Alfalfa Plants Research Articles

MsFtsH8 Enhances the Tolerance of PEG-Simulated Drought Stress by Boosting Antioxidant Capacity in Medicago sativa L.

Drought is a major abiotic stress that limits the growth and yield of alfalfa, a vital forage legume. The plant metalloproteinase Filamentation temperature-sensitive H (FtsH) is an ATP- and Zn2+-dependent enzyme that plays a significant character in the plant’s response to environmental stress. However, its functional role in drought resistance remains largely unexplored. This study investigates the drought tolerance role of alfalfa MsFtsH8 by analyzing the growth, physiology, and gene expression of overexpressing plants under drought conditions. The results demonstrated that both MsFtsH8-overexpressing Arabidopsis and alfalfa plants exhibited superior growth condition and enhanced membrane stability. The overexpressing alfalfa plants also showed reduced MDA levels, higher proline content, lower H2O2 accumulation, an increased activity of antioxidant-related enzymes (SOD, POD, and CAT) activity, and an elevated expression of antioxidant-related genes. These results indicated that the overexpression of MsFtsH8 enhanced growth, improved osmotic regulation, reduced ROS levels, and increased antioxidative capacity, ultimately leading to greater drought tolerance in alfalfa. Our findings suggest that MsFtsH8 mitigates oxidative damage caused by drought by modulating the plant’s antioxidant system, thus improving drought tolerance in alfalfa. This study provides a molecular basis and candidate genes for enhancing drought resistance in alfalfa through genetic engineering.

Calcium oxide nanoparticles ameliorate cadmium toxicity in alfalfa seedlings by depriving its bioaccumulation, enhancing photosystem II functionality and antioxidant gene expression

Cadmium (Cd) is a highly toxic and carcinogenic pollutant that poses significant risks to living organisms and the environment, as it is absorbed by the plant roots and accumulates in different parts of crop during its production. A promising sustainable strategy to counteract these threats to use calcium oxide nanoparticles (CaO-NPs) as soil supplements in fodder crops. This approach has shown notable morpho-physiological and biochemical improvements under metal toxicity conditions. However, the specific mechanisms driving Cd tolerance, particularly at physio-biochemical level and antioxidant related genes expression in fodder crops including alfalfa remain unexplored. CaO-NPs supplementation can trigger various signaling pathways that lead to enhance the photosynthetic pigments formation, stomatal conductance, CO2 assimilation rate and quantum yield of photosystem II. In this study, we evaluated various doses of CaO-NPs (0, 25, 50, and 100 mg kg−1) for their efficacy in reducing Cd bioavailability and toxicity in alfalfa plants. Our results demonstrated that Ca2+ and Cd2+, which share the same ionic radius, compete for ion transport through channels. The small size and high availability of CaO-NPs facilitate their rapid translocation within plant tissues, reducing metal uptake by 61 % in shoots and 30 % in roots. Notably, application of CaO-NPs at 100 mg kg−1 significantly increased shoot length (44 %) and root lengths (35 %) as compared to Cd-treated control plants. The highest dose of CaO-NPs also improved photosynthetic efficiency and gas exchange attributes including (gs, Tr, Pn and Ci) by 66 %, 27 %, 33 % and Ci 21 %, respectively, compared with the Cd treated control. Moreover, CaO-NPs (at 100 mg kg−1) alleviated metal-induced oxidative stress by boosting antioxidant enzyme activity like SOD (25 %) POD (42 %), CAT (72 %) and APX (87 %) and diminishing reactive oxygen species (ROS) production when compared with sole Cd treatment. Scanning and transmission electron microscopy revealed that CaO-NPs positively impacted stomatal conductance and mitigated Cd toxicity in leaf ultrastructure. Additionally, the highest dose of CaO-NPs markedly upregulated the expression of antioxidant-related genes, MsCu/Zn SOD, MtPOD, MtCAT, and MtAPX in roots and shoots by 0.67 and 1.03 fold-change (FC), 0.61 and 0.53 FC, 0.54 and 0.88 FC, and 0.46 and 0.66 FC, respectively. In conclusion, CaO-NPs demonstrate significant potential for environmentally friendly mitigation of Cd stress in alfalfa by reducing its uptake, thereby supporting sustainable agriculture.

