Journal of Soil and Plant Interactions
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University of Maragheh
Abstract: (232 Views)
Biosurfactants are amphiphilic molecules produced by living organisms, particularly bacteria. Recent studies have shown their potential to act as plant growth stimulants. The objective of this study was to evaluate the effects of biosurfactants on plant growth. To achieve this, biosurfactant-producing bacteria were initially isolated from the phyllosphere of wild plants. Subsequently, biosurfactants were extracted and purified. After evaluating their quality, four superior biosurfactants were selected and addressed by S1 to S4 codes. A pot experiment was conducted in the greenhouse using a completely randomized factorial design to assess the effects of foliar spraying at concentrations of 0, 0.1, 0.2, and 0.4 g. L-1 on the growth stimulation of spearmint and radish plants. At the end of the experiment, the plants’ growth traits were measured and evaluated. The results showed that the effect of biosurfactants was strongly influenced by their applied concentrations. At all concentrations, the highest growth stimulation was observed at 0.1 g L-1, and the lowest effects were observed at 0.4 g L-1. Additionally, the type of biosurfactant was found to play a significant role in growth stimulation. Biosurfactant S1 exhibited the most pronounced stimulatory effect, where the highest fresh weight of radish tubers was recorded under the S1 biosurfactant with 0.1 g.L-1 treatment, showing a 333% increase compared to the control. Similarly, in spearmint, the highest fresh weight was observed in the same treatment (S1-0.1), showing a 51% increase compared to the control. Therefore, biosurfactants, especially when used at optimal concentrations, appear to have a high potential for stimulating plant growth and improving plant quality. These compounds could serve as sustainable and environmentally friendly technologies for optimizing plant performance and agricultural productivity.
Keywords: Foliar spraying, plant fresh weight, plant dry weight, bio-stimulant
Background and Objective: The increasing global population has led to reliance on chemical pesticides and fertilizers, raising environmental concerns. This has shifted focus toward bio-based plant growth stimulants, which are eco-friendly and enhance soil health. Bacterial biosurfactants, due to their growth-promoting effects and stress tolerance enhancement, are promising bio-stimulants. These molecules reduce water surface tension, improve solubility of hydrophobic compounds, and are used in agriculture, pharmaceuticals, and bioremediation. Their low toxicity, biodegradability, and antimicrobial properties make them superior to chemical surfactants.
Recent studies suggest that biosurfactants can stimulate plant growth and activate defense mechanisms. For example, rhamnolipids from Pseudomonas aeruginosa enhance resistance to pathogens and induce the production of key plant hormones like salicylic acid and jasmonic acid. Biosurfactants also improve metal bioavailability in soil, facilitating plant uptake, which is beneficial in calcareous soils.
This study aimed to isolate and purify biosurfactant-producing bacteria from the phyllosphere of non-agricultural plants and evaluate their effects on the growth of radish and spearmint in greenhouse conditions.
Methods: In July 2020, healthy leaves from non-agricultural plants (Lactuca serriola, Populus nigra, Zygophyllum fabago, and Elaeagnus angustifolia) were collected from the Yousefabad region near Maragheh. Leaves were washed, disinfected, and processed to release epiphytic bacteria. Predominant colonies were purified, and hemolytic activity on blood agar identified biosurfactant-producing bacteria. Selected strains were grown in Minimal Salt Medium (MSM) for biosurfactant production. Biosurfactants were separated via centrifugation, acid precipitation, and extraction with diethyl ether. The quality of biosurfactants was evaluated using oil displacement, oil spreading, surface tension, and emulsification index tests. A greenhouse experiment (2021, Maragheh University) assessed the effects of purified biosurfactants (S1: Lactuca serriola, S2: Populus nigra, S3: Zygophyllum fabago, S4: Elaeagnus angustifolia) on radish and spearmint growth under concentrations of 0.1, 0.2, and 0.4 g L-1. Plants were grown in randomized pots using loamy soil, and biosurfactants were foliar-sprayed thrice at weekly intervals. Control plants were treated with water only. Post-harvest analysis included fresh and dry weight measurements, SPAD chlorophyll index, and photosynthetic pigment quantification. Statistical analysis (SAS, Duncan’s test, p<0.05) revealed significant growth enhancements in biosurfactant-treated plants.
Results: In radish S1-0.1 treatment increased crown diameter by 87.5% compared to the control. S1-0.1 and S3-0.2 treatments increased aboveground height by 113.8% and 108.8%, respectively. S1-0.1 treatment increased fresh tuber weight by 333%, and S4-0.2 resulted in the highest dry weight (five times the control) and, also S1-0.1 increased fresh and dry weights by 211% and 239%, respectively. S1-0.1 had the highest chlorophyll a content and increased chlorophyll b by 71%. S1-0.1 increased carotenoids by 74% and increased the spad chlorophyll index by 83%.
In spearmint S1-0.1 increased fresh weight by 51%. S1-0.2, S3-0.1, and S3-0.2 increased dry weight by 176%, 185%, and 161%, respectively. S1-0.1 increased stem height by 47% and lateral branches by 60.7%. S1-0.1 increased chlorophyll a by 40.9% and carotenoids by 57%. S1-0.1, S2-0.4, and S4-0.1 significantly increased chlorophyll b.
