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  • Open access
  • 85 Reads
Assessment of the effect of outer membrane vesicles of endophytic bacteria on the growth and physiological response of Arabidopsis thaliana

The world faces a challenge to produce a sufficient amount of food for the constantly growing human population in a sustainable manner. It means the usage of pesticides and fertilizers with minimized adverse effects on the environment and wide application of the beneficial microorganisms. Bacteria produce outer membrane vesicles (OMVs) that might affect plant development.

The aim of the study was to evaluate the impact of OMVs on the Arabidopsis thaliana condition. The experiments were conducted with endophytic bacteria. To obtain OMVs the specific protocols for their isolation have been developed. OMVs morphology, size and surface charge were performed with the use of SEM, TEM. OMVs were added on the surface of sterilized seeds of A. thaliana that were grown on Murashige and Skoog agar medium for 14-21 days. To assess the impact of OMVs on plants the rate of seeds germination, the biomass and length of shoots and roots were measured. Moreover, the level of oxidative stress and activity of antioxidant enzymes in plants were evaluated.

Experiments conducted so far have shown that OMVs produced by tested strains had a great ability to induce the germination and growth of seedlings. The OMVs originated from the tested bacteria differently influenced the length of plant roots. Serratia sp. OMVs inhibited the growth of A. thaliana seedlings whereas OMVs released by Pseudomonas sp. stimulated it. Furthermore, OMVs produced by both bacterial strains had a great effect on the activity of plant oxidative enzymes.

The knowledge on plant response to OMVs is limited. Therefore, the preliminary studies seem to be important to obtain knowledge that may be applicable in the development of the new natural compounds used as plant growth stimulators.

The research was financed by grant No. 2020/37/B/NZ8/00855 (OPUS 19) (National Science Centre).

  • Open access
  • 10 Reads
Performance of Gradient Boosting Learning Algorithm for Crop Stress Identification in the Greenhouse Cultivation
Published: 15 April 2022 by MDPI in 1st International Electronic Conference on Horticulturae session Posters

Greenhouse cultivation is one of the most crucial circular economy systems in agriculture that allows high resource use efficiency and low environmental impact. The data generated in high-tech and sophisticated greenhouse operations are provided by a variety of different sensors that enable a better understanding of the operational environment. In this study a learning algorithm namely Gradient Boosting Machine was tested using a database that was generated in greenhouse experiments in order to estimate different types of stress in a tomato crop. The examined model performs qualitative classification of the data, depending on the type of stress (water, high or low temperature). For the comparison, a 10-fold cross validation strategy on the 10,763 samples from the training set was selected. The dataset was divided in two parts, one for training 80% (8,610) and a second one for validation 20% (2,152). The cross-validation process was repeated 50 times. Among the parameters used as input for model building, leaf temperature had the highest significance with a ratio of 0.51. According to the results, the Gradient Boosting algorithm defined all the cases with high accuracy. The model built could identify the complete set of 379 samples of plants with low temperature stress, the 1305 out of 1321 samples of the plants without stress and the 431 out of the 452 samples of the plants with water stress. The accuracy of the model in identifying the type of stress was 98%. This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021), implemented by the State Scholarships Foundation (ΙΚΥ).

  • Open access
  • 37 Reads
Mineral Interaction in Biofortified Tomatoes (Lycopersicum esculentum L.) with Magnesium

Magnesium is considered an essential nutrient for humans, where about 60 % of Mg plays an important role in skeletal development. However, its deficiency can trigger several health pathologies (namely, asthma, Alzheimer’s disease, hypertension, type-2 diabetes). In plants, Mg is especially important, being involved in protein synthesis and correlated with chlorophyll pigments. Its deficiency can compromise photosynthesis and can also lead to shorter roots and necrotic zones in leaves. Mineral deficiency (namely, Mg) in plants can lead to a global problem considering the increase of human population and the needs to produce more food and that nutritionally meet human needs, being necessary adopt new technology and approaches. In this context, this study aimed to understand the mineral interactions with Mg biofortification in Lycopersicum esculentum (H1534 variety). Biofortification was promoted during the life cycle of the culture throughout six leaf applications with four concentrations (4%, 8%, 12%, and 16%) of MgSO4, equivalent to 702, 1404, 2106 and, 2808 g ha-1. At harvest, 4% MgSO4 treatment showed the highest content of Mg and P, and the lowest content of Fe and Zn. Additionally, the highest treatment showed the lowest content of Mg and on the other hand, the highest content of Fe. In conclusion, despite the synergistic and antagonistic relationships between minerals in the different concentrations of Mg applied, there were no significant changes in total soluble solids content in the fruits.

