Response of corn (zea mays l.) in the pre-tassel initiation period to temperature and photoperiod

Abstract

Controlled-environment facilities were used to examine the effects of temperature and photoperiod on tassel-initiation time, leaf number and rate of leaf initiation of two corn hybrids. The effect of diurnal temperature range on tassel-initiation time and leaf number was also investigated. There was a consistent decrease in time to tassel initiation as temperature was increased from 15° to 25°C regardless of photoperiod. There was no difference in tassel initiation time at 25° and 30°C under all photoperiods for both hybrids. Photoperiod increased the time to tassel initiation at all temperatures, however, the change in time was more pronounced at low temperature (15°C). Temperatures of 15, 20 and 25°C had little effect on changing the number of leaves. However, the 30°C-treatment resulted in an appreciable increase in leaf number over that of other temperature treatments. As photoperiod was extended, leaf number increased at all temperatures for both hybrids. Average leaf number increased by 2.1 for each hybrid by lengthening photoperiod from 10 to 20 h. The rate of leaf initiation was nearly doubled for United 108 and more than doubled for Guelph GX 122 when temperature was increased from 15° to 30°C. The two hybrids exhibited a pronounced difference in leaf-initiation rate at high temperature (30°C). There was a small change in the rate of leaf initialtion with photoperiod. It is concluded that the increase in leaf number with increasing photoperiod resulted from the prolongation of the time to tassel initiation. At low mean temperature (15°C), there was an appreciable delay in tassel-initiation time as the diurnal range was increased from 0.0 to 17.2°C. The delay at these ranges became smaller at the 20°C-mean temperature. At 25°C-mean temperature, there was a pronounced delay with an increase of range from 8.6 to 17.2°C. The number of leaves increased with mean temperature and diurnal range. However, the effect of temperature range became less pronounced at high mean temperature.