Summary• Hydrogen peroxide (H 2 O 2 ), ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC) and salicylic acid (SA) concentrations and ACC synthase (ACS) gene expression were measured to establish whether the high sensitivity of the Populus deltoides × maximowiczii clone Eridano to ozone (O 3 ) exposure, compared with the O 3 -resistant Populus deltoides × euramericana clone I-214, is attributable to differences in the modulation of signal transduction pathways.• In a time-course experiment, Populus deltoides (poplar) clones were exposed to acute fumigation with 150 nl l − 1 O 3 for 5 h.• The two poplar clones showed differences in ethylene evolution, I-214 displaying earlier and less pronounced ethylene emission than Eridano. In both clones, ethylene evolution was accompanied by increased ACS transcript levels and enhanced emission of free ACC. I-214 exhibited a greater basal concentration of free SA and a lower concentration of the conjugated pool. However, a slight accumulation of free SA at the end of the 5-h exposure was found only in Eridano, together with an earlier minimal increase in the concentration of conjugated SA.• The results show that both clones react to O 3 by producing H 2 O 2 , ethylene and SA, but the difference in sensitivity to the pollutant is probably attributable to differences in the kinetics and magnitude of this response.

Spinach is one of the most important green-leafy vegetables, consumed worldwide, and its intake is beneficial for human beings. In this crop, produce yield and quality are closely related to plant nitrogen (N) nutrition. A precise supply of N is also essential for high environmental and economic sustainability. Main aims of the work were: i) to establish relationships between produce yield or quality and mineral N availability in the root zone; and ii) to define an optimal mineral N level to be maintained in the root zone for spinach. Eight experiments were carried out during a four-year-long period under typical Mediterranean climate conditions. Different amounts of N fertilisers were supplied leading to twenty different levels of mineral N in the root zone. Experimental measurements included climate parameters, plant growth, tissue and soil analyses, produce yield and quality indicators. A segmented linear model significantly represented the relationship between crop yield (1.7 to 21.7 t ha–1) and soil mineral N concentration (7.6 to 41.0 mg kg–1). Basing on this model, an optimal mineral N threshold was fixed at 23.4 mg kg–1. Above this threshold, crop yield did not show any significant variations as well as tissue characteristics and produce quality. Plants grown under suboptimal N levels showed reduction in growth, tissue mineral (nutrients) content, and SPAD index. The proposed models could be implemented in fertilisation protocols for the optimization of N supply and the estimation of spinach growth and yield.

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

Landfill leachate can release pollutants into the environment. Nevertheless, it can be treated using a phytodepuration system via constructed wetlands to reduce contaminants. Moreover, this leachate can also increase the availability of macro and micronutrients in soil and water. In this trial, the reuse of untreated and treated wastewater from municipal solid waste (MSW) for fertigation was assessed. Plantlets of Viola × wittrockiana (pansy) were grown in a greenhouse and five fertigation treatments were applied: W9.0 (pure wastewater, EC 9.0 dS m−1), W4.5 (diluted wastewater, EC 4.5 dS m−1), DW4.5 (depurated wastewater, EC 4.5 dS m−1), PW4.5 (phytodepurated wastewater, EC 4.5 dS m−1), and T (tap water, control, EC 1.5 dS m−1). The treatment with untreated wastewater had a negative effect on plant dry weight, leaf size, specific leaf area, water content, and the number of closed and open flowers, due to the high concentration of SO42− in the fertigation water. It also reduced the content of Cu, Mn, Fe, and Zn with respect to the control, because of the dry biomass diminution. Conversely, fertigation with phytodepurated wastewater enhanced root and shoot dry weight, water content, and the number of closed and open flowers. Cu and Mn contents in flowers surpassed the content detected in plants fertigated with untreated leachates. These findings demonstrate that phytodepurated wastewater obtained from MSW can be employed for the fertigation of this species.

The agricultural district of Pistoia (Tuscany, Italy) is one of the most important sites in Europe for the production of Hardy Ornamental Nursery Stock (HONS). One of the main problems of this sector is the environmental impact of the pot cultivation, mainly due to an incorrect irrigation scheduling that leads to high nitrogen and phosphorus losses. The aim of this research has been to compare the effects of the traditional fertigation versus new fertilization strategies, based on the use of controlled slow-release fertilizers (CRFs), on plant growth and on nitrogen and phosphorus runoff in two container HONS species (Photinia x fraseri and Prunus laurocerasus). Every week, plant height, cumulate irrigation and drainage volume were measured on four replicates for each treatment and species. Every four weeks two average samples of drainage water and irrigation water for each treatment and species were analysed, determining total nitrogen and phosphorus content, in order to draft a water and nutrient balance. The three different fertilization strategies did not produce any relevant effect on the final plant height and all plants were ranked in the top quality market category.The data confirmed that the use of CRFs could contribute to a huge reduction of nitrogen and phosphorus runoff in the environment and could be a winning strategy for the fertilization of HONS in the nitrate vulnerable zone.