Chemistry Reference
In-Depth Information
kernel [21; 40; 42] or a more synchronous fertilization of florets within the ear [44;45], did
not show a clear trend with the year of the hybrid release [10]. The inherent greater stand
uniformity of the single-cross modern than in double-cross older hybrids was not an
additional factor influencing kernel set per unit PGRs; since, plant size variability at the
critical period for kernel set was similar among hybrids of different decades [9].
Dry matter partitioning to
the ear
Grain efficiency factor
1.6
1000
a
**
b
800
**
1.2
**
600
0.8
**
400
0.4
**
200
older hybrid (1965)
newer hybrid (1993)
0.0
0
1.5
3.0
4.5
6.0
>6
.0 .4 .8 .2 .6
Ear growth rate (g d
-1
)
Plant growth rate (g d
-1
)
Figure 4.
Dry matter partitioning to the ear (a) and grain efficiency factor (b), for an older (DKF880) and
a newer (DK752) maize hybrid released in Argentina in different decades (year of release between
brackets). Bars indicate standard error. ** indicates significant differences between hybrids at P< 0.05.
Adapted from Echarte et al. [10].
The modifications to the features of the relationship between KNP and PGRs (i.e. lower
threshold PGRs for kernel set and greater potential kernel number) were associated with a
more uniform HI across resource availabilities in newer than in older maize hybrids (Figure
5; 9). At low resource availability, decreases in HI were sharper in older hybrids. At high
resource availability per plant, decreases in HI of non-prolific plants were less pronounced
in newer than in older hybrids (Figure 5; 9);
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
Older hybrid
(1965)
Newer hybrid
(1993)
0.0
0.0
0
200 400 600 800
0
200 400 600 800
Final shoot biomass per plant (g pl
-1
)
30 to 16 8 4 to 2
30 to 16 8 4 to 2
Plant density (plants m
-2
)
Figure 5.
Relationship between harvest index per plant and final shoot biomass per plant in an older
(DKF880) and a newer (DK752) maize hybrid released in Argentina in different decades (year of release
between brackets). Triangles represent harvest index of prolific plants. Bottom bars represent the plant
densities used to obtain the corresponding ranges of shoot biomass per plant. Adapted from Echarte
and Andrade (9).
