Photosynthetic responses of durum wheat to chemical/microbiological fertilization management under salt and drought stresses

AbstractThe current research was carried out to evaluate the stress tolerance potential of durum wheat plants, in response to the inoculation of native plant growth-promoting bacteria (PGPB), through assessing PSII photochemistry and photosynthetic traits, as well as grain yield and plant height, and to investigate the possibility of using PGPB as a sustainable alternative or in combination with traditional fertilization plans. A greenhouse experiment included chemical/microbiological fertilization and stress (salinity and drought) treatments. The results indicated that the application of bacterial consortium of four PGPB markedly augmented some biochemical and functional traits in photosystem II, such as effective quantum yield of PSII photochemistry (Y(II)), electron transport rate of PSII (ETR), photosynthesis capacity, transpiration rate and stomatal conductance in unstressed plants, and prevented severe changes in the mentioned traits under drought and salinity conditions. The application of PGPB contributed to enhanced grain yield, too. Furthermore, a better performance of the PGPB inoculation was found in combination with half-dose of the recommended chemical fertilizers. In conclusion, PGPB inoculants maintain or improve the photosynthesis efficiency of durum wheat, grain yield and plant height, particularly under stress conditions, and can help to minimize the consumption of chemical fertilizers

Isolation of Bacteria with Potential Plant-Promoting Traits and Optimization of Their Growth Conditions

This research aimed at investigating the isolation and identification of bacterial strains with biological nitrogen-fixing capability and phosphate, potassium, and zinc solubilization activities from a durum wheat field under two different tillage practices including 10 years of conventional tillage (CT) and no-tillage (NT) practices. Attempts were also extended to estimate their relative abundances in the soil as well as to develop accurate mathematical models in determining the effect of different temperatures, NaCl concentrations and pH on the growth, and activity of selected isolates. Twelve effective bacterial strains, including Pseudomonas, Acinetobacter, and Comamonas genera, were identified with a great potential to solubilize the insoluble forms of phosphate (from 11.1 to 115.5 mg l−1 at pH 8), potassium (from 32.2 to 35.6 mg l−1 at pH 7), and zinc (from 1.11 to 389.90 mg l−1 at pH 9) as well as to fix N2 gas (from 19.9 to 25.2 mg l−1). To our knowledge, this is the first report of the ability of Comamonas testosteroni and Acinetobacter pittii to fix nitrogen and to solubilize insoluble potassium compound, respectively. Three families, Moraxellaceae, Pseudomonadaceae, and Comamonadaceae, showed a higher percentage of abundance in the NT samples as compared to the CT, but only significant difference was observed in the relative abundance of Pseudomonadaceae (P < 0.01). These strains could be definitively recommended as inoculants to promote plant growth in the wide ranges of pH, salinity levels (with maximum growth and complete inhibition of growth from 0.67–0.92% to 3.5–9.3% NaCl, respectively), and temperatures (2.1–45.1 °C)

Plant Growth and Root Morphology Are Affected by Earthworm-Driven (Eisenia sp.) Changes in Soil Chemico-Physical Properties: a Mesocosm Experiment with Broccoli and Faba Bean

Earthworms are "ecosystem engineers" that improve soil water and nutrient content, soil macroporosity, and aeration, and provide suitable habitats for microbial populations. This study aimed at defining if the presence of epigeic earthworms (Eisenia sp.) affected the growth and development of two plant species (Brassica oleracea and Vicia faba) via the modifications of soil chemico-physical properties. A mesocosm experiment, in which plants were grown outdoors for 4 months with or without earthworms, was performed. The two plant species were selected based on their different habitus and root architecture and morphology. Soil macroporosity (M-soil) and water holding capacity (WHCsoil) were determined. Earthworm-driven bioturbation (B-soil) was measured by filling mesh bags with artificial soil. Earthworm abundance and biomass, together with plant morphometric parameters (root and leaf morphology by imaging and microscope techniques), were measured at the end of the trial. The presence of earthworms increased M-soil (on average +16%) and WHCsoil (on average +9%) and this was accompanied by a remarkable degree of B-soil. In most of the cases, earthworms enhanced plant growth in the two plant species studied, with a significant positive influence on the majority of the shoot and root traits. A significant increase of stomatal density (on average +24%) occurred in the leaves of both the plant species in the presence of earthworms. Our results confirmed the hypothesis that bioturbation by Eisenia sp. had a significant positive effect on plant growth, independently from the plant species cultivated, and that these growth-promoting effects were mediated by changes in soil chemico-physical parameters. By taking into account the essential role of earthworms in maintaining healthy soils and the vegetation they support, soils can become more resilient against environmental perturbations and climate change

