G. Barbieri

Systemin-dependent salinity tolerance in tomato: evidence of specific convergence of abiotic and biotic stress responses

Plants have evolved complex mechanisms to perceive environmental cues and develop appropriate and coordinated responses to abiotic and biotic stresses. Considerable progress has been made towards a better understanding of the molecular mechanisms of plant response to a single stress. However, the existence of cross-tolerance to different stressors has proved to have great relevance in the control and regulation of organismal adaptation. Evidence for the involvement of the signal peptide systemin and jasmonic acid in wound-induced salt stress adaptation in tomato has been provided. To further unravel the functional link between plant responses to salt stress and mechanical damage, transgenic tomato (Lycopersicon esculentum Mill.) plants constitutively expressing the prosystemin cDNA have been exposed to a moderate salt stress. Prosystemin over-expression caused a reduction in stomatal conductance. However, in response to salt stress, prosystemin transgenic plants maintained a higher stomatal conductance compared with the wild-type control. Leaf concentrations of abscissic acid (ABA) and proline were lower in stressed transgenic plants compared with their wild-type control, implying that either the former perceived a less stressful environment or they adapted more efficiently to it. Consistently, under salt stress, transgenic plants produced a higher biomass, indicating that a constitutive activation of wound responses is advantageous in saline environment. Comparative gene expression profiling of stress-induced genes suggested that the partial stomatal closure was not mediated by ABA and/or components of the ABA signal transduction pathway. Possible cross-talks between genes involved in wounding and osmotic stress adaptation pathways in tomato are discussed.

Effects of soil salinity from long-term irrigation with saline-sodic water on yield and quality of winter vegetable crops

Abstract From 1988 onwards a study was carried out to evaluate the long-term effects of increasing water salinity (0%, 0.125%, 0.25%, 0.5% and 1% of commercial NaCl) on some vegetable crops growing in a clay-loam soil. In 1992 and 1993 the effects of the residual soil salinity on yield and some aspects of yield quality were studied in lettuce, endive and fennel grown during irrigation-free seasons on a field which had undergone the same irrigation treatment since 1988. Within the range of electrical conductivity of the saturated-soil extract (ECe) between 2.0 dS m −1 (treatment 0%) and 6.0 dS m −1 (treatment 1%) the marketable yield decreased by about 60% in endive and fennel and by about 15% in lettuce which proved more tolerant than the other crops. Gas exchange rates and stomatal conductance were reduced by salinity in lettuce. Soil salinity affected product quality: lettuce and endive appeared to be more sensitive to tipburn and necrotic symptoms occurring in the crop under saline-sodic conditions; fennel heart length, width, and thickness were also significantly reduced and the heart shape tended to be modified in plants grown on salt-affected plots. The results, obtained by analyzing the salt tolerance model of Maas-Hoffman and its descriptive parameters, place lettuce, endive and fennel in the moderately sensitive category. In terms of ECe, the threshold ranged from 1.8 dS m −1 (fennel) to 2.7 dS m −1 (lettuce) while the slope varied between 5.8% per dS m −1 (lettuce) and 15.7% per dS m −1 (endive).

Nutritional quality of ten leafy vegetables harvested at two light intensities

The nutritional composition of ten leafy vegetables (chicory, green lettuce, lambs lettuce, mizuna, red chard, red lettuce, rocket, spinach, Swiss chard, and tatsoi) and quality traits of the selected leafy vegetables in relation to the light intensity (low and high Photosynthetically Active Radiation; PAR) at time of harvest were determined. Irrespective of the light intensity at time of harvest, the highest leaf dry matter (DM), proteins, nitrate, P, K and Ca contents were observed in rocket followed by mizuna. The highest lipophilic antioxidant activity (LAA) was recorded in red lettuce and rocket, whereas ascorbic acid (AA) and total phenolic (TP) contents of red lettuce were higher compared to the other leafy vegetables. When leafy vegetables were harvested at low as opposed to high PAR, the leaf content was higher in DM, protein, K, Ca and Mg, hydrophilic antioxidant activity (HAA), and LAA by 12.5%, 10.0%, 12.6%, 23.7%, 14.1%, 11.9%, and 18.5%, respectively. The highest values in TP for chicory, green lettuce, lambs lettuce, mizuna, red chard, and red lettuce, were observed under high PAR.

