Stefania De Pascale

Irrigation with saline water improves carotenoids content and antioxidant activity of tomato

Summary The combined effect of increasing concentrations of NaCl in the irrigation water and fertilization with different nitrogen sources on the chemical composition of tomato (Lycopersicon esculentum Mill.) fruit was investigated. Increasing water salinity from 0.5.dS m-1 (non-salinized control) to 15.7.dS m-1 resulted in both reduced fruit size and fruit water content, whereas it caused an increase in soluble solids, carbohydrates, sodium and chloride concentrations. Titratable acidity increased upon irrigation with saline water, whereas the fruit redness significantly decreased. In addition, salinity reduced P, K+, Mg2+ and NO3- fruit concentrations. Total carotenoids and lycopene concentrations expressed on both fresh- and dry-weight basis gradually increased from the non-salinized control to the 4.4.dS m-1 treatment (approximately 0.25% NaCl w/v) and they decreased at electrical conductivities of the irrigation water higher than 4.4.dS m-1. Overall these data show that it is possible to improve carotenoid content and antioxidative activity of tomato, with an acceptable yield reduction, by irrigating with saline water containing NaCl up to 0.25% (w/v).

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.

The role of biostimulants and bioeffectors as alleviators of abiotic stress in crop plants

The use of bioeffectors, formally known as plant biostimulants, has become common practice in agriculture and provides a number of benefits in stimulating growth and protecting against stress. A biostimulant is loosely defined as an organic material and/or microorganism that is applied to enhance nutrient uptake, stimulate growth, enhance stress tolerance or crop quality. This review is intended to provide a broad overview of known effects of biostimulants and their ability to improve tolerance to abiotic stresses. Inoculation or application of extracts from algae or other plants have beneficial effects on growth and stress adaptation. Algal extracts, protein hydrolysates, humic and fulvic acids, and other compounded mixtures have properties beyond basic nutrition, often enhancing growth and stress tolerance. Non-pathogenic bacteria capable of colonizing roots and the rhizosphere also have a number of positive effects. These effects include higher yield, enhanced nutrient uptake and utilization, increased photosynthetic activity, and resistance to both biotic and abiotic stresses. While most biostimulants have numerous and diverse effects on plant growth, this review focuses on the bioprotective effects against abiotic stress. Agricultural biostimulants may contribute to make agriculture more sustainable and resilient and offer an alternative to synthetic protectants which have increasingly falling out of favour with consumers. An extensive review of the literature shows a clear role for a diverse number of biostimulants that have protective effects against abiotic stress but also reveals the urgent need to address the underlying mechanisms responsible for these effects.Graphical abstractBiostimulants have protective effects against abiotic stress.

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.

Hydroponic Cultivation Improves the Nutritional Quality of Soybean and Its Products

Hydroponic cultivation allows the control of environmental conditions, saves irrigation water, increases productivity, and prevents plant infections. The use of this technique for large commodities such as soybean is not a relevant issue on fertile soils, but hydroponic soybean cultivation could provide proteins and oil in adverse environmental conditions. In this paper, the compositions of four cultivars of soybean seeds and their derivates, soy milk and okara, grown hydroponically were compared to that of the same cultivar obtained from soil cultivation in an open field. Besides proximal composition, the concentrations of phytic acid and isoflavones were monitored in the seeds, soy milk, and okara. Results demonstrated that, independent from the cultivar, hydroponic compared to soil cultivation promoted the accumulation of fats (from 17.37 to 21.94 g/100 g dry matter) and total dietary fiber (from 21.67 to 28.46 g/100 g dry matter) and reduced isoflavones concentration (from 17.04 to 7.66 mg/kg dry matter), whereas protein concentration was unaffected. The differences found in seed composition were confirmed in the respective okara products, but the effect of cultivation system was not significant looking at the soy milk composition. Data showed that hydroponic cultivation improved the nutritional quality of soybean seeds with regard to fats and dietary fiber. They also suggest that specific cultivars should be selected to obtain the desired nutritional features of the soybean raw material depending on its final destination.

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.

Plant and soil resistance to water flow in faba bean (Vicia faba L. major Harz.)

