Grain yield components in maize. II- Postsilking crop growth and kernel weight.

MADDONNI, G.A.; OTEGUI, M.E.; BONHOMME, R.

FIELD CROPS RESEARCH

Elsevier

Lugar: Amsterdam; Año: 1998 vol. 56 p. 257 - 264

0378-4290

            Maize  kernel weight  (KW) results from kernel growth during two stages of grain filling, the lag phase (formative period) and the effective grain filling phase. Environmental conditions may affect kernel biomass accumulation in each phase. This work analyzed: (i) changes in duration and rate of kernel growth on a thermal time (ºC day) basis, and (ii) KW response to postsilking biomass production kernel-1 (source/sink ratio). Sowing date, plant population, and nitrogen fertilization experiments were conducted in France and Argentina to induce changes in assimilate availability per kernel. Hybrids of different KW were tested. Hybrids differed in the duration of the lag phase, which determined kernel growth rate during the effective grain filling period for hybrids with similar grain filling duration (c.a. 745°C day). Environments with low air temperature (< 19 ºC) and decreased incident solar radiation determined a reduced final KW due to reductions in photoassimilate production and its partition to the grains. A value of 240-270 mg kernel-1 during grain filling was determined as a threshold to have mobilization or storage of reserves. Small-kernel hybrids (KW < 300 mg), with large kernel number (3500 to 5500 kernels m-2), depended more on reserve mobilization than large-kernel hybrids (KW > 300 mg) with reduced kernel number (2800 to 4000 kernels m-2). For the former, grain yield increments should not be based on increased kernel number but on increased biomass production.