Effects of soil salinity and top removal on growth and yield of broadbean as a green vegetable

Abstract In 1994 the effects of soil salinity and top removal were studied on faba bean for green consumption, grown during the irrigation-free season on a clay-loam soil which since 1988 had undergone the same irrigation treatments of increasing water salinity (0%; 0.125%; 0.25%; 0.5% and 1% of commercial NaCl). The response to salt tolerance was evaluated by using two models: The Maas and Hoffman model Yr = 100 − S(ECe) − T) and the van Genuchten model Yr = 100/[1 + ( EC e EC e50 ) p ]. Within the range of electrical conductivity of the saturated soil extract (ECe) between 2 dS m−1 and 6 dS m−1, soil salinity reduced plant height by 60%, leaf area by 70%, total above ground dry matter by 45%, mean pod weight by 15% and the number of pods per plant (48%). Leaf dry matter and specific leaf weight (SLW) were positively related to salinity. Higher salinity stress decreased the seed yield by 67% due to a reduction in weight and number of seeds, and also affected product quality. The results obtained by analysing the salt tolerance model of Maas-Hoffman and its descriptive parameters, place broadbean for green consumption in the moderately salt-sensitive category. In terms of relative yield per surface unit, from the Maas and Hoffman model the threshold value was 1.7 dS m−1 and yield was reduced at the rate of 15% (dS m−1)−1: the salinity level at 50% yield reduction (ECe50) was 5 dS m−1, compared to 4.7 dS m−1 of the van Genuchten model. With regard to pod yield per plant, the values of parameters were 1.8 dS m−1 (threshold) and 13% (dS m−1)−1 (slope) and the salinity level at 50% yield reduction (ECe50) was 5.6 dS m−1, compared to 5.4 dS m−1 of the van Genuchten model. Top removal at the beginning of pod set was ineffective. At low soil salinity the only effect of top removal was higher early production, indicating a more efficient partition of assimilates to growing pods and, therefore, rapid pod enlargement and higher yield at the first harvest.

Polyphenol Metabolite Profile of Artichoke Is Modulated by Agronomical Practices and Cooking Method

In this paper artichoke phenolic pattern was characterized using an Orbitrap Exactive Mass Spectrometer at high mass accuracy and conventional HPLC MS/MS. Twenty four phenolic acids and 40 flavonoids were identified, many of them not previously reported in artichoke. Variations in phenolic compounds were investigated in relation to mycorrhization: results showed that inoculation with mycorrhizae greatly influences metabolite profile proving to be a good strategy to enhance the biosynthesis of secondary metabolites in this plant. This practice also caused a different distribution of the main phenolic compounds within head parts. Both steaming and microwaving cooking treatments caused an increase in antioxidant activity: the lower the initial concentration the higher the effect. A similar trend was observed looking at the phenolic compounds concentration: it increased because of cooking treatments the lower the initial content, the highest the increase. Steamed artichoke showed higher phenols content than microwaved ones.

Seasonal and multiannual effects of salinisation on tomato yield and fruit quality

The effects of short- and long-term salinisation were studied by comparing tomato growth on a soil exposed to one-season salinisation (short term) vs growth on a soil exposed to >20 years salinisation (long term). Remarkable differences were associated to substantial modifications of the soil physical-chemical characteristics in the root zone, including deteriorated structure, reduced infiltration properties and increased pH. Fresh yield, fruit number and fruit weight were similarly affected by short- and long-term salinisation. In contrast, the marketable yield was significantly lower in the long-term salinised soil - a response that was also associated to nutritional imbalance (mainly referred to P and K). As reported for plants growing under oxygen deprivation stress, the antioxidant capacity of the water soluble fraction of salinised tomato fruits was enhanced by short-term salinisation, also. Overall, long-term salinisation may cause physiological imbalances and yield reductions that cannot be solely attributed to hyperosmotic stress and ionic toxicity. Therefore, the ability of plants to cope with nutritional deficiency and withstand high pH and anoxia may be important traits that should be considered to improve plant tolerance to long-term salinised soils.

