Gibberellins (GAs) are growth hormones strongly involved in a wide variety of physiological activities. Currently, gibberellins are commercially used to enhance phenotypic characteristics, earliness, and productivity of many vegetable and ornamental crops. In this work, the efficacy of supplementation of low levels of gibberellic acid (0, 10⁻⁸, 10⁻⁶, and 10⁻⁴ M GA₃) through the mineral nutrient solution of a floating system on yield and quality of leaf lettuce and rocket plants was tested. The marketability of plants was lost when 10⁻⁴ M GA₃ was added to the mineral nutrient solution. This study demonstrated that the addition of 10⁻⁴ M GA₃ exceeded the acceptable threshold for use in hydroponics production systems. Below the concentration of 10⁻⁴ M, the presence of GA₃ in the mineral nutrient solutions (MNS), especially at 10⁻⁶ M GA₃, stimulated plant growth and enhanced the yield. Various morphological and physiological traits were enhanced by GA₃ treatments (biomass accumulation, leaf expansion, stomatal conductance, water use efficiency (WUE), Nitrogen use efficiency (NUE), etc.), with superimposable trends in both lettuce and rocket. The addition of 10⁻⁶ M GA₃ to the nutrient solution of a hydroponic floating system can promote growth and quality of lettuce and rocket plants.

Mediterranean areas with intensive agriculture are characterized by high salinity of groundwater. The use of this water in hydroponic cultivations can lead to nutrient solutions with an electrical conductivity that overcomes the tolerance threshold of many vegetable species. Plant growth-promoting rhizobacteria (PGPR) were shown to minimize salt stress on several vegetable crops but the studies on the application of PGPR on leafy vegetables grown in hydroponics are rather limited and have not been used under salt stress conditions. This study aimed to evaluate the use of plant growth-promoting bacteria to increase the salt tolerance of leaf lettuce grown in autumn and spring in a floating system, by adding a bacterial biostimulant (1.5 g L⁻¹ of TNC Bactorr^S13 a commercial biostimulant containing 1.3 × 10⁸ CFU g⁻¹ of Bacillus spp.) to mineral nutrient solutions (MNS) with two salinity levels (0 and 20 mM NaCl). Leaf lettuce plants showed a significant reduction of growth and yield under salt stress, determined by the reduction of biomass, leaf number, and leaf area. Plants showed to be more tolerant to salinity in autumn than in spring. The inhibition of lettuce plant growth due to salt stress was significantly alleviated by the addition of the bacterial biostimulant to the MNS, which had a positive effect on plant growth and fresh and dry biomass accumulation of the unstressed lettuce in both cultivation seasons, and maintained this positive effect in brackish MNS, with similar or even significantly higher values of morphologic, physiologic, and yield parameters than those recorded in control unstressed plants.

Environmental conditions and growing techniques may influence the characteristics of eggplant fruits and their content in phenolic compounds. Grafting is a non chemical alternative for overcoming the effects of intensive and continuous cropping that can modify plant and fruit characteristics. The rootstocks preferred for eggplant are hybrids of tomato or tomato KVFN. Also species taxonomically close, as Solanum torvum, have been used and showed good vigour, compatibility and resistance to wilt disease. Information on yield and quality of grafted eggplants onto this rootstock is conflicting. Therefore, the aim of this study was to evaluate yield and quality of eggplant cultivars (Birgah, Black Bell, Black Moon and Longo) grafted or ungrafted onto Solanum torvum. Plants were grown from October 2009 to May 2010 in an unheated plastic greenhouse on solarized soil. Grafted plants had lower mortality, while yield and quality of fruits were mostly influenced by cultivars. The differences recorded for growth and yield of the tested cultivars might be due to different growth characteristics, graft affinity and compatibility. Longo and Black Moon were not influenced by grafting, while grafted plants of Birgah and Black Bell had a higher unmarketable production. Grafting onto Solanum torvum changed the color of fruits that were darker and with a less vivid color. Browning of inner tissue was not influenced by grafting. Total phenolic content was greater in the ungrafted plants

Vegetable plants are more sensitive to salt stress during the early growth stages; hence, the availability of poor-quality brackish water can be a big issue for the nursery vegetable industry. Microbial biostimulants promote growth and vigor and counterbalance salt stress in mature plants. This study aimed to evaluate the application of plant growth-promoting microorganisms for improving salt tolerance of lettuce and tomato seedlings irrigated with different water salinity levels (0, 25, and 50 mM NaCl) during nursery growth. Two commercial microbial biostimulants were applied to the substrate before seeding: 1.5 g L⁻¹ of TNC Bactorr^S13 containing 1.3 × 10⁸ CFU g⁻¹ of Bacillus spp.; 0.75 g L⁻¹ of Flortis Micorrize containing 30% of Glomus spp., 1.24 × 10⁸ CFU g⁻¹ of Agrobacterium radiobacter, Bacillus subtilis, Streptomyces spp. and 3 × 10⁵ CFU g⁻¹ of Thricoderma spp. Many morpho-physiological parameters of lettuce and tomato seedlings suffered the negative effect of salinity. The use of the microbial biostimulants modified seedling growth and its response to salt stress. They had a growth-promoting effect on the unstressed seedlings increasing fresh and dry biomass accumulation, leaf number, and leaf area and were successful in increasing salinity tolerance of seedlings especially when using Flortis Micorizze that enhanced salinity tolerance up to 50 mM NaCl. The inoculation of the substrate with microbial biostimulants could represent a sustainable way to improve lettuce and tomato transplant quality and to use brackish water in vegetable nurseries limiting its negative effect on seedling growth.