Nutrient deficiency effects on root architecture and root-to-shoot ratio in arable crops

Sulfur deficiency affects the accumulation and the allocation to shoots of cadmium and of some macro- (P, K, Ca, Mg) and micro-nutrients (Cu, Mn, Mo, Zn) in durum wheat at heading

Cadmium (Cd), which is naturally present in soils, is transferred to durum wheat grains at levels that have worrying consequences for food safety. There have been some reports that adding sulfur (S) to plants reduces Cd accumulation in shoots by increasing its retention in roots due to complexation of Cd by S-containing ligands. Consequently, low S availability in some agricultural soils could favor Cd contamination of durum wheat grains. We conducted a greenhouse experiment to test whether S deficiency would reduce Cd retention in roots, thus favoring its allocation to shoots. Durum wheat was grown in a nutrient solution containing a low level of Cd (100 nM) with sufficient (+ S) or deficient (-S) sulfate levels and harvested at heading. Surprisingly, in the -S treatment, more Cd was retained in roots and less allocated to shoots than in the + S treatment, and the same applied to P, K, Ca, Mg, Cu, Mn, Mo, and Zn. The reduced aboveground biomass resulting from S deficiency explained both the reduced net uptake (i.e., the total quantities of elements in the plant) and the reduced allocation of elements to shoots. Depending on the relative effects of S deficiency on shoot biomass compared to the effects of a reduction in S uptake and allocation to shoots, the reduced supply of S increased the concentrations of Cd and of P, K, Mn, Mo, and Zn in the shoot, whereas the concentration of Cu decreased, and that of Ca and Mg remained unchanged. The higher concentration of Cd in the shoots of S-deficient plants suggests that attention should be paid to the consequences of insufficient S for Cd contamination of durum wheat.

Livestock-Crop-Mushroom (LCM) Circular System: An Eco-Friendly Approach for Enhancing Plant Performance and Mitigating Microbiological Risks

Mushroom production using agroforestry biowaste is a great green cycling agriculture alternative. Therefore, the current study explored the Livestock-Crop-Mushroom (LCM) circular production model, starting with co-composting of straw and cow manure as a'St' biofertilizer further used for mushroom cultivation that ultimately produced a'StM' biofertilizer. The two biofertilizers were tested for their impacts on plant growth and potential microbial risks. The results show significant growth of oats stimulated by biofertiliser use. Both'St' and'StM' increased plant biomass, while with the latter, the crude protein content (+5.1%) and root biomass were also higher. Reduced abundances of resistome genes (30%) and pathogens (25%) were observed during the oat growth. Further, metagenomics analysis also indicated a reduction in antibiotic-resistance genes by -20% in soils with oats treated by'St' and -46% in'StM' biofertilizer treatment. The'StM' had a three-fold stronger inhibitory effect on oat rhizosphere soil pathogens than'St'. Moreover, compared to'St','StM' suppressed pathogens in seeds and stems, with specific beneficial biomarker microbes in different plant parts. Overall, the antibiotic resistance gene related to oxytetracycline decreased more than three-fold in the LCM system. This study demonstrates the substantial potential and scalability of the LCM circular system within the agricultural domain.

Cellulose-based biodegradable superabsorbent hydrogel: A sustainable approach for water conservation and plant growth in agriculture

Innovative deficit irrigation technologies are imperative to overcome challenges posed to crop growth/yield and agriculture sustainability due to water scarcity in arid and semiarid regions. In the current study, superabsorbent biodegradable hydrogel based on carboxymethylcellulose sodium salt (NaCMC) and hydroxy ethyl cellulose (HEC) has been developed using citric acid (CA) as a crosslinker. The hydrogel has demonstrated excellent water absorption, retention, and release properties. Moreover, hydrogel (2 %) modified soil (HMS) has depicted increased porosity (57 %) and reduced soil density (1.06 g/cm3), compared to unmodified soil (UMS) with porosity of 53 % and density of 1.16 g/cm3, as well as, the water use efficiency of the plants (25.25 %-45.52 % over UMS) grown in HMS, which is vital for comprehending soil properties and their impact on water retention and aeration. The plant growth study in HMS concerning critical growth parameters such as germination rate, Seedling Vigour Index (SVI), Root Shoot Ratio (RSR), crop growth ratio (CGR), and chlorophyll content of three plants, i.e., one summer-grown plant-cucumber and two winter-grown plants- tomato and mung bean, has manifested promising results. Decisive parameters such as seedling viability (4.51 %), plant growth rate (3.77 %), and photosynthetic ability (16.74 %) were increased for chosen plants grown in HMS as compared to UMS. Improved growth parameters and photosynthetic ability of plants in HMS have suggested ameliorated nutrient and water absorption rates, increased resource utilization, and improved response to extrinsic resource allotment caused by hydrogel modification. Statistical analyses supported the trends in plant growth. Thus, hydrogel modification of the soil can effectively mitigate water use by retaining moisture efficiently and positively facilitating growth.

