Non-leguminous Plants Research Articles

Physiological and Photochemical Screening of Leguminous and Non-leguminous Plants Interacting with Nitrogen-Fixing Microbe Pseudomonas fluorescens (NAFP-19) Modulating Stress Tolerance in a Sub-optimal Condition

Physiological and Photochemical Screening of Leguminous and Non-leguminous Plants Interacting with Nitrogen-Fixing Microbe Pseudomonas fluorescens (NAFP-19) Modulating Stress Tolerance in a Sub-optimal Condition

The ‘fertilizer island effect’ cannot eliminate competition between leguminous shrubs and symbiotic herbs in desert ecosystems

The ‘fertilizer island effect’ — a phenomenon engendered by shrubs — promotes the growth of symbiotic herbs and the stabilization of community structures in scrublands. Specifically, leguminous shrubs contribute significantly to the nitrogen input in desert ecosystems. However, the impact of these inputs on the nutrient balance in symbiotic herbs has seldom been explored. To enhance our understanding of the nutrient balance between nitrogen-fixing legume shrubs and symbiotic non-legume herbaceous plants in desert ecosystems, we focused on a typical legume shrub (Eremosparton songoricum) that grows in the Gurbantunggut Desert of northern China. Subsequently, we examined the biomass, ecological stoichiometry, and rhizosphere soil properties of two plant species (annual plant: Ceratocarpus arenarius; and ephemeral plant: Centaurea pulchella) growing across four horizontal distance ranges from E. songoricum. The results indicated that the closer a herbaceous plant was to the leguminous shrubs, the lower was its biomass and nutrient content. In contrast, herbaceous plants growing further away from the shrubs exhibited better growth conditions. The total biomass of Cer. arenarius and Cen. pulchella was greatest at a distance of D4 (90–100 cm), being 3.07, 2.15, and 1.23 times higher for Cer. arenarius and 2.05, 1.18, and 1.26 times higher for Cen. pulchella compared to distances of D1 (0–10 cm), D2 (30–40 cm), and D3 (60–70 cm), respectively. Meanwhile, the physicochemical properties of the rhizosphere root varied inversely with distance, with nutrient levels decreasing horizontally from D1 to D4 and vertically from 0–5 cm > 5–10 cm > 10–20 cm, showcasing a distinct ‘fertilizer island effect’. As the distance increased, the above-ground and below-ground parts of the symbiotic non-leguminous plants started to rely on different types of soil nutrients from different depths to maximize nutrient acquisition. According to the structural equation model, although soil fertility was higher closer to the central leguminous plants, the biomass of nearby herbaceous plants was lower. In summary, in desert ecosystems, the competitive dynamics exerted by leguminous shrubs significantly overshadowed the nutrient provisioning role of the ‘fertilizer island effect’. Furthermore, the utilization of nutrients by symbiotic non-leguminous plants did not exhibit species-specific patterns, and the dominant shrub continued to play a pivotal role. The evidence from this study promotes a deeper understanding of species coexistence mechanisms and ecological stability in desert environments.

Biosynthesis and metabolic engineering of isoflavonoids in model plants and crops: a review.

Isoflavonoids, the major secondary metabolites within the flavonoid biosynthetic pathway, play important roles in plant defense and exhibit free radical scavenging properties in mammals. Recent advancements in understanding the synthesis, transport, and regulation of isoflavonoids have identified their biosynthetic pathways as promising targets for metabolic engineering, offering potential benefits such as enhanced plant resistance, improved biomass, and restoration of soil fertility. This review provides an overview of recent breakthroughs in isoflavonoid biosynthesis, encompassing key enzymes in the biosynthetic pathway, transporters influencing their subcellular localization, molecular mechanisms regulating the metabolic pathway (including transcriptional and post-transcriptional regulation, as well as epigenetic modifications). Metabolic engineering strategies aimed at boosting isoflavonoid content in both leguminous and non-leguminous plants. Additionally, we discuss emerging technologies and resources for precise isoflavonoid regulation. This comprehensive review primarily focuses on model plants and crops, offering insights for more effective and sustainable metabolic engineering approaches to enhance nutritional quality and stress tolerance.

