Biostimulant Potential Research Articles

Application of Biohumus at different substrate replacement rates in the germination and cultivation of Zea mays

Research objective: This research aims to evaluate the biostimulant potential of biohumus in different substrate replacement rates on the growth of Zea mays seedlings. This is to increase knowledge of the use of biohumus in plant cultivation, which could be used in the formulation of new growing media and organic fertilisers. Materials and Methods: The experiments, which began in January 2023, were conducted in the CREA-OF greenhouses in Pescia (Pt), on seedlings of Zea mays. The experimental groups were: group control, irrigated with water and substrate previously fertilized; group with 10% biohumus, irrigated and fertilised substrate; group with 20% biohumus, irrigated and fertilized substrate; group with 30% biohumus, irrigated and fertilized substrate; group with 40% biohumus, irrigated and fertilized substrate; group with 50% biohumus, irrigated and fertilized substrate; group with 60% biohumus, irrigated and fertilized substrate; group with 70%, irrigated and fertilized substrate; group with 100% biohumus, irrigated and fertilized substrate. On May 18, 2023, plant height, vegetative weight, roots volume and length, the number of microorganisms and pH in the substrate were determined. Results and Discussion: The experiment showed that the use of biohumus enriched with microorganisms can significantly improved the vegetative and root growth of sown Zea mays seedlings. In general, a significant increase in plant height, vegetative and root weight, and root length was observed from 20% substitution of biohumus in the substrate. The theses that show a particularly clear improvement for all agronomic parameters analysed are those with 50% and 60% biohumus, peat substitution. Plants that received biohumus grew better than those that did not, and cereal plants grew better than those that were grown in plain soil. The nutrient content of biohumus stimulates the growth of the following crops: tomatoes, peppers, garlic, sweet corn, aubergines, bananas. Among other things, it stimulates the growth of chrysanthemum, marigold, geranium, petunia, and poinsettia flowers, as well as acacia and eucalyptus. Due to its macro- and micronutrient content, biohumus has a positive effect on plants (leaf area, root volume, root branching), and improves the soil's biological functions. Plants that received biohumus grew better than those that did not, and cereal plants grew better than those that were grown in plain soil. The growth of barley and cereals improved on a maize farm after biohumus was applied. There was a significant improvement in soil porosity on a maize farmland. Among the benefits of using biohumus as a fertiliser are: it eliminates harmful insects, reduces the infestation of harmful insects, reduces pathogen infestation of plants, fertilizes the soil, and improves the soil structure as a soil conditioner. Conclusions: In order to maintain soil health and fertility, farmers need a sustainable alternative that is economically viable and productive. As part of ecological agriculture, the protection of food, agricultural and human ecosystems is emphasized, along with the improvement of soil fertility and the development of secondary income for farmers. The use of biohumus provides the best answer to ecological agriculture, which is synonymous with 'sustainable agriculture'. This article provides a basis for further research

Plant extracts from mediterranean vegetation in the cultivation and defence of Plectranthus coleidos and Plectranthus amboinicus

Research objective: This research aims to evaluate the biostimulant potential of some Mediterranean vegetation extracts for the stimulation and defence of some Plectranthus amboinicus and Plectranthus coleidos plants. This is to increase knowledge on these plant extracts that could be used for the formulation of new plant biostimulants. Materials and Methods: The experiments, which started in May 2022, were conducted in the greenhouses of CREA-OF in Pescia (Pt), Tuscany, Italy (43°54′N 10°41′E) on Plectranthus amboinicus and Plectranthus coleidos. The experimental groups were: group control; group with oak macerated; group with myrtus macerated; group with wild fennel macerated; group with lentiscus macerated; group with inula macerated. On January 20, 2023, plant height, leaves number, vegetative weight, roots volume and length, the number of microorganisms in the substrate, plant dead number and pH were determined. Results and Discussion: The experiment showed that the use of plant extracts as biostimulants can significantly improve vegetative and root growth and reduce plant mortality of Plectranthus amboinicus and Plectranthus coleidos. In general, a significant increase in plant height and number of leaves as well as vegetative and root biomass was observed in plants treated with all plant biostimulants, particularly with the treatments of macerated oak, macerated fennel and macerated inula. The treatments with macerated oak and macerated fennel were the best in all two Plectranthus species. Observations conducted on treatments with phytotherapeutic agents demonstrate their effectiveness as stimulants of the plants' self-defence mechanisms. In addition, some preparations appear to act as repellents and substances that make many pests lose their appetite or stimulus to feed. Their activity seems to be determined by the minerals and certain molecules present in the plants used to prepare the macerates. This is why some of these substances have been placed under observation by scientific research to verify their effects. However, the objective difficulty of obtaining reproducible results limits research and experimentation activities in this field and directs them towards the characterisation of the active ingredients that play a primary role in insecticide, fungicide, bactericide or herbicide action. Conclusions: Herbal medicines are always used in aqueous form by performing the treatment with an atomiser or, more rarely, by adding the extract to irrigation water. The extract is obtained by steeping the herbs in water or by preparing an infusion or decoction. The test showed that the use of extracts obtained from plants by macerating Mediterranean shrub species can have biostimulant activity against aromatic succulents such as Plectranthus amboinicus and Plectranthus coleidos. Very interesting aspects especially with regard to the study of new formulations obtained from plants and applicable in organic farming.

