Agriculture Reference
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when grown at various hydroponic iron concentrations, ranging from 0 to 20
M
Fe. Interestingly, these differences were more evident in plants grown at low Fe
concentrations (iron limiting conditions) than at high iron concentrations (suffi-
ciency conditions), revealing a genotype x environment interaction. Finally, the use
of isotope labelling has been used to evaluate nutrient uptake capacity. In maize,
nitrogen-15 labelling was used to study NUpE (Coque et al.
2008
), showing that
28.3 % of whole-plant nitrogen was taken up after silking, and 93 % of this post-
silking nitrogen uptake was allocated to kernels.
A similar approach could be used to analyse the roots to shoot translocation of
nutrients. As an example, in order to understand why
Noccaea caerulescens
has
good properties for phytoremediation, Xing et al. (
2008
) investigated the root-to-
shoot translocation of Cd and Zn in different genotypes. The percentages of Cd and
Zn transported to shoots within 24 h exposure varied widely among the 11 acces-
sions analysed. Interestingly, the translocation efficiency did not correlate with the
uptake for either metal, suggesting independent variation in uptake and transloca-
tion among different accessions of
Noccaea
.
Post-genomic studies integrating all “omics” sciences can depict precise pictures
of nutrient assimilation in plants (Hirai et al.
2004
). Sulpice et al. (
2013
) studied the
response of 97 accessions of
Arabidopis
to different nitrogen and carbon condi-
tions, an important number of traits showed significant natural variation between
accessions. For example, biomass differed between the 97 accessions by 3.1-fold
and 2.8-fold in high and low nitrogen, respectively, relative to the accession with
the lowest biomass in that growth regime. The impact of low nitrogen and low
carbon differed between accessions, with some accessions showing a greater than
70 % decrease in biomass and others showing no decrease. Moreover, accessions
that maintained a relatively high biomass in low nitrogen tended to show only a
small increase in biomass in high nitrogen, whereas accessions that showed a
relatively small biomass in low nitrogen showed a large (greater than 3-fold)
increase in biomass in high nitrogen. The total nitrogen concentration in the rosette
was unrelated to the biomass difference between low and high nitrogen The
nitrogen content (mg/N per rosette) was strongly related to the response of an
accession to nitrogen; accessions that maintained biomass in low nitrogen
contained more nitrogen in the rosette than accessions that showed a large gain in
biomass in high nitrogen. These results imply that accessions differ in the extent to
which they can acquire nitrogen from low nitrogen soil and that this is far more
important for the response of biomass to nitrogen supply than changes in the
nitrogen content of the rosette.
As for uptake efficiency, natural variation for remobilisation efficiency can be
directly investigated by measuring nutrient content in the seeds. For instance, Khan
et al. (
2012
) revealed differences in oil content in the seeds of various
Acacia
species, revealing some species as a novel source of edible vegetable fat. As for the
studies conducted on N uptake, an isotope labelling technique is suitable to inves-
tigate the remobilisation efficiency. This was shown in the work of Coque
et al. (
2008
), who investigated N remobilisation in maize with the aim of mapping
and characterising loci involved in the variation of quantitative traits (QTL) related
μ
