Pre-flowering growth and development of the inflorescences of maize. I. Primordia production and apical dome volume
1992
Jacobs, B.C. | Pearson, C.J.
The growth and development of the main stem and the two uppermost axillary apices of maize were studied during the period from emergence until flowering. Plants were grown in the field under varying levels of applied nitrogen fertilizer at two times of sowing. The effects of daylength were isolated from those of temperature by making comparisons of growth and development on a thermal time basis. The growth and development of the terminal (male) apex and the two uppermost axillary (female) apices followed the same patterns, with apex volumes increasing curvilinearly with increase in number of leaf or husk primordia. The RGR (relative growth rate of volume) of the terminal apex was, however, only approximately one-tenth of the axillary apices. There was no difference in growth and development between the first and second axillary apices before flowering: other factors, such as accumulation of dry weight, rather than primordia production, must be responsible for an axillary apex's potential to bear grain. Applied N, and to a lesser extent short days, increased the rates of growth and development of all the apices. For example, applied N increased the RGR (volume) of the apical domes, and the rate of production of spikelet primordia, by about 25%. All axillary apices and treatments showed a single relationship between number of spikelets and surface area of the ear: a favourable environment (e.g. high N) simply accelerated the progression of spikelet production and area expansion along this single path. We conclude that this path is probably determined genetically and that N and time of sowing influence potential yield of maize through effects on the surface area of the ear but not on the density of spikelets formed.
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