Insights into accumulation of active ingredients and rhizosphere microorganisms between Salvia miltiorrhiza and S. castanea.

Salvia miltiorrhiza is an important traditional herbal medicine, and its extracts could be used for treating cardiovascular disease. Although these medicinal compounds are functionally similar, their wild relative, S. castanea, produces significantly different concentrations of these compounds. The reason for their differences is still unknown. In a series of soil and plant-based analyses, we explored and compared the rhizosphere microbiome of S. miltiorrhiza and S. castanea. To further investigate the geographical distribution of S. castanea, MaxEnt models were used to predict the future suitable habitat areas of S. castanea in China. Results revealed the distributions and structure of the rhizosphere microbial community of S. miltiorrhiza and S. castanea at different times. In addition, differences in altitude and soil moisture resulting from changes in climate and geographical location are also critical environmental factors in the distribution of S. castanea. The findings of this study increase our understanding of plant adaptation to their geographical environment through secondary metabolites. It also highlights the complex interplay between rhizospheric factors and plant metabolism, which provides the theoretical basis for the cultivation of S. miltiorrhiza and the use of S. castanea resources.

Soil applied silicon and manganese combined with foliar application of 5-aminolevulinic acid mediate photosynthetic recovery in Cd-stressed Salvia miltiorrhiza by regulating Cd-transporter genes.

Salvia miltiorrhiza is an important medicinal plant that experiences significant growth and biomass losses when cultivated on cadmium (Cd) contaminated soils. High Cd accumulation in plant tissues also increases the risk of metal entry into the food chain. In this study, we proposed that Cd accumulation in S. miltiorrhiza can be restricted through plant growth regulators and nutrient management. Therefore, S. miltiorrhiza seedlings were transplanted into mixed nutrient soil for two weeks, then treated with 30 mg kg-1 CdCl2, 200 mg kg-1 Na2SiO3·9H2O, and 100 mg kg-1 MnSO4, and simultaneously sprayed with 10 mg L-1 ALA on the leaves one week later. This study showed that elevated Cd accumulation significantly reduced plant growth and biomass. This growth inhibition damaged photosynthetic machinery and impaired carbon assimilation. In contrast, 5-aminolevulinic acid (ALA) significantly promoted the biomass of S. miltiorrhiza, and the dry weight of plants treated with ALA combined with manganese (Mn)/silicon (Si) increased by 42% and 55% as compared with Cd+Mn and Cd+Si treatments. Exogenously applied ALA and Si/Mn significantly activated antioxidant enzymes and promoted the growth recovery of S. miltiorrhiza. Further, exogenous ALA also reduced the Cd concentration in S. miltiorrhiza, especially when combined with Si. Compared with the Cd+Si treatment, the Cd+Si+ALA treatment reduced the Cd concentration in roots and leaves by 59% and 60%, respectively. Gene expression analysis suggested that ALA and Si significantly up-regulated genes associated with Cd transport. Other genes related to heavy metal tolerance mechanisms are also regulated to cope with heavy metal stress. These results indicated that the combined action of ALA and Si/Mn could reduce Cd-toxicity by increasing chlorophyll content and changing oxidative stress and can also affect Cd accumulation by regulating gene expression.

Chromium toxicity, speciation, and remediation strategies in soil-plant interface: A critical review.

In recent decades, environmental pollution with chromium (Cr) has gained significant attention. Although chromium (Cr) can exist in a variety of different oxidation states and is a polyvalent element, only trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)] are found frequently in the natural environment. In the current review, we summarize the biogeochemical procedures that regulate Cr(VI) mobilization, accumulation, bioavailability, toxicity in soils, and probable risks to ecosystem are also highlighted. Plants growing in Cr(VI)-contaminated soils show reduced growth and development with lower agricultural production and quality. Furthermore, Cr(VI) exposure causes oxidative stress due to the production of free radicals which modifies plant morpho-physiological and biochemical processes at tissue and cellular levels. However, plants may develop extensive cellular and physiological defensive mechanisms in response to Cr(VI) toxicity to ensure their survival. To cope with Cr(VI) toxicity, plants either avoid absorbing Cr(VI) from the soil or turn on the detoxifying mechanism, which involves producing antioxidants (both enzymatic and non-enzymatic) for scavenging of reactive oxygen species (ROS). Moreover, this review also highlights recent knowledge of remediation approaches i.e., bioremediation/phytoremediation, or remediation by using microbes exogenous use of organic amendments (biochar, manure, and compost), and nano-remediation supplements, which significantly remediate Cr(VI)-contaminated soil/water and lessen possible health and environmental challenges. Future research needs and knowledge gaps are also covered. The review's observations should aid in the development of creative and useful methods for limiting Cr(VI) bioavailability, toxicity and sustainably managing Cr(VI)-polluted soils/water, by clear understanding of mechanistic basis of Cr(VI) toxicity, signaling pathways, and tolerance mechanisms; hence reducing its hazards to the environment.