Remediation of Hydrocarbons in Soil by Medicago sativa Plant

Remediation of Hydrocarbons in Soil by Medicago sativa Plant

Hydrogen Peroxide Is Involved in Methane-Alleviated Cadmium Toxicity in Alfalfa (Medicago sativa L.) Seedlings by Enhancing Cadmium Chelation onto Root Cell Walls.

Although previous studies have demonstrated that methane (CH4) can mitigate the toxicity of cadmium (Cd) in alfalfa seedlings, the CH4-rich water used in these studies may create hypoxic conditions, potentially influencing the experimental outcomes. Therefore, this study aimed to investigate whether CH4 can reduce Cd toxicity in alfalfa seedlings without the interference of hypoxia and to analyze its underlying mechanisms. Here, it was observed that supplementing oxygen with saturated CH4-rich water can significantly alleviate the inhibition of 75 μM CdCl2 on the growth of alfalfa (Medicago sativa L.) seedlings. Less Cd accumulation was also observed in both root and shoot parts, which could be explained by the CH4-altered cell wall components in alfalfa seedling roots, including covalent and ionic soluble pectin, and the degree of demethylation in pectin, thus enabling a higher proportion of Cd binding to the cell walls and reducing the entry of Cd into the cells. The above actions of CH4 were accompanied by an increase in hydrogen peroxide (H2O2) content and NADPH oxidase activity, which could be blocked by the addition of the NADPH oxidase inhibitor diphenylene iodonium (DPI). Taken together, these results implied that exogenously applied CH4 could alleviate Cd toxicity in alfalfa seedlings by enhancing Cd chelation onto the root cell walls, which might be closely associated with NADPH oxidase-dependent H2O2 signals. These findings could provide insight into the mechanism through which CH4 alleviates Cd toxicity in alfalfa plants.

Biological Decline of Alfalfa Is Accompanied by Negative Succession of Rhizosphere Soil Microbial Communities.

The growth and biological decline of alfalfa may be linked to the rhizosphere microbiome. However, plant-microbe interactions in the rhizosphere of alfalfa and associated microbial community variations with stand age remain elusive. This study explored the successional pattern of rhizosphere microbial communities across different aged alfalfa stands and its relationship with alfalfa decline. Rhizosphere soils were collected from 2- and 6-year-old alfalfa stands. Control soils were collected from interspaces between alfalfa plants in the same stands. Soil bacterial and fungal communities were characterized by 16S and ITS rRNA gene sequencing, respectively. Specific microbial taxa colonized the rhizosphere soils, but not the control soils. The rhizosphere-specific taxa mainly included potentially beneficial genera (e.g., Dechloromonas, Verrucomicrobium) in the young stand and harmful genera (e.g., Peziza, Campylocarpon) in the old stand. Alfalfa roots regulated soil microbial communities by selective promotion or inhibition of distinct taxa. The majority of time-enriched taxa were reported as harmful fungi, whose relative abundances were negatively correlated with plant traits. Time-depleted taxa were mostly known as beneficial bacteria, which had relative abundances positively correlated with plant traits. The relative abundances of functional bacterial genes associated with vancomycin biosynthesis, zeatin biosynthesis, and amino acid metabolism trended lower in rhizosphere soils from the old stand. An upward trend was observed for fungal pathogens and wood saprotrophs with increasing stand age. The results suggest that root activity drives the negative succession of rhizosphere microbial communities during alfalfa decline in old stands.

Accumulation of microcystin toxin in irrigation water and alfalfa (Medicago sativa) forage plant, and assessing the potential risk to animal health

Microcystin (MC) toxin produced by cyanobacteria has become a significant concern for societies worldwide. The risk of MC in drinking water has been assessed to human health. Nonetheless, its risk to animal health has not been thoroughly evaluated. This study investigated MCs in irrigation water and alfalfa plant from nearby farmlands. Both irrigation water and alfalfa shoots contained greater MC concentrations (1.8–17.4 μg L−1 and 0.053–0.128 μg g−1) during summer than winter (2.4 μg L−1 and 0.017 μg g−1). These MC concentrations showed a correlation with the predominance of cyanobacteria in the sites, triggering the potential risk of these microorganisms in irrigation waters. Accordingly, there would be a high risk (risk quotient, RQ > 1) during summer and a moderate risk (0.1<RQ < 1) during winter for cattle and sheep that drink polluted irrigation water or eat contaminated alfalfa plants. Therefore, the study suggests that cyanotoxins in forage plants and irrigation water sources should be regularly monitored to protect animals from consuming contaminated food and water.

