Physiological Properties Influencing Floret Dynamics Under Stress in a Maize Hybrid and Its Parental Inbred Lines.

Plant dry matter and grain yield of genetically identical plants within a plant stand that is uniform in terms of spatial plant distribution and plant emergence may vary in the order of 2 to 7 fold at physiological maturity. The degree of plant-to-plant variability is associated with stress during the life cycle and is greater in older than in newer maize hybrids. A study was carried out to investigate the physiological mechanisms that are associated with the plant-to-plant variability. The frequency distributions of individual plant dry matter in the maize hybrid CG60×CG102 and its two parental inbred lines, grown at 4, 8, 12, 16 plants/m² in 2007 and 2008 were monitored during the life cycle using a morphometric methodology. Uniform plants were selected at the 8-leaftip stage in 2007 and 4-leaftip stage in 2008.  Besides plant dry matter from the 12-leaftip stage to physiological maturity, rate of leaftip appearance, rate of spikelet initiation, plant and ear growth rate during the silking period, and kernel number and harvest index at physiological maturity were determined. Both hybrid and inbred CG60 showed the curvilinear relationship between kernel number per plant (KNP) and plant growth rate around silking (PGR_s), however, there is no relationship between KNP and PGR_s for CG102. The kernel number of CG102 can be better explained by the ear growth rate around silking in each year, indicating that partitioning is important.