ORIGINAL PAPER Time series in analysis of yerba-mate biennial growth modified by environment Miroslava Rakocevic & Simoni Fernanda Martim # ISB 2010 Abstract To assess differences in the lag-effect pattern in the relationship between yerba-mate biennial growth and environmental factors, a time-series analysis was per- formed. A generalized Poisson regression model was used to control time trends, temperature, growing degree days (GDD), rainfalls and night length (NL). It was hypothesized that the active growth and growth pauses in yerba-mate are controlled endogenously and modified by environment, and that genders would respond differently to environmental modifications. The patterns in the lag effect from the distributed-lag models were similar to those of time-series models with meteorological data means with lag=0. GDD and NL were principal factors affecting biennial yerba-mate shoot elongation and the number of green leaves of females grown in monoculture, besides their significant effects on metamer emission and leaf area in males grown in monoculture. NL also had a significant influence on shoot elongation and leaf area of both genders grown in forest understorey (FUS), indicating that yerba-mate growth is synchronized by an internal clock sensitive to temperature adjustments. The morphological plasticity and the adapta- tion efforts of yerba-mate were more pronounced in monoculture than in FUS. Sexual dimorphism was expressed—males were more sensitive to environmental changes than females, especially in monoculture. Growth modifications were much more intense when plants were grown in a cultivation system that is less like yerba-mate natural habitat (monoculture) than in one resembling its natural habitat (FUS). Our data support the ecological specialization theory. Keywords Growing degree days . Ilex paraguariensis . Night length . Sexual dimorphism . Shoot elongation Introduction Plant growth and development are affected by environmen- tal factors such as temperature, flux and duration of photosynthetically active radiation (PAR), availability of nutrients, and water. Growth and development of whole organisms show a temperature response, which results from the integrated effect of temperature on many individual physiological processes. For example, for maize grown under field conditions, temperature indices can explain over 95% of development variability (Kiniry and Keener 1982). Day/night length also plays an important role in physiology and growth, considering that many processes change profoundly between day and night. Diurnal rhythms are defined as the time to complete one cycle of 24 h (Dunlap et al. 2004), and are endogenously generated and self- sustaining. They persist under constant light and tempera- ture. All diurnal rhythms have temperature compensation, meaning that the period remains relatively constant over a range of temperatures (McClung 2001). Our particular interest in determining the growth process susceptibility to environmental variation is focused on yerba- mate (Ilex paraguariensis St. Hil., Aquifoliaceae). This species is a subtropical, evergreen, dioecious, South- American tree that has a traditional economical importance M. Rakocevic (*) IAPAR, Rodovia Celso Garcia Cid, km 375, P.B. 481, 86047-902 Londrina, PR, Brazil e-mail: miroslava@iapar.br S. F. Martim Embrapa Informática Agropecuária, Avenida André Tosello 209, P.B. 6041, 13083-886 Campinas, SP, Brazil DOI 10.1007/s00484-010-0322-4 Int J Biometeorol (2011) 55:161–171 Received: 3 January 2010 / Revised: 1 March 2010 / Accepted: 16 April 2010 / Published online: 3 June 2010