Chemistry Reference
In-Depth Information
and the US in different decades [1; 12]. Most of the shoot biomass accumulation increments
in those hybrids, occurred during the grain-filling period [13; 14]; and they were mainly
associated with an increased capacity of maintaining higher leaf photosynthetic rate of
green leaf area (i.e., functional “stay green”) during the grain-filling period [15-17]. The next
sections will review the main processes influencing grain yield numerical components
determination (i.e. kernel number and kernel weight) and their changes in Argentinean
maize hybrids released in different decades. Implications on stress tolerance and resource
use efficiency will be also discussed.
Kernel number
Kernel number is the main yield component accounting for grain yield increments over the
years [18; 19]. Figure 1 illustrates a conceptual framework of the main processes
contributing to kernel number determination in maize.
Figure 1.
General model for kernel number determination in maize (Adapted from Andrade et al. (20)).
Kernel number per plant is a function of the physiological condition of the crop or plant at a
period of 15 days bracketing silking (i.e. critical period for kernel number determination; 21-
26) or between -227 and 100°C day from silking [27]. As such, kernel number is a function of
photosynthesis at silking [22] and it is closely related with plant growth rate during the
critical period for kernel set [18; 28]. The relationship between kernel number per plant
(KNP) and plant growth rate during the critical period for kernel set (PGRs) was described
by two successive curves to account for the first and second ear in prolific hybrids, or a
single curve in non-prolific hybrids [18; 28; 29]. A particular feature of the KNP-PGRs
relationship is the significant PGRs threshold for kernel set that results in abrupt reductions
