Improvement of morphophysiological and anatomical attributes of plants under abiotic stress conditions using plant growth-promoting bacteria and safety treatments.

Drought and salinity are the major abiotic stress factors negatively affecting the morphophysiological, biochemical, and anatomical characteristics of numerous plant species worldwide. The detrimental effects of these environmental factors can be seen in leaf and stem anatomical structures including the decrease in thickness of cell walls, palisade and spongy tissue, phloem and xylem tissue. Also, the disintegration of grana staking, and an increase in the size of mitochondria were observed under salinity and drought conditions. Drought and salt stresses can significantly decrease plant height, number of leaves and branches, leaf area, fresh and dry weight, or plant relative water content (RWC%) and concentration of photosynthetic pigments. On the other hand, stress-induced lipid peroxidation and malondialdehyde (MDA) production, electrolyte leakage (EL%), and production of reactive oxygen species (ROS) can increase under salinity and drought conditions. Antioxidant defense systems such as catalase, peroxidase, glutathione reductase, ascorbic acid, and gamma-aminobutyric acid are essential components under drought and salt stresses to protect the plant organelles from oxidative damage caused by ROS. The application of safe and eco-friendly treatments is a very important strategy to overcome the adverse effects of drought and salinity on the growth characteristics and yield of plants. It is shown that treatments with plant growth-promoting bacteria (PGPB) can improve morphoanatomical characteristics under salinity and drought stress. It is also shown that yeast extract, mannitol, proline, melatonin, silicon, chitosan, α-Tocopherols (vitamin E), and biochar alleviate the negative effects of drought and salinity stresses through the ROS scavenging resulting in the improvement of plant attributes and yield of the stressed plants. This review discusses the role of safety and eco-friendly treatments in alleviating the harmful effects of salinity and drought associated with the improvement of the anatomical, morphophysiological, and biochemical features in plants.

Untargeted metabolomic in basil cell cultures - a case study of Ocimum basilicum L. var. minimum Alef.

AIMS: Due to the lack of experimental databases, together with the chemical complexity and the dynamic nature of plants' metabolome, most of the metabolites in complex biological materials (like plant in vitro tissue cultures) are not-annotated, unidentified metabolites. In this study, a method for further metabolite characterization and classification based on the UPLC-HESI-HRMS/MS approach for small-leaved basil (Ocimum basilicum L. var. minimum Alef.) callus and cell suspension culture is presented. KEY RESULTS: A total of 2168 metabolic features were detected, out of which the database for exact mass metabolic profiling for 1949 metabolites is presented here since there is no available database dedicated to O. basilicum. We further focused on secondary metabolites (particularly phenolic compounds). The presence of 60 different phenolic compounds belonging mainly to the groups of flavonoids, glycosides, terpenoids, and phenolic acids is confirmed. By comparing relative abundances of phenolic compounds from callus culture and cell suspension culture, both grown on two types of media, via svd-PCА, univariate analysis, post-hoc tests, and heatmapping of metabolites, we provided a practical example of how resources presented here can be further applied in tissue culture-based basil metabolomics studies. UTILITY: This study represents the first approach toward routine targeted investigation of secondary metabolites in basil in vitro cultures and provides various opportunities for new-generation analyses.

Coastal Halophytes: Potent Source of Bioactive Molecules from Saline Environment.

This study represents a comparative analysis of secondary metabolites content, antioxidant, and antimicrobial activity of 24 halophytes from coastal saline habitats of the Balkan Peninsula (Montenegro, Albania, and Greece). Total content of phenolics, flavonoids, tannins, anthocyanins, antioxidant, and antimicrobial activity was determined for dry methanolic (DME) and crude water extracts (CWE) and compared with well-known medicinal plants. The total phenolic content ranged from 13.23 to 376.08 mg of GA/g of DME, and from 33.68 to 511.10 mg/mL of CWE. The content of flavonoids ranged from 12.63 to 77.36 mg of RU/g of DME, and from 12.13 to 26.35 mg/mL of CWE. Total tannins and anthocyanins varied from 0.05 to 2.44 mg/mL, and from 1.31 to 39.81 µg/L, respectively. The antioxidant activity ranged from 1147.68 to 15.02 µg/mL for DME and from 1613.05 to 21.96 µg/mL for CWE. The best antioxidant properties, and the highest content of phenolic compounds, were determined for Polygonum maritimum and Limonium vulgare with values similar to or higher compared to the medicinal plants. Halophytes with significant antimicrobial potential were Limonium vulgare, L. angustifolium, and Artemisia maritima. Some of the analyzed coastal halophytes can be considered rich natural sources of phenolic compounds, with favorable antioxidative and antimicrobial properties.

Improvement of Germination and Early Growth of Radish (Raphanus sativus L.) through Modulation of Seed Metabolic Processes.