The rhizosphere of a drought-tolerant plant species in Morocco: A refuge of high microbial diversity with no taxon preference.

Arid and semi-arid areas are facing increasingly severe water deficits that are being intensified by global climate changes. Microbes associated with plants native to arid regions provide valuable benefits to plants, especially in water-stressed environments. In this study, we used 16S rDNA metabarcoding analysis to examine the bacterial communities in the bulk soil, rhizosphere and root endosphere of the plant Malva sylvestris L. in Morocco, along a gradient of precipitation. We found that the rhizosphere of M. sylvestris did not show significant differences in beta-diversity compared to bulk soil, although, it did display an increased degree of alpha-diversity. The endosphere was largely dominated by the genus Rhizobium and displayed remarkable variation between plants, which could not be attributed to any of the variables observed in this study. Overall, the effects of precipitation level were relatively weak, which may be related to the intense drought in Morocco at the time of sampling. The dominance of Rhizobium in a non-leguminous plant is particularly noteworthy and may permit the utilization of this bacterial taxon to augment drought tolerance; additionally, the absence of any notable selection of the rhizosphere of M. sylvestris suggests that it is not significatively affecting its soil environment.

Antimicrobial and Phytohormone production potential of Azotobacter chroococcum and its effect on the growth of non-leguminous plants

The overuse of chemical fertilizers in agriculture leads to a decrease in the fertility of soil and increases chemical pollution, which has adverse effects on living things. Biofertilizers have a solution towards chemical fertilizer to improve soil fertility and crop production. Therefore, the present study was undertaken to isolate different isolates of Azotobacter sp. to identify effective isolates for plant growth promoting activities and biological control. Six Azotobacter sp. were isolated and their plant growth promoting activities were checked. The isolate AC3 produced the highest amount (64 μg/ml) of IAA and produced HCN and 72 μg/ml of ammonia. The isolates AC1 and AC4 lacked the HCN production. Isolate AC3 showed a 26 mm zone of clearance on Pikovaskys agar, solublized the highest 71 μg/ml of inorganic phosphate and had the ability to produce siderophores. The isolate AC3 showed good antimicrobial potential against pathogens. Isolate AC3 was identified as Azotobacter chroococcum on the basis of morphological and biochemical characteristics. The bioactive compound was produced by using Azotobacter chroococcum and purified by column chromatography. Fraction 1 showed good antimicrobial activity against all the pathogens. The highest zone of inhibition was 15 mm against F. oxysporum. FT-IR analysis of fraction 1 revealed carboxylic acid, alkane and carbonyl functional groups. Azotobacter chroococcum had a greater effect on the growth of non-leguminous plants in the bacterially inoculated pot than in the control.

The Attributes of Biofertilizer as an Alternative to Chemical Fertilizer: A Mini Review

Traditional soil management relies heavily on inorganic fertilizers, raising environmental and health concerns. A fertile soil requires a precise ratio of inorganic and organic components, with topsoil crucial for plant growth. Essential plant elements include macronutrients (nitrogen, phosphorus, potassium) and micronutrients (zinc, iron). Soil composition must balance minerals, air, water, and living matter. Macronutrients (nitrogen, phosphorus, potassium) are pivotal in plant growth. Potassium influences water regulation, root development, and crop resilience. Phosphorus, crucial for seed development, is essential for legume development. Nitrogen from nitrates, ammonium, and urea is indispensable for protein synthesis and overall plant growth. Biofertilizers, containing active microorganisms, offer an alternative to inorganic fertilizers. They enhance soil fertility, water and nutrient uptake, and plant tolerance to environmental variables. Nitrogen-fixing bacteria, phosphate solubilizing microorganisms (PSM), silicate solubilizing bacteria (SSB), plant growth-promoting rhizobacteria (PGPR), and arbuscular mycorrhizal fungi (AM fungi) are common groups of bacteria that play different specific roles in defining biofertilizer. Bacterial genera such as Rhizobium (a symbiotic nitrogen fixer known for forming nodules on legumes), Azotobacter (a free-living nitrogen fixer known for enhancing sugar content in crops), Azospirillum (a bacterium known for enhancing nitrogen content in non-leguminous plants) and Anabaena-Azollae (a symbiotic relationship between a cyanobacterium and lower plants known in fixing nitrogen and promotes growth in various crops). As agriculture continues to evolve, embracing biofertilizers represents a promising step toward a more sustainable and resilient future.