Study the interactional effect between various concentrations of (Fe) and (Sinorhizobium Meliloti) on growth, and nitrogen fixation process in Alfafa (Medicago Sativa) Plants.

Study the interactional effect between various concentrations of (Fe) and (Sinorhizobium Meliloti) on growth, and nitrogen fixation process in Alfafa (Medicago Sativa) Plants.

Customized Plant Growth Promotion with Soil- and Cultivar-Compatible Microbial Biofertilizers

Organic fertilizers and microbial biofertilizers are now widely recognized to effectively complement traditional mineral fertilizers for plant growth. The present study shows that bio-organic fertilizers can be enhanced by the addition of functional plant-growth-promoting rhizobacteria (PGPR) that provide additional benefits to plants. We hypothesized that not all beneficial soil bacteria are functional in different farm soils and plant varieties; hence, the most effective PGPR that are suitable to each farm’s individual cropping conditions were selected. Five different field soils and their respective crops were tested for compatibility with six microbial biofertilizers (including three new bacterial strains) to supplement a commercially available bio-organic fertilizer. In pot trials with lucerne plants, four out of the six microbial treatments led to significant (p &lt; 0.05) growth promotion benefits (up to 79.8% more leaves and dry weight) compared to mock-treated or bio-organic fertilizer-only-treated control plants. A trial with industrial hemp demonstrated that compatibility with PGPR occurs in a cultivar-specific manner, leading to growth promotion ranging from −3.4% to 68.9%, with each cultivar displaying a preference for a different PGPR. Finally, pot trials with Rhodes grass and two different soils demonstrated high yield increases compared to control plants, with Bacillus amyloliquefaciens 33YE being most effective for one soil and Bacillus velezensis UQ9000N/Pseudomonas lini SMX2 for the other soil. Yield advantages reduced after several cuts of grass, but a repeat biofertilizer treatment at 69 days after the initial treatment restored high yield advantages, with the same PGPR again being most effective. These results demonstrate the importance of customization of microbial inoculants to identify the most compatible PGPR–cultivar–soil interaction. The customization of microbial biofertilizers to soils and plant cultivars, combined with complementary fertilizer applications, can potentially lead to more reliable and more sustainable agricultural practices.

Effect of alfalfa downy mildew (Peronospora aestivalis) infection on the growth and development of Therioaphis trifolii (Homoptera: Aphidiidae)

Downy mildew disease, which is caused by Peronospora aestivalis (Mastigomycotina: Peronosporaceae) and the spotted alfalfa aphid Therioaphis trifolii (Hemiptera: Aphididae), affects Medicago sativa (alfalfa) production. P. aestivalis and T. trifolii frequently occur together under natural conditions. In this study, alfalfa-P. aestivalis-T. trifolii were used as the research objects to explore the effects of different degrees of P. aestivalis infection on the growth and reproduction of T. trifolii, and the life table of T. trifolii population was constructed based on the fecundity parameters. The results revealed that alfalfa downy mildew infection had a significant effect on T. trifolii population. T. trifolii fed on mildly infected alfalfa plants exhibited the longest life span (18.9 d) and the highest number of nymphs (30.6) compared to those fed on alfalfa in other treatments. In terms of population life table parameters, the intrinsic rate of increase (0.626) and finite rate of increase (1.869) of T. trifolii fed on moderately infected alfalfa were the highest, and the generation time (8.310) and population doubling time (1.108) were the shortest, indicating that moderately infected alfalfa are conducive to T. trifolii population development. This study provides insights into the effects of alfalfa downy mildew on the main reproductive parameters and population of T. trifolii on M. sativa.

Impact of alternate partial root-zone irrigation on the rhizosphere microbiota of alfalfa plants inoculated with rhizobia.