Exogenous Application of 5-Aminolevulinic Acid Promotes Coloration and Improves the Quality of Tomato Fruit by Regulating Carotenoid Metabolism.

5-Aminolevulinic acid (ALA) plays an important role in plant growth and development. It can also be used to enhance crop resistance to environmental stresses and improve the color and internal quality of fruits. However, there are limited reports regarding the effects of ALA on tomato fruit color and its regulatory mechanisms. Therefore, in this study, the effects of exogenous ALA on the quality and coloration of tomato fruits were examined. Tomato (Solanum lycopersicum "Yuanwei No. 1") fruit surfaces were treated with different concentrations of ALA (0, 100, and 200 mg⋅L-1) on the 24th day after fruit setting (mature green fruit stage), and the content of soluble sugar, titratable acid, soluble protein, vitamin C, and total free amino acids, as well as amino acid components, intermediates of lycopene synthetic and metabolic pathways, and ALA metabolic pathway derivatives were determined during fruit ripening. The relative expression levels of genes involved in lycopene synthesis and metabolism and those involved in ALA metabolism were also analyzed. The results indicated that exogenous ALA (200 mg⋅L-1) increased the contents of soluble sugars, soluble proteins, total free amino acids, and vitamin C as well as 11 kinds of amino acid components in tomato fruits and reduced the content of titratable acids, thus improving the quality of tomato fruits harvested 4 days earlier than those of the control plants. In addition, exogenous ALA markedly improved carotenoid biosynthesis by upregulating the gene expression levels of geranylgeranyl diphosphate synthase, phytoene synthase 1, phytoene desaturase, and lycopene ß-cyclase. Furthermore, exogenous ALA inhibited chlorophyll synthesis by downregulating the genes expression levels of Mg-chelatase and protochlorophyllide oxidoreductase. These findings suggest that supplementation with 200 mg⋅L-1 ALA not only enhances the nutritional quality and color of the fruit but also promotes early fruit maturation in tomato.

Combined effect of Bacillus fortis IAGS 223 and zinc oxide nanoparticles to alleviate cadmium phytotoxicity in Cucumis melo.

Cadmium (Cd), prevailing in most of the agricultural lands of the world contaminates food chain, thereby causing several health implications. It has become the main heavy metal contaminant in most of the agricultural lands of Pakistan due to the widespread use of phosphate fertilizers besides application of irrigation water contaminated with industrial and mining effluents. Plant growth promoting bacteria (PGPB) are capable to enhance growth and metal stress tolerance in supplemented plants. Zinc oxide nanoparticles (ZnO-NPs) are capable to alleviate various abiotic stresses when applied to plants. During current research, the efficacy of single and combined application of Bacillus fortis IAGS 223 and ZnO-NPs was evaluated for alleviation of Cd (75 mg kg-1) induced phytotoxicity in Cucumis melo plants. For this purpose, C. melo plants, subjected to Cd stress were treated with B. fortis IAGS 223 and ZnO-NPs (20 mg kg-1), either alone or in combination. The growth relevant characteristics including photosynthetic pigments, hydrogen peroxide (H2O2), malondialdehyde (MDA), and activities of antioxidative enzymes as well as Zn and Cd contents in treated plants were examined. The individual application of ZnO-NPs and B. fortis IAGS 223 slightly enhanced all the above-mentioned growth characteristics in plants under Cd stress. However, the combined application of ZnO-NPs and B. fortis IAGS-223 considerably modulated the activity of antioxidant enzymes besides upgradation of the biochemicals and growth parameters of Cd stressed plants. The decreased amount of stress markers such as H2O2, and MDA in addition with reduction of Cd contents was observed in shoots of ZnO-NPs and B. fortis IAGS-223 applied plants. B. fortis IAGS-223 inoculated plants supplemented with ZnO-NPs, exhibited reduced amount of Cd as well as protein bound thiols and non-protein bound thiols under Cd stress. Subsequently, the reduced Cd uptake improved growth of ZnO-NPs and B. fortis IAGS-223 applied plants. Henceforth, field trials may be performed to formulate appropriate combination of ZnO-NPs and B. fortis IAGS-223 to acquire sustainable crop production under Cd stress.