Targeted knockout of early nodulin-like 3 (MusaENODL3) gene in banana reveals its function in resistance to Xanthomonas wilt disease.

Nodulins and nodulin-like proteins play an essential role in the symbiotic associations between legumes and Rhizobium bacteria. Their role extends beyond the leguminous species, as numerous nodulin-like proteins, including early nodulin-like proteins (ENODL), have been identified in various non-leguminous plants, implying their involvement in functions beyond nodulation, such as nutrient transport and growth modulation. Some ENODL proteins have been associated with plant defense against pathogens, as evident in banana infected with Xanthomonas campestris pv. musacearum (Xcm) causing banana Xanthomonas wilt (BXW) disease. Nonetheless, the specific role of ENODL in plant defense remains to be fully elucidated. The MusaENODL3 gene was found to be repressed in BXW-resistant banana progenitor 'Musa balbisiana' and 20-fold upregulated in BXW-susceptible cultivar 'Gonja Manjaya' upon early infection with Xcm. To further unravel the role of the ENODL gene in disease resistance, the CRISPR/Cas9 system was employed to disrupt the MusaENODL3 gene in 'Gonja Manjaya' precisely. Analysis of the enodl3 edited events confirmed the accurate manipulation of the MusaENODL3 gene. Disease resistance and gene expression analysis demonstrated that editing the MusaENODL3 gene resulted in resistance to BXW disease, with 50% of the edited plants remaining asymptomatic. The identification and manipulation of the MusaENODL3 gene highlight its potential as a critical player in plant-pathogen interactions, offering new opportunities for enhancing disease resistance in crops like banana, an important staple food crop and source of income for resource-poor farmers in the tropics. This study provides the first evidence of the direct role of the ENODL3 gene in developing disease-resistant plants.

Allantoin: A Potential Compound for the Mitigation of Adverse Effects of Abiotic Stresses in Plants.

Stress-induced alterations vary with the species of plants, the intensity and duration of the exposure, and stressors availability in nature or soil. Purine catabolism acts as an inherent defensive mechanism against various abiotic stresses and plays a pivotal role in the stress acclimatisation of plants. The intermediate metabolite of purine catabolism, allantoin, compensates for soil nitrogen deficiency due to the low carbon/nitrogen ratio, thereby maintaining nitrogen homeostasis and supporting plant growth and development. Allantoin accounts for 90% of the total nitrogenous compound in legumes, while it contributes only 15% in non-leguminous plants. Moreover, studies on a variety of plant species have reported the differential accumulation of allantoin in response to abiotic stresses, endowing allantoin as a stress modulator. Allantoin functions as signalling molecule to stimulate stress-responsive genes (P5CS; pyrroline-5-carboxylase synthase) and ROS (reactive oxygen species) scavenging enzymes (antioxidant). Moreover, it regulates cross-talk between the abscisic acid and jasmonic acid pathway, and maintains ion homeostasis by increasing the accumulation of putrescine and/or spermine, consequently enhancing the tolerance against stress conditions. Further, key enzymes of purine catabolism (xanthine dehydrogenase and allantoinase) have also been explored by constructing various knockdown/knockout mutant lines to decipher their impact on ROS-mediated oxidative injury in plants. Thus, it is established that allantoin serves as a regulatory signalling metabolite in stress protection, and therefore a lower accumulation of allantoin also reduces plant stress tolerance mechanisms. This review gives an account of metabolic regulation and the possible contribution of allantoin as a photo protectant, osmoprotectant, and nitrogen recycler to reduce abiotic-stress-induced impacts on plants.