Nutrient and Water Availability Influence Rice Physiology, Root Architecture and Ionomic Balance via Auxin Signalling

Water and soil nutrients are the vital ingredients of crop production, and their efficient uptake is essentially dependent on root development, majorly regulated by auxin. For a water-loving crop like rice, how water availability regulates nutrient acquisition, additionally, how ambient nutrient level modulates water uptake, and the role of auxin therein is not well studied. While investigating the cross-talks among these components, we found water to be essential for auxin re-distribution in roots and shaping the root architecture. We also found that supplementing rice seedlings with moderate concentrations of mineral nutrients facilitated faster water uptake and greater nutrient enrichment in leaves compared to adequate nutrient supplementation. Additionally, moderate nutrient availability favoured greater stomatal density, stomatal conductance, photosynthesis, transpiration rate and water use efficiency when water was not limiting. Further, auxin supplementation enhanced root formation in rice, while affecting their water uptake ability, photosynthesis and transpiration causing differential mineral-specific uptake trends. The present study uncovers the existence of an intricate crosstalk among water, nutrients and auxin signalling the knowledge of which will enable optimizing the growth conditions for speed breeding of rice and harnessing the components of auxin signalling to improve water and nutrient use efficiency of rice.

Soil pH and Rice Chlorophyll Content as Indicators of Grain Productivity and Microbial Community in Acid-Exposed Paddy Mesocosms

The objective of this study was to evaluate the applicability of soil pH and chlorophyll content as predictive indicators of damage in paddy fields affected by HCl spills, based on causal relationships. Five doses of HCl (e.g., 1, 50, 100, 200, and 500-fold of PNEC) were added to the paddy mesocosm during the rice heading stage. In the 7th week after the acid addition, rice grain quality (e.g., 1000-grain weight and filled grain ratio), soil microbial diversity (e.g., Operational Taxonomic Units (OTUs) and Shannon index), and soluble nutrients (e.g., NH4+, NO3-, SiO2, P2O5, and basic cations) were measured. Causal relationships among variables were analyzed using the Partial Least Square Path Model (PLS-PM). At the dose of 500×PNEC, all rice plants lodged when pH < 4. At 100×PNEC and 200×PNEC, the number of immature grains increased, resulting in a reduction in grain quality of over 18%. At 200×PNEC, the microbial OTUs and the Shannon index decreased by 30%. Notably, the proportion of Planctomycetes, the dominant phylum in the control soil, decreased. The reduction of Planctomycetes led to excessive NH4+ accumulation in the soil, which leads to an undesirable increase of chlorophyll content thereby deteriorating grain quality. The causal relationship suggests that information of soil pH and leaf chlorophyll can aid us in predicting damage for grain quality and microbial diversity.

Genome-wide association studies and transcriptomics reveal mechanisms explaining the diversity of wheat root responses to nutrient availability

Nutrient availability profoundly influences plant root system architecture, which critically determines crop productivity. While Arabidopsis has provided important insights into the genetic responses to nutrient deficiency, translating this knowledge to crops, particularly wheat, remains a subject of inquiry. Here, examining a diverse wheat population under varying nitrogen (N), phosphorus (P), potassium (K), and iron (Fe) levels, we uncover a spectrum of root responses, spanning from growth inhibition to stimulation, highlighting genotype-specific strategies. Furthermore, we reveal a nuanced interplay between macronutrient deficiency (N, P, and K) and Fe availability, emphasizing the central role of Fe in modulating root architecture. Through genome-wide association mapping, we identify 11 quantitative trait loci underlying root traits under varying nutrient availabilities, including homologous genes previously validated in Arabidopsis, supporting our findings. In addition, utilizing transcriptomics, reactive oxygen species (ROS) imaging, and antioxidant treatment, we uncover that wheat root growth inhibition by nutrient deficiency is attributed to ROS accumulation, akin to the role of ROS in governing Arabidopsis root responses to nutrient deficiency. Therefore, our study reveals the conservation of molecular and physiological mechanisms between Arabidopsis and wheat to adjust root growth to nutrient availability, paving the way for targeted crop improvement strategies aimed at increasing nutrient use efficiency.

Effects of polyculture on nutrient removal from residential raw sewage using field-scale artificial floating islands

Nutrient pollution poses a significant challenge to global water bodies, particularly from non-point sources due to their diffuse nature. This study investigated the effectiveness of Artificial Floating Islands (AFIs) as a phytoremediation technology to address this issue. We constructed and monitored a field-scale AFI system in the equalization basin of a wastewater treatment plant for preliminary treatment of residential raw sewage. Focusing on a polyculture of two native aquatic plants - Carex comosa (bristly sedge) and Eleocharis obtusa (blunt spike-rush) - we assessed how polyculture influenced nutrient assimilation and evaluated the overall performance of polyculture AFI systems under natural conditions. Our results showed that polyculture simultaneously affected plants' capacity of nutrient assimilation and biomass production. The potential competition within the polyculture systems promoted the growth of C. comosa while suppressing E. obtusa. The enhanced nutrient assimilation in C. comosa plant tissues was mainly attributed to its increased biomass production. Additionally, we observed a negative correlation between pH and the storage of total oxidized nitrogen (NO2- + NO3-), ammonium (NH4+), and orthophosphate (PO43-), with the highest nutrient storage occurring at a near-neutral pH of 7.5. Environmental factors such as pH and water temperature interacted with the effects of polyculture on nutrient assimilation, with C. comosa in polyculture systems showing the highest sensitivity to these factors. Throughout the study, polyculture AFIs exhibited the highest nutrient assimilation, with peak values of 2968 mg/m2 for NH4+, 1767 mg/m2 for PO43-, and 12 mg/m2 for NO2- + NO3-, outperforming the two monoculture AFIs. Notably, nutrient assimilation in polyculture AFI systems did not average the performance of monoculture systems but demonstrated higher values and greater robustness under varying environmental conditions. These findings highlight the potential of using polyculture to extend the operational lifespan, enhance performance, and reduce the constructional costs of field-scale AFI systems for managing nutrient pollution.