Galactoglucomannan oligosaccharides alleviate cadmium toxicity by improving physiological processes in maize

Phosphate fertilisers and past mining activity are significant source of cadmium (Cd) pollution; thus, the concentration of Cd in agricultural soils has been substantially rising. Various substances have been tested for their potential to alleviate the toxicity of Cd and stimulate the accumulation of Cd in plant organs. This study brought new insight of the impact of galactoglucomannan oligosaccharides (GGMOs) on the maize plants grown under/in Cd stress. The application of GGMOs reduced concentration of Cd in the maize leaves and thus GGMOs increased their growth (by 24%), concentration of photosynthetic pigments (up to 39.4%), effective quantum yield of photosystem II (up to 29.6%), and net photosynthetic rate (up to 19.6%). The concentrations of stress markers increased in the Cd and Cd + GGMOs treatment; however, significantly lower concentration was detected in the Cd + GGMOs treatment (malondialdehyde by 21.7%, hydrogen peroxide by 13%). The concentration of auxin increased almost by two-fold in the Cd + GGMOs treatment compared to the Cd treatment. The recovered auxin level and enhanced nutrient uptake are proposed mechanisms of GGMOs’ action during stress. GGMOs are molecules with biostimulant potential that could support vitality of maize plants in Cd stress.

Biocontrol and growth promoting effect of Trichoderma spp. isolate from rhizosphere soils of some Algerian areas

Trichoderma species are ubiquitous fungi in the environment exhibiting enormous potential in biotechnology especially due to their plant health benefits, such as conferring stimulation growth and disease resistance to their hosts.The aim of this study was to identify isolated Trichoderma strains by molecular tools and evaluate their in vitro antagonistic activity against four common phytopathogenic fungi as well as their biostimulant activity. Tewenty two Trichoderma strains were isolated from different rhizosphere soils and eleven species were identified at the species level among these strains, however, two Trichoderma strains could not be identified. These results were obtained using tef1 marker known as highly efficient barcode marker for Trichoderma species identification. At the moment, the following species are reported for the first time in Algeria: T. tomentosum, T. hamatum, T. aureoviride, T. citrinoviride, T. samuelsii et T. hispanicum. All isolated Trichoderma strains were tested in dual cultures against four plant pathogens: Ascochyta rabiei, Botrytis cinerea, Drechslera graminea and Fusarium graminearum. Most of Trichoderma strains showed effective antagonistic activity either by overgrowing up to pathogen colonies or coiling around them. T. gamsii showed the highest Percentage of Radial Inhibition Growth (PRIG%) with rates varying between 51,9 % to 65,5 %. Then, tomato root seedlings were inoculated with spore suspension of Trichoderma isolates and thirty days after growth culture, some plant growth parameters were measured. We observed that Trichoderma strains which exhibited high biostimulant potential, had not raised biocontrol performance proving that the Trichoderma strains do not necessarily raised the dual performances.

Microalgae from Nordic collections demonstrate biostimulant effect by enhancing plant growth and photosynthetic performance.

