A greenhouse experiment was conducted in Summer and Fall 2011 at the experimental farm of Tuscia University, central Italy, to study the effect of nutrient solution concentration (4, 20, 36, 52, or 68 mequiv·L−1) on biomass production, mineral composition, and concentrations of the major polyphenols in ‘Romolo’ artichoke and ‘Bianco Avorio’ cardoon grown in a floating system. Leaf dry biomass, leaf number, and macroelement concentrations (nitrogen, potassium, calcium, and magnesium) of artichoke and cardoon increased in response to an increase in the nutrient solution concentration, whereas an opposite trend was observed for the total polyphenols, phenolic acids (chlorogenic acid, cynarin, and caffeic acid), and the flavonoid luteolin. Artichoke and cardoon gave maximum biomass production and leaf number at 45 and 54 mequiv·L−1, respectively. Cardoon showed higher biomass and leaf number (average 1.13 kg·m−2 and 14.0 n./plant, respectively) than those observed in artichoke (average 1.07 kg·m−2 and 12.7 n./plant, respectively). The chlorogenic acid, cynarin, caffeic acid, and luteolin concentrations were higher by 204%, 462%, 580%, and 445% in cardoon leaf tissue than in that of artichoke. An improvement of leaf quality (total polyphenols, phenolic acids, and flavonoids) was obtained at the expense of leaf yield through the use of lower fertilizer concentrations in the nutrient solution.
Youssef Rouphael, Mariateresa Cardarelli, Luigi Lucini, Elvira Rea, and Giuseppe Colla
Daniela Borgognone, Mariateresa Cardarelli, Luigi Lucini, and Giuseppe Colla
Supplemental calcium application has been reported to alleviate the detrimental effect of NaCl-induced salinity on crop growth. Iso-molar solutions of NaCl and NaCl plus CaCl2 were used to study the osmotic and ionic effects of salinity on leaf dry biomass production and nutraceutical quality of cardoon (Cynara cardunculus L. var. altilis DC) grown in a floating system. A basic nutrient solution (control; T1) was enriched with 15 mm of NaCl + 10 mm of CaCl2 (T2), 30 mm of NaCl (T3), 30 mm of NaCl + 20 mm of CaCl2 (T4), or 60 mm of NaCl (T5). NaCl at 60 mm induced a 52% reduction of total leaf dry biomass compared with the control (T1); the iso-molar solution enriched with 20 mm of CaCl2 (T4) increased the total leaf dry biomass production in comparison with treatment containing NaCl at 60 mm (T5). Moreover, at moderate salinity (T2 and T3), the partial replacement of NaCl with 10 mm of CaCl2 (T2) in treatment containing 30 mm of NaCl did not help to reduce the adverse effect of NaCl on total leaf dry biomass production. Results of leaf mineral analysis demonstrated that the partial replacement of NaCl with CaCl2 reduced the accumulation of sodium and the nutrient imbalance. Nutrient solutions enriched with CaCl2 did not increase the accumulation of the osmoprotectant proline in leaves. Nutraceutical value of cardoon leaves was generally improved by saline treatments compared with the control. The regression analysis between phenolic compounds and antioxidant activity showed that total phenols and chlorogenic acid were the major determinants of antioxidant activity in cardoon leaf biomass. In conclusion, the partial replacement of NaCl with CaCl2 improved the leaf dry biomass production of cardoon only at the highest salinity levels with a limited effect on nutraceutical quality of leaves.
Mariateresa Cardarelli, Youssef Rouphael, Elvira Rea, Luigi Lucini, Marco Pellizzoni, and Giuseppe Colla
Three greenhouse experiments were carried out to compare the responses of Aloe arborescens and Aloe barbadensis with organic fertilization (standard or reduced fertilization level), arbuscular mycorrhiza [with AM (+AM) or without AM (–AM)], and salinity (1 or 80 mm NaCl) in terms of plant growth, leaf yield, mineral composition, and nutraceutical value. In all experiments, the yield of fresh leaves was significantly higher by 320%, 252%, and 72%, respectively, in A. barbadensis in comparison with A. arborescens. Doubling the fertilizer dose, plant growth parameters increased, but the bioactive compounds were negatively affected. The highest antioxidant activity was recorded with A. barbadensis using both fertilization regimes, whereas the highest values of anthraquinones aloin were observed in A. barbadensis using a reduced fertilization regime and when plants were inoculated with AM fungi. β-polysaccharide concentration was significantly higher in A. barbadensis in comparison with A. arborescens and was increased by 33% when plants were inoculated with AM fungi. In both Aloe species, increasing the salinity decreased the leaf fresh weight and total dry biomass but increased the aloin and β-polysaccharides content by 66% and 21%, respectively. The results suggest that cultural practices such as organic fertilization, inoculation with AM fungi, and irrigation with saline water can represent effective tools to achieve a more favorable phytochemical profile.