Radish (Raphanus sativus L.) is a vegetable cultivated worldwide because of its large succulent hypocotyls. The priming method initiates metabolic processes at early stages and regulates the metabolic events in seed necessary for germination. This research was conducted to examine the influence of various priming treatments on physiological performance (germination, growth, lipid peroxidation, primary and secondary metabolism) and antioxidant activity of radish seedlings. On the basis of germination and growth characteristics, vigor index, and relative water content in leaves, it was confirmed that priming treatments with 0.01% ascorbic acid (AA) and 1% KNO3 improves the initial stages of radish development. Furthermore, the efficiency of AA as a priming agent was confirmed through the reduction of malondialdehyde (MDA) level compared to unprimed seedlings. On the other hand, hormopriming with indole-3-acetic acid (IAA) significantly increased the concentration of photosynthetic pigments and total soluble leaf proteins compared to non-primed seedlings. The highest content of total phenolic compounds, including flavonoids, were obtained after hormopriming with 1 mM IAA and halopriming with 1% MgSO4. On the basis of the percentage of inhibition of DPPH radicals, it was confirmed that treatments with IAA and AA can improve the antioxidant activity of radish seedlings. This study provides useful information regarding the possibilities of pregerminative metabolic modulation through the seed priming for the biochemical and physiological improvement of radish, and this topic should be further investigated in order to determine the potential use of AA and IAA as suitable priming agents in radish commercial production.

The Short-Term Metabolic Modulation of Basil (Ocimum basilicum L. cv. 'Genovese') after Exposure to Cold or Heat.

Chilling stress in spring and mid-season heat stress are important environmental stresses that can significantly affect plant productivity. The objectives of this study were to understand the effects of cold (4 and 10 °C) or heat (30 and 40 °C) stress on biochemical and physiological traits in leaves and roots of basil (Ocimum basilicum L. cv. 'Genovese') young plants. After short-time exposure to mild and severe temperature stresses, both photosynthetic pigments' and protein, as well as enzymatic and non-enzymatic defense components in basil leaves and roots, were quantified and compared with the control non-stressed plants. It was shown that both cold and heat treatment increase the content of chlorophyll a, chlorophyll b, and carotenoids. Chilling correlated with higher content of soluble proteins in leaves, whereas the concentration of these osmoprotectants in roots was higher under both cold and heat stress. For all tested antioxidant enzymes, higher activity was measured in leaves, and activity was related to temperature stress. SOD, CAT, A-POX, and P-POX activities was induced under heat stress, while the higher activity of SOD, CAT, P-POX, and G-POX was recorded under cold stress, compared to the control. In addition to the induced activity of enzymatic components, the content of secondary metabolites including total phenolics, flavonoids, and total anthocyanins, was several times higher compared to the non-stressed plants. Furthermore, total phenolic content was higher in roots than in leaves. Significant positive correlation can be seen among photosynthetic pigments, SOD, total phenolics, and flavonoids under severe temperature stress (4 or 40 °C) in basil leaves, while for roots, positive correlation was found in the content of secondary metabolites and activity of CAT or peroxidases. Obtained results are discussed in terms of phenotyping of O. basilicum cv. 'Genovese' response to heat and chilling stress, which should contribute to a better understanding of merged responses to cold and heat tolerance of this valuable crop.

Temporal, Plant Part, and Interpopulation Variability of Secondary Metabolites and Antioxidant Activity of Inula helenium L.

Variations in abiotic environmental factors have significant effects on quantity and quality of secondary metabolites, which is particularly important for plant species that possess biologically active compounds. The purpose of this study is determination of the total phenolic content, flavonoid concentration, and antioxidant activity of the different parts of Inula helenium L. (Asteraceae) sampled from different populations and in different time periods. The amounts obtained for the total phenolics varied from 16.73 to 89.85 mg of gallic acid (GA)/g. The concentration of flavonoids ranged from 9.32 to 376.22 mg of rutin (Ru)/g. The IC50 values of antioxidant activity determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical method varied from 161.60 to 1563.02 µg/ml. The inflorescence and roots possessed high concentration of phenolic compounds and significant antioxidant activity, while leaves contained the highest concentration of flavonoids. Additionally, the quantity of the phenolics, as well as antioxidant activity, significantly varied among the different populations due to different impacts of environmental factors. This research showed that I. helenium represents an abundant source of bioactive substances, and that the quantity of these compounds greatly differs among the different populations as well as in the same populations regarding the different time periods as well as plant parts.

In vitro biological activity of secondary metabolites from Seseli rigidum Waldst. et Kit. (Apiaceae).

The antioxidant, antimicrobial activity, total phenolic content and flavonoid concentration of Seseli rigidum Waldst. et Kit. were evaluated. Five different extracts of the aboveground plant parts were obtained by extraction with distilled water, methanol, acetone, ethyl acetate and petroleum ether. Total phenols were determined using the Folin-Ciocalteu's reagent, with the highest values obtained in the acetone extract (102.13 mg GAE/g). The concentration of flavonoids, determined by using a spectrophotometric method with aluminum chloride and expressed in terms of rutin equivalent, was also highest in the acetone extracts (291.58 mg RUE/g). The antioxidant activity was determined in vitro using DPPH reagent. The greatest antioxidant activity was expressed in the aqueous extract (46.15 µg/ml). In vitro antimicrobial activities were determined using a microdilution analysis method; minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) were determined. Methanolic extract had the greatest influence on bacilli (MIC at 0.0391 mg/ml), but the best antimicrobial effect had acetone and ethyl acetate extracts considering their broad impact on bacteria. According to our research, S. rigidum can be regarded as promising candidate for natural plant source with high value of biological compounds.