We investigated the biostimulant potential of six microalgal species from Nordic collections extracted with two different procedures: thermal hydrolysis with a weak solution of sulfuric acid accompanied by ultrasonication and bead-milling with aqueous extraction followed by centrifugation. To this aim, we designed a phenotyping pipeline consisting of a root growth assay in the model plant Arabidopsis thaliana, complemented with greenhouse experiments to evaluate lettuce yield (Lactuca sativa L. cv. Finstar) and photosynthetic performance. The best-performing hydrolyzed extracts stimulated Arabidopsis root elongation by 8 - 13% and lettuce yield by 12 - 15 %. The in situ measured photosynthetic performance of lettuce was upregulated in the efficient extracts: PSII quantum yield increased by 26 - 34%, and thylakoid proton flux increase was in the range of 34 - 60%. In contrast, aqueous extracts acquired by bead-milling showed high dependence on biomass concentration in the extract and an overall plant growth enhancement was not attained in any of the applied dosages. Our results indicate that hydrolysis of the biomass can be a decisive factor for rendering effective plant biostimulants from microalgae. This article is protected by copyright. All rights reserved.

Temperature-induced modulation of stress-tolerant PGP genes bioprospected from Bacillus sp. IHBT-705 associated with saffron (Crocus sativus) rhizosphere: A natural -treasure trove of microbial biostimulants.

There is a renewed interest in sustainable agriculture wherein novel plant growth-promoting rhizobacteria (PGPR) are being explored for developing efficient biostimulants. The key requirement of a microbe to qualify as a good candidate for developing a biostimulant is its intrinsic plant growth-promoting (PGP) characteristics. Though numerous studies have been conducted to assess the beneficial effects of PGPRs on plant growth under normal and stressed conditions but not much information is available on the characterization of intrinsic traits of PGPR under stress. Here, we focused on understanding how temperature stress impacts the functionality of key stress tolerant and PGP genes of Bacillus sp. IHBT-705 isolated from the rhizosphere of saffron (Crocus sativus). To undertake the study, Bacillus sp. IHBT-705 was grown under varied temperature regimes, their PGP traits were assessed from very low to very high-temperature range and the expression trend of targeted stress tolerant and PGP genes were analyzed. The results illustrated that Bacillus sp. IHBT-705 is a stress-tolerant PGPR as it survived and multiplied in temperatures ranging from 4°C-50°C, tolerated a wide pH range (5-11), withstood high salinity (8%) and osmolarity (10% PEG). The PGP traits varied under different temperature regimes indicating that temperature influences the functionality of PGP genes. This was further ascertained through whole genome sequencing followed by gene expression analyses wherein certain genes like cspB, cspD, hslO, grpE, rimM, trpA, trpC, trpE, fhuC, fhuD, acrB5 were found to be temperature sensitive while, cold tolerant (nhaX and cspC), heat tolerant (htpX) phosphate solubilization (pstB1), siderophore production (fhuB and fhuG), and root colonization (xerC1 and xerC2) were found to be highly versatile as they could express well both under low and high temperatures. Further, the biostimulant potential was checked through a pot study on rice (Oryza sativa), wherein the application of Bacillus sp. IHBT-705 improved the length of shoots, roots, and number of roots over control. Based on the genetic makeup, stress tolerance potential, retention of PGP traits under stress, and growth-promoting potential, Bacillus sp. IHBT-705 could be considered a good candidate for developing biostimulants.

Potential use of Sargassum muticum as source of plant biostimulants after three different drying methods

Seaweed derived biostimulants are gaining attention as an important tool in sustainable agriculture. This offers a unique opportunity to alleviate the environmental impact of Sargassum muticum (Ochrophyta, Phaeophyceae) as an invasive species by finding new applications for its biomass. In this sense, incorporating green extraction technologies is fundamental to ensure environmental-friendly goals. This research was initiated in an attempt to contribute to an integral valorization system of S. muticum biomass, exploring the biostimulant potential of the solubles obtained from pressed solids, through an autohydrolysis treatment. In addition, we compared the effect of three different liquid phase drying techniques (spray-drying, freeze-drying and convective air-drying). Low stress drying techniques as spray-drying showed better conservation of bioactive compounds and biostimulant potential. A bioassay with Nastrium officinale showed no phytotoxic effects despite high electric conductivity in most of the extracts and concentrations. Dried extracts showed mainly an amorphous structure but occasional crystal formation when spray-dried at low temperatures (Tout = 50 ºC) and after convective air drying (T = 40 ºC). Significant increases in root development were achieved at a concentration of 5 mg L−1 of spray-dried extracts and 50 mg L−1 in case of freeze-dried extracts. Munoo-Liisa vitality index showed best results with 50 mg L−1 of freeze-dried extracts. This study provides important information about the influence of different drying techniques on the physicochemical properties and biostimulant potential of S. muticum aqueous extracts and contributes to the integral valorization of its biomass.

