Can Adverse Effects of Acidity and Aluminum Toxicity Be Alleviated by Appropriate Rootstock Selection in Cucumber?

Low-pH and aluminum (Al) stresses are the major constraints that limit crop yield in acidic soils. Grafting vegetable elite cultivars onto appropriate rootstocks may represent an effective tool to improve crop tolerance to acidity and Al toxicity. Two greenhouse hydroponic experiments were performed to evaluate growth, yield, biomass production, chlorophyll index, electrolyte leakage, mineral composition, and assimilate partitioning in plant tissues of cucumber plants (Cucumis sativus L. "Ekron") either non-grafted or grafted onto "P360" (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne; E/C) or figleaf gourd (Cucurbita ficifolia Bouché; E/F). Cucumber plants were cultured in pots and supplied with nutrient solutions having different pH and Al concentrations: pH 6, pH 3.5, pH 3.5 + 1.5 mM Al, and pH 3.5 + 3 mM Al (Experiment 1, 14 days) and pH 6, pH 3.5, and pH 3.5 + 0.75 mM Al (Experiment 2, 67 days). Significant depression in shoot and root biomass was observed in response to acidity and Al concentrations, with Al-stress being more phytotoxic than low pH treatment. Significant decrease in yield, shoot, and root biomass, leaf area, SPAD index, N, K, Ca, Mg, Mn, and B concentration in aerial parts (leaves and stems) in response to low pH with more detrimental effects at pH 3.5 + Al. Grafted E/C plants grown under low pH and Al had higher yield, shoot, and root biomass compared to E/F and non-grafted plants. This better crop performance of E/C plants in response to Al stress was related to (i) a reduced translocation of Al from roots to the shoot, (ii) a better shoot and root nutritional status in K, Ca, Mg, Mn, and Zn concentration, (iii) a higher chlorophyll synthesis, as well as (iv) the ability to maintain cell membrane stability and integrity (lower electrolyte leakage). Data provide insight into the role of grafting on Al stress tolerance in cucumber.

Salinity source-induced changes in yield, mineral composition, phenolic acids and flavonoids in leaves of artichoke and cardoon grown in floating system.

BACKGROUND: Leaves of artichoke (Cynara cardunculus L. subsp. scolymus (L.) Hegi) and cardoon (Cynara cardunculus L. var. altilis DC) are traditionally used as herbal medicine. Moderate salt stress could enhance antioxidant activity and phytochemicals in leaves. The aim of this study was to evaluate the effect of chloride salts (NaCl, KCl and CaCl2) on biomass production, mineral composition, phenolic and flavonoid contents and antioxidant activity in leaves of artichoke and cardoon grown in a floating system. RESULTS: In both crops, NaCl and KCl treatments reduced biomass production, while similar values were recorded in CaCl2 and control treatments. In both crops, KCl treatment enhanced total phenolic and flavonoid contents, antioxidant activity and target polyphenols in leaves harvested at 48, 82 and 105 days after sowing (DAS), while leaf quality was improved by NaCl and CaCl2 treatments only at 82 and 105 DAS. Irrespective of salinity, leaves of cardoon had higher total phenolic and flavonoid contents, antioxidant activity and target polyphenols than those of artichoke. CONCLUSION: The results showed that application of KCl can be considered an effective way to produce high-quality leaves of artichoke and cardoon during the whole cropping cycle, although resulting in a 30% reduction in plant biomass.

Graft union formation in artichoke grafting onto wild and cultivated cardoon: an anatomical study.