Isolation of bioactive compounds from Rumex hastatus extract and their biological evaluation and docking study as potential anti-oxidant and anti-urease agents.

Herein, the methanolic extract of Rumex hastatus was prepared and subjected to silica gel column chromatographic separation for purification. The chromatographic analysis yielded four bioactive compounds namely, 1,8-dihydroxy-3-methyl-anthraquinone (C1, chrysophanol), 3-methoxy-7-methyl-1,5-dihydroxy-anthraquinone (C2), 6-methyl-1,3,7-trihydroxy-anthraquinone (C3), and 4-hydroxycinnamic acid (C4). The structures of all the isolated bio-entities were elucidated by spectroscopic analysis (1D, 2D-NMR, and MS). The biological potentialities of bioactive compounds were evaluated by determining their antioxidant and anti-urease activities. The results revealed that compound 1 showed the highest nitrite radical scavenging activity (IC50  = 0.39 mM) followed by C2 and C4 (IC50  = 0.45) mM and C3 (IC50  = 0.47 mM). Similarly, the determined IC50  values for anti-urease activity were C2 (IC50  = 0.39 mM), C1 (IC50  = 0.40), C4 (IC50  = 0.41), and C3 (IC50  = 44). Molecular docking study revealed maximum interactions among the hydroxyl group of all compounds. In conclusion, Rumex hastatus extract could be a promising alternative to chemical additives in pharmaceutical industries due to its noteworthy biological activities. PRACTICAL APPLICATIONS: As we have shown in this study that Rumex hastatus is a prolific source of biologically active compounds with potent antioxidant and anti-urease activities, therefore, R. hastatus extract could be used as a promising alternative to chemical additives in pharmaceutical industries due to its unique compounds and noteworthy biological activities.

Selenium mitigates the chromium toxicity in Brassicca napus L. by ameliorating nutrients uptake, amino acids metabolism and antioxidant defense system.

The phytotoxicity of chromium (Cr) makes it obligatory for the researchers to develop strategies that seek to hinder its accumulation in food chains. While, protective role of selenium (Se) has not been discussed in detail under adverse conditions in oilseed rape. Here, our aim was to investigate the potential use of Se (0, 5 and 10 µM) in alleviating the Cr toxicity (0, 100 and 200 µM) in Brassica napus L. Results delineated that Se-supplementation notably recovered the Cr-phytotoxicity by reducing the Cr accumulation in plant tissues and boosted the inhibition in plant growth and biomass. Under Cr stress, the exogenously applied Se significantly recovered the impairment in photosynthesis related parameters (chlorophyll a, chlorophyll b, carotenoids, net photosynthetic rate, stomatal conductance, and photochemical efficiency of photosystem II), and counteracted the reduction in nutrients uptake and improved the essential amino acids (EAAs) levels. In addition, Se activated the antioxidants enzymes included in AsA-GSH cycle (SOD, CAT, APX, GR, DHAR, MDHAR, GSH, and AsA) and glyoxalase (Gly) system (Gly I and Gly II) and minimized the excessive generation of reactive oxygen species (ROS) and methylglyoxal (MG) contents in response to Cr stress. In a nutshell, Se (more effective at 5 µM) alleviated the Cr and MG induced phytotoxicity and oxidative damages by minimizing their (Cr and MG) accumulation and enhanced the plant growth, nutrients element level, nutrition quality by improving EAAs, antioxidant and Gly system. By considering the above-mentioned biomarkers, the addition of exogenous Se in Cr polluted soils might be effective approach to decrease the Cr uptake and its linked phytotoxicity in B. napus.

Protective mechanisms of melatonin against selenium toxicity in Brassica napus: insights into physiological traits, thiol biosynthesis and antioxidant machinery.

