Effect of Temperature on Rate of Leaf Appearance and Flowering Date in Maize1

Abstract

Classification of development in maize (Zea mays L.) based on temperature is important because of the need in agriculture to determine the adaptability of genotypes to particular environments and to predict flowering dates for breeding purposes. An equation predicting the effect of temperature on rate of development of maize was obtained by measuring the rate of leaf appearance of six short‐season maize hybrids. The hybrids were grown in growth cabinets at constant day/night temperatures ranging from 10 to 35 C, in 5 C increments, with a 15‐hour photoperiod. Rate of leaf appearance was also measured on plants grown under 16 regimes of differential day/ night temperature. The predictive value of the temperature vs. rate of leaf appearance curve was compared with calendar days from planting to silking and accumulated heat units from planting to silking, calculated by both the Degree Days and Ontario Corn Heat Unit (OCHU) methods, using date of flowering for 22 hybrids grown during 3 years at four locations.Polynomial regression analysis of data for maize plants grown at constant day/night temperatures produced a cubic equation for rate of leaf appearance (leaves/day) vs. ambient temperature. This equation (Y = 0.0997 − 0.0360T + 0.00362T2 − 0.0000639T3) could be used to predict rate of leaf appearance in fluctuating temperature environments. For field‐collected data, the equation for rate of leaf appearance vs. temperature was superior to calendar days but similar to the Degree Days and OCHU methods in predicting dates of silking. Adjustment of the predicted time to silking by accounting for the effect of mean temperature during the first 30 days after planting on maximum leaf number (increase of 0.2 leaves/C increase in temperature) enhanced the precision of the derived equation in predicting date of silking.