Kinetic, morphological, and photosynthetic parameters of absorption of nitrogen forms in olive cultivars (Olea europaea L.)

Key message

Knowledge of the efficiency of nitrogen absorption contributes to the selection of olive cultivars that are more efficient in absorbing N even at low concentrations in the environment.

Abstract

Fertilization of olive trees (Olea europaea L.) generally follows standardized nitrogen (N) doses, without considering the specific efficiency of each cultivar in N absorption. The lack of knowledge about kinetic parameters can result in excessive application, increasing environmental risks and impairing oil quality. The study aimed to characterize the most efficient olive cultivars in the absorption of N, NO₃⁻, and NH₄⁺ forms, and to determine whether kinetic, photosynthetic variables, and root morphological parameters contribute to the selection of cultivars that are more efficient in the use of N. Four olive cultivars were grown hydroponically for 21 days in nutrient solution and transferred to 0.03 mol L⁻¹ CaSO₄ solution for 15 days. Subsequently, the plants received nutrient solution again and periodic collection began during a 61-h kinetic absorption march. The cultivar Coratina was the most efficient in NO₃⁻ absorption, presenting higher V_max (maximum absorption speed) and lower K_m (Michaelis–Menten constant) and C_min (minimum concentration) values, which allows N absorption at low concentrations due to the affinity of root transporters. Its greater length, surface area, and quantity of fine roots favored this efficiency. It also presented better photosynthetic parameters and greater N accumulation in roots. Arbequina and Koroneiki had high K_m and C_min for NO₃⁻ and NH₄⁺, while Arbosana presented lower C_min values for NH₄⁺. These results show that different cultivars have distinct nutritional strategies and that physiological and morphological parameters are essential in choosing the best cultivars and optimizing nitrogen fertilization, ensuring greater sustainability and productivity in olive cultivation.