Search Results

A greenhouse experiment was carried out to determine growth, yield, fruit quality, gas exchange and mineral composition of watermelon plants (Citrullus Lanatus L. `Tex'), either ungrafted or grafted onto two commercial rootstocks `Macis' [Lagenaria siceraria (Mol.) Standl.] and `Ercole' (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) and cultured in NFT. Plants were supplied with a nutrient solution having an electrical conductivity (EC) of 2.0 or 5.2 dS·m^–1. The saline nutrient solution had the same basic composition, plus an additional of 29 mm of NaCl. Increased salinity in the nutrient solution decreased total yield. The reduction in total yield in saline treatments compared to control was due to a reduction in the fruit mean mass and not to the number of fruit per plant. Total fruit yield was 81% higher in grafted than in ungrafted plants. The lowest marketable yield recorded on ungrafted plants was associated with a reduction in both fruit mean mass and the number of fruits per plant in comparison to grafted plants. Salinity improved fruit quality in all grafting combinations by increasing dry matter (DM), glucose, fructose, sucrose, and total soluble solid (TSS) content. Nutritional qualities of grafted watermelons such as fruit DM, glucose, fructose, sucrose, and TSS content were similar in comparison to those of ungrafted plant. In all grafting combinations, negative correlations were recorded between Na⁺ and Cl^– in the leaf tissue and net assimilation of CO₂ Grafting reduced concentrations of sodium, but not chloride, in leaves. However, the sensitivity to salinity was similar between grafted and ungrafted plants and the higher total yield from grafting plants was mainly due to grafting per se.

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.

Limited water supply in the Mediterranean region is a major problem in irrigated agriculture. Grafting may enhance drought resistance, plant water use efficiency, and plant growth. An experiment was conducted in two consecutive growing seasons to determine yield, plant growth, fruit quality, leaf gas exchange, water relations, macroelements content in fruits and leaves, and water use efficiency of mini-watermelon plants [Citrullus lanatus (Thunb.) Matsum. and Nakai cv. Ingrid], either ungrafted or grafted onto the commercial rootstock ‘PS 1313’ (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne), under open field conditions. Irrigation treatments were 1.0, 0.75, and 0.5 evapotranspiration rates. In both years (2006 and 2007), marketable yield decreased linearly in response to an increase in water stress. When averaged over year and irrigation rate, the total and marketable yields were higher by 115% and 61% in grafted than in ungrafted plants, respectively. The fruit quality parameters of grafted mini-watermelons such as fruit dry matter and total soluble solids content were similar in comparison with those of ungrafted plants, whereas titratable acidity, K, and Mg concentrations improved significantly. In both grafting combinations, yield water use efficiency (WUE_y) increased under water stress conditions with higher WUE values recorded in grafted than ungrafted plants. The concentration of N, K, and Mg in leaves was higher by 7.4%, 25.6%, and 38.8%, respectively, in grafted than in ungrafted plants. The net assimilation of CO₂, stomatal conductance, relative water content, leaf, and osmotic potential decreased under water stress conditions. The sensitivity to water stress was similar between grafted and ungrafted plants, and the higher marketable yield from grafted plants was mainly the result of an improvement in nutritional status and higher CO₂ assimilation and water uptake from the soil.

The current research aimed 1) at evaluating the effects of three biostimulants (legume-derived protein hydrolysate, PH; plant and seaweed extract, PE and SWE) on yield performance and nutritional quality, mineral profiling, antioxidant activities, lycopene, total phenols and ascorbic acid of greenhouse tomato (Solanum lycopersicum L.) under soil culture and 2) to assess the economic profitability of biostimulant applications. Plants were sprayed four times during the growing cycle with a solution containing 1, 3, and 3 mL·L⁻¹ of PE, SWE, and PH, respectively. Foliar applications of biostimulants improved the early and total marketable yield of fresh tomato. The increase of total yield by PE, SWE, and PH was 11.7%, 6.6% and 7.0%, respectively, in comparison with untreated plants. Legume-derived PH increased lycopene, total soluble solids, and K and Mg contents, thereby increasing the nutritional value of the fruits. The applications of SWE, and to a lesser degree PH, enhanced the Ca concentration in the fruit tissue. Our findings indicated that the three tested biostimulants, although they increased the total production cost, improved the nutrient status and yield performance of the crop to a level resulting in net economic benefits.

