutrient at the root-soil interface. Furthermore, localized organic matter depositions associated with intense microbial activity can result in increased availability of the immobile nutrient iron (Fe) within relatively localized patches in soils. PO4, Phosphate; SO42−, sulfate; K+, potassium ion; Mn2+, manganese ion; Na+, sodium ion.
Figure 2.
Figure 2.
RSA responses to nitrogen availability. A, Excess supply of ammonium (++NH4+) or nitrate (++NO3) leads to a systemic repression of root growth, where high ammonium inhibits mostly PR elongation and high nitrate represses mainly LR elongation. Compared with sufficient nitrogen supply, mild nitrogen deficiency (−N) increases the lengths of PR and LRs, whereas severe nitrogen deficiency inhibits PR elongation as well as LR emergence and elongation. These distinct RSA responses likely reflect different strategies of the plants to cope with limited nitrogen availability. Figure based on Gruber et al. (2013). B, Examples of signaling pathways involved in modulating RSA responses to the supply of nitrate to otherwise nitrogen-deficient plants (Vidal et al., 2010, 2013) and mild (Ma et al., 2014) or severe (Krouk et al., 2010; Araya et al., 2014) nitrogen deficiency. Details are in the text. Aux/IAA, AUXIN RESISTANT/INDOLE-3-ACETIC ACID INDUCIBLE; miR393, microRNA393.
Figure 3.
Figure 3.
Effect of nutrient availabilities on root developmental processes. A, Effect of nutrients on stem cell niche (SCN) identity, meristematic activity, and cell elongation. B, Local and systemic regulation of LR emergence or LR initiation by a local availability (+) or the limitation (−) of the indicated nutrients. C, Effect of nutrients on rhizodermal development at hair (1) and nonhair (2) cell positions or on root hair elongation (3) or morphology (4). Hair and nonhair positions are represented in pink and green, respectively. Thicker arrows indicate that the respective nutrient deficiency has a comparatively stronger effect on the designated change in root hair development. D, In response to phosphorus deficiency, the expression of ETC1 is up-regulated to increase root hair density (Savage et al., 2013). In addition, this nutrient deficiency also induces AL6, which, in turn, activates the indicated downstream targets that stimulate root hair elongation (Chandrika et al., 2013). Details are in the text. NPC4, NONSPECIFIC LIPASE4; SQD2, SULFOQUINOVOSYLDIACYLGLYCEROL2; PS2, PHOSPHATE STARVATION-INDUCED GENE2.

Similar articles

See all similar articles

Cited by 56 articles

See all "Cited by" articles

Publication types

MeSH terms

LinkOut - more resources

Feedback