Several studies have pointed out the promising use of nutritional diagnosis methods for the determination of optimum nutrient contents in plant tissues. The present investigation was carried out in different oases in Southern Tunisia to determine reference values for the interpretation of leaf analyses of date palm (Phoenix dactylifera) Deglet Nour cultivar with the Critical Value Approach (CVA) and the Compositional Nutrient Diagnosis (CND). A database (n = 100) of yield and mineral concentrations taken from date palm leaflets in October, at the maturity stage of dates, was used. The yield cut-off between low-yield and high-yield subpopulations, selected from cumulative variance ratio functions across survey data, was 76 kg palm⁻¹ and the global nutrient imbalance index (CNDr²) was 10.06. Critical CND nutrient indices were found to be symmetrical around zero as follows: (1.59; +1.59) for I_N, (−0.44, +0.44) for I_P, (−0.63, +0.63) for I_K, (−0.94, +0.94) for I_Ca, (−1.05, +1.05) for I_Mg, (−0.80, +0.80) for I_Fe, (−0.74, +0.74) for I_Cu, (−0.80, +0.80) for I_B, (−0.93, +0.93) for I_Zn, (−1.04, +1.04) for I_Mn, and (−1.03, +1.03) for the residual value. Compared to CND, the CVA approach shows weak detection of the nutrients that cause nutritional imbalance. CND indices revealed, except for N, the presence of nutrient imbalances and the necessity to correct the mineral nutrition of date palm in the Kebeli oases.

Date palm pollen storage is becoming more and more necessary due to the asynchronous maturation of male and female flowers that, frequently, occurs, during the last years in Tunisia. However, little information is available on the pollen viability and favorable storage conditions. The present study aims to compare date palm pollen storage at three temperatures (25 ± 2°C, 4°C and −20°C) and to evaluate the aptitude of pollens from different geographical origins to conserve their in vitro germinative potency. Results revealed that, after the fresh pollen, the overall pollen in vitro germinations were significantly improved with storage at −20°C (41.04 ± 23.84%) and 4°C (20.07 ± 22.19%) compared with storage at 25 ± 2°C (4.27 ± 4.39%). For each used temperature, the in vitro germination was not affected by the pollen origins. In fact, almost similar reactions were observed for fresh and stored pollen at 25 ± 2°C and 4°C. On the other hand, pollen stored at −20°C had reacted independently from the origin. However, the aptitude of pollens from similar origins to preserve their in vitro germination potencies under the three storage temperatures reveals some similarities. Physiologic characteristics of pollens were not related to the geographic origins and did not significantly affect their aptitude for storage