Effect of varying concentrations of Tryptamine on the development of Zea Mays

Rhizobium is a widely acknowledged bacterium due to its symbiotic relationship, particularly with leguminous forages. It forms nodules, a specialized structure, in approximately 90% of the Fabaceae family and exhibits various methods to enhance soil fertility. Rhizobium can form a symbiotic relationship with non-leguminous plants due to its exceptional colonization abilities, which can contribute to enhanced crop growth. Physiological precursors are utilized in conjunction with rhizobium due to their superior water solubility, consistent hormone supply, and cost-effectiveness. The aim of this investigation was to assess the impact of precursor, both with and without Tryptamine, on the growth parameters of maize. A total of six treatments consisting of tryptamine dilutions were planned for the experiment. The findings indicate that Tryptamine @ 10-4 (T5) resulted in the greatest shoot length (43.6 cm), fresh weight (11.78 g) and dry weight (1.67 g), root length (36 cm), fresh weight (4.91 g) and dry weight (1.99 g), as well as chlorophyll (a) and (b) levels (1.05 and 0.77 mg g-1). The efficacy of precursor application has been determined and warrants further examination in diverse ecologies.

Riparian vegetation's effects on the evolution of an experimental meandering channel driven by an upper vortex flow

AbstractFew investigations of river evolution have incorporated the series of upper vortex flow disturbances induced by quasi‐knickpoints, and it is unclear whether the regulating ability of riparian vegetation in maintaining meandering channel patterns is valid. In this study, we therefore conducted meander evolution experiments to confirm the effects of vegetation species and vegetation strength on this complex system. Two nonleguminous plants with salinity and alkalinity resistance had non‐uniform degrees of normal seedling growth and different root network lengths. Our findings show that braided swales formed between the upstream developing zone of the vortex flow and the nearest bend and the riparian vegetation generally consolidated the single‐thread channel planform without branching outward under the conditions of flooding flow. Transverse point bars on inner banks were replaced by downstream scroll bars in the overall channel for long time, unless riparian vegetation and flood scour were coupled. Shallow‐rooted plants were inadequate to withstand the inner‐banks being cut by the upper vortex flow. Deep‐rooted plants can significantly stabilize bank lines and thalwegs but are vulnerable to locally low vegetation coverage. Using evolutionary spectral analysis based on thalwegs, we found that the streamwise high‐frequency distribution of bed topography was primarily concentrated downstream of the bifurcation interface when a flood was present in the unvegetated scenario, shrank to the isolated turning interface of the upper reach and the large‐scale spiral swale of the lower reach in the shallow‐rooted scenario and stood out along the area disturbed by bare roots in the deep‐rooted scenario. This experimental study broadens our understanding of vegetation effects in hydro‐bio‐geomorphological system engineering.

Denitrification process of Casuarina root nodule endophyte Frankia.

To examine the characteristic of denitrification in Frankia, a symbiotic nitrogen-fixing microbe associated with non-leguminous plants, and its role as a N2O source or sink, Casuarina root nodule endophyte Frankia was isolated using sectioning method, which was then purely cultured to investigate the denitrification process under NO3- addition. The results showed that after addition of NO3- to the medium under anaerobic condition, the concentration of NO3- decreased with time, while the concentrations of NO2- and N2O initially increased and then decreased over time. Key denitrification genes and nitrogenase gene were detected at 26 h, 54 h and 98 h during incubation. Abundances of these genes significantly differed among each other, and their dynamics were asynchronous. Redundancy analysis of the effect of NO3-, NO2-, N2O concentrations on abundances of denitrification genes and nitrogenase gene indicated that 81.9% of the total variation in gene abundances could be explained by the first two axes. Frankia had a denitrifying activity under anaerobic condition, with denitrification genes, including nitrous oxide reductase gene (nosZ), being identified. Our results suggested that Frankia possessed a complete denitrification pathway and the ability of N2O reduction under anaerobic condition.