Revisiting the oldest manure of India, Kunapajala: Assessment of its animal waste recycling potential as a source of plant biostimulant

India's oldest documented manure, most commonly referred to as Kunapajala, has a long history of over 1,000 years in crop cultivation. Kunapajala is primarily an in-situ decomposition technology of animal waste and can potentially provide an eco-friendly pipeline for recycling bio-waste into essential plant nutrients. This traditional animal manure, in addition, also contains dairy excreta (e.g., feces and urine), dairy products (e.g., milk and ghee), natural resources (e.g., honey), broken seeds or grains, and their non-edible by-product waste. Here, we aimed to assess the waste recycling and plant biostimulant potential of Kunapajala prepared from livestock (e.g., Black Bengal goats) or fish (e.g., Bombay duck) post-processed wastes over different decomposition periods, e.g., (0, 30, 60, and 90-days). In this study, an in-situ quantification of livestock- (lKPJ) and fish-based Kunapajala (fKPJ) reveals a dynamic landscape of essential plant primary nutrients, e.g., (0.70 > NH4-N < 3.40 g•L−1), (100.00 > P2O5 < 620.00 mg•L−1), and (175.00 > K2O < 340.00 mg•L−1), including other physico-chemical attributes of Kunapajala. Using correlation statistics, we find that the plant-available nutrient content of Kunapajala depicts a significant (p < 0.0001) transformation over decomposition along with microbial dynamics, abundance, and diversities, delineating a microbial interface to animal waste decomposition and plant growth promotion. Importantly, this study also reports the indole 3-acetic acid (IAA) content (40.00 > IAA < 135.00 mg•L−1) in Kunapajala. Furthermore, the bacterial screening based on plant growth-promoting traits and their functional analyses elucidate the mechanism of the plant biostimulant potential of Kunapajala. This assay finally reports two best-performing plant growth-promoting bacteria (e.g., Pseudomonas chlororaphis and Bacillus subtilis) by the 16S ribotyping method. In support, in-planta experiments have demonstrated, in detail, the bio-stimulative effects of Kunapajala, including these two bacterial isolates alone or in combination, on seed germination, root-shoot length, and other important agronomic, physio-biochemical traits in rice. Together, our findings establish that Kunapajala can be recommended as a source of plant biostimulant to improve crop quality traits in rice. Overall, this work highlights Kunapajala, for the first time, as a promising low-cost microbial technology that can serve a dual function of animal waste recycling and plant nutrient recovery to promote sustainable intensification in agroecosystems.

An experimental Study Investigating the Effects on Brassica oleracea: Estuarine Seaweeds as Biostimulants in Seedling Development?

Estuarine eutrophication due to the nutrient run-off from the agricultural fields encourages the establishment of several opportunistic seaweeds. These fast-growing seaweeds, considered an untapped resource, with a circular economy approach, can be employed as soil plant fertilizer. In agriculture, there is a global trend toward shifting from chemical-based conventional farming to sustainable agriculture. In this context, this study aimed to understand the biostimulant potential of the aqueous extracts from seaweeds harvested in Mondego estuary located on the Atlantic coast of Portugal, namely Ulva lactuca (Sea lettuce), Fucus ceranoides (Estuary Wrack) and Gracilaria gracilis (Slender Wart Weed), in kale (Brassica oleracea L.) seed germination and seedling development. The results showed that Gracilaria gracilis extract enhanced kale seed germination, presenting a higher seedlings weight (0.076 ± 0.004 g) and length (15.48 ± 0.59 cm), when compared with seedlings obtained in distilled water used as a control (weight = 0.059 ± 0.002 g; length = 13.10 ± 0.54 cm). Fucus ceranoides showed the lowest influence on seedling development (weight = 0.062 ± 0.002 g; length = 12.97 ± 0.59 cm). However, these results demonstrated that seaweed aqueous extracts can indeed enhance seed germination and seedling development.