In order to develop a non-chemical method such as grafting effective against well-known artichoke soil borne diseases, an anatomical study of union formation in artichoke grafted onto selected wild and cultivated cardoon rootstocks, both resistant to Verticillium wilt, was performed. The cardoon accessions Belgio (cultivated cardoon) and Sardo (wild cardoon) were selected as rootstocks for grafting combinations with the artichoke cv. Romolo. Grafting experiments were carried out in the autumn and spring. The anatomical investigation of grafting union formation was conducted by scanning electron microscopy (SEM) on the grafting portions at the 3rd, 6th, 10th, 12th day after grafting. For the autumn experiment only, SEM analysis was also performed at 30 d after grafting. A high affinity between artichoke scion and cardoon rootstocks was observed, with some genotype differences in healing time between the two bionts. SEM images of scion/rootstock longitudinal sections revealed the appearance of many interconnecting structures between the two grafting components just 3d after grafting, followed by a vascular rearrangement and a callus development during graft union formation. De novo formation of many plasmodesmata between scion and rootstock confirmed their high compatibility, particularly in the globe artichoke/wild cardoon combination. Moreover, the duration of the early-stage grafting process could be influenced not only by the scion/rootstock compatibility, but also by the seasonal conditions, being favored by lower temperatures and a reduced light/dark photoperiod.

Effects of saline stress on mineral composition, phenolic acids and flavonoids in leaves of artichoke and cardoon genotypes grown in floating system.

BACKGROUND: Cynara cardunculus is a species native to the Mediterranean basin. It includes globe artichoke and cultivated cardoon as well as their progenitor wild cardoon. The species is a source of biophenols, and its leaf extracts have been widely used in herbal medicine as hepatoprotectors and choleretics since ancient times. The aim of this study was to determine the effect of increasing the level of salinity in the nutrient solution (1 or 30 mmol L⁻¹ NaCl) on biomass production, mineral composition, radical-scavenging activity, caffeoylquinic acids and flavonoids in three artichoke ('Romolo', 'Violetto di Provenza' and 'Violetto di Romagna') and three cultivated cardoon ('Bianco Avorio', 'Bianco Gigante Inerme' and 'Gigante di Romagna') cultivars grown in a floating system. RESULTS: Increased salinity in the nutrient solution decreased the leaf dry biomass and leaf number of artichoke and cultivated cardoon cultivars. Salinity reduced macro- and microelement accumulation in leaves (e.g. N, K, Ca, Mg, Fe, Mn and B) but improved their antioxidant activity, total polyphenols, chlorogenic acid, cynarin and luteolin. The cultivated cardoons, especially 'Bianco Avorio' and 'Gigante di Romagna', showed higher biomass and leaf number than those observed in artichoke genotypes. 'Violetto di Provenza' exhibited the highest content of chlorogenic acid, closely followed by 'Violetto di Romagna', whereas for cynarin content the highest values were recorded in 'Violetto di Provenza', 'Bianco Avorio' and 'Gigante di Romagna'. The highest content of luteolin was recorded in 'Gigante di Romagna' and 'Bianco Avorio', while the highest content of apigenin was observed in 'Gigante di Romagna'. CONCLUSION: The results showed that the floating system could be considered an effective tool to improve quality aspects through proper management of the salt concentration in the nutrient solution. They also suggest that specific cultivars should be selected to obtain the desired profile of bioactive compounds.

Organo-mineral fertilisers from glass-matrix and organic biomasses: a new way to release nutrients. A novel approach to fertilisation based on plant demand.

BACKGROUND: A glass-matrix fertiliser (GMF), a by-product from ceramic industries, releases nutrients only in the presence of complexing solutions, similar to those exuded by plant roots. This ensures a slow release of nutrients over time, limiting the risk of their loss in the environment. With the aim to improve fertiliser performance, GMF was mixed with vine vinasse (DVV), pastazzo (a by-product of the citrus processing industry, PAS) or green compost (COMP) and nutrient release was evaluated by citric and chloridric acid extraction, at different concentrations. RESULTS: Theoretical and actual nutrients release were compared to evaluate possible synergistic effects due to the organic component added to the mineral fertiliser: phosphorus (+7.1%), K (+4.8%), Fe (+8.5%) and Zn (+5.5%) were released more efficiently by 2% citric acid from GMF + DVV, while Ca availability was increased (+5.3%) by 2% citric acid from GMF + PAS mixture. Both DVV and COMP increased by 12-18% the Fe release from GFM matrix. CONCLUSION: Organic biomasses added to GMF increased the release of some macro and micronutrients through an 'activation effect', which suggests the employment of these organo-mineral fertilisers also in short-cycle crops production. Moreover, the re-use of some agro-industrial organic residues gives another 'adding value' to this novel organo-mineral fertilfertilisers.