OsSYMRK Plays an Essential Role in AM Symbiosis in Rice (Oryza sativa).

Arbuscular mycorrhizal (AM) fungi establish mutualistic symbiosis with a wide range of terrestrial plants, including rice. However, the mechanisms underlying the initiation of AM symbiosis are yet to be elucidated, particularly in nonleguminous plants. We previously demonstrated that chitin elicitor receptor kinase 1 (OsCERK1), a lysin motif receptor-like kinase essential for chitin-triggered immunity, also plays a key role in AM symbiosis in rice. However, the mechanisms underlying the regulation of switching between immunity and symbiosis by OsCERK1 are yet to be fully elucidated. SYMBIOSIS RECEPTOR-LIKE KINASE (SYMRK)/DOES NOT MAKE INFECTIONS 2 (DMI2) is a leucine-rich repeat receptor-like kinase associated with both root nodule symbiosis and AM symbiosis in legumes. The homolog of SYMRK in rice, OsSYMRK, has a shorter form than that in legumes because OsSYMRK lacks a malectin-like domain (MLD). The MLD reportedly contributes to symbiosis in Lotus japonicus; however, the contribution of OsSYMRK to AM symbiosis in rice remains unclear. Phylogenetic analyses indicated that the MLD of SYMRK/DMI2 is widely conserved even in mosses and ferns but absent in commelinids, including rice. To understand the function of OsSYMRK, we produced an Ossymrk knockout mutant using genome editing technology. AM colonization was mostly abolished in Ossymrk with a more severe phenotype than Oscerk1. Ca2+ spiking against chitin tetramer was also diminished in Ossymrk. In contrast, comparable defense responses against chitin heptamer to the wild type were observed in Ossymrk. Bimolecular fluorescence complementation studies demonstrating an interaction between OsSYMRK and OsCERK1 indicate that OsSYMRK may play an important role in switching from immunity to symbiosis through the interaction with OsCERK1 in rice.

Exploring a rhizobium to fix nitrogen in non-leguminous plants by using a tumor-formation root pathogen

Over 110 million tons of nitrogen fertilizer every year is used for crop production. Scientists have dreamed of enabling rhizobial nitrogen fixation in non-leguminous crops to mitigate the increasing demand for nitrogen fertilizer. However, despite decades of research, rhizobial nitrogen fixation in non-host plants has not been demonstrated. Here, we reported that an N-fixing rhizobium and a clubroot pathogen Plasmodiophora brassicae exhibited a synergistic effect on fixing nitrogen in cruciferous plants. Rhizobia were found to invade P. brassicae-infected rapeseed (Brassica napus) roots in the field. The colonization of rhizobium on rapeseed roots was confirmed by co-inoculating Mesorhizobium huakuii with P. brassicae under controlled laboratory conditions. M. huakuii infection could alleviate clubroot symptoms and promote the growth of diseased rapeseeds. M. huakuii could fix nitrogen in P. brassicae-infected plants based on the results of 15N isotope dilution tests. The expression of homologs of legume genes required for symbiosis and early-nodulin genes was significantly upregulated in Arabidopsis during early infection by P. brassicae. More importantly, M. huakuii could even fix nitrogen in P. brassicae-resistant rapeseed cultivar and promote plant growth when co-inoculated with P. brassicae. Our findings provide a new avenue to understand the interaction of rhizobia with non-host plants, stimulate the exploration of fixing nitrogen in non-leguminous plants by nitrogen-fixing rhizobia, and develop a strategy for both disease control and nitrogen fixation on non-host crops.

