Plant adaptations to severely phosphorus-impoverished soils

Abstract

Mycorrhizas play a pivotal role in phosphorus (P) acquisition of plant roots, by enhancing the soil volume that can be explored. Non-mycorrhizal plant species typically occur either in relatively fertile soil or on soil with a very low P availability, where there is insufficient P in the soil solution for mycorrhizal hyphae to be effective. Soils with a very low P availability are either old and severely weathered or relatively young with high concentrations of oxides and hydroxides of aluminium and iron that sorb P. In such soils, cluster roots and other specialised roots that release P-mobilising carboxylates are more effective than mycorrhizas. Cluster roots are ephemeral structures that release carboxylates in an exudative burst. The carboxylates mobilise sparingly-available sources of soil P. The relative investment of biomass in cluster roots and the amount of carboxylates that are released during the exudative burst differ between species on severely weathered soils with a low total P concentration and species on young soils with high total P concentrations but low P availability. Taking a modelling approach, we explore how the optimal cluster-root strategy depends on soil characteristics, thus offering insights for plant breeders interested in developing crop plants with optimal cluster-root strategies. DOI: https://doi.org/10.1016/j.pbi. 2015.04.002 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-121418 Accepted Version Originally published at: Lambers, Hans; Martinoia, Enrico; Renton, Michael (2015). Plant adaptations to severely phosphorusimpoverished soils. Current Opinion in Plant Biology,[25][26][27][28][29][30][31] AbstractMycorrhizas play a pivotal role in phosphorus (P) acquisition of plant roots, by enhancing the soil volume that can be explored. Non-mycorrhizal plant species typically occur either in relatively fertile soil or on soil with a very low P availability, where there is insufficient P in the soil solution for mycorrhizal hyphae to be effective. Soils with a very low P availability are either old and severely weathered or relatively young with high concentrations of oxides and hydroxides of aluminium and iron that sorb P. In such soils, cluster roots and other specialised roots that release P-mobilising carboxylates are more effective than mycorrhizas. Cluster roots are ephemeral structures that release carboxylates in an exudative burst. The carboxylates mobilise sparingly-available sources of soil P. The relative investment of biomass in cluster roots and the amount of carboxylates that are released during the exudative burst differ between species on severely weathered soils with a low total P concentration and species on young soils with high total P concentrations but low P availability. Taking a modelling approach, we explore how the optimal cluster-root strategy depends on soil characteristics, thus offering insights for plant breeders interested in developing crop plants with optimal cluster-root strat...

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

“…Mycorrhizas allow plants to scavenge P that is in the soil solution beyond the zone that roots and root hairs can deplete. Many nonmycorrhizal species, in contrast, have evolved root specialisations that combine morphological and physiological adaptations (e.g., cluster roots and dauciform roots that release large amounts of carboxylates) capable of extracting all of their required nutrients from the soil without the use of mycorrhizas (Lambers et al 2015d;2008;Shane and Lambers 2005). Cluster-rooted plants (e.g., Lupinus and Hakea species) efficiently mine P from P-impoverished soils by quickly producing clusters of fine, densely packed rootlets that release carboxylates in an 'exudative burst' to solubilise P that is tightly sorbed to soil particles (Lambers et al 2008;Shane et al 2004;Watt and Evans 1999).…”

Root microbiota drive direct integration of phosphate stress and immunity

“…Thus, plants possess adaptive phosphate starvation responses (PSR) to manage low Pi availability that typically occurs in the presence of plant-associated microbes. Common strategies for increasing Pi uptake capacity include rapid extension of lateral roots foraging into topsoil where Pi accumulates 7 and establishment of beneficial relationships with some soil microorganisms 8, 9 . For example, the capacity of a specific mutualistic fungus to colonize Arabidopsis roots is modulated by plant phosphate status implying coordination between the PSR and the immune system 8, 10 .…”

Altered Expression of a Malate-Permeable Anion Channel, OsALMT4, Disrupts Mineral Nutrition

“…The release of organic and inorganic compounds from roots, especially carboxylates and protons, is an effective strategy by which some species increase P acquisition from soil (Ryan et al, 2001;Neumann and Martinoia, 2002;Vance et al, 2003;Lambers et al, 2015b;RamirezFlores et al, 2017). Plants that use these strategies also tend to have higher tissue concentrations of Mn because the carboxylates released, especially citrate and malate, help mobilize Mn in the soil for uptake by roots (Lambers et al, 2013).…”