Impact of long term soil management practices on the fertility and weed flora of an almond orchard

oil management techniques can definitely influence soil quality, and particularly soil organic matter content, biological complexity, structure, and water holding capacity. Tillage may also have a negative effect by increasing erosion and organic matter oxidation processes, which have unavoidable repercussions on fertility. The objective of the current research was to test the effects of five different management techniques applied for 35 years on a rain-fed almond grove (Prunus amygdalus Batsch) in a hot-dry environment on some physicochemical, hydrological, and biological parameters. The following soil management techniques were compared: no-till (NT), with weed control by preemergence herbicides; NT, with chemical weed control by foliar herbicides; NT, with weed control by mowing; tillage, with sowing and field bean green manuring; and conventional tillage. The current survey supplied interesting results, considering the typical soil and climate conditions of the tested area (southern Italy), characterized by high summer temperatures, low rainfall, clay loam soil, and an arable layer of 0.40 m. The most influenced values are those concerning the organic matter due to the supply of biomass resulting from weed mowing or field bean green manuring. The NT system with a single mowing in the spring seems to induce a higher water holding capacity (–15,000 hPa) as compared with the traditionally plowed soil. The biomass incorporation through field bean green manure resulted in a higher available water content (11.82%). All practices favoring an increase in organic matter induced a subsequent increase of microbial biomass content. The number of existing families and species of weed flora was largely influenced by different soil management techniques, as shown by the greater adaptation of grasses to the management practices involving weed control by foliar herbicide or mowing, and of several species associated with the technique involving the application of preemergence herbicides. In general, the almond orchard management involving minimum soil disturbance and the supply of biomass resulting from specially sown cover crops or weed development have shown substantial benefits to the physicochemical, hydrologic, and biologic soil properties

Functional and anatomic response of the retina and the choroid to intravitreal bevacizumab for macular edema.

Purpose: This study evaluated the rate of change of best corrected visual acuity (BCVA), central retinal sensitivity, and retinal and choroidal thickness in patients with macular edema after intravitreal bevacizumab. Methods: This was a prospective, nonrandomized, interventional study. Thirty-four consecutive eyes (34 patients) with macular edema were included in the study. Choroidal neovascularization was present in 21 cases, stage 1 retinal angiomatous proliferation in 6 cases, branch retinal vein occlusion in 4 cases, and diabetic edema in 3 cases. Evaluation of BCVA (Early Treatment Diabetic Retinopathy Study [ETDRS] logarithm of the minimum angle of resolution [LogMAR]), central retinochoroidal thickness (RCT) at standardized A-scan, combined optical coherence tomography/microperimetric assessment of central retinal thickness (RT), central scotoma, and fixation behavior was performed during 12 months after treatment. Choroidal thickness was considered as the difference between RCT and RT. All patients received two initial intravitreal bevacizumab injections (1.25 mg/0.05 mL) at a 1-month interval. Results: BCVA and RT during follow-up were significantly better than at baseline. BCVA was improved of 0.32 +/- 0.3 LogMAR (P &lt; 0.001) at month 1,0.18 +/- 0.4 LogMAR (P = 0.05) at month 6, and 0.14 +/- 0.2 (P = 0.09) at month 12. RT was reduced by 172.9 +/- 192.8 mu m (P &lt; 0.001) at month 1,157.7 +/- 134.2 mu m (P = 0.003) at month 6, and 164.3 +/- 122.3 (P = 0.002) at month 12. Mean retinal sensitivity significantly increased during the first month; it decreased afterward, but an improvement if compared with baseline was present at each visit during follow-up. In 23.5% of cases, a choroidal thinning was present during follow-up, and in this group visual acuity at baseline and final visual improvement were significantly greater if compared with patients showing a choroidal thickening. Conclusion: Intravitreal bevacizumab for macular edema determines significant functional and anatomic improvement at the 12-month follow-up. Visual acuity at baseline and following treatment could be influenced by the choroidal involvement