Trends of Soil and Solution Nutrient Sensing for Open Field and Hydroponic Cultivation in Facilitated Smart Agriculture

Efficient management of soil nutrients is essential for optimizing crop production, ensuring sustainable agricultural practices, and addressing the challenges posed by population growth and environmental degradation. Smart agriculture, using advanced technologies, plays an important role in achieving these goals by enabling real-time monitoring and precision management of nutrients. In open-field soil cultivation, spatial variability in soil properties demands site-specific nutrient management and integration with variable-rate technology (VRT) to optimize fertilizer application, reduce nutrient losses, and enhance crop yields. Hydroponic solution cultivation, on the other hand, requires precise monitoring and control of nutrient solutions to maintain optimal conditions for plant growth, ensuring efficient use of water and fertilizers. This review aims to explore recent trends in soil and solution nutrient sensing technologies for open-field soil and facilitated hydroponic cultivation, highlighting advancements that promote efficiency and sustainability. Key technologies include electrochemical and optical sensors, Internet of Things (IoT)-enabled monitoring, and the integration of machine learning (ML) and artificial intelligence (AI) for predictive modeling. Blockchain technology is also emerging as a tool to enhance transparency and traceability in nutrient management, promoting compliance with environmental standards and sustainable practices. In open-field soil cultivation, real-time sensing technologies support targeted nutrient application by accounting for spatial variability, minimizing environmental risks such as runoff and eutrophication. In hydroponic solution cultivation, precise solution sensing ensures nutrient balance, optimizing plant health and productivity. By advancing these technologies, smart agriculture can achieve sustainable crop production, improved resource efficiency, and environmental protection, fostering a resilient food system.

Preliminary study on unlocking growth and yield potential of USDA foxtail millet (Setaria italica L.) lines with NPK fertilization

Foxtail millet (Setaria italica L.) is nutritionally superior to other cereals of the family Poaceae, with the potential to perform better in marginal environments. In the present context of climate change, ecologically sound and low-input foxtail millet varieties can be chosen for agricultural sustainability. The planned research was carried out at the green house of the Department of Agronomy, University of Agriculture, Faisalabad, Pakistan, to investigate the impact of various levels of NPK fertilizer on the growth, development, and yield of foxtail millet lines from USDA germplasm. Eight lines of foxtail millet; U2, V19, V73, V93, V101, V106, V107, and V111, were under study along with NPK fertilizers' treatments; T1 = 000 NPK as a control, T2 = 20:15:15 NPK, T3 = 30:20:20 NPK, T4 = 40:25:25 NPK, and T5 = 50:30:30 NPK (kg ha- 1). NPK treatments were applied twice during the study periods: first dose was applied after one week of the emergence of seedlings and the second dose was applied at the age of four weeks of seedlings. The time to 50% emergence ranged from 4.33 (V111) to 5.92 (U2) days, and the emergence was highest in V111 (10.02), and V19 had the lowest emergence index of 4.95. Furthermore, all genotypes achieved a complete final emergence percentage of 100, except U2 (92.89%) and V19 (89.33%). The highest growth rate and assimilation rate were observed in V111 and V107 under the impact of treatment 5. Among the different treatments, T3 resulted in the maximum plant height, panicle length, and grain yield per panicle. The highest panicle weight and grain yield per panicle were observed in line V106. Line V107 synthesized the highest chlorophyll a while V93 produced highest chlorophyll b contents which is statistically similar toV19. Line V19 had the highest total chlorophyll and V93 produced the highest carotenoid contents. Application of NPK at the rate of 50:30:30 kg ha- 1 produced maximum chlorophyll a (23%), b (15.8%), total chlorophyll contents (14.2%), plant fresh biomass (2.06%), and grain yield (23.6%) as compared to control treatment. Overall, T3 (30:20:20) and T5 (50:30:30) were observed to be better as compared to other treatments. With respect to growth, yield, and chlorophyll contents, lines U2, V19, V93, V106, V107, and V111 were observed to be potentially superior.

Unveiling the molecular symphony: MicroRNA160a-Auxin Response Factor 18 module orchestrates low potassium tolerance in banana (Musa acuminata L.)