Effect of foliar-applied Euphorbia hirta towards controlling bacterial diseases in tomato crops and enhancing fruit yield and shelf life

ABSTRACT Bacterial diseases are a major cause of yield loss in tomato plants worldwide, and there is a need to identify strategies for control of these diseases. Bacterial wilt caused by Ralstonia solanacearum (RS) and bacterial spot caused by Xanthomonas axonopodis pv vesicatoria (Xav) are amongst the bacterial diseases affecting tomato crops. The current study investigates Euphorbia hirta (E. hirta) methanol extract (EHM) for its antibacterial activity against RS, and Xav induced diseases in tomato plants, along with its biostimulant potential in increasing fruit yield. EHM at 1280 mg/L exhibited 90% inhibition in the growth of both RS and Xav bacteria. Further, evaluation of EHM on Arka Vikas, a susceptible tomato variety, showed that pre-treatment of 15 days and 45 days tomato plants with 1280 mg/L EHM exhibited moderate resistance to bacterial wilt and spot disease, respectively, with increased tomato yield and improved chlorophyll b levels compared to control plants. The effectiveness of EHM in increasing fruit yield was further confirmed using field evaluation on ‘Namdhari NS 538’ variety of tomato plants. A 3.5-fold increase in numbers and weight of tomato was observed with foliar application of EHM (1280 mg/L). A significant reduction in fruit spoilage along with an increase in mRNA level of ethylene receptor factor (ERF1) was also observed. The study is the first to demonstrate the cost-effective and eco-friendly antibacterial and biostimulant potential of EHM (1280 mg/L) for tomato plants.

Design of a hydroponic test to evaluate the biostimulant potential of new organic and organomineral products

Currently, the use of biostimulants is increasing due to the need for greater productivity in agriculture. The European Union presented a new fertilizer regulation, UE 2019/1009, appearing for the first time the concept of biostimulants. Its main objective is to improve the efficiency of plants in the absorption and assimilation of nutrients or their tolerance to biotic or abiotic stresses, regardless of the nutrient content of the product. The objective of this work consisted in the development of a methodology to test in a short-term experiment the efficiency of commercial products as potential biostimulants in a crop of Capsicum annuum L. in strictly hydroponic conditions. Plants were irrigated with the respective product at the recommended dose in water, without the addition of other nutritional sources for 15 days. At the end of the test, the weights of the root and aerial part, the humidity, the chlorophyll indexes, and nutritional leaf content, as well as the volume and morphology of the roots and plants were obtained to evaluate the biostimulant effects on the plant growth and development. The water consumption was also evaluated to analyze whether any of the products generates greater water savings. The study concluded that the nutritive solutions with biostimulants produced a greater increase in the weight of the plant and a lower percentage of leaf moisture, as well as higher values of leaf chlorophyll. On the other hand, it was humic, fulvic, and algae biostimulants that presented the best values in terms of water savings. The methodology developed could be set to test in the short term the biostimulant potential of new products.

Effect of Laser Biostimulation on Germination of Sub-Optimally Stored Flaxseeds (Linum usitatissimum)

Sub-optimal storage of grains could deteriorate seed germination and plant viability. Recent research studies have established that laser biostimulation of seeds could be used as a safe and sustainable alternative to chemical treatment for improving crop germination and growth. Herein, the efficacy of this novel technique is evaluated to see if poor germinability caused by sub-optimal storage of flaxseeds (Linum usitatissimum) could be reversed using laser biostimulation. Healthy flaxseeds were first subjected to sub-optimal storage conditions (30 °C for ten weeks) to degrade their germinability. Two low-cost lasers, including a single-wavelength red laser (659 nm) and a dual-wavelength green/infrared laser (531 and 810 nm (ratio ~10:1)) were then used on two groups viz. healthy (properly stored) and sub-optimally stored (artificially degraded (AD)) seeds and irradiated for 0 (control), 5, 10, and 15 min using total power densities of 7.8 and 6.2 mW/cm2, respectively. In the case of AD seeds, 5-min dual-wavelength laser treatment was found to be the most efficient setting as it improved the mean germination percentage, mean germination time, germination speed, germination rate index, wet weight, and dry weight by 29.3, 16.8, 24.2, 24.2, 15.7, and 20.6%, respectively, with respect to control samples. In the case of healthy seeds, dual-wavelength laser treatment could induce significant enhancement in seeds’ root length, wet weight, and dry weight (improved by 26, 23, and 8%, respectively) under 10 min of irradiation. On the other hand, the effect of applied red laser treatment was not very promising as it could only induce significant enhancement in the mean germination time of AD seeds (improved by 17%). Overall, this study demonstrates the potential of laser biostimulation in reversing the adverse effect of poor crop storage. We believe these findings could spur the development of a physical tool for manipulating seed germination and plant growth.