  • Open access
  • 73 Reads
Biological activities of phenolics in different parts of local cultivar of globe artichoke (Cynara cardunculus, var. scolymus L.)

Different parts of Cynara cardunculus, var. scolymus L. have been used in traditional medicine to treat various disorders and as coagulant in cheese making. In this work, phenolics from different parts of glob artichoke of the local cultivar “Violet d’Alger” (outer and inner bracts, stem, choke and heart) were extracted by Soxhlet method and partially purified. Extraction yield and purification yield were determined and phenolic compounds were analyzed by Folin-Ciocalteu method. Thin-layer chromatography was performed and the antioxidant capacity by 2,2-diphenyl 1-picrylhydrazyl (DPPH.) scavenging assay was achieved. Antibacterial and antifungal activities were estimated against the following bacteria and fungi: Bacillus subtilis, Geobacillus stearothermophilus, Staphylococcus aureus, Escherichia coli, Aspergillus fumigatus, and Candida albicans. Results showed that all extracts had considerable amounts of phenolics with a concentration-dependent antioxidant capacity and an effectiveness against bacterial and fungal strains. Among the different parts of globe artichoke, choke exhibited the highest phenolic content, antioxidant capacity and antimicrobial effect.

  • Open access
  • 46 Reads
Monitorization of mineral content and location after 3 months of storage of naturally enriched potato (Solanum tuberosum L.) with Calcium

Potato (Solanum tuberosum L.) is one of the most important staple food crops and one of the most consumed worldwide. As such, is a suitable food matrix for biofortification studies, namely with Ca, as it is an essential mineral for plant growth and development, being required for several structural issues. In this context, this study aimed to monitor the mineral content and location of Ca and other essential minerals (K, P, S, Fe, and Zn) and assess some quality parameters (color of the pulp, total soluble solid and dry weigh content) in tubers of Solanum tuberosum L. (Agria variety) after three months of storage, submitted to a Ca biofortification process with four foliar sprays with three concentrations of calcium nitrate (0.5, 2 and 4 kg.ha-1) and two concentrations of calcium chloride (3 and 6 kg.ha-1). It was found out that in most treatments, Ca, K, S, Fe, and Zn have higher content in the epidermis region and that control tubers showed a lower dry weight content compared to the biofortified ones. Moreover, after three months of storage, naturally enriched tubers maintain a preferential accumulation of Ca in the epidermis region (as seen in harvest) and showed a decrease in the dry weight content in control and biofortified tubers (compared to harvest data). Additionally, no significant differences were observed in the colorimetric parameters of pulp tubers and in the total soluble solid content, presenting similar data to the harvest ones. In conclusion, the storage process of biofortified tubers affected a quality parameter – dry weight content – being relevant for industrial processing and a criterion for potato tubers classification. In this context, only Ca(NO3)2 2kg.ha-1, CaCl2 3 and 6 kg.ha-1 treatments presented suitable for industrial processing after 3 months under storage conditions.

