Effect of temperature on kernel growth rate of maize grown in a temperate maritime environment

Abstract

Abstract Maize ( Zea mays L.) kernel growth rates were estimated during the linear period of grain-filling for 10 field sowings of cultivar Pioneer P3901 and 12 field sowings of cultivar Pioneer P3709. The objective of the study was to determine the relationship between kernel growth rate and air temperature in a cool climate, and to compare this relationship with published controlled-environment studies and with the quadratic function used to describe kernel growth in the CERES-maize crop simulation model. The crops were grown in a temperate maritime environment at latitude 40.3°S, and mean air temperatures during the periods for which kernel growth rates were measured ranged from 12.5 to 19.3°C. Measured kernel growth rates ranged from 3.6 to 9.2 mg kernel −1 day −1 . Between 13.5 and 19.3°C, the rates were linearly related to temperature, increasing by 0.59 and 0.44 mg kernel −1 day −1 °C −1 for P3901 and P3709 respectively. Kernel growth rates were markedly reduced at mean air temperatures below 13.5°C, indicating that there was either a non-linear response of the potential kernel growth rate to temperature over the 12 to 19°C temperature range, or that assimilate supply limited the actual kernel growth rate in the field at low temperatures. Non-linear regression procedures were used to fit kernel growth rates from four sowings in one season to linear and quadratic thermal-time models using hourly mean air temperatures. There were no apparent assimilate limitations during kernel growth in this season, and hourly mean air temperatures ranged from 0 to 27°C. The results supported the use of a non-linear function to describe the overall response of kernel growth rate to temperature, which in turn cautions against the use of mean daily temperatures to derive such a relationship. The quadratic model provided the best fit to the data, and gave a higher base temperature than that used in the CERES-maize model (10°C vs. 6°C).