Potassium (K) is an essential nutrient for the growth and development of most plants. In banana (Musa acuminata L.), microRNA160a (miR160a) is suggested to potentially contribute to the response to low K+ stress by modulating the auxin signaling pathway. However, further investigation is required to elucidate its specific regulatory mechanism. This study presents evidence highlighting the critical role of the miR160a-Auxin Response Factor 18 (ARF18) module in conferring low K+ tolerance in banana. Both miR160a and its predicted target gene ARF18 displayed elevated expression levels in banana roots, with their expression profiles significantly altered under low K+ stress. The inhibitory effect of mac-miR160a on the expression of MaARF18-like-2 was confirmed through tobacco transient transformation and dual-Luciferase reporter assay. Surprisingly, Arabidopsis lines overexpressing mac-miR160a (mac-miR160a OE) exhibited enhanced tolerance to low K+ stress. Conversely, Arabidopsis lines overexpressing MaARF18-like-2 (MaARF18-like-2 OE) displayed increased sensitivity to K+ deficiency. Additionally, RNA sequencing (RNA-seq) analysis revealed that MaARF18-like-2 mediates the response of Arabidopsis to low K+ stress by influencing the expression of genes associated with Ca2+, ion transport, and reactive oxygen species (ROS) signaling. In conclusion, our study provides novel insights into the molecular mechanism of the miR160a-ARF18-like-2 module in the plant response to low K+ stress.

Adaptation of potato cultivars to phosphorus variability and enhancement of phosphorus efficiency by Bacillus subtilis

BACKGROUND

Plants utilize a variety of mechanisms to adapt to fluctuations in phosphorus (P) availability. Potatoes, in comparison to other crops, often display reduced phosphorus use efficiency (PUE) due to their underdeveloped root systems; therefore, understanding the mechanisms underlying PUE is critical for improving it. This study aimed to evaluate the morphological and physiological responses of potatoes to different P levels, with a focus on root system alterations and PUE. Two potato cultivars, a table potato (cv. Milva) and a starch potato (cv. Lady Claire), were subjected to varying P levels (0.5, 2, 5, and 30 mg P L-1 supplied as KH2PO4) in a hydroponic system. Additionally, the plants grown under 0.5 and 2 mg P L-1 were treated with plant growth-promoting Bacillus subtilis (B. subtilis), compared to untreated controls, to investigate the effectiveness of B. subtilis in addressing P deficiency. B. subtilis inoculation was performed by adding a bacterial suspension weekly to the hydroponic nutrient solution.

RESULTS

The findings illustrated Milva's ability to efficiently allocate P and sugars to its roots under low P levels, thereby enhancing biomass and facilitating increased P uptake and PUE. Conversely, Lady Claire exhibited lower P assimilation efficiency under low P levels but demonstrated improved efficiency under high P availability. The concentration of P in the nutrient solution affected P uptake and several factors believed to be involved in P utilization, such as root morphology, sugar and indole-3-acetic acid concentration in the roots, and acid phosphatase activity. Gene expression analyses underscored the pivotal roles of StPHT1;1 and StPHT2;1 in P translocation to shoots, particularly in Lady Claire. Inoculation with B. subtilis improved P acquisition efficiency by 10% under low phosphorus levels (P0.5 and P2), particularly in Lady Claire, where shoot and root phosphorus contents increased by 13-25% and 4-13%, respectively. Additionally, B. subtilis displayed higher efficacy in mitigating P deficiency in Lady Claire compared to Milva, particularly under low P levels (P0.5 and P2).

CONCLUSION

Milva showed greater phosphorus efficiency than Lady Claire under low P conditions, attributed to higher P and sugar levels in roots, enhancing root growth, P uptake, and translocation to shoots, particularly to young leaves. However, Lady Claire demonstrated a notable increase in P uptake and enhanced responsiveness to B. subtilis inoculation, particularly under low P levels (P0.5 and P2). These findings provide valuable insights for optimizing P management strategies to improve PUE in potatoes, especially under low P levels.

The overlooked effects of environmental impacts on root:shoot ratio in experiments and soil-crop models

Process-based soil-crop models are becoming increasingly important to estimate the effects of agricultural management practices and climate change impacts on soil organic carbon (C). Although work has been done on the effects of crop type and climate on the root:shoot (biomass) ratio, there is a gap in research on the effects of specific environmental or management conditions such as drought, temperature, nutrient limitation, elevated CO2 or tillage on the root:shoot ratio and thus, atmospheric C sequestration. In this study, we quantified the effects of these factors on the root:shoot biomass ratio by reviewing the current literature, presented common simulation approaches and performed model simulations using different examples. Finally, we identified different research gaps with respect to the root:shoot ratio with the aim of better estimating and predicting atmospheric C sequestration. A predominantly positive response of the root:shoot ratio was observed in case of elevated CO2 (~12 %), low soil N levels (~44 %), and drought (~14 %). Soil tillage did not affect root:shoot ratio of the major field crops but increased it by ~15 % in case of wheat. There are only few field studies on air temperature increase and the results vary widely (mean - 48 %). The responses of tested models to the mentioned effects root:shoot ratio were slightly positive in case of CO2 elevation (0 to 2 %) and tillage (0 to 8 %), slightly to clearly positive in the case of drought and N limitation depending on the model (1 to 40 %), and very variable in case of the air temperature scenarios. Our study reveals large model uncertainty (especially on temperature effects), particularly for below ground processes that highlight knowledge gaps in simulating root:shoot ratio. We advocate for the need of more model-oriented specific experiments under abiotic stresses to help model improvement. Such research effort would enable more robust and reliable root:shoot ratio simulations.