Intravitreal triamcinolone, bevacizumab and pegaptanib for occult choroidal neovascularization.

PURPOSE: To evaluate best-corrected visual acuity (BCVA) and foveal thickness (FT) changes in occult subfoveal choroidal neovascularization (CNV) from age-related macular degeneration (AMD) after intravitreal bevacizumab (IVB, 1.25 mg/0.05 ml), pegaptanib (IVP, 0.3 mg/0.09 ml) and triamcinolone acetonide (IVTA, 4 mg/0.1 ml) injected on an as needed basis. METHODS:   Retrospective, interventional, comparative study. BCVA (Early Treatment Diabetic Retinopathy Study LogMAR) and FT by optical coherence tomography (OCT) were evaluated during 12 months from first treatment. Patients were retreated if signs of neovascular activity were still present on angiography or OCT. RESULTS: Forty-eight eyes received IVB, 43 eyes received IVP, 52 eyes received IVTA. BCVA and FT at baseline were 1.22 ± 0.49 LogMAR and 410.2 ± 41.83 μm in the IVB group, 1.25 ± 0.43 LogMAR and 452.3 ± 44.83 μm in the IVP group and 1.31 ± 0.4 LogMAR and 456.6 ± 48.27 μm in the IVTA group. BCVA and FT improved in the three groups during follow-up. A significantly greater improvement of BCVA was present at month-3, month-6 and at month-12 in the IVB and IVP groups (p = 0.01). Improvement of FT was greater in the IVTA group at month-3 (p = 0.02), while it was greater in the anti-Vascular Endothelial Growth Factor (VEGF) groups at month-6 and month-12 (p = 0.01). A postoperative increase of intraocular pressure was detected in 9/52 (17.3%) eyes treated with IVTA, and in two cases it was resistant to topical therapy. CONCLUSION:   Intravitreal injection of anti-VEGF drugs administered on an as needed basis for AMD-related occult CNVs provided functional and anatomic improvement during 12 months of follow-up

Differential olive grove management regulates the levels of primary metabolites in xylem sap

Aims The conventional management adopted in many Mediterranean olive orchards makes them more vulnerable to climate change and attacks by pathogens, due to the decreased chemical plant defenses. In this scenario, a metabolomic analysis was carried out on the xylem sap (Xsap) of olive plants (Olea europaea L.) grown in the Salento peninsula (Italy). Methods Trials were carried out in two olive groves, one organically and one conventionally managed (controls), successively both converted to sustainable management (i.e. frequent light pruning, soil and foliar fertilization, cover crops). The Xsap was extracted from the shoots of olive plants using a Scholander pressure chamber pressurized with N2 and gas chromatography-mass spectrometry metabolite profiling was performed in the Xsap. Results An untargeted gas chromatography mass spectrometry (GC-MS) based metabolomic analysis of primary metabolites (including underivatized volatiles) of the Xsap revealed relative abundances of 153 identified metabolites and 336 unknown features across the 12 samples from four groups of samples. Among them, more than half were involved in the primary metabolism. Many of the compounds with increased levels under sustainable management (such as amino acids, soluble sugars, sugar alcohols) have a well-known role as osmoprotectants or are involved in plant defense, growth and development during stress or recovery stages. Conclusions Sustainable management in olive groves can increase the ability of plants to overcome environmental stressors and enhance ecosystem balance