The insecticidal potential of Bacillus velezensis CE 100 against Dasineura jujubifolia Jiao & Bu (Diptera: Cecidomyiidae) larvae infestation and its role in the enhancement of yield and fruit quality of jujube (Zizyphus jujuba Miller var. inermis Rehder)

Jujube (Zizyphus jujuba Miller var. inermis Rehder) is highly susceptible to jujube gall midge (Dasineura jujubifolia Jiao & Bu) larvae infestation, which causes rolled leaf damage, leaf galls, discoloration, and a decline in fruit yield. In this study, we demonstrate the larvicidal potential of cuticle-degrading chitinase and protease produced by Bacillus velezensis CE 100 against jujube gall midge larvae and the plant growth-promoting effect on jujube fruit yield. The laboratory insecticidal assay involving bacterial broth culture and crude enzymes of B. velezensis CE 100 revealed that both treatments caused gall midge larvae mortality rates of up to 85.5% and 96.7%, respectively. Both treatments caused severe degradation of the larvae cuticle, such as deformation of the exoskeleton and loss of sensilla. Foliar application of the bacterial broth culture in the jujube field reduced the rate of rolled leaf damage by 3.8-fold more than that in the control group. In addition, B. velezensis CE 100 produced indole-3-acetic acid (IAA) up to 3.5 mg/mL, which improved root development, and exhibited the potential for nitrogen-fixation and phosphate solubilization to improve nutrient availability and uptake. Compared to the control, applying the bacterial treatment in the jujube field increased the leaf chlorophyll content by 1.3-fold and improved the fruit yield by 2.4-fold. For the first time, we demonstrate the dual larvicidal and bio-stimulation potential of entomopathogenic B. velezensis CE 100 in managing gall midge larvae and the improvement of jujube fruit production, respectively.

A fast method to evaluate in a combinatorial manner the synergistic effect of different biostimulants for promoting growth or tolerance against abiotic stress

BackgroundAccording to the most popular definition, a biostimulant is any substance or microorganism applied to plants with the aim to enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits, regardless of its nutrient content. Therefore, a biostimulant can help crops to withstand abiotic stress, while maintaining or even increasing productivity. We have previously designed a sequential system, based on two different model organisms, the baker’s yeast Saccharomyces cerevisiae and the plant Arabidopsis thaliana, to evaluate the potential of different natural extracts as biostimulants employing a blind-test strategy.ResultsIn this report, we further expand this concept to evaluate different biostimulants in a combinatorial approach to reveal the potential additive, synergistic or antagonistic effects of different combinations of biostimulants in order to design new formulations with enhanced effects on plant growth or tolerance to abiotic stress. The method is based on yeast assays (growth tests in solid medium, and continuous growth in liquid cultures) and plant assays (mass accumulation in hydroponic culture) to assess effects on early growth.ConclusionsWith this novel approach, we have designed new formulations and quantified the ability to enhance growth and promote biomass accumulation under normal conditions and in the presence of abiotic stresses, such as drought, salinity or cold. This method enables a fast screen of many different products in a combinatorial manner, in order to design novel formulations of natural extracts with biostimulant potential.