  • Open access
  • 43 Reads
Fertilization with ZnO and ZnSO 4 : Mineral analyses in Vitis vinifera grapes cv. Fernão Pires

Nutrition of the world population has become a concern, making research for strategies to enhance crop production necessary. Thus, the study of nutrients and the interactions between them is highly necessary since they are important for plant physiology and influence the growth of crops. Zinc is an essential micronutrient required for normal function of plants. Its deficiency is associated with losses in yield and nutritional quality. Vine, being a crop susceptible to Zn deficits, is among the most cultivated fruit plants in the world. In this study, the reactions of the variety Vitis Vinifera Fernão Pires, located in a field in Palmela, Portugal (N 38º 35'41.467 '' W 8º 50'44.535”), to three foliar sprays of ZnO and ZnSO4 with concentrations of 150 g ha-1 and 450 g ha-1 were studied. Using a XRF analyzer, the mineral content of the grapes and leaves was determined, which showed increases in the contents of Zn. It was found that the highest concentration (450 g ha-1) of ZnSO4 and ZnO, led to increases of 1.3 and 1.9-fold respectively. Importantly, XRF analysis confirmed that K and P contents of ZnO and ZnSO4-treated plants are similar to controls, indicating that there are no significant antagonistic and/or synergistic effects. Furthermore, to study the conditions of nutrient availability in the soil, parameters such as pH, organic matter and humidity were evaluated. This work showed that fertilization with ZnSO4 and ZnO was effective in increasing the concentration of Zn, without negatively affecting the contents of the crucial nutrients K and P, which is important to improve crop quality.

  • Open access
  • 76 Reads
Postharvest quality and storability of organically versus conventionally grown tomatoes: A comparative approach

In various parts of India, tomatoes are grown using eco-friendly indigenous organic manures prepared from cow products, for sustainable food production by small and marginal farmers. The main objective of the study was to compare the postharvest quality characteristics and storability between organically grown tomatoes using indigenous organic manures and those grown conventionally. The organic (OT) and conventional (CT) tomatoes procured from selected farms were observed for 28 days at ambient and refrigerated storage conditions. The postharvest quality characteristics and storability of tomatoes were assessed at the interval of 0, 7, 14, 21, 28 days and observed till senescence. Physiological loss of weight (PLW), total soluble solid (TSS), titratable acidity (TA), pH, color, lycopene, ascorbic acid content, respiration rate and microbial stability were assessed to determine the postharvest quality and storability of OT and CT respectively. The study revealed that organic tomatoes stored at refrigerated condition had lower physiological loss of weight (2.78%), respiration rate (27.61µLCO2g-1h-1) and loss in firmness (27.14%) compared to conventional tomatoes indicating the higher storability and delayed senescence. The titratable acidity showed a decreasing trend while pH increased significantly for both samples stored at ambient and refrigerated conditions. A slower rate of increment in redness and chroma values were observed for OT at refrigerated storage condition compared to ambient temperature. Ascorbic acid content was also found to be significantly higher in OT (23.53mg/100g) compared to CT (13.85mg/100g). Additionally, the result showed increased lycopene content in OT during storage compared to CT. Microbial study revealed that total aerobic mesophilic count and yeast- mold was highest on 28th day of storage. Therefore, the study revealed that tomatoes grown with indigenous liquid organic manures had superior postharvest quality and storability in comparison to conventionally grown tomatoes at refrigerated condition which owes to the increased longevity of the produce.

  • Open access
  • 114 Reads
LED lighting in vertical farming systems enhances bioactive compounds and productivity of vegetables crops

One of the greatest challenges of modern agriculture is to produce more with less, to producing healthier, safer food under sustainable systems, this includes a focus on increasing the efficiency of finite resources such as water and nutrients and increasing the sustainable productivity of crops under innovative systems with LED lights on soilless culture. The aim of this research was to perform a bibliometric analysis on the benefits of vertical farming production systems on the nutraceutical quality parameters of horticultural crops, additionally, the main parameters used to evaluate the quality and productivity of crops were identified. The methodology and results were analysed over a period of 4 years using the different quality parameters of lighting-LED as the main light source. The main plant species studied were lettuce, cabbage, cucumber, and spinach. The results showed that use of 16 h light photoperiods increased nutritional compounds such as antioxidants, phenols, and total sugar concentration, but in general, a moderately positive effect on plant growth and development was observed. The most used light intensities were between the range of 150 to 300 µmol m-2 s-1, and the specific spectrum-LED peaks between 450-495 nm (blue) and 620-750 nm (red and far-red). Therefore, the use of LED vertical farming systems as an alternative to increase the nutritional parameters of horticultural plants is a viable option since, in a short period of time and without geographical differentiation, it contributes to the production of nutraceutical compounds. It also contributes to a reduction of natural resource use, such as water, since one hundred percent of the research was carried out on the crops through hydroponic systems, which have the capacity to reuse water and nutrients.

