Relationship between photosynthetic activity duration (PAD) and achene oil weight during grain filling in the cultivar Kerbel (2012 experiment, from Andrianasolo, 2014). PAD was computed from weekly photosynthetic activity measurements between mid-filling and end of grain filling, and integrated over time. Symbols were distinguished by nitrogen treatment (circle: limiting nitrogen situations; triangle: non-limiting nitrogen situations). Model was fitted with a bi-linear model; root mean squared error (RMSE) and coefficient of determination (R²) are indicated.