Mannosylerythritol lipids as green pesticides and plant biostimulants

Biosurfactants can be applied in the formulation of personal care products, as food additives, and as biocontrol agents in the agricultural sector. Glycolipids and lipopeptides represent an important group of microbial-based biosurfactants with biostimulating properties. Among them, the mannosylerythritol lipids also presented antimicrobial activity, mostly against Gram-positive bacteria and phytopathogenic fungi. In this sense, mannosylerythritol lipids are a potential safer green alternative for partially replacing synthetic pesticides. This review aimed to critically discuss the current state of the art and future trends of mannosylerythritol lipids as green pesticides and biostimulants for seed germination and plant growth. Due to their chemical structure, mannosylerythritol lipids are likely related to energy pathways such as glycolysis and Krebs cycle, i.e. a direct cellular biostimulant potential. In this case, experimental evidence from other glycolipids indicated that structural and chemical changes as a potential drug vehicle due to morphological changes caused by biosurfactant-membrane interaction. In addition, like other biosurfactants, mannosylerythritol lipids can trigger self-defense mechanisms, leading to a lower frequency of phytopathogen infections. Therefore, mannosylerythritol lipids have the potential for biostimulation and antiphytopathogenic action, despite that to date no data are available on mannosylerythritol lipids as biostimulants and green pesticides simultaneously. Based on the current state of the art, mannosylerythritol lipids have great potential for a biotechnological advance toward more sustainable agriculture. © 2022 Society of Chemical Industry.

Biostimulant Effects of an Aqueous Extract of Duckweed (Lemna minor L.) on Physiological and Biochemical Traits in the Olive Tree

Biostimulants are becoming increasingly popular in agriculture for their ability to induce beneficial effects in crops, paving the way towards the identification of new materials with biostimulant potential. This study evaluated the potential of different concentrations of an aqueous extract (0.25%, 0.50%, and 1.00%, dry weight/water volume, respectively) obtained from duckweed (Lemna minor L.) to stimulate olive plants. Leaf net photosynthesis (Pn), leaf transpiration rate (E), stomatal conductance (gs), sub-stomatal CO2 concentration (Ci), chlorophyll content and other plant growth parameters were investigated. As a result, the extract improved Pn, gs, Ci, chlorophyll content and plant biomass production (leaf fresh and dry weight). Furthermore, the duckweed extract generally increased the uptake of nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn), while it did not influence the content of sodium (Na), manganese (Mn) and copper (Cu). The untargeted metabolomic profiling of the extract revealed the presence of signalling compounds (including phytohormones), phenolics and glutathione. Such broad diversity of bioactives may support the stimulatory potential observed in olive. In summary, this study revealed for the first time that duckweed could be seen as a promising species to obtain extracts with biostimulant properties in olive trees.

Transcriptional characterization of the biostimulant effect of Moringa oleifera leaf extracts using Arabidopsis thaliana as a model.

Plant food production is affected by multiple abiotic and biotic stresses. To overcome these limiting factors, synthetic agrochemicals are widely used. However, more stringent worldwide regulatory policies and the public demand to reduce their application have led to the search for new ecofriendly alternatives such as biostimulants. Their commercial use is still limited, mostly due to the lack of knowledge of the molecular mechanisms responsible for their effects on plant metabolism. The horseradish Moringa oleifera has been described as a source of metabolites with biostimulant potential in agriculture. In particular, its leaf extracts (MLE) have been used to improve food production by enhancing plant growth and abiotic and biotic stress tolerance. Nevertheless, the molecular basis of changes induced by the application of MLE, in particular to the plant transcriptome, are poorly understood. In this work, using Arabidopsis thaliana as model, we determined that MLEA induced tolerance to salinity and protection against the phytopathogen Botrytis cinerea. Additionally, we characterized the transcriptional changes of phytohormone-induced genes that were caused by MLE. Our work provides novel and valuable information that can help researchers to characterize the biostimulant effects induced by the miracle plant Moringa oleifera.

Plant growth biostimulant activity of the green microalga Desmodesmus subspicatus

The plant biostimulant activity of the green microalga Desmodesmus subspicatus was investigated, focusing on its potential application to organic crops. Different concentrations of D. subspicatus biomass suspensions were applied to tomato seedlings (Solanum lycopersicum) via a foliar spray. The treatments promoted root growth and foliar area, which increased when the suspension was applied at concentrations of 1 g L−1 and 0.4 g L−1, respectively. To elucidate the major constituents responsible for this potential activity, the biomass of D. subspicatus was submitted to aqueous extraction and dialysis (1 kDa cut-off), giving rise to the non-dialyzable fraction E (12.3%). Size-exclusion chromatography performed on fraction E using a Bio-Gel P-2 column yielded six subfractions. Gas chromatography-mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) analyses of the E subfractions revealed the presence of glycosides as major constituents (approx. 81%), including one acidic glycoside, [6-sulfo-α-D-quinovopyranosyl-(1→1)-glycerol], and two neutral galactosyl glycosides, [α-D-galactopyranosyl-(1→6)-β-D-galactopyranosyl-(1→1)-glycerol] and [β-D-galactopyranosyl-(1→1)-glycerol]. Ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) analyses of fraction E resulted in the identification of the phytohormone zeatin (35 μg g−1). To evaluate the biostimulant potential of fraction E, different concentrations (0.5, 1.0, 1.5, and 2.0 g L−1) were tested for their effects on tomato seed germination, hypocotyl volume, and length. All tested concentrations induced increased hypocotyl lengths and volumes compared with standard treatment (water), at rates equivalent to those in response to a commercial product derived from Ascophyllum nodosum brown seaweed. These results indicated that the biomass suspension and aqueous extract of D. subspicatus showed plant growth biostimulant activity. Glycosides, together with zeatin, may play important roles in biostimulant activity.