  • Open access
  • 63 Reads
The effect of fertilization regime on growth parameters of Sonchus oleraceus and two genotypes of Portulaca oleracea

Wild edible plants of the Mediterranean represent an extraordinary food source and are basic ingredients in the “Mediterranean diet”. However, there is a scarcity of information about their commercial interest or cultivation practices. This study was conducted to evaluate how different amounts of inorganic and organic fertilization affected plant growth parameters of Sonchus oleraceus and Portulaca oleracea. The experiment was performed in greenhouse conditions, in pots containing soil, sand and vermiculite in the volume ratios of 1-1-1 during 12 weeks. The control treatment had no fertilization; inorganic fertilization (N-P-K) were 100 mL of 100-100-100 mg L-1; 300-100-100 mg L-1; 600-100-100 mg L-1; 300-200-100 mg L-1; 300-300-100 mg L-1; 300-200-200 mg L-1; 300-200-300 mg L-1; and 100 mL of organic compost extract to reach same equivalence than 300 mg L-1 of N) and 100 mL of organic compost extract + P inorg (equivalent to 300 mg L-1 of N and 200 mg L-1 of P). All treatments were applied weekly. All treatments assayed showed significantly higher leaf and stem weight compared to the control treatment, being the highest values recorded for the treatment of 600-100-100 in both plant species (S. oleraceus and P. oleracea). Treatment (600-100-100) showed significantly higher N content than the rest of treatments, but not P and K. The plant nutrients content of Mg, Fe, S and Ca did not differ among the tested fertilization regimes. Soil nutrients content (N, P, K, Fe, Ca) showed no differences between treatments. We conclude that nitrogen had a main role improving plants growth parameters and yield in both wild plant species being the beneficial effect depending on the fertilizer doses and origin (inorganic or organic) applied.

  • Open access
  • 67 Reads
The response of drought-stressed green pea (Pisum sativum L.) to boron nanoparticle application

Maintaining pea-growing areas is becoming increasingly difficult because they are highly sensitive to environmental stresses, especially drought. Green peas (Pisum sativum L.) are a very important source of amino acids in the diet of humans, poultry, and livestock nutrition, as well as in crop rotation. To reduce the potential adverse effects of drought on peas, this study aimed to investigate the effects of different concentrations of boron nanoparticles (B NPs) on plants via different routes of exposure: through leaves spraying and root watering. The research was carried out in a greenhouse, 10 green pea seeds (‘Respect’) were sown in 10 L vegetative pots and were thinned up to 7 plants per pot after germination. When the peas reached the 39 BBCH growth stage (had 9 or more visibly extended internodes) they were foliar sprayed to full wetness (ca. 14±0.5 mL plant−1) or watered (100±1 mL per pot) with suspensions containing different concentrations of B NPs: 0 (watered or sprayed with distilled water), 0.0125, 0.025, and 0.05 mg mL-1 During the 10-day drought period, low substrate moisture (30%) was maintained for peas exposed to B NPs, other plants (controls) were grown under normal substrate moisture (80%). At the end of the experiment, peas were harvested to assess the interactive effects of B NPs and drought on plants growth and enzymatic (SOD, GR, APX) and non-enzymatic (TPC, FRAP) antioxidants activity. The results showed that foliar spraying or watering at a concentration of 0.05 mg L-1 B NPs had a strong positive effect on pea leaf area, shoot height, fresh biomass, root length, and the number of nodules when plants grown in drought conditions. Positive effects on the activity of enzymatic (SOD, GR, APX) and non-enzymatic (TPC, FRAP) antioxidants in the pea plant were found. In general B NPs protected green peas from the adverse effects of drought stress if the appropriate concentration and application to the plant were selected.