Sulphur fertilisation affects yield and quality in friarielli (Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort.) grown in a floating system

Summary The influence of nitrogen and sulphur fertilisation on yield and quality was studied in two ecotypes of friarielli (Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort.) grown in a floating system. In the first experiment, we assessed the effects of different levels of N fertilisation on friarielli yield. In a second experiment, we tested three concentrations of S in the nutrient solution [2.6 mM, 4.0 mM, and 8.5 mM; corresponding to N:S concentration ratios of 10:1, 6.5:1, and 3:1, respectively] with the objective of fine-tuning the nutritional requirements for N and S to optimise both friarielli yield and quality. The main findings can be summarised as follows: (i) friarielli can be grown efficiently in a hydroponic system; (ii) both yield and quality in friarielli are strongly dependent on the N:S ratio of the nutrient solution; (iii) S may affect shoot nitrate accumulation in response to N availability; (iv) the response to S fertilisation is genotype-specific; (v) the anti-oxidant capacity of shoots increases with increasing S concentrations in the nutrient solution; and (vi) 26 mM N and an N:S concentration ratio of 10:1 in the nutrient solution are suggested for the best performance of hydroponically-grown friarielli.

Monitoring nitrogen forms in soil/plant systems under different fertilizer managements. A preliminary investigation

Abstract A field experiment was carried out on maize ( Zea mays , L.) to study the effects of different fertilizer management on nitrogen status in soil and plant response. Three different fertilizers, mineral (MN), mineral plus buffalo manure (MN + BM) and organo-mineral with peat (OMP), were added at the usual (140, 61 and 116 kg ha −1 ) and the reduced (70, 31 and 58 kg ha −1 ) rates of N, P and K. respectively. Soil samples were analyzed for N by both the Kjeldahl method and the electro-ultrafiltration technique (EUF). The soil Kjeldahl-N concentrations were scarcely affected by the different fertilizer treatments, while the EUF-N concentrations were closely correlated with the amounts of N added. The EUF also discriminated between the NO 3 -N and the sum of the ammonium and the easily extractable organic N forms (EUF-N org + NH 4 ). The largest proportions of EUF-Norg + NH 4 were found in the untreated plots and in the plots treated with buffalo manure. The different fertilizer treatments significantly affected grain yield, which ranged from a minimum of 6.3 t ha −1 from the untreated plots, to a maximum of 11.9 t ha −1 from those supplied with 140 kg N, 61 kg P and 116 kg K ha −1 by OMP fertilizer. The highest agronomic efficiency index for N was exhibited in the OMP treatment at the reduced rate. The grain yield was closely correlated with the total extractable EUF-N, but different relationships were found between the rate of N added, the level of EUF-NO,-N in soil and grain yield for the different fertilizer treatments.

Effect of bacterial root symbiosis and urea as source of nitrogen on performance of soybean plants grown hydroponically for Bioregenerative Life Support Systems (BLSSs)

Soybean is traditionally grown in soil, where root symbiosis with Bradyrhizobium japonicum can supply nitrogen (N), by means of bacterial fixation of atmospheric N2. Nitrogen fertilizers inhibit N-fixing bacteria. However, urea is profitably used in soybean cultivation in soil, where urease enzymes of telluric microbes catalyze the hydrolysis to ammonium, which has a lighter inhibitory effect compared to nitrate. Previous researches demonstrated that soybean can be grown hydroponically with recirculating complete nitrate-based nutrient solutions. In Space, urea derived from crew urine could be used as N source, with positive effects in resource procurement and waste recycling. However, whether the plants are able to use urea as the sole source of N and its effect on root symbiosis with B. japonicum is still unclear in hydroponics. We compared the effect of two N sources, nitrate and urea, on plant growth and physiology, and seed yield and quality of soybean grown in closed-loop Nutrient Film Technique (NFT) in growth chamber, with or without inoculation with B. japonicum. Urea limited plant growth and seed yield compared to nitrate by determining nutrient deficiency, due to its low utilization efficiency in the early developmental stages, and reduced nutrients uptake (K, Ca, and Mg) throughout the whole growing cycle. Root inoculation with B. japonicum did not improve plant performance, regardless of the N source. Specifically, nodulation increased under fertigation with urea compared to nitrate, but this effect did not result in higher leaf N content and better biomass and seed production. Urea was not suitable as sole N source for soybean in closed-loop NFT. However, the ability to use urea increased from young to adult plants, suggesting the possibility to apply it during reproductive phase or in combination with nitrate in earlier developmental stages. Root symbiosis did not contribute significantly to N nutrition and did not enhance the plant ability to use urea, possibly because of ineffective infection process and nodule functioning in hydroponics.