Measurement and modelling of gas exchange of leaves and pods of oilseed rape

A generic steady-state gas exchange model was adapted to leaves and pods of the cruciferous species oilseed rape (Brassica napus L.). Parameter–nitrogen relationships were established to account for effects of organ senescence and nitrogen content. Components of dark respiration related to photosynthetic and to non-photosynthetic tissue of siliques were treated separately. A two-step calibration and validation approach relying on light response curves and diurnal time courses of CO2 exchange rate (A) and transpiration rate (E) measured on leaves and pods was used paying special attention on robustness, reliability, and universality of model parameterisation. Simulations of diurnal time courses of A and E of leaves and pods including the effects of nitrogen content and senescence on A and E correspond well to the observations. The model can be used to analyse and quantify eco-physiological patterns of gas exchange of both leaves and pods of oilseed rape, included as a submodel into existing canopy-scale gas exchange or growth models of this cultivar and adapted easily to other cruciferous species.