a b s t r a c tIn recent years, the interest toward the applicability of Light-Emitting Diode (LED) lights for indoor cultivation has significantly grown. The present work addressed the physiological and phytochemical plant responses to LED lights in indoor cultivation of leafy and fruit vegetable crops (namely sweet basil, Ocimum basilicum L.; and strawberry, Fragaria × Ananassa), with the final aim of improving both productivity and nutritional quality. Artificial light treatments were applied in a multi-sectorial growth chamber equipped with lamps with different light incidence and spectra (with red:blue ratio ranging 0.7-5.5). In all experiments, increased plant biomass, fruit yield and energy use efficiency (EUE) were associated to LED treatments, confirming the superiority of LED compared to the traditional fluorescent lamps. Interestingly, LED lighting enabled to increase antioxidant compounds and reduce nitrates content in basil leaves. A spectral red:blue ratio of 0.7 was necessary for proper plant development and improved nutraceutical properties in both crops.

Fresh water resources are limited and their use in agricultural production is expected to come under increasing constraints. Eighteen Syrian lines of potato (Solanum tuberosum L.) were screened for drought tolerance by measuring aerial and root growth in vitro. Drought stress was evaluated by adding 2, 4, 6, 8 and 10 % (w:v) of sorbitol to MurashigeSkoog medium and compared to 0 % for the control. Water potential of media ranged from −0.58 MPa to −2.5 MPa. Water-stress in culture adversely affected plant growth, and genotypes differed for their responses. Plant length and stem thickness, leaf area, root number length and thickness, and plant fresh and dry weights and plant water content were measured and all decreased due to drought. Grouping lines by cluster analysis for response to drought resulted in: (1) a tolerant group of six lines, (2) a moderately tolerant group of seven lines, and (3) a susceptible group of five lines. The variation in germplasm indicated that potato varieties can be developed for production under some levels of drought.

Water availability is considered as a determinant factor that affects plant growth. The commercial medicinal values of an aromatic plant rely on the presence of secondary metabolites that are affected under water shortage. Two-year-oldThymus citriodorusplants were subjected to different polyethylene glycol (PEG-6000) levels (0, 2%, and 4%) under greenhouse condition. PEG treatment lasted for 15 days. Thyme plant showed a morphological drought avoidance mechanism by maintaining the root system development through shoot fresh weight reduction resulting in promoted root absorption capacity and sustained plant growth. Moreover, stressed plants were able to maintain water use efficiency and root : shoot ratio suggesting a strong relation between root water uptake and water use saving strategies. Furthermore, thyme plants reduced tissue dehydration through stomatal closure and improved root water uptake. Content of volatile oil constituents of geraniol and diisobutyl phthalate increased upon drought stress while pseudophytol was reduced. Unexpectedly, thymol was not reported as a main oil element under either control or mild stress condition, while it was increased upon high drought stress in measure of 4.4%. Finally, carvacrol significantly accumulated under high drought stress (+31.7%) as compared to control plants.

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Grafted plants are often more tolerant to salinity than nongrafted controls. In order to distinguish differential response components in grafted melon (Cucumis melo L.), salt stress was imposed on several rootstock–scion combinations in four experiments. The rootstock used was an interspecific squash (Cucurbita maxima Duch. × Cucurbita moschate Duch.), RS841, combined with two cantaloupe (C. melo var. cantalupensis) cultivars, namely London and Brennus, against both self-grafted and nongrafted controls. Physiological, morphological and biochemical adaptations to 0, 40 and 80 mM NaCl were monitored. Upon salinity, plant biomass and leaf area were improved by grafting per se, since self-grafted plants performed similarly to the heterografted ones. However, improvements in the exclusion of Na+ and the uptake of K+ were due only to the rootstock genotype, since ionic composition was similar in self-grafted and nongrafted plants. These results indicate that the favourable effects of grafting on plant growth cannot be ascribed to a more efficient exclusion of Na+ or enhanced nutrient uptake. On the other hand, growth improvements in both self- and heterografted plants were associated with a more efficient control of stomatal functions (changes in stomatal index and water relations), which may indicate that the grafting incision may alter hormonal signalling between roots and shoots.

Urban horticulture is increasingly popular for social and economic benefits. However, edible urban crops may be contaminated by airborne pollutants, thus leading to serious health risks. Therefore, a better understanding of contamination risks of urban cultivation is needed in order to define safe practices. In particular, whereas it is commonly accepted that the contamination of urban-grown food comes from airborne pollutants, little is known on a possible contamination by soils. Here, we studied trace metal risk in horticultural crops grown in an experimental urban allotment garden in Bologna, Italy. Seven experiments were conducted between June and November 2015 on tomato, sweet basil, onion, lettuce, kale, bulb fennel and radish. Treatments included two growing systems, soil and soilless, and two fertilization managements, mineral and organic. Trace metal concentrations were measured in soils, substrates and edible plant tissues. We identified preferentially translocated metals by partitioning analysis of tomato, sweet basil and kale. Results showed that crops grown in a soilless system have a lower metal content of −70 % for Cr, −61 % for Cu, −45 % for Cd and −81 % for Ni, compared with those grown in soil. This finding demonstrates that the major contamination risk in an urban area is unexpectedly related to soil pollution.

Higher antioxidative enzymatic activities in Savoy versus White cabbage after treatment with 100 mmol L(-1) NaCl were associated with improved water relations, thus suggesting a possible physiological pathway for alleviating perceived salt stress.

Salinity is a major constraint for plant growth in world areas exposed to salinization. Sorghum bicolor (L.) Moench is a species that has received attention for biomass production in saline areas thanks to drought and salinity tolerance. To improve the knowledge in the mechanisms of salt tolerance and sodium allocation to plant organs, a pot experiment was set up. The experimental design combined three levels of soil salinity (0, 3, and 6 dS m−1) with three levels of water salinity (0, 2–4, and 4–8 dS m−1) and two water regimes: no salt leaching (No SL) and salt leaching (SL). This latter regime was carried out with the same three water salinity levels and resulted in average +81% water supply. High soil salinity associated with high water salinity (HSS-HWS) affected plant growth and final dry weight (DW) to a greater extent in No SL (−87% DW) than SL (−42% DW). Additionally, HSS-HWS determined a stronger decrease in leaf water potential and relative water content under No SL than SL. HSS-HWS with No SL resulted in a higher Na bioaccumulation from soil to plant and in translocation from roots to stem and, finally, leaves, which are the most sensitive organ. Higher water availability (SL), although determining higher salt input when associated with HWS, limited Na bioaccumulation, prevented Na translocation to leaves, and enhanced selective absorption of Ca vs. Na. At plant level, higher Na accumulation was associated with lower Ca and Mg accumulation, especially in No SL. This indicates altered ion homeostasis and cation unbalance.