Ear temperature and pollination timing effects on maize kernel set

Maize (Zea mays L.) kernel set can be improved through synchronous pollination within and between ears. Reductions in kernel set could be expected because of asynchronous pollination between early- and late-appearing silks. We analyzed the effect of (i) selective ear heating around the time of silking, and (ii) different time gaps between early- and late-pollinated silks in an attempt to modify kernel set. Tip ear heating was expected to minimize the advantage of early silking ovaries. Lateral heating and pollination gaps were expected to exaggerate this advantage. Three pollination gaps (2, 4, and 6 d) were tested for two plant populations (3 and 9 plants m(-2)). Ear temperature in the heated zone averaged 4.5degreesC above air temperature. Temperature in the nonheated side closely followed air temperature. Treatments promoted greater differences in maize kernel number (KN) per car (73% variation) than in the number of silks exposed 5 d after silking (6% variation). Lateral ear heating reduced KN per ear in comparison with the nonheated control, but tip ear heating did not modify KN per car. At 9 plants m(-2), synchronous pollination resulted in similar to15% increase in KN per plant. Pollination gaps of 2 and 4 d reduced KN per plant drastically (up to 51%), but the reduction was smaller for the 6-d gap. This study (i) gives evidence of the negative impact of delayed pollination timing among silks on kernel set, which was not related to reduced silk receptivity, and (ii) defines the time gap for maximum interference of early- on late-pollinated ovaries, a period shorter than 4 d.