Phyllochron responds to acclimation to temperature and irradiance in maize

Crop models need accurate simulation of leaf canopy development. Thermal interval for leaf tip appearance (phyllochron) is critical for predicting duration of vegetative development. Phyllochron in maize is shorter in temperate than in tropical and subtropical environments. As existing data has been evaluated in a narrow range of environments, underlying mechanisms that affect phyllochron have not been adequately examined. The objectives of this study were to quantify the response of phyllochron to environmental variables and determine its stability across maize cultivars, to aid modelers in developing tools which accurately predict phenology. Maize was grown in field experiments at Wageningen, The Netherlands, Temple, Texas, USA, and three sites in Mexico, and in controlled environments at Wageningen. The experiment at Temple included grain sorghum and shading treatments to alter irradiance of the crop. Detailed data on leaf production and environmental conditions were collected. These data were combined with published data from held studies. Maize phyllochron acclimated to temperature and increased as mean daily temperature before tassel initiation increased from 12.5 to 25.5 degrees C, and increased in maize and sorghum in response to low irradiance. Temperature was the dominant influence, with phyllochron increasing by 1.7 degrees Cd per degrees C increase in daily mean temperature, as daily mean temperature before tassel initiation increased from 12.5 to 25.5 degrees C, and declined or remained constant when mean daily temperature before tassel initiation exceeded 25.5 degrees C. Only small differences in phyllochron occurred among cultivars. Phyllochron increased by 2-4 degrees Cd MJ(-1) photosynthetically active radiation (PAR) as irradiance decreased from 9.6 to 1.1 MJ PARm(-2) day(-1). (C) 1998 Elsevier Science B.V. All rights reserved.