BACKGROUND: The ubiquitous signaling molecule melatonin (N-acetyl-5-methoxytryptamine) (MT) plays vital roles in plant development and stress tolerance. Selenium (Se) may be phytotoxic at high concentrations. Interactions between MT and Se (IV) stress in higher plants are poorly understood. The aim of this study was to evaluate the defensive roles of exogenous MT (0 µM, 50 µM, and 100 µM) against Se (IV) (0 µM, 50 µM, 100 µM, and 200 µM) stress based on the physiological and biochemical properties, thiol biosynthesis, and antioxidant system of Brassica napus plants subjected to these treatments. RESULTS: Se (IV) stress inhibited B. napus growth and biomass accumulation, reduced pigment content, and lowered net photosynthetic rate (Pn) and PSII photochemical efficiency (Fv/Fm) in a dose-dependent manner. All of the aforementioned responses were effectively alleviated by exogenous MT treatment. Exogenous MT mitigated oxidative damage and lipid peroxidation and protected the plasma membranes from Se toxicity by reducing Se-induced reactive oxygen species (ROS) accumulation. MT also alleviated osmotic stress by restoring foliar water and sugar levels. Relative to standalone Se treatment, the combination of MT and Se upregulated the ROS-detoxifying enzymes SOD, APX, GR, and CAT, increased proline, free amino acids, and the thiol components GSH, GSSG, GSH/GSSG, NPTs, PCs, and cys and upregulated the metabolic enzymes γ-ECS, GST, and PCS. Therefore, MT application attenuates Se-induce oxidative damage in plants. MT promotes the accumulation of chelating agents in the roots, detoxifies Se there, and impedes its further translocation to the leaves. CONCLUSIONS: Exogenous MT improves the physiological traits, antioxidant system, and thiol ligand biosynthesis in B. napus subjected to Se stress primarily by enhancing Se detoxification and sequestration especially at the root level. Our results reveal better understanding of Se-phytotoxicity and Se-stress alleviation by the adequate supply of MT. The mechanisms of MT-induced plant tolerance to Se stress have potential implications in developing novel strategies for safe crop production in Se-rich soils.

Silicon nanoparticles enhanced the growth and reduced the cadmium accumulation in grains of wheat (Triticum aestivum L.).

The application of silicon (Si) under heavy metal stress is well known, but the use of Si nanoparticles (NPs) under metal stress in not well documented. Thus, the experiments were performed to investigate the impacts of soil and foliar applied Si NPs on wheat (Triticum aestivum L.) growth and cadmium (Cd) accumulation in grains under Cd toxicity. The plants were grown under natural environmental conditions and were harvested after physiological maturity (124 days after sowing). The results demonstrated that Si NPs significantly improved, relative to the control, the dry biomass of shoots, roots, spikes and grains by 24-69%, 14-59%, 34-87%, and 31-96% in foliar spray and by 10-51%, 11-49%, 25-69%, and 27-74% in soil applied Si NPs, respectively. The Si NPs enhanced the leaf gas exchange attributes and chlorophyll a and b concentrations, whereas diminished the oxidative stress in leaves which was indicated by the reduced electrolyte leakage and enhancement in superoxide dismutase and peroxidase activities in leaf under Si NPs treatments over the control. When compared with the control, the foliar spray of Si NPs reduced the Cd contents in shoots, roots, and grains by 16-58%, 19-64%, and 20-82%, respectively, whereas soil applied Si NPs reduced the Cd concentrations in shoots, roots, and grains by 11-53%, 10-59%, and 22-83%, respectively. In comparison with the control, Si concentrations significantly (p ≤ 0.05) increased in the shoots and roots in both foliar and soil supplementation of Si NPs. Our results suggested that Si NPs could improve the yield of wheat and more importantly, reduce the Cd concentrations in the grains. Thus, the use of Si NPs might be a feasible approach in controlling Cd entry into the human body via crops.

Dual behavior of selenium: Insights into physio-biochemical, anatomical and molecular analyses of four Brassica napus cultivars.

Selenium (Se) is a prerequisite metalloid for humans and animals. But, its essentialness or phytotoxicity is still obscure. Here, we investigated the dual effects of sodium selenite (0, 25, 50 or 100 µM) on the physio-biochemical, anatomical and molecular alterations in different Brassicca napus L. cultivars (viz. Zheda 619, Zheda 622, ZY 50, and ZS 758). Findings revealed that Se-supplementation markedly boosted the plant growth and biomasses by improving mineral uptake, water-soluble protein, sugar, photosynthetic efficiency regarding the pigments and gas exchange parameters. Higher Se-levels impaired the photosynthetic efficiency, deplete nutrients-uptake, osmotic stress by proline accumulation and higher Se-accumulation in roots led to growth and biomass reduction. Se-supplementation minimized the accumulation of ROS (hydrogen peroxide, superoxide radical), malondialdehyde and methylglyoxal (MG) levels by activating the enzymes engaged in AsA-GSH cycle and ROS-MG detoxification. But, elevated-Se impaired the oxidative metabolism by desynchronizing the antioxidants as revealed by decreasing levels of ascorbic acid, activities and expression levels of catalase, glutathione reductase, and dehydro-ascorbate reductase. Up-regulation of secondary metabolites genes (PAL, PPO) revealed the role of Se in regulating transcriptional networks involved in oxidative stress. The damages in leaf and root ultra-structures disclosed the Se-phytotoxicity. Together, outcomes uncovered the protective mechanism of Se (till 25 µM) by reinforcing the plant morphology, photosynthesis, osmo-protection, redox balance, enzyme activities for ROS-MG detoxification by reducing ROS and MG components. Excessive-Se prompt phytotoxicity by impairing above mentioned parameters, especially at 100 µM Se. Among all B. napus cultivars, Zheda 622 was discovered as highly-susceptible and ZS 758 showed greatest-tolerance against Se stress.