Water is an important constraint on alfalfa (Medicago sativa) production in arid and semiarid areas, and alternate irrigation in root areas has water-saving potential for alfalfa production. To investigate the impact of alternate partial root-zone irrigation (APRI) on the rhizosphere soil microorganisms of alfalfa, this study subjected alfalfa plants to different irrigation methods and irrigation levels. The growth status and rhizosphere soil microbial community diversity of alfalfa plants under alternate root-zone watering treatment were analyzed through laboratory experiments and high-throughput sequencing. The results showed that at soil moisture levels of 80% field moisture capacity (FMC) and 60% FMC, APRI had no significant impact on the biomass or nodule number of alfalfa. However, 40% FMC significantly reduced the individual plant dry weight, chlorophyll content, and nodule number of the alfalfa plants. APRI increased the relative abundance of Actinomycetes in the alfalfa rhizosphere soil. Moreover, at 60% FMC, the MBC and MBN of rhizosphere, relative abundance of Actinobacteria and unclassified K fungi and Chao 1 index of bacteria significantly increased under APRI treatment. While relative abundance of Ascomycetes and Proteobacteria in the alfalfa rhizosphere significantly reduced under 60% FMC + APRI treatment. In summary, under the same irrigation conditions, APRI did not significantly affect the growth of alfalfa in the short term. And 60%FMC + APRI treatment did significantly affect the groups, structure and diversity of the rhizosphere soil microbial communities.

NaHS immersion alleviates the stress effect of chromium(III) on alfalfa seeds by affecting active oxygen metabolism

ABSTRACT Objective This study aimed to investigate the regulatory effects of exogenous hydrogen sulfide (H2S) on seed germination, seedling growth, and reactive oxygen species (ROS) homeostasis in alfalfa under chromium (Cr) ion (III) stress. Methods The effects of 0–4 mM Cr(III) on the germination and seedling growth of alfalfa were first assessed. Subsequently, following seed NaHS immersion, the influence of H2S on alfalfa seed germination and seedling growth under 2 mM Cr(III) stress was investigated, and the substance contents and enzyme activities associated with ROS metabolism were quantified. Results Compared to the control group, alfalfa plant germination was delayed under 2 mM Cr(III) stress for up to 48 h (p < 0.05). At 120 h, the total seedling length was approximately halved, and the root length was roughly one-third of the control. Treatment with 0.02–0.1 mM NaHS alleviated the delay in germination and root growth inhibition caused by 2 mM Cr(III) stress, resulting in an increased ratio of root length to hypocotyl length from 0.57 to 1 above. Additionally, immersion in 0.05 mM NaHS reduced hydrogen peroxide (H2O2) and oxygen-free radicals (O2 · –) levels (p < 0.05), boosted glutathione (GSH) levels (p < 0.05), and notably enhanced catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities (p < 0.05) compared to the 2 mM Cr(III) stress treatment group. Conclusion Seed immersion in NaHS mitigated the delay in germination and inhibition of root elongation under 2 mM Cr(III) stress. This effect is likely attributed to the regulation of intracellular ROS homeostasis and redox balance through enzymatic and non-enzymatic systems; thus, providing a potential mechanism for combating oxidative stress.

Role of malic acid in enhancing the efficiency of barley (Hordeum vulgare L.) and alfalfa (Medicago sativa L.) plants for phytoremediation of salt affected soil

Soil salinization is a growing global problem that influences plant growth and crop productivity. Most of the reclamation efforts in the past have focused on the installation of surface drainage systems. Other management approaches, such as excessive leaching and chemical amendments, have also been used on a limited scale to enhance the productivity of these soils. Phytoremediation can be cost-effective and environmentally sound technology.A laboratory experiment was carried out to study the role of malic acid which is low molecular weight organic acid (LMWOA) in enhancing the efficiency of barley and alfalfa plants for the phytoremediation of salt-affected soil. Seeds of barley and alfalfa were cultured in pots and irrigated with full strength Hoagland nutrient solution with three concentrations of seawater (SW) (10%, 20% and 30%) and a mixture of seawater with malic acid (MA) at 2, 4 and 6 mM l-1 (MA+SW), Hoagland solution was used as control. After twelve weeks, plants were harvested, and three types of soils (barley soil, alfalfa soil, and plant-free soil) were subjected to physical and chemical analysis for EC (electrical conductivity), TOC (total organic carbon), pH, potassium, sodium, and chloride ions. Results indicated a significant decrease was recorded in soil EC, pH, potassium, sodium, and chloride ions and a significant increase in soil TOC in barley and alfalfa soil compared with plant-free soil. Treatments with (MA+SW), especially at (2+10%) resulted in a significant increase in ions availability and phytoremediation activity in barley and alfalfa soils comparing with plant-free soil.

