Modeling Daily Leaf Respiration of Evening Primrose Crop through Development Phase, Air Temperature and Nitrogen Applications.

Evening primrose seeds are rich in linocetic acid. The objectives were to define the effect of the development phases and nitrogen fertilizations (Nf) and to model leaf respiration. Evening primrose plants were planted in pots under three Nf (0, 80 and 160 kg N ha^-1). Leaf respirations during the day (Lrd) and during the night (Lrn) were measured at all the development phases on plants of the three Nf. A CIRAS-2 infrared system was used to measure Lr on growing leaves. Lrd and Lrn were higher at the first development phases and lower for the last phases. During the rosette, elongation and flowering phases, Lrd was affected positively by Nf, while Lrn was only affected also positively during the rosette phase. For all the rest development phases neither Lrd nor Lrn were affected by Nf. As the cycle advanced the leaf nitrogen concentration reduced, which then also reduced Lrd and Lrn. Lrd was modeled using a linear relationship that included the Nf as a term in the equation. Lrn was modeled by an exponential equation that included the development (degree-days) and the Nf. Leaf respiration was different for the development phases of the evening primrose crop. The leaf respiration during the day and the night were affected positively by the nitrogen fertilizations at the first development phases. Both leaf respiration during the day and night were modeled as a function of the degree-days and nitrogen fertilizations.