Genetic diversity and biogeography of T. officinale inferred from multi locus sequence typing approach.

Taraxacum officinale (Asteraceae) is widely distributed weedy plant used as a traditional medicinal herb. The population genetics and historical biogeography of this plant have remained relatively unexplored. This study explores phylogeny, population genetics and ancestral reconstructions adopting multi locus sequence typing (MLST) approach. MLST sequences dataset was generated from genomics and chloroplast DNA sequences obtained from 31 T. officinale haplotypes located in 16 different countries. Phylogenetic analysis distributed these haplotypes in well differentiated geographic clades. The study suggested a close relationship between Europe and adjacent Asian countries. Populations of these regions predominantly formed common haplogroups, showed considerable level of gene flow and evidence for recombination events across European and Asian population. Biogeographical inferences obtained by applying statistical dispersal-vicariance analysis (S-DIVA) and Bayesian binary MCMC (BBM) analysis showed that T. officinale was putatively originated in Europe. Molecular clock analysis based on ITS dataset suggested that the divergence between Europe and East Asian populations can be dated to 1.07 Mya with subsequent dispersal and vicariance events. Among different spatial process long distance seed dispersal mediated by wind had potentially assisted the population expansion of T. officinale.

Silicon and water-deficit stress differentially modulate physiology and ultrastructure in wheat (Triticum aestivum L.).

Plants combat drought stress by coordinating various metabolic enzymes, and endogenous phytohormones, such as indole acetic acid (IAA) and abscisic acid (ABA). In the present study, 37-day-old wheat seedlings were subjected to the Hoagland solution with 20% PEG for 7 days (to create the artificial osmotic stress environment) in the greenhouse, and were supplemented with an optimized concentration (1.0 mM) of silicon (Si) to alleviate the negative effects of former stress on physiological, biochemical and phytohormones contents. Exogenous Si significantly improved plant growth parameters under osmotic stress compared to PEG treatment alone (the increase was up to 6 and 9% for shoot and root fresh weight, 4 and 12% for shoot and root dry weight, respectively). Moreover, Si significantly decreased the H2O2, MDA contents, electrolyte leakage, antioxidant enzyme activity (POD), and mineral contents (K and Ca) under osmotic stress but markedly increased the ascorbic acid(AsA), soluble sugar and mineral (Mg and Si) contents. Interestingly, Si application under water-deficit stress differently modulated the endogenous levels of ABA, IAA and JA in wheat plants compared to PEG treatment alone. This study suggests that exogenous Si improves the plant growth by modulating the nutrient (Na, Mg and Si) uptake and phytohormone levels in wheat under water-deficit stress.

Effect of different hormonal combinations on regeneration of callus of Gomphrena globosa L.

The main aim of this study was to observe the effect of different hormonal combinations on regeneration of callus of Gomphrena globosa L. For this purpose callus was obtained from seeds G. globosa inoculated on MS medium supplemented with 4 mg L(-1) 2, 4-D and 10% coconut milk. After callus formation callus was inoculated on Murashige and Skoog's medium supplemented with different combinations of BAP, NAA and GA3 to observe different responses such as regeneration, callus friability, callus proliferation and pigmentation. In BAP and NAA root regeneration was observed at 1.5 mg L(-1) BAP+1 mg L(-1) NAA whereas rest of the combinations showed callus proliferation. In BAP and GA3, root regeneration was observed in most of the combinations and some combinations also showed shoot induction. Shoot regeneration was observed on 0.5 mg L(-1) BAP + 7 mg L(-1) GA3 and 1 mg L(-1) BAP + 0.2 mg L(-1) GA3. The effect of all these combinations on auxin, acid phosphatase and soluble protein content was also observed.