The fertilizer nitrogen (N) inputs to some potted plants such as ornamental cabbage (Brassica oleracea L. var. acephala D.C.) are frequently higher than the actual demand. Optimization of N fertilization rate and selecting N-efficient cultivars are important approaches to increase the nitrogen use efficiency (NUE) and to reduce environmental pollution from nitrate leaching. The aim of this study was to assess the effect of increasing levels of nitrate (0.5, 2.5, 5, 10, or 20 mm of NO₃ ⁻) in the nutrient solution on plant growth, quality, soil plant analysis development (SPAD) index, chlorophyll fluorescence, leaf pigments, mineral composition, and NUE in five ornamental cabbage cultivars (Coral Prince, Coral Queen, Glamour Red, Northern Lights Red, and White Peacock), grown in closed subirrigation system. ‘Glamour Red’ and ‘Northern Lights Red’ needed 3.3 and 2.9 mm of NO₃ ⁻ in the supplied nutrient solution, respectively, to produce 50% of predicted maximum shoot dry weight (SDW), whereas the vigorous cultivars Coral Prince, Coral Queen, and White Peacock needed 5.5, 4.7, and 4.3 mm of NO₃ ⁻, respectively. Total leaf area (LA), SDW, SPAD index, N, Ca, and Mg concentrations increased linearly and quadratically in response to an increase of the nitrate concentration in the nutrient solution. Irrespective of cultivars, fertilizing above 10 mm NO₃ ⁻ produced high-quality plants (quality index of 5) and resulted in sufficiently high tissue concentrations of N, P, K, Ca, Mg, and Fe.

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.

Identification of rootstocks capable of improving the nitrogen use efficiency (NUE) of the scion could reduce N fertilization and nitrate leaching; however, screening different graft combinations under field conditions can be costly and time-consuming. This study evaluated a rapid and economical methodology for screening of melon rootstocks for NUE. Two experiments were designed. In the first, melon plants (Cucumis melo L. cv. Proteo) either ungrafted or grafted onto four commercial rootstocks: ‘Dinero’ and ‘Jador’ (Cucumis melo L.), ‘P360’, and ‘PS1313’ (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) grown in hydroponics were compared in terms of shoot dry biomass, leaf area, root-to-shoot ratio, SPAD index, shoot N uptake, and nitrate reductase (NR) activity at the early developmental stage in response to nitrate availability (0.5, 2.5, 5, 10, or 15 mm of NO₃ ^–). The second experiment was aimed to confirm whether the use of a selected rootstock with high NUE (‘P360’) could improve crop performance and NUE of grafted melon plants under field conditions. In the first experiment, carried out under greenhouse conditions, melon plants grafted onto ‘Dinero’, ‘Jador’, and ‘P360’ rootstocks needed 5.7, 5.2, and 6.1 mm of NO₃ ^–, respectively, to reach half-maximum shoot dry weight, whereas plants grafted onto ‘PS1313’ rootstock and the control treatment (ungrafted plants) needed 9.1 and 13.1 mm of NO₃ ^–, respectively. Total leaf area, SPAD index, and shoot N uptake increased linearly and quadratically in response to an increase of the N concentration in the nutrient solution. At 2.5 mm of NO₃ ^–, melon plants grafted onto both C. melo and Cucurbita maxima × Cucurbita moschata rootstocks had the highest NR activity, whereas no significant difference was observed at 10 mm of NO₃ ^–. In the second experiment, carried out under open field conditions, increasing the N fertilization rates from 0 to 120 kg·ha⁻¹ increased the total and marketable yields of melon plants, whereas the NUE decreased. When averaged over N levels, the marketable yield, NUE, and N uptake efficiency were higher by 9%, 11.8%, and 16.3%, respectively, in ‘Proteo’ grafted onto ‘P360’ than in ungrafted ‘Proteo’ plants.

A greenhouse experiment was conducted to determine the influence of long-term cadmium (Cd) exposure (0, 25, or 50 µm of Cd) on crop productivity, fruit quality, leaf chlorophyll content, fluorescence, and mineral composition in plants of tomato (Solanum lycopersicum L. cv. Ikram), either nongrafted, self-grafted, or grafted onto rootstocks of tomato (Maxifort or Unifort) and eggplant (Black Beauty). Both moderate (25 µm) and high (50 µm) concentration of Cd in root environment considerably decreased the fruit yield and fruit number in response to Cd levels, whereas mean fruit weight decreased but was similar to both Cd supply levels. The fruit yield, shoot and root biomass, and leaf area (LA) were higher in plants grafted onto tomato rootstocks and especially onto Maxifort in comparison with nongrafted or self-grafted plants and especially grafted onto Black Beauty. The higher plant performance of tomato rootstock–grafted plants were related to higher chlorophyll fluorescence and photosynthetic pigments concentration in leaves associated with better nutrient translocation and availability (higher Ca, Mg, Fe, Mn, and Cu) in leaves. The content of Cd was also lower in leaves and fruits of Maxifort-grafted plants. Concerning fruit quality, especially peel color, toxicity symptoms, and Cd concentration, Black Beauty followed by Maxifort-grafted plants were better than the other grafting combinations. However, plants grafted onto Black Beauty rootstock resulted in lowest fruit yield and plant growth attributes due to lower nutrient uptake and translocation indicating some incompatibility reaction between Black Beauty rootstock and Ikram scion.

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.