Agriculture Reference
In-Depth Information
Efficient Mineral Nutrition: Phosphate as Nutritional Trait
of Interest
Implications for Phosphorus Uptake
Phosphorus (P) is an essential macronutrient with multiple functions in plant
macromolecular structures as a component of nucleic acids and phospholipids,
with crucial roles in energy metabolism, participation in signal transduction path-
ways via phosphorylation/dephosphorylation and controlling key enzyme reactions
(Theodorou and Plaxton
1993
; Schachtman et al.
1998
; Marschner
2012
). In many
agricultural systems, P is one of the most limiting nutrients for crop production and
is a major constraint for yield (Vance et al.
2003
; Raghothama
2005
; Kirkby and
Johnston
2008
), with shoot growth, tiller number and tiller weight all influenced by
P availability (R
¨
mer and Schilling
1986
; Bollons and Barraclough
1997
). Critical
P concentrations in wheat range from 0.5 to 0.4 % in dry matter (DM) at tillering
and 0.2-0.3 % in DM at booting (Finck
1991
; Marschner
2012
). The amount of
readily available P may be raised through P fertilisation and agronomic strategies
such as fertiliser placement or the application of the “critical value” concept (Bahl
and Singh
1986
; Strong et al.
1997
; Kirkby and Johnston
2008
; Syers et al.
2008
).
Phosphorus fertiliser derived from rock phosphate is a finite and non-renewable
resource (Cordell et al.
2009
). Furthermore, P derived from P fertiliser may cause
environmental problems associated with eutrophication (Gaxiola et al.
2001
), espe-
cially as a result of overuse (Fig.
4.1
). Hence, a major challenge for future crop
production will be to produce higher yields with fewer inputs such as P fertiliser
(Gregory and George
2011
). One strategy would be to develop crop genotypes that
require smaller amounts of fertiliser and therefore using nutrients more efficiently,
bred based on trait-focused screens of germplasm collections (Gregory and George
2011
). Nevertheless, little progress has been made in breeding cultivars with high P
utilisation efficiency or P acquisition efficiency (Calder´n-V´zquez et al.
2011
;
Rose et al.
2011
), and the recovery (uptake) of applied P, which ranges between
25 and 60 % depending on the method used, is still modest (Syers et al.
2008
).
Nutrient acquisition via the plant root system is a crucial factor for agricultural
productivity and crop yield (Lynch
1995
). Consequently, the amount of available P
is not only determined by the ability of the soil to replenish P ions, but is also
influenced by the extent and efficiency of uptake by the plant roots. Thus, cropping
system-specific and plant-specific approaches must be taken into account in order to
raise P acquisition efficiency (PAE) and P use efficiency (PUE) and a consideration
of root traits in genetic selection might result in significant improvements for crops
(Vance et al.
2003
).
Soil phosphorus is the most immobile, inaccessible and unavailable of all
macronutrient elements (Holford
1997
) and is taken up by plants mainly in its
inorganic form as phosphate (P
i
) (George and Richardson
2008
).
Edaphic and climate factors and cropping systems have a strong impact on the
proliferation and rate of replenishment of the available P
i
pool, which can be