Beneficial or detrimental? How nickel application alters the ionome of soybean plants

The use of nickel (Ni) in agriculture may represent one of the most significant cases of plant hormesis ever reported, as plants exhibit both positive and negative responses depending on the level of exposure to this element. For a more comprehensive understanding of this effect, the next step is to conduct studies on the dynamics of pre-existing chemical elements in the system (ionomic profile), especially when introducing Ni as a novel nutrient for the plants. This micronutrient is of particular interest to the fertilization of leguminous plants, such as the soybean, due to its additional effects on the biological nitrogen fixation process. This study thus evaluated the influence of five doses of Ni (0.0, 0.5, 1.0, 3.0, and 9.0 mg of Ni kg-1) on the ionomic profile of soybean genotypes using modern quantification techniques. The results revealed that the addition of Ni reduced the concentration of cationic micronutrients manganese (Mn), iron (Fe), zinc (Zn), and copper (Cu), while it increased the concentration of macronutrients nitrogen (N) and magnesium (Mg). The application of Ni also resulted in a reduction of the potentially toxic element aluminum (Al). Correlations were also observed for these elements, indicating that Ni could be a controlling agent in elemental absorption and translocation. The ionome of the leaf tissues exhibited the most significant alterations, followed by the grains, nodules, and roots. Exogenous agronomic doses of Ni proved beneficial for the growth and production of soybean plants, although a genotypic effect was observed. The treatment with 9.0 mg of Ni kg-1, resulted in a new ionomic profile related to toxicity, demonstrating suboptimal plant development. Thus, the application of Ni in appropriate doses had a significant impact on the ionomic profile of soybeans, improving plant development and implying resistance to potentially toxic elements such as Al.

Phosphorus pool distributions and adsorption-desorption characteristics of soil aggregates in cut slopes of a permafrost zone in the Qinghai-Tibetan Plateau

Soil phosphorus (P) has attracted considerable attention from researchers because of its role in the restoration and stabilization processes of cut slopes in permafrost regions. However, the soil P pool distributions and adsorption-desorption characteristics in alpine cut slopes remain unclear. In this context, we examined in this study the P pools in the aggregates of surface cut soil slopes (0-10 cm) in areas with three permafrost types, including perennially frozen soil (PF), seasonally frozen ground (SFG), and non-frozen soil (NFS) in the Qinghai-Tibet Plateau, China. In addition, we assessed the P adsorption-desorption characteristics and their correlations with the P pools. The results showed the significant effects of the permafrost types on the contents of total P (TP), available P (AP), labile P (LP), moderately labile P (MLP) and stable P (SP). The inorganic P (IP) contents were higher than those of organic P (OP) in the cut soil slopes of the three permafrost types. In addition, H2O-Pi and NaHCO3-Pi accounted for small proportions of IP, while NaHCO3-Po accounted for the smallest proportion of OP. On the other hand, the SP contents in the soil aggregates were generally higher than those of MLP and LP. In fact, the LP contents in the PF, SFG, and NFS were 72.55, 44.68, and 49.42 mg/kg, respectively. The AP contents in the cut soil slopes of the three permafrost types were significantly correlated with the MLP and LP contents. Moreover, the P adsorption-desorption characteristics of the SFG and NFS were closely related to AP and MLP. Compared with the PF and NFS, the SFG exhibited low and high P adsorption and desorption capacities, respectively. The findings of this study provided an important theoretical basis for the restoration of cut slopes in alpine permafrost regions.

Screening Aspergillus flavus, Talaromyces purpureogenus, and Trichoderma koningiopsis for Plant-Growth-Promoting Traits: A Study on Phosphate Solubilization, IAA Production, and Siderophore Synthesis

The global rise in population has led to an increased demand for food production, necessitating the adoption of sustainable agricultural practices. Traditional methods often rely on synthetic chemicals that negatively impact both human health and the environment. This study aimed to screen soil fungal strains for plant-growth-promoting traits, specifically focusing on their ability to solubilize phosphates, produce indole-3-acetic acid (IAA), and synthesize siderophores. Fungal strains were identified using rDNA sequencing of the ITS regions, and their growth-promoting abilities were assessed in vitro. Aspergillus flavus JKJ7, Talaromyces purpureogenus JKJ12, and Trichoderma koningiopsis JKJ18 exhibited varying degrees of phosphate solubilization, with T. purpureogenus JKJ12 solubilizing the highest amount of tricalcium phosphate (TCP), while A. flavus JKJ7 was the most effective in solubilizing phytic acid calcium salt (PCS). In terms of IAA production, A. flavus JKJ7 produced the highest auxin concentration (68.51 mg/L), followed by T. koningiopsis JKJ18 and T. purpureogenus JKJ12. Additionally, A. flavus JKJ7 produced the highest amount of siderophores (83.7%), indicating its potential for improving iron uptake in plants. Principal Component Analysis (PCA) revealed distinct functional capabilities among the strains, particularly in phosphate solubilization and IAA production, suggesting their complementary use in consortium formulations. These results indicate that these fungal strains possess significant plant-growth-promoting traits and could be used as bioinoculants for sustainable agriculture, either as single strains or in combination.