Environmental microplastic interact with heavy metal in polluted soil from mine site in the North of Tunisia: Effects on heavy metal accumulation, growth, photosynthetic activities, and biochemical responses of alfalfa plants (Medicago saliva L.)

As emerging persistent pollutants, microplastic (MPs) pollution attracted increasing attention worldwide since it is posing several environmental concerns. MPs interact with heavy metals in soil and may provoke damages on soil properties and ultimately impaired plants and human health. The present study aims to evaluate alfalfa plants (Medicago sativa) response after exposure to heavy metal polluted soils from mine site in the North of Tunisia in presence of environmental microplastic. For that, soils were sampled from two sites of Jebel Ressass mine in addition to a control soil. Plants were exposed to the three soils in presence of two increasing rates of microplastics D1 (1 mg/kg of soil) and D2 (100 mg/kg of soil) for 60 days. After harvest, agronomic parameters, chlorophyll content as well as heavy metal accumulation in plants were analyzed. Furthermore, oxidative status was evaluated in terms of malondialdehyde accumulation (MDA), catalase (CAT) activities and glutathion-S-transferase (GST). Overall, our finding highlights that MPs disrupted agronomic parameters and the photosynthetic activities of alfalfa plants. Additionally, our results revealed that the presence of MPs in polluted soils cause an increase on heavy metal accumulation in alfalfa shoots. Biochemical analyses demonstrated that the combined exposure to MPs and heavy metal induced oxidative stress in alfalfa plants by increasing CAT activity and MDA accumulation. The present investigation highlights the ecological risks of microplastics in terrestrial environment.

The Alternative Host with the Most: Understanding the Ecology of Xanthomonas hortorum pv. carotae on Noncarrot Crops in Central Oregon.

Bacterial blight of carrot, caused by Xanthomonas hortorum pv. carotae (Xhc), is an economically important disease in carrot (Daucus carota subsp. sativus) seed production. The objectives of this study were to determine if Xhc was present on noncarrot crops grown in central Oregon and, if detected, evaluate its ability to colonize alternative hosts. Surveys of three carrot seed fields and adjacent fields of rye (Secale cereale), alfalfa (Medicago sativa), parsley root (Petroselinum crispum var. tuberosum), and Kentucky bluegrass (Poa pratensis) demonstrated that Xhc was present on noncarrot crops. Greenhouse experiments were conducted to determine the ability of Xhc to colonize crops cultivated in the region. Carrot, alfalfa, curly parsley (Petroselinum crispum), Kentucky bluegrass, mint (Mentha × piperita), parsley root, roughstalk bluegrass (Poa trivialis), and wheat (Triticum aestivum) plants were spray-inoculated with Xhc and destructively sampled at 1, 7, 14, and 28 or 25 days post-inoculation. Xhc populations were quantified using viability quantitative PCR and dilution plating. A significant (P ≤ 0.03) effect of crop was observed at 1, 14, and 28 or 25 days in both experiments. While carrot hosted the most Xhc at the final timepoint, other crops supported epiphytic Xhc populations including wheat and both bluegrasses. Mint, parsley root, and alfalfa hosted the least Xhc. Bacterial blight symptoms were observed on carrots but not on noncarrot crops. This suggests that crops grown in central Oregon have the potential to be asymptomatically colonized by Xhc and may serve as reservoirs of the pathogen in carrot seed production systems.

Biostimulant induce growth, chlorophyll content and fresh herbage yield of alfalfa (Medicago sativa L.) and variegated alfalfa (Medicago × varia Martyn) plant