Biostimulation potential of biochar for remediating the crude oil contaminated soil and plant growth.

Crude oil contamination is a serious environmental threat to soil and plants growing in it. Biochar has the potential of biostimulation for remediation of crude oil-contaminated soil. Therefore, the current research was designed to analyze the bio-stimulatory impact of biochar for remediating the crude oil contaminated soil (10%, and 15%), and growth of maize under glasshouse conditions. Biochar was produced by pyrolysis of Australian pines at 350 °C. Soil incubations were done for 20 days. The results of soil analysis showed that the crude oil degradation efficiency of biochar was 34%. The soil enzymatic activities had shown 38.5% increase in fluorescein diacetate (FDA) hydrolysis and 55.6% increase in dehydrogenase activity in soil incubated with biochar in comparison to control. The soil microbial diversity was improved to 41% in biochar treated soil with respect to untreated one, while microbial respiration rate had shown a 33.67% increase in soil incubated with biochar with respect to control under oil stress. Gas Chromatography Mass spectrometry (GC-MS) analysis had shown the high content of low molecular weight hydrocarbons (C9-C13) in the soil incubated with biochar in comparison to untreated soil. Biochar showed a significant increase in fresh and dry biomass (25%, 14.61%), leaf area (10%), total chlorophyll (11%), water potential (21.6%), osmotic potential (21%), and membrane stability index (12.7%). Moreover, biochar treatment showed a higher increase in the contents of proline (29%), total amino acids (18%), soluble sugars (30.4%), and antioxidant enzymes like superoxide dismutase (16.5%), catalase (11%), and peroxidase (12%). Overall, the results of the present study suggest the bio-stimulating potential of biochar for degradation of hydrocarbons in crude oil contaminated soil and their growth-stimulating effects on maize.

Effects of electrical biostimulation and silver ions on porcine fibroblast cells.

The medical applications of electrical biostimulation and silver ions have been evaluated in laboratory experiments and clinical studies for more than two decades. Their effects on preventing infection and promoting wound healing have been described. However, little is known about the role of electrical biostimulation and/or silver ion on changes in cellular transcriptome dynamics. To our knowledge, few studies have been conducted to investigate the potential of electrical biostimulation and silver ions in cell reprogramming. Besides, it is essential to assess any possible adverse effects or potential benefits of the silver ions on mammalian cells to address its safety concerns and to improve silver medical products. In this study, we investigated transcriptomic changes in porcine fibroblast cells in response to electrical biostimulation in the presence of silver ions. Exposed cells presented distinct morphological changes after treatment, which was mainly due to the exposure of silver ions rather than the electrical current itself. Gene expression analyses suggested that electrical biostimulation and silver ions did not increase the expression of pluripotency genes. Interestingly, a set of genes related to cellular metabolic processes were differentially expressed after cells were exposed to electrically generated silver ions for 21 hours. We found that 2.00 mg/L of electrically generated silver ion caused an increase of ATP generation and an increase of the total pool of NAD+ and NADH, while ROS production did not change. Aside from toxic effects, the results reported herein demonstrate the alternative effects of silver ions on mammalian cells, especially an oxidative phosphorylation burst. To our knowledge, this response of mammalian cells to silver ions has not been described previously. Although the function of this burst is not understood, it may lead to alterations in cellular activities such as metabolic remodeling and cell reprogramming, and/or serve an as-yet unknown function in neutralization or detoxification of the silver ions within the cells.