Plants Under Stress: Exploring Physiological and Molecular Responses to Nitrogen and Phosphorus Deficiency

Nitrogen (N) and phosphorus (P) are essential mineral macronutrients critical for plant structure and function. Both contribute to processes ranging from cellular integrity to signal transduction. Since plants require these nutrients in high concentrations, replenishing them in soil often involves chemical fertilizers. However, the main source of P, rock phosphate, is non-renewable and in decline. N, second only to carbon, oxygen, and hydrogen in plant requirements, is vital for synthesizing proteins, nucleic acids, and plant pigments. Although N is available to plants through biological fixation or fertilizer application, the frequent application of N is not a sustainable solution due to environmental concerns like groundwater contamination and eutrophication. Plants have developed sophisticated mechanisms to adapt to nutrient deficiencies, such as changes in root architecture, local signaling, and long-distance signaling through the phloem. A dual deficiency of N and P is common in the field. In addition to individual N and P deficiency responses, this review also highlights some of the most recent discoveries in the responses of plants to the combined N and P deficiencies. Understanding the molecular and physiological responses in plants to mineral deficiency will help implement strategies to produce plants with high mineral use efficiency, leading to the reduced application of fertilizers, decreased mineral runoff, and improved environment.

Root plasticity improves maize nitrogen use when nitrogen is limiting: an analysis using 3D plant modelling

Plant phenotypic plasticity plays an important role in nitrogen (N) acquisition and use under nitrogen-limited conditions. However, this role has never been quantified as a function of N availability, leaving it unclear whether plastic responses should be considered as potential targets for selection. A combined modelling and experimentation approach was adopted to quantify the role of plasticity in N uptake and plant yield. Based on a greenhouse experiment we considered plasticity in two maize (Zea mays) traits: root-to-leaf biomass allocation ratio and emergence rate of axial roots. In a simulation experiment we individually enabled or disabled both plastic responses for maize stands grown across six N levels. Both plastic responses contributed to maintaining a higher N uptake, and plant productivity as N availability declined compared with stands in which plastic responses were disabled. We conclude that plastic responses quantified in this study may be a potential target trait in breeding programs for greater N uptake across N levels while it may only be important for the internal use of N under N-limited conditions in maize. Given the complexity of breeding for plastic responses, an a priori model analysis is useful to identify which plastic traits to target for enhanced plant performance.

Growth, Biochemical Traits, Antioxidant Enzymes, and Essential Oils of Four Aromatic and Medicinal Plants Cultivated in Phosphate-Mine Residues

Revegetation emerges as a promising approach to alleviate the adverse impacts of mining residues. However, it is essential to evaluate the characteristics of these materials and select suitable plant species to ensure successful ecosystem restoration. This study aimed to investigate the effects of phosphate-mine residues (MR) on the growth, biochemical properties, and essential oil concentration of Rosmarinus officinalis L., Salvia Officinalis L., Lavandula dentata L., and Origanum majorana L. The results showed that R. officinalis L. appeared to be particularly well-suited to thriving in MR soil. Our finding also revealed that L. dentata L., O. majorana L., and S. officinalis L. grown in MR exhibited significantly lower growth performance (lower shoot length, smaller leaves, and altered root structure) and higher antioxidant activities, with an alterations of photosynthetic pigment composition. They showed a decrease in total chlorophylls when grown on MR (0.295, 0.453, and 0.562 mg g-1 FW, respectively) compared to the control (0.465, 0.807, and 0.808 mg g-1 FW, respectively); however, they produced higher essential oil content (1.8%, 3.06%, and 2.88%, respectively). The outcomes of this study could offer valuable insights for the advancement of revegetation technologies and the utilization of plant products derived from phosphate-mine residues.

Diagnostic species are crucial for the functioning of plant associations in inland salt marshes

Salt marsh vegetation is considered unique and valuable and has been legally protected in Europe for years but is still declining. Its protection is related to vegetation syntaxonomical units. The characteristic combination of diagnostic species is used to create this syntaxonomical system. The aim of our novel study was to assess whether diagnostic species are sufficient for characterising vegetation functioning. Moreover, we included biochemical traits not considered to date in vegetation ecology. We hypothesised that (1) diagnostic species are crucial for the functioning of inland salt marsh vegetation and (2) their morphological and biochemical traits define the functioning of typical salt marsh associations. We chose three typical inland associations to test our hypotheses and measured the morphological and biochemical functional traits of their diagnostic plant species. Our research has shown that diagnostic species play a crucial role not only in distinguishing typical inland salt marsh associations but also in determining their functioning. Among the analysed associations, Salicornietum ramosissimae was the most adaptable to osmotic and oxidative stress under soil salinity. Triglochino maritimae-Glaucetum maritimae showed the lowest salt resistance, as indicated by the highest osmotic and oxidative stress and stress responses. Our findings may facilitate the practical application of new approaches and protection strategies for inland salt marsh habitats.