The use of biostimulants is associated with promoting plant growth by stimulating cell division and improving nutrient availability and uptake. A study was conducted at the University of Debrecen, Hungary, to examine the effect of biostimulants on alfalfa growth, chlorophyll content and fresh herbage yield. The experiment was arranged in a randomised complete block design with three biostimulant treatments plus control replicated three times. Data collected were subjected to analyses of variance using Genstat, where significantly different means were separated at a probability of 5% using the least significant difference. The findings show no different variation in plant height or chlorophyll content (SPAD) throughout the early stages of growth. Nonetheless, a notable impact was noted in the latter stages (28 days after biostimulant treatment application) on the growth of the alfalfa plant. Biostimulant treatments did not had effect on fresh yield for second through fourth cuts, but the fifth cut showed a significant effect, with T1 treatment recording the highest herbage yield of 19745 kg ha-1 followed by T2 (Tricho Immun plus Ino Green) and T3 (Tricho Immun), with yields of 19528 kg ha-1 and 17273 kg ha-1, respectively, while the T0 (control) recorded the lowest herbage yield of 12060 kg ha-1. However, the average mean yield indicated the application of biostimulants significantly increased fresh yield herbage by 20.5%. Correlation coefficient values suggested plant height at both 14 and 28 DAH (days after harvest) strongly correlated with fresh herbage yield (r = 0.7756 and 0.7455) which reflected in the increase in fresh herbage yield. Therefore, our results suggest that the use of biostimulants in alfalfa cultivation holds promise for improving growth and yield potential through their positive effects on chlorophyll content and the growth of alfalfa plant.

Virulent Fusarium isolates with diverse morphologies show similar invasion and colonization strategies in alfalfa.

Root rot is a major disease that causes decline of alfalfa production, and Fusarium is a major pathogen associated with root rot. In this study, 13 Fusarium isolates were obtained from alfalfa with root rot in Gansu Province, the major alfalfa production region in China. The isolates were characterized by molecular genotyping (ITS, TEF 1-α and RPB2 fragments) and identified as six species, which included the F. acuminatum, F. incarnatum, F. oxysporum, F. proliferatum, F. redolens, and F. solani. We found that their morphology varied significantly at both the macro- and micro-levels, even for those from the same species. We developed a low cost and fast pathogenicity test and revealed that all isolates were pathogenic to alfalfa with typical root rot symptoms such as leaf yellowing and brown lesions on the root and stem. However, the virulence of the isolates differed. We also found that the conidia of all isolates germinated as early as 24 hours post inoculation (hpi), while hyphae colonized the root extensively and invaded the xylem vessel by 48 hpi. Together our results reveal that different virulent Fusarium isolates use a similar invasion strategy in alfalfa. This natural plant-fungus pathosystem is intriguing and warrants further examination, particularly with regard to efforts aimed at mitigating the impact of multiple similar vascular pathogens on infected alfalfa plants.

Systems management strategies for increasing alfalfa use in warm‐humid regions

AbstractAlfalfa use (Medicago sativa L.; “lucerne”) in warm, humid regions of the world represents a potential area of expansion for the alfalfa industry. The objective of this review paper is to demonstrate how alfalfa forage breeding and systems research efforts have identified opportunities for increasing alfalfa contributions in these regions, along with potential pathways for seed industry and farming operations to increase adoption. Our review draws primarily on reports from the Southeast United States and Argentina. Significant technological advancements in plant screening and selection have identified alfalfa plant populations that are more adapted to the growing conditions experienced in these regions, which are often characterized by mild temperature, long growing seasons, and multiple other abiotic and biotic stressors. Management systems research conducted in the United States and Argentina has demonstrated the use of alfalfa for conserved forage, grazing, or dual‐purpose use in monoculture or mixtures with warm‐season grasses such as bermudagrass (Cynodon spp.). These trials report increased forage production, nutritive value, and ecosystem services of alfalfa–grass mixtures when compared with traditionally N‐fertilized warm‐season grass‐based systems. Grazing‐based alfalfa systems in Argentina have demonstrated methods for utilizing alfalfa as part of beef, dairy, and finishing systems. Some approaches for expanding alfalfa production in the region include targeted marketing efforts for adapted varieties and demonstrating alfalfa applications within existing farming frameworks. This includes educational programming efforts and on‐farm demonstrations to promote alfalfa use as a component of the livestock diets, integration into grass‐based systems, crop rotations, and wildlife use. Continued emphasis on a systems approach to alfalfa inclusion represents an opportunity for improved forage and livestock production in warm, humid regions of the world.

Degradation of petroleum hydrocarbon contaminants by Rhodococcus erythropolis KB1 synergistic with alfalfa (Medicago sativa L.).