Conclusion: The greenhouse study demonstrated that biosurfactants extracted from bacterial sources significantly improved the growth and photosynthetic efficiency of radish and spearmint plants. S1 biosurfactant in 0.1 mg L-1 concentration, consistently showed the best performance, enhancing morphological traits and photosynthetic pigments. These findings suggest that biosurfactants, particularly at optimal concentrations, can serve as natural alternatives to chemical fertilizers, promoting sustainable agriculture.
Keywords: Foliar spraying, plant fresh weight, plant dry weight, bio-stimulant
Background and Objective: The increasing global population has led to reliance on chemical pesticides and fertilizers, raising environmental concerns. This has shifted focus toward bio-based plant growth stimulants, which are eco-friendly and enhance soil health. Bacterial biosurfactants, due to their growth-promoting effects and stress tolerance enhancement, are promising bio-stimulants. These molecules reduce water surface tension, improve solubility of hydrophobic compounds, and are used in agriculture, pharmaceuticals, and bioremediation. Their low toxicity, biodegradability, and antimicrobial properties make them superior to chemical surfactants.
Recent studies suggest that biosurfactants can stimulate plant growth and activate defense mechanisms. For example, rhamnolipids from Pseudomonas aeruginosa enhance resistance to pathogens and induce the production of key plant hormones like salicylic acid and jasmonic acid. Biosurfactants also improve metal bioavailability in soil, facilitating plant uptake, which is beneficial in calcareous soils.
This study aimed to isolate and purify biosurfactant-producing bacteria from the phyllosphere of non-agricultural plants and evaluate their effects on the growth of radish and spearmint in greenhouse conditions.
Methods: In July 2020, healthy leaves from non-agricultural plants (Lactuca serriola, Populus nigra, Zygophyllum fabago, and Elaeagnus angustifolia) were collected from the Yousefabad region near Maragheh. Leaves were washed, disinfected, and processed to release epiphytic bacteria. Predominant colonies were purified, and hemolytic activity on blood agar identified biosurfactant-producing bacteria. Selected strains were grown in Minimal Salt Medium (MSM) for biosurfactant production. Biosurfactants were separated via centrifugation, acid precipitation, and extraction with diethyl ether. The quality of biosurfactants was evaluated using oil displacement, oil spreading, surface tension, and emulsification index tests. A greenhouse experiment (2021, Maragheh University) assessed the effects of purified biosurfactants (S1: Lactuca serriola, S2: Populus nigra, S3: Zygophyllum fabago, S4: Elaeagnus angustifolia) on radish and spearmint growth under concentrations of 0.1, 0.2, and 0.4 g L-1. Plants were grown in randomized pots using loamy soil, and biosurfactants were foliar-sprayed thrice at weekly intervals. Control plants were treated with water only. Post-harvest analysis included fresh and dry weight measurements, SPAD chlorophyll index, and photosynthetic pigment quantification. Statistical analysis (SAS, Duncan’s test, p<0.05) revealed significant growth enhancements in biosurfactant-treated plants.
Results: In radish S1-0.1 treatment increased crown diameter by 87.5% compared to the control. S1-0.1 and S3-0.2 treatments increased aboveground height by 113.8% and 108.8%, respectively. S1-0.1 treatment increased fresh tuber weight by 333%, and S4-0.2 resulted in the highest dry weight (five times the control) and, also S1-0.1 increased fresh and dry weights by 211% and 239%, respectively. S1-0.1 had the highest chlorophyll a content and increased chlorophyll b by 71%. S1-0.1 increased carotenoids by 74% and increased the spad chlorophyll index by 83%.
In spearmint S1-0.1 increased fresh weight by 51%. S1-0.2, S3-0.1, and S3-0.2 increased dry weight by 176%, 185%, and 161%, respectively. S1-0.1 increased stem height by 47% and lateral branches by 60.7%. S1-0.1 increased chlorophyll a by 40.9% and carotenoids by 57%. S1-0.1, S2-0.4, and S4-0.1 significantly increased chlorophyll b.
Conclusion: The greenhouse study demonstrated that biosurfactants extracted from bacterial sources significantly improved the growth and photosynthetic efficiency of radish and spearmint plants. S1 biosurfactant in 0.1 mg L-1 concentration, consistently showed the best performance, enhancing morphological traits and photosynthetic pigments. These findings suggest that biosurfactants, particularly at optimal concentrations, can serve as natural alternatives to chemical fertilizers, promoting sustainable agriculture.
Type of Study: Research |
Subject:
Plant growth promoting microrganisms in the rhizosphere
Received: 2025/01/12 | Accepted: 2025/04/20
Received: 2025/01/12 | Accepted: 2025/04/20
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Journal of Soil and Plant Interactions by http://jspi.iut.ac.ir is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License which allows users to read, copy, distribute and make derivative works for non-commercial purposes from the material, as long as the author of the original work is cited properly.
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License which allows users to read, copy, distribute and make derivative works for non-commercial purposes from the material, as long as the author of the original work is cited properly.
