Development, including leaf appearance, of agricultural and forest crops strongly depends on air temperature. Leaf appearance can be studied and quantified using the concept of phyllochron, defined as the time interval between the appearance of successive leaves on a stem, expressed as °C day leaf -1. The objective of this research was to estimate the base temperature for leaf appearance and the phyllochron for Eucalyptus grandis (Hill ex Maiden) and Eucalyptus saligna (Smith) seedlings. A field and a greenhouse experiment were carried out in the experimental area of the Department of Plant production of the Federal University of Santa Maria, Rio Grande do Sul, Brasil. Sowing was carried out at different times in the field and on 03/10/2005 in the greenhouse. Base temperature was estimated by the minimum mean square error of the regression between main stem leaf number (NF) and accumulated thermal time (STa) approach and the phyllochron was estimated by the inverse of the slope of the regression NF against STa. The estimated base temperature was 8.0°C for Eucalyptus saligna and 10°C for Eucalyptus grandis. The phyllochron in Eucalyptus grandis was 32.0 ºC day leaf -1 and in Eucalyptus saligna was 30.7 ºC day leaf -1. These two phyllocron values were not statistically different.
Development; temperature; phenology
