Rita Maggini

Modeling Salinity Build-Up in Recirculating Nutrient Solution Culture

Abstract This paper presents a simple model for the changes in ion concentration and electrical conductivity (EC) of the recirculating nutrient solution in a closed-loop soilless culture of tomato (Lycopersicon esculentum Mill.). The model was designed on the basis of a balanced equation for plant nutrient uptake: for macrocations (K+, Mg2+ and Ca2+), a linear dependence of concentration on crop water uptake was assumed, while for non-essential ions, such as sodium (Na+), a non-linear function was used. The model was developed for closed-loop hydroponic systems in which crop water uptake (namely, transpiration) is compensated by refilling the mixing tank with complete nutrient solution. In these systems, EC gradually increases as a result of the accumulation of macro-elements and, principally, of non-essential ions, like Na+, for which the apparent uptake concentration (i.e., the ratio between nutrient and water uptake) is lower than their concentration in the irrigation water. For model calibration, data from both the literature and a previous work were used, while validation was performed with data from original experiments conducted with tomato plants in different seasons and using water with different sodium chloride (NaCl) concentrations (10 and 20 meq/L). The results of validation indicate that the model may be a useful tool for the management of closed-loop hydroponics, because it simulates rather well the salt accumulation that occurs in the recirculating nutrient solution when it is prepared with irrigation water of poor quality. Furthermore, the model is able to estimate the amount of crop evapotranspiration that leads to a value of EC at which flushing is necessary, thus enabling one to predict the water and nitrogen runoff of the semi-closed soilless culture.

Rosmarinic acid content in basil plants grown in vitro and in hydroponics

The accumulation of selected caffeic acid derivatives (CADs), in particular rosmarinic acid (RA), was investigated in different tissues (leaves, roots and plantlet shoots) of sweet basil (Ocimum basilicum L.) plants grown either in vitro or in hydroponic culture (floating system) under greenhouse conditions. Two cultivars with green leaves (Genovese and Superbo) and one with purple leaves (Dark Opal) were tested. The content of CADs in HCl-methanol extracts was determined by HPLC. LC-MS and LC-MS-MS were used to confirm the identification of the metabolites of interest. Apart from rosmarinic acid (RA) and a methylated form of this substance, no other CADs were detected at significant level in any of the analyzed samples. The content of RA ranged approximately from 4 to 63 mg/g DW, depending on the growing system. The highest RA content was found during the in vitro multiplication, in the acclimatized plants and in the roots of hydroponically-grown seedlings at full bloom. In vitro, 6-benzyladenine reduced the accumulation of RA in purple-leaf Dark Opal cultivar, but an opposite effect of this growth regulator was observed in the green-leaf genotypes. Our findings suggest the possibility to scale-up RA production by means of in vitro or hydroponic culture of sweet basil.

In vitro culture of sweet basil: gas exchanges, growth, and rosmarinic acid production

Five in vitro culture systems with different ventilation rates were used to investigate the influence of vessel environment on photosynthesis, dark respiration, ethylene evolution, and rosmarinic acid (RA) production in sweet basil (Ocimum basilicum L.) micropropagated shoots. The systems under comparison were two bioreactors with either temporary (RITA™) or stationary (Growtek™) immersion, and three types of vessels (Magenta™, Microbox ECO2™, and PCCV25™) that are largely used for plant micropropagation. Shoots of green-leaved cv. Genovese and purple-leaved cv. Dark Opal were cultured on a modified Murashige and Skoog medium containing 0.25 mg dm−3 6-benzylaminopurine. The instantaneous rates of photosynthesis, dark respiration, and ethylene production were determined by gas chromatography measuring CO2 and ethylene concentrations in vessel headspaces. The tissue RA content was determined by HPLC in HCl-methanol extracts. The explant growth and morphology were significantly affected by culture conditions and cultivars. The largest biomass production was observed under the photomixotrophic culture conditions provided by Growtek™, whereas the highest RA content in shoot tissues was found in the RITA™ photomixotrophic system, where ethylene accumulated to the greatest extent.

RESPONSE TO SODIUM CHLORIDE SALINITY AND EXCESS BORON IN GREENHOUSE TOMATO GROWN IN SEMI-CLOSED SUBSTRATE CULTURE IN A MEDITERRANEAN CLIMATE

The effects of sodium chloride (NaCl) salinity and boron (B) toxicity were investigated in greenhouse tomato (Solanum lycopersicum L.) plants grown in closed soilless culture under the typical climatic conditions occurring in the Mediterranean regions. The experiment was conducted under semi-commercial conditions. Two NaCl (2.0 and 10.0 mol m−3) and B (27.8 and 185.0 mmol m−3) concentrations were combined to produce four different types of raw water used to prepare the nutrient solutions. The fertigation treatment did not affect significantly the uptake of water and mineral elements apart from that of sodium (Na), chloride (Cl), and B. The use of B-enriched water increased the accumulation of this element in the leaves, which showed marginal chlorosis and necrosis within 35–40 days from planting. No or minor effects of NaCl and B concentrations in the irrigation water were found on leaf area development, biomass accumulation, crop yield and fruit quality.

Agronomic, Nutraceutical, and Organoleptic Performances of Wild Herbs of Ethnobotanical Tradition

ABSTRACT There is a lack of information on how to grow wild herbs as nutraceutical foods. Ten wild herbs were collected in natural and/or anthropized environments and assessed for their agronomic performance as fresh-cut (or ready-to-eat) leafy vegetables and their nutraceutical and organoleptic attributes. Seed dormancy prevented acceptable germination in many species. However, a physiological seed treatment (soaking with sodium hypochlorite followed by incubation for 3 months at 4°C in sand moistened with potassium nitrate solution) allowed satisfactory germination, usually above 80%. Cultivation in alveolar containers produced highly diversified fresh-cut productivity (250–550 g·m−2), lower than that of lettuce (Lactuca sativa L.; >900 g·m−2) grown as a reference fresh-cut green vegetable. Antioxidant power was often much greater in wild herbs (20.0 to 62.0 mmol Fe2+·kg−1 fresh weight [FW]) than in lettuce (21.0 mmol Fe2+·kg−1 FW). Evaluation of the sensory profile indicated that softness and sweet taste of lettuce were generally preferred to the more robust flavors of wild herbs. Hardness and bitter taste produced a poor appreciation of most wild herbs. However, exceptions were evidenced due to characteristics of spiciness [Alliaria petiolata (M.Bieb) Cavara & Grande] and/or crunchiness (Silene vulgaris [Moench] Garcke). Frequent distrust for most herbs was expressed as an example of food neophobia that generally occurs for unknown bitter flavors. Most of the wild herbs were not suitable as fresh-cut leafy vegetables, but some species could be ingredients for mixed products with better flavor and health properties.