Early exposure to phosphorus starvation induces genetically determined responses in Sorghum bicolor roots

KEY MESSAGE

We identified novel physiological and genetic responses to phosphorus starvation in sorghum diversity lines that augment current knowledge of breeding for climate-smart crops in Europe. Phosphorus (P) deficiency and finite P reserves for fertilizer production pose a threat to future global crop production. Understanding root system architecture (RSA) plasticity is central to breeding for P-efficient crops. Sorghum is regarded as a P-efficient and climate-smart crop with strong adaptability to different climatic regions of the world. Here we investigated early genetic responses of sorghum RSA to P deficiency in order to identified genotypes with interesting root phenotypes and responses under low P. A diverse set of sorghum lines (n = 285) was genotyped using DarTSeq generating 12,472 quality genome wide single-nucleotide polymorphisms. Root phenotyping was conducted in a paper-based hydroponic rhizotron system under controlled greenhouse conditions with low and optimal P nutrition, using 16 RSA traits to describe genetic and phenotypic variability at two time points. Genotypic and phenotypic P-response variations were observed for multiple root traits at 21 and 42 days after germination with high broad sense heritability (0.38-0.76). The classification of traits revealed four distinct sorghum RSA types, with genotypes clustering separately under both low and optimal P conditions, suggesting genetic control of root responses to P availability. Association studies identified quantitative trait loci in chromosomes Sb02, Sb03, Sb04, Sb06 and Sb09 linked with genes potentially involved in P transport and stress responses. The genetic dissection of key factors underlying RSA responses to P deficiency could enable early identification of P-efficient sorghum genotypes. Genotypes with interesting RSA traits for low P environments will be incorporated into current sorghum breeding programs for later growth stages and field-based evaluations.

Can urea-coated fertilizers be an effective means of reducing greenhouse gas emissions and improving crop productivity?

Given the significance of nitrogen (N) as the most constraining nutrient in agro-ecosystems, it is crucial to develop an updated model for N fertilizers management to achieve higher crop yields while minimizing the negative impacts on the environment. Coated urea is touted as one of the most important controlled-release N fertilizers used in agriculture to reduce cropland emissions and improve nitrogen use efficiency (NUE) for optimal crop yields. The sustainability of coated urea depends on the trade-offs between crop productivity, NUE and greenhouse gas emissions (CO2, CH4 and N2O); however, role of various agro-edaphic factors in influencing these trade-offs remains unclear. To determine the effects of soil properties, climatic conditions, experimental conditions, and type of coated urea on greenhouse gas emissions, NH3 losses, crop productivity, and NUE, we conducted a meta-analysis using data from 76 peer-reviewed studies. Our results showed that the application of coated urea under field conditions contributed to a greater reduction in N2O emissions (-48.67%) and higher NUE (58.72%), but crop yields were not significant. Across different climate regions, subtropical monsoon climate showed a perceptible mitigation for CO2, CH4 and NH3 (-78.38%; -83.33%; -27.46%), while temperate climate reduced N2O emissions by -70.36%. For different crops, only rice demonstrated reduction in CO2, CH4, N2O and NH3 losses. On the other hand, our findings revealed a mitigating trade-off between CO2 and CH4 emissions on medium-textured soils and N2O emissions on fine-textured soils. A significant reduction in N2O and NH3 losses was evident when coated urea was applied to soils with a pH > 5.5. Interestingly, application of coated urea to soils with higher C/N ratios increased NH3 losses but showed a noticeable N2O reduction. We found that polymer-coated urea reduced CH4 and N2O emissions and NH3 losses at the expense of higher CO2 emissions. Moreover, application of a lower dose of coated urea (0-100 kg N ha-1) enhanced CO2 and CH4 mitigation, while N2O mitigation increased linearly with increasing dose of coated urea. Most importantly, our results showed that the application of coated urea leads to a large mismatch between NUE, crop yields and greenhouse gas mitigation. By and large, the application of coated urea did not correspond with higher crop yields despite significant reduction in the emissions and improved NUE. Overall, these results suggest that site-specific agro-edaphic conditions should be considered when applying coated urea to reduce these emissions and N volatilization losses for increasing NUE and crop yields.

