Non-linear mixed-effects modeling for photosynthetic response of Rosa hybrida L. under elevated CO₂in greenhouses - Short communication

Abstract

Ozturk I., Ottosen C.O., Ritz C., Streibig J.C., 2011. Non-linear mixed-eff ects modeling for photosynthetic response of Rosa hybrida L. under elevated CO 2 in greenhouses. Hort. Sci. (Prague), 38: 43-47.Photosynthetic response to light was measured on the leaves of two cultivars of Rosa hybrida L. (Escimo and Mercedes) in the greenhouse to obtain light-response curves and their parameters. Th e aim was to use a model to simulate leaf photosynthetic carbon gain with respect to environmental conditions. Leaf gas exchanges were measured at 11 light intensities from 0 to 1,400 μmol/m 2 s, at 800 ppm CO 2 , 25°C, and 65 ± 5% relative humidity. In order to describe the data corresponding to diff erent measurement dates, the non-linear mixed-eff ects regression analysis was used. Th e model successfully described the photosynthetic responses. Th e analysis indicated signifi cant diff erences in light saturated photosynthetic rates and in light compensation points. Th e cultivar with the lower light compensation points (Escimo) maintained a higher carbon gain despite its lower (but not-signifi cant) quantum effi ciency. Th e results suggested acclimation response, as carbon assimilation rates and stomatal conductance at each measurement date were higher for Escimo than Mercedes. Diff erences in photosynthesis rates were attributed to the adaptive capacity of the cultivars to light conditions at a specifi c day when the experiments were undertaken.Keywords: miniature rose; irradiance; response curve; carbon assimilation Hort. Sci. (Prague)Vol. 38, 2011, No. 1: 43-47 Exploring the diff erences in effi ciency in energy conversion, and photosynthetic capacity in diff erent cultivars and/or species under various abiotic conditions is an important strategy to investigate the underlying mechanisms in carbon assimilation. Even though pot-grown plants in greenhouses are supplied with standardized nutrients, water, and light levels, these plants still experience strong variation in light and temperature over the day and across seasons (Poorter et al. 2010). Studies shown that there is evidence for inter-and intra-specifi c variability in net photosynthesis rate of plants (Ottosen, Mentz 2000; Barman et al. 2008). Th is suggests that individual responses exhibit random deviations.Studies of gas exchange provide a tool for evaluating the impact of abiotic conditions on crop produc-

Crop growth and development in closed and semi-closed greenhouses

“…To accommodate for these two characteristics, Peek et al (2002) proposed the use of nonlinear mixed effects models in photosynthesis response curves. However, only a few studies applied the nonlinear mixed-effects model to their data analysis to investigate treatment differences (Peek et al, 2002;Heschel et al, 2004;McElrone and Forseth, 2004;Ozturk et al, 2011).…”