Petroleum hydrocarbons are a stubborn pollutant that is difficult to degrade globally, and plant-microbial degradation is the main way to solve this type of pollutant. In this study, the physiological and ecological responses of alfalfa to petroleum hydrocarbons in different concentrations of petroleum hydrocarbon-contaminated soil with KB1 (Rhodococcus erythropolis) were analyzed and determined by laboratory potting techniques. The growth of alfalfa (CK) and alfalfa with KB1 (JZ) in different concentrations of petroleum hydrocarbons contaminated soil was compared and analyzed. The results of the CK group showed that petroleum hydrocarbons could significantly affect the activity of alfalfa antioxidant enzyme system, inhibit the development of alfalfa roots and the normal growth of plants, especially in the high-concentration group. KB1 strain had the ability to produce IAA, form biofilm, fix nitrogen, produce betaine and ACC deaminase, and the addition of KB1 could improve the growth traits of alfalfa in the soil contaminated with different concentrations of petroleum hydrocarbons, the content of soluble sugars in roots, and the stress resistance and antioxidant enzyme activities of alfalfa. In addition, the degradation kinetics of the strain showed that the degradation rate of petroleum could reach 75.2% after soaking with KB1. Furthermore, KB1 can efficiently degrade petroleum hydrocarbons in advance and significantly alleviate the damage of high concentration of petroleum hydrocarbons to plant roots. The results showed that KB1 strains and alfalfa plants could effectively enhance the degradation of petroleum hydrocarbons, which provided new ideas for improving bioremediation strategies.

The trade-off regulation of arbuscular mycorrhiza on alfalfa growth dose-dependent on gradient Mo exposure

Molybdenum (Mo) is an essential nutrient for leguminous plants, but the effects of Mo exposure on plant growth, especially in relation to soil microorganisms, are not fully understood. This study employed alfalfa (Medicago sativa L.) to evaluate the physiochemical responses to gradient soil Mo variations and explore the potential regulatory role of rhizosphere microorganism - arbuscular mycorrhizal fungi (AMF) in modulating Mo's impact on plant physiology, with a focus on metabolic pathways. The results showed that Mo exerted hormetic effect (facilitation at low doses; inhibition at high doses) on alfalfa growth, promoting biomass (below 90.94 mg/kg, with a 63.98 % maximum increase), root length (below 657.11 mg/kg, with a 39.29 % maximum increase), and plant height (below 304.03 mg/kg, with an 18.4 % maximum increase). Excess Mo (1000 mg/kg) resulted in a reduction in photosynthesis and biomass growth due to increased oxidative stress (p < 0.05). Within the stimulatory zones, AMF enhanced Mo accumulation in alfalfa, augmenting its phytological effects. Exceed the stimulatory zones, AMF enhanced alfalfa Fe uptake and reduced the generation of reactive oxygen species (ROS) induced by excess Mo by shifting the redox homeostasis-controlled enzyme from peroxidase (POD) to superoxide dismutase (SOD), thereby improving alfalfa's tolerance to Mo. Metabolomic analysis further revealed that AMF promoted the biosynthesis of indole acetic acid (IAA) and various amino acids in Mo-stressed alfalfa (p < 0.05), which accelerated alfalfa growth and mitigated Mo-induced phytotoxicity. These insights provide a foundation for developing sustainable management strategies for Mo-exposed soils using AMF inoculants, such as minimizing Mo fertilizer application in Mo-deficient soils and facilitating the reclamation of Mo-contaminated soils.

SYSTEM DEFENSE OF FORAGE SPECIES SUBMITTED TO LOW TEMPERATURES

This work aims to evaluate the enzymatic system defense of forages exposed to low temperatures. The forage plants alfalfa, sorghum, black oat, marandu grass, pearl millet, mombasa grass, and Bermuda grass were subjected to temperatures of 0.2; -0.9; -1.8; -2.7; -4.1; -4.6 and -6.2 oC for 1 h in a growth chamber in a completely randomized design with six replicates for each species. From the crude leaf extracts were evaluated the enzymes ascorbate peroxidase (APX), catalase (CAT), and superoxide dismutase (SOD) activities. Regression analyses compared the treatments. The biochemical responses of forage species to cold stress are different. The enzymes APX and SOD would play an important role in the response to oxidative stress in the forage species black oat and mombasa grass. In marandu grass and sorghum, SOD was the main cell protector. Pearl millet had a positive stimulus in CAT production, Bermudagrass increases the protein content and SOD activity, and alfalfa increases the protein content and APX activity.