Microscopic and ultramicroscopic anatomical characteristics of root nodules in Podocarpus macrophyllus during development

To understand the morphological and structural characteristics of root nodules in Podocarpus macrophyllus and their development, this study prepared P. macrophyllus root nodule samples at the young, mature and senescent stages. Optical microscopy and transmission electron microscopy (TEM) revealed that new nodules can be formed on roots and senescent nodules; new nodules formed on the roots are nearly spherical and have an internal structure similar to finite nodules; new nodules on senescent nodules are formed by extension and differentiation of the vascular cylinder of the original nodules; and these new nodules are nested at the base of the original nodules, which create growth space for new nodules by dissociating the cortical tissue; clusters of nodules are formed after extensive accumulation, and the growth pattern is similar to that of infinite nodules; the symbiotic bacteria of P. macrophyllus root nodules mainly invade from the epidermal intercellular space of the roots and migrate along the intercellular space of the nodule cortex; infected nodule cortex cells have a well‐developed inner membrane system and enlarged and loose nuclei; and unique Frankia vesicles, and rhizobia cysts, and bacteriophages can all develop. Compared with common leguminous and nonleguminous plant nodules, P. macrophyllus root nodules are more complex in morphology, structure and composition. From the perspective of plant system evolution, the nodules in P. macrophyllus most likely represent two evolutionary patterns inlcuding the Rhizobium nodules in leguminous angiosperms and Frankia nodules in nonleguminous angiosperms. The conclusion of this study provides a theoretical basis for the developmental biology of P. macrophyllus root nodules and the evolutionary pattern of plant symbionts.

Interannual variations in natural abundance of nitrogen stable isotopes in soil and plant and their implications in a meadow steppe

Nitrogen is the most limiting nutrient for ecosystems. The natural abundance of δ15N (15N/14N) can efficiently indicate ecosystem nitrogen cycling processes. We investigated the interannual variations in natural abundance of δ15N in soil-plant system and soil net nitrogen mineralization in a meadow steppe of Inner Mongolia. Results across the four sampling years (2017-2020) showed that the content of soil NO3--N (9.83-14.79 mg·kg-1) was significantly higher than that of NH4+-N (3.92-5.00 mg·kg-1) and that δ15N value of soil NH4+ (13.3‰-18.3‰) was significantly higher than that of NO3-(3.76‰-6.14‰). The δ15N value of soil NO3- was negatively correlated with soil NO3- content. The δ15N value of soil NH4+ was relatively higher in the dry years, while the δ15N value of soil NO3- significantly decreased in the wetter and drier years. Soil net mineralization and ammonification rates were significantly higher in the dry years than that of the wet years, while soil nitrification rates showed no correlation with annual precipitation. The δ15N values of plants were not related to that of soils, but nega-tively correlated with plant nitrogen content. Both δ15N values and nitrogen contents were significantly and positively correlated between the leguminous and non-leguminous plants, suggesting that legume could facilitate nitrogen uptake of non-leguminous plants. These results could provide supporting data for nitrogen cycling and their responses to changes in precipitation in grassland soil-plant systems.

Effects of mineral levels and leaf extracts of some plants on soil pH and growth rate of selected non-leguminous plants