An experiment was conducted to determine soil and plant resistance to water flow in faba bean under field conditions during the growing season. During each sampling period transpiration flux and leaf water potential measured hourly were used with daily measurements of root and soil water potential to calculate total resistance using Ohms law analogy. Plant growth, root density and soil water content distributions with depth were measured. Leaf area and root length per plant reached their maximum value during flowering and pod setting (0.31 m2 and 2200 m, respectively), then decreasing until the end of the growing period. Root distribution decreased with depth ranging, on average, between 34.2% (in the 0–0.25 m soil layer) and 18.1% (in the 0.75–1.0 m soil layer). Mean root diameter was 0.6 mm but most of the roots were less than 0.7 mm in diameter. Changes in plant and soil water potentials reflected plant growth characteristics and climatic patterns. The overall relationship between the difference in water potential between soil and leaf and transpiration was linear, with the slope equal to average plant resistance (0.0165 MPa/(cm3 m-1 h-1 10-3). Different regression parameters were obtained for the various measurement days. The water potential difference was inversely related to transpiration at high leaf stomatal resistance and at high values of VPD. Total resistance decreased with transpiration flux in a linear relationship (r=−0.68). Different slope values were obtained for the different measurement days. Estimated soil resistance was much lower than the observed total resistance to water flow. The change from vegetative growth to pod filling was accompanied by an increase in plant resistance. The experimental results support previous findings that resistance to water flow through plants is not constant but is influenced by plant age, growth stage and environmental conditions. A more complex model than Ohms law analogy may be necessary for describing the dynamic flow system under field conditions.

Agro-biology for bioregenerative Life Support Systems in long-term Space missions: General constraints and the Italian efforts

Abstract Future Space stations and Space habitats/outposts should be envisioned as self-sufficient ecological closed or semi-closed systems. The Italian Space Agency (ASI) projects have involved many research groups from complementary areas with a final goal of designing a facility for plant cultivation in Space. It has been critical to (i) identify, for this particular environment, highly productive species able to optimize O2 production/CO2 consumption, and (ii) develop high-tech controlled environments. Research activities have included seedling production in simulated microgravity and in Space with the two-fold objective of (i) integrating the crew diet with fresh food, and (ii) studying specific biological phenomena. Another research topic concerned pollen biology as a critical component for seed-to-seed cycles but also for gametophytic selection. In this context, a review of the main scientific topics on plant Space biology and of the Italian efforts on agro-biology for bioregenerative Life Support Systems will be presented and discussed in this paper.

Response to salinity stress of Rhizobium leguminosarum bv. viciae strains in the presence of different legume host plants

We investigated the effect of residual salts from the previous summer’s irrigation on two non-irrigated cover crops—broad bean and common vetch—and on their rhizobial symbiontics. Before sowing, seeds were inoculated with a salt-tolerant strain and a salt-sensitive strain of Rhizobium leguminosarum biovar viciae. An increase in the electrical conductivity of the saturated-soil extract from 2.0 dS m−1 to 6.0 dS m−1 caused a severe reduction of broad bean biomass, while growth of common vetch was almost unaffected by the salinity level. Our results clearly indicate that common vetch as a cover crop may increase the availability of nitrogen in soil more than broad bean also in saline environments. A high ability of both inoculated strains to nodulate Vicia plants was observed under controlled conditions. In contrast, inoculated strains were not able to nodulate plants in salinized soils, showing lower competitiveness compared to natural rhizobial population. Indeed, the new isolates from nodules were salt-sensitive when tested in vitro. The complex interaction among bacteria, plant and soil determined the survival of endogenous salt sensitive rhizobial strains and limited the success of inoculation with exogenous salt resistant rhizobia.

The effect of uni-axial clinostat rotation on germination and root anatomy of Phaseolus vulgaris L.

ABSTRACT Phaseolus vulgaris L. seed germination and seedling root anatomy were investigated on a slowly rotating clinostat in 1g. Clinostat rotating seeds were oriented as follows: the first group with the longer axis parallel to the rotation pole (horizontal), the other with the longer axis normal to the rotation pole with due attention to the position of the root apex primordium in the dry seeds (vertical). Germination time, percent germination and curvature of developing roots were monitored. Furthermore, the anatomy of the root apex was quantitatively analysed. Seeds placed on the clinostat germinated earlier than controls, and columella cells of roots developed while rotating lost the strict polarity with the nucleus positioned near the proximal periclinal cell wall and amyloplasts sedimented on the distal periclinal wall. Irrespective of seed orientation on the rotation axis, loss of cell polarity occurred as well as a decrease in starch content, modification in cell size, and damage to statocytes whose walls appeared partially digested. Cell size in the elongation zone was also larger in roots rotating on the clinostat than in controls, both in vertically and horizontally placed specimens. Our results demonstrate that prolonged rotation has an effect on the statocyte that continuously perceives gravity from ever-changing directions, although this effect is irrespective of seed position on the rotating axis in P. vulgaris.