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Mandarins are one of the most important citrus fruits in the world in terms of tons produced. The late-season varieties of mandarin have a great economic value due to their high production in a season with few mandarin varieties. The objective is to carry out a preliminary study of characterization and comparison of the morphological and biochemical properties of the late varieties ‘Afourer’, ‘Tango’, and ‘Orri’. The characterization consisted of physicochemical parameters related to the quality of the fruits, highlighting the total antioxidant activity using ABTS and DPPH, the organic acids and sugars using HPLC and the metabolomics of the juice by 1H-NMR. Afourer’ mandarins were heavier and larger (120.75 g, 67.60 mm) than the other two varieties studied. Mandarins of the ‘Orri’ variety showed a different organic acid profile compared to the other varieties studied, and a higher amount of sugars (13.49 g/100 mL). ‘Tango’ variety mandarins grown on the Forner-Alcaide rootstock stood out for having a larger weight (113.52 g), a more intense color, and a greater amount of phenolic compounds (966.85 mg AGE/L Forner) than the fruits grown on Citrus macrophylla. The metabolomics analysis showed that these mandarin varieties had mainly non-essential amino acids.

In Europe, the cultivation of blood oranges for fresh consumption is increasing due to their excellent organoleptic and nutraceutical properties, which give this fruit the status of functional food. Blood orange has a higher content of bioactive compounds, which confer additional benefits for human health. The main morphological and qualitative parameters were studied together with the content of primary metabolites by 1H NMR and secondary metabolites by HPLC-ESI-DAD-MSn from eight varieties of blood orange grafted on Citrus macrophylla. Tarocco Dalmuso was the variety with the highest values of weight (350.6 g), caliber (86.4 mm and 88.6 mm) and juice content (214.2 g). Tarocco Gallo obtained the most interesting qualitative parameters (13.95 °Brix; 22.75 MI). The most intense red juice was in Sanguinelli (a* = 9.45) and, in crust, it was in Tarocco Scirè (a* = 40.13). The most abundant primary metabolites were proline, aspartate and asparagine, citric acid and sucrose. The results showed that the juice of the Moro had the highest levels of total flavones and flavanones (90.07 and 592.88 mg L−1, respectively), and Sanguinelli in total anthocyanins (101.06 mg L−1). To conclude, Tarocco Dalmuso obtained the best values of agronomic parameters, and Moro and Sanguinelli in the content of phenolic compounds.

The elaboration and definition of “metabolic fingerprints” can subsidize both the identification and determination of plant varieties, as well as the increase in knowledge about the responses and adaptations of plants to external and/or internal factors. The lemon tree (Citrus limon Burm.) is one of the most important crops in the Spanish southeast and is often consumed around the world. Although the study and characterization of its fruits are common due to its economic interest, its leaves are limited to specific functionalized studies related to the objective of the work (extraction of essential oils, stabilizing agent, aromatic extracts, etc.). So, this study aimed to identify the primary and secondary metabolites of Citrus limon Burm. (‘Verna’ variety) leaf samples cultivated under different conditions (three rootstocks and three culture media). In total, 19 metabolites were identified for all samples, of which 9 were amino acids, 5 organic acids, 3 sugars and 2 intermediate metabolites. The results pointed to a limited influence, both of the substrate and of the crop rootstock, on the metabolomic differentiation of lemon leaves. Knowledge and foliar metabolomic differentiation can offer important information that supports the application of crop foliar treatments but also helps in the management of diseases and pests.

Cadmium is absorbed by plants rapidly and without control through the same channels as other essential metals, interfering with their transport and utilization. Many studies have shown that selenium could be utilized as a way to avoid this unwanted transport and other negative effects of Cd. For this reason, the present research study was conducted with four treatments (−Cd/−Se, +Cd/−Se, +Cd/+SeF, and +Cd/+SeR) to determine the type of application of Se that is best (foliarly and/or via the root) as regards the reduction of the toxic effects of Cd on plants. Our results showed that the Cd excess in the nutrient solution resulted in a decrease in the total dry biomass of the plants grown under these conditions, and this decrease was due to the reduction of the growth of the shoot (48% +Cd/−Se, 45% +Cd/+SeF, and 38% +Cd/+SeR, relative to −Cd/−Se). This reduction in growth was due to: (i) the toxicity of Cd itself and (ii) the nutritional disequilibrium suffered by the plants. It seems that under hydroponic conditions, the addition of Se to the nutrient solution, and therefore its absorption through the roots (lower antioxidant activity, superoxide dismutase, H2O2 concentration and higher catalase activity), greatly delayed and reduced the toxic effects of Cd on the pepper plants, as opposed to the foliar application of this element.