Chemistry Reference
In-Depth Information
N-NO
3
for maximum yield; 73). Protein concentration was negatively correlated with grain
yield (r=-0.79, p=0.06) in agreement with previous findings [74-76]. The decline in protein
concentration in kernels might have been the result of non-proportional increments of N
and carbon fluxes to the kernels over the years. In addition, lower protein concentration in
kernels were associated with low source-sink ratios [65; 77]. Similar trends in protein
concentration over the years were reported for other crops [78; 79] and for US maize hybrids
released during the period 1930-1991 [3]. On the contrary, protein concentration in kernels
increased in Canadian hybrids released in different decades [80]. The increment in both,
grain yield and protein concentration, might be associated with the increased source-sink
ratio in Canadian maize hybrids [54]. As well, similar protein concentration under high N
availability in Argentinean maize hybrids released in different decades might have been
related to N luxury consumption [81; 82]. Oil kernel concentration was stable in hybrids
released between 1965 and 1984; but it was reduced in hybrids released in 1993 (r
2
=0.84,
p<0.05, Figure 9). Oil is mainly located in the embryo [83; 84] and it is probable that the
embryo-endosperm ratio has decreased with the year of the hybrid release. In agreement,
embryo-endosperm ratio was greater in US hybrids selected for high oil concentration [85].
Hybrid
Year of release
Protein (g kg
-1
)
No N fertilized
N fertilized
DKF880
1965
95.0 a
98.7 a
M400
1978
93.0 ab
95.7 a
DK4F36
1982
81.0 bc
86.7 a
DK4F37
1985
77.7 c
88.3 a
DK664
1993
78.0 c
86.7 a
DK752
1993
79.7 c
93.0 a
SE within columns
4.04
SE within rows 3.85
Table 1.
Protein concentration (g kg
-1
) in grains of Argentinean maize hybrids released between 1965
and 1993 under
two nitrogen treatments (i.e. N fertilized and no N fertilized). From Echarte [11].
70
60
50
40
No N-fertilized
N fertilized
30
1960 1970 1980 1990 2000
Year of release
Figure 9.
Oil concentration (g kg
-1
) in grains of Argentinean maize hybrids released between 1965 and
1993 under
two nitrogen treatments (i.e. N fertilized and no N-fertilized). From Echarte [11].