Abstract. Njogu MJ, Murungi JI, Wanjau RN. 2021. Effects of mineral levels and leaf extracts of some plants on soil pH and growth rate of selected non-leguminous plants. Cell Biol Dev 5: 76-89. The purpose of this study was to determine the effect of growth rate on non-leguminous plants such as wheat (Triticum aestivum L.), kale (Brassica oleracea var acephala), and coriander (Coriandrum sativum L.) grown on acidic soils treated with leaves and leaf extracts of plants known to have a high buffering capacity and mineralization capacity, i.e., Jacaranda mimosifolia D. Don, Cordia africana Lam, Croton macrostachyus Hochst. ex Delile, Vitex keniensis Turril, Tithonia diversifolia (Hemsl.) A.Gray, Manihot esculenta Crantz, Carica papaya L., and Helianthus annuus L. For this investigation, the leaves and leaf extracts were applied to the soil with a pH of 4.75. Leaf extracts and leaves of eight species were combined according to the macronutrient content and mineralization of chosen plants discovered in Nyandarua County, Kenya. Wheat, kale, and coriander growth rates were determined by comparing the dry mass of uprooted seedlings from the trial and control studies every fourteen days for 60 days. Flame photometry, atomic absorption spectrometry (AAS), UV/visible spectroscopy, and turbidimetry were used to determine macronutrients in leaf extracts. The analysis of variance (ANOVA) and Student-Newman-Keuls (SNK) tests were used to analyze the data. For 60 days, the mean pH value of leaf extracts ranged from 4.580.27a to 7.440.04d. K+; 189.95±0.17c, Ca2+; 367.33±0.67e, Mg2+; 114.33e±0.33, PO43-; 55.38±0.23f, NO3-; 322.25±0.40f, and SO42-; 56.48±0.23e had the greatest mean levels in leaves (?g/g). Macronutrient levels were significantly different in soil treated with leaves and leaf extract (Le), commercial NPK fertilizers (Cf), and untreated soil (Us). Wheat (dry mass) grew at a mean rate of 1.27±0.13b g/wk (Le), 1.26±0.12b g/wk (Cf) and 0.32±0.02a g/wk (Us), while in (height) was 7.29±1.43b cm/wk (Le), 6.20±1.95b cm/wk (Cf), 3.98±0.97a cm/wk (Us). For kales 0.20±0.01a g/wk (Le), 0.30±0.02a g/wk (Cf), and 0.03±0.01b g/k (Us), while in (height) 2.15±0.85c cm/wk (Le), 2.57±0.88b cm/wk (Cf), and 1.04±0.02a cm/wk (Us). The mean growth rate for corianders was 0.16±0.01a g/wk (Le), 0.17±0.02a g/wk (Cf), and 0.10±0.01a g/k (Us), while in (height) 1.85±0.56b cm/wk (Le), 1.86±0.58b cm/wk (Cf) and 0.79±0.18a cm/wk (Us). This study's findings show that the plant's leaves and leaf extracts can be used in place of inorganic fertilizers and should be recommended for agroforestry in low-pH environments.

Convergent Variation in the Leaf Traits of Desert Plants in the Ebinur Lake Basin

Elucidating the relationship between the variation of plant leaf functional traits and the environment is necessary for understanding the adaptation mechanism of plants and predicting changes in ecosystem structure. In this study, the leaf traits of desert plants in Ebinur Lake National Wetland Nature Reserve in Xinjiang, China were studied from the aspects of plant life forms (annuals, perennials and shrubs), phylogenetic signals, and relation to soil properties, using the principal component analysis, variance decomposition, and one-way analysis of variance. The results showed that: (1) There were significant differences in leaf carbon concentration (annuals>shrubs>perennials), leaf nitrogen concentration (shrubs ≥ perennials ≥ annuals), and leaf moisture content (perennials ≥ annuals ≥ shrubs) among the life forms, but there was no significant difference in leaf phosphorus concentration. Besides, soil nitrogen and phosphorus were significantly positively correlated with leaf carbon concentration and leaf nitrogen concentration. (2) There were significant differences in leaf carbon concentration, leaf nitrogen concentration, specific leaf area, and leaf moisture content between C3 and C4 plants, while the differences in P and leaf dry matter content were not significant. Besides, there were significant differences in leaf carbon concentration, leaf nitrogen concentration, specific leaf area, and leaf moisture content between leguminous and non-leguminous plants. Leguminous plants had higher leaf carbon concentration, leaf nitrogen concentration, and specific leaf area than non-leguminous plants, while non-leguminous plants had higher leaf moisture content than leguminous plants. (3) One way ANOVA analysis showed that taxonomy had a more significant effects on leaf carbon concentration, leaf nitrogen concentration, specific leaf area, and leaf moisture content than soil properties, and the coefficient of variation of leaf carbon concentration was greater than 50%. The phylogenetically independent contrasts analysis showed that the phylogenetic signal of all leaf traits was detected in all species and low (K value < 1, p > 0.05), indicating that the functional traits were weakly affected by phylogenetics. Therefore, desert plants in the Ebinur Lake Basin evolved to adapt to arid environments, and leaf traits showed convergent variation.

