Silk Elongation in Maize

Abstract

In maize (Zea mays L.), the gradient in floret development and silk length along the ear at silking determines a time lag between early‐ and late‐appearing silks, which results in pollination asynchrony between them. This asynchrony is partially responsible of reduced kernel set at the ear tip, and hybrids differ in this trait. The objective of this work was to analyze the pattern of floret and silk differentiation and elongation at different spikelet positions (Sn) along the apical ear of two hybrids of contrasting ear size (DEA ≅ 500 spikelets ear−1; DK696 ≅ 800 spikelets ear−1). At silking, both hybrids had reached approximately the same proportion of final ear length (about 44%), but DK696 had differentiated a greater number of spikelets row−1 (46 spikelets) than DEA (33 spikelets). Silk initiation rate was always faster than spikelet initiation rate, and silk extension dynamics was similar for all spikelet positions. Silks from the base of the ear were always longer than those from the tip (S25 in DEA or S35 in DK696). Before pollination, silks experienced an early phase of exponential elongation followed by a phase of linear growth. A drastic reduction in elongation rate followed silk emergence, which did not occur when ears were bagged and pollination was prevented. Convergence in silking among spikelets along the ear could be attained by (i) synchronous silk initiation among spikelet positions, followed by a similar pattern of silk elongation in all florets (hybrid DEA), or (ii) increased silk elongation rate in apical florets (hybrid DK696).