Differences in ionomic responses to nutrient deficiencies among plant species under field conditions

The ionome is defined as the mineral element composition of an organism or tissue and is genetically and environmentally influenced. Although nutrient deficiency changes the plant ionome, the differences among different species have not been elucidated fully. In the present study, we examined the ionomic responses to nutrient deficiency in wheat (Triticum aestivum L.), maize (Zea mays L.), sunflower (Helianthus annuus L.), and soybean (Glycine max (L.) Merr.) to understand the differences in response to nutrient deficiency among different plant species. The plants were cultivated in fields with four fertilizer treatments: complete fertilization, without nitrogen, without phosphorus, and without potassium. Each plant species was sampled just before the flowering stage, and mineral concentrations of each organ were analyzed. The species-specific and nonspecific changes in accumulation by the treatment were observed in different elements. Under phosphorus deficiency, sunflower showed a different variation in the ionome profile than the other species, particularly in the increased accumulation of many metal elements. Increased accumulation of many elements was observed in all plant species under potassium deficiency. Under nitrogen deficiency, leaf molybdenum accumulation was increased in non-leguminous plants. An unknown role of molybdenum in the metabolic responses to the nitrogen deficiency was predicted. To carry out further research based on the results of such ionomics studies may reveal the unknown function of essential elements in metabolic responses in plants.

Green manure incorporation accelerates enzyme activity, plant growth, and changes in the fungal community of soil.

Green manure can sustain agricultural production, preserve biodiversity, and mitigate soil degradation caused by long-term application of chemical fertilizers. Moreover, the application of green manure can improve soil health through increased soil biological activities. Nevertheless, little attention has been paid to the effects of leguminous and non-leguminous plants on phosphorus- and carbon-related enzyme activities and fungal community composition in soil. In this study, a pot experiment was carried out to elucidate the effects of two green manures on plant growth promoting potential, phosphorus- and carbon-related enzyme activities, and soil fungal community composition. Two green manure treatments (Brassica juncea and hairy vetch), poultry compost and control (no amendment) were applied and soil samples were collected after incorporation of green manure and after plant harvest. The results revealed that plant growth with hairy vetch was significantly higher than that with B. juncea and poultry compost, and soil enzyme activities were markedly higher with hairy vetch than with B. juncea. Both green manure amendments altered the soil fungal community composition. It is possible that the incorporation of green manure into soil and their mineralization and decomposition were controlled by the carbon: nitrogen ratio of the manures and that these manures were easily degradable by soil fungi. In particular, the incorporation of leguminous (hairy vetch) green manure with a low carbon: nitrogen ratio resulted in better plant growth through fast mineralization. Our findings suggest that green manure incorporation is an effective practice and provides substantial benefits to the soil-plant system.

Humic Substances in Combination With Plant Growth-Promoting Bacteria as an Alternative for Sustainable Agriculture.

Plant growth-promoting bacteria (PGPB) and humic substances (HSs) are promising options for reducing the use of pesticides and mineral fertilizers. Although many studies have shown the effects of PGPB and HSs separately, little information is available on plant responses to the combined application of these biostimulants despite the great potential for the simultaneous action of these biological inputs. Thus, the objective of this review is to present an overview of scientific studies that addressed the application of PGPB and HSs to different crops. First, we discuss the effect of these biostimulants on biological nitrogen fixation, the various effects of the inoculation of beneficial bacteria combined with the application of HSs on promoting the growth of nonleguminous plants and how this combination can increase bacterial colonization of plant hosts. We also address the effect of PGPB and HSs on plant responses to abiotic stresses, in addition to discussing the role of HSs in protecting plants against pathogens. There is a lack of studies that address the role of PGPB + HSs in biocontrol. Understanding the factors involved in the promotion of plant growth through the application of PGPB and HSs can assist in the development of efficient biostimulants for agricultural management. This approach has the potential to accelerate the transition from conventional cultivation to sustainable agrosystems.