Building microbial consortia to enhance straw degradation, phosphorus solubilization, and soil fertility for rice growth

Straw pollution and the increasing scarcity of phosphorus resources in many regions of China have had severe impacts on the growing conditions for crop plants. Using microbial methods to enhance straw decomposition rate and phosphorus utilization offers effective solutions to address these problems. In this study, a microbial consortium 6 + 1 (consisting of a straw-degrading bacterium and a phosphate-solubilizing bacterium) was formulated based on their performance in straw degradation and phosphorus solubilization. The degradation rate of straw by 6 + 1 microbial consortium reached 48.3% within 7 days (The degradation ability was 7% higher than that of single bacteria), and the phosphorus dissolution rate of insoluble phosphorus reached 117.54 mg·L- 1 (The phosphorus solubilization ability was 29.81% higher than that of single bacteria). In addition, the activity of lignocellulosic degrading enzyme system was significantly increased, the activities of endoglucanase, β-glucosidase and xylanase in the microbial consortium were significantly higher than those in the single strain (23.16%, 28.02% and 28.86%, respectively). Then the microbial consortium was processed into microbial agents and tested in rice pots. The results showed that the microbial agent significantly increased the content of organic matter, available phosphorus and available nitrogen in the soil. Ongoing research focuses on the determination of the effects and mechanisms of a functional hybrid system of straw degradation and phosphorus removal. The characteristics of the two strains are as follows: Straw-degrading bacteria can efficiently degrade straw to produce glucose-based carbon sources when only straw is used as a carbon source. Phosphate-solubilizing bacteria can efficiently use glucose as a carbon source, produce organic acids to dissolve insoluble phosphorus and consume glucose at an extremely fast rate. The analysis suggests that the microbial consortium 6 + 1 outperformed individual strains in terms of both performance and application effects. The two strains within the microbial consortium promote each other during their growth processes, resulting in a significantly higher rate of carbon source consumption compared to the individual strains in isolation. This increased demand for carbon sources within the growth system facilitates the degradation of straw by the strains. At the same time, the substantial carbon consumption during the metabolic process generated a large number of organic acids, leading to the solubilization of insoluble phosphorus. It also provides a basis for the construction of this type of microbial consortium.

Impact of fertilization depth on sunflower yield and nitrogen utilization: a perspective on soil nutrient and root system compatibility

Introduction

The depth of fertilizer application significantly influences soil nitrate concentration (SNC), sunflower root length density (RLD), sunflower nitrogen uptake (SNU), and yield. However, current studies cannot precisely capture subtle nutrient variations between soil layers and their complex relationships with root growth. They also struggle to assess the impact of different fertilizer application depths on sunflower root development and distribution as well as their response to the spatial and temporal distribution of nutrients.

Methods

The Agricultural Production Systems sIMulator (APSIM) model was employed to explore the spatial and temporal patterns of nitrogen distribution in the soil at three controlled-release fertilizer (CRF) placement depths: 5, 15, and 25 cm. This study investigated the characteristics of the root system regarding nitrogen absorption and utilization and analyzed their correlation with sunflower yield formation. Furthermore, this study introduced the modified Jaccard index (considering the compatibility between soil nitrate and root length density) to analyze soil-root interactions, providing a deeper insight into how changes in CRF placement depth affect crop growth and nitrogen uptake efficiency.

Results

The results indicated that a fertilization depth of 15 cm improved the modified Jaccard index by 6.60% and 7.34% compared to 5 cm and 25 cm depths, respectively, maximizing sunflower yield (an increase of 9.44%) and nitrogen absorption rate (an increase of 5.40%). This depth promoted a greater Root Length Density (RLD), with an increases of 11.95% and 16.42% compared those at 5 cm and 25 cm, respectively, enhancing deeper root growth and improving nitrogen uptake. In contrast, shallow fertilization led to higher nitrate concentrations in the topsoil, whereas deeper fertilization increased the nitrate concentrations in the deeper soil layers.

Discussion

These results provide valuable insights for precision agriculture and sustainable soil management, highlighting the importance of optimizing root nitrogen absorption through tailored fertilization strategies to enhance crop production efficiency and minimize environmental impact.

Abiotic Stresses in Plants: From Molecules to Environment

Plants face several challenges during their growth and development, including environmental factors (mainly abiotic ones), that can lead to/induce oxidative stress-specifically, adverse temperatures (both hot and cold), drought, salinity, radiation, nutrient deficiency (or excess), toxic metals, waterlogging, air pollution, and mechanical stimuli [...].

Trichoderma viride improves phosphorus uptake and the growth of Chloris virgata under phosphorus-deficient conditions

Introduction

Phosphorus (P) readily forms insoluble complexes in soil, thereby inhibiting the absorption and utilization of this essential nutrient by plants. Phosphorus deficiency can significantly impede the growth of forage grass. While Trichoderma viride (T. viride) has been recognized for promoting the assimilation of otherwise unobtainable nutrients, its impact on P uptake remains understudied. Consequently, it is imperative to gain a more comprehensive insight into the role of T. viride in facilitating the uptake and utilization of insoluble P in forage grass.

Methods

This research explored the influence of T. viride inoculation on P absorption and the growth of Chloris virgata (C. virgata) across various P sources. We treated plants with control P (P), tricalcium phosphate (TCP), calcium phytate (PHY), and low P (LP), with and without T. viride inoculation (P+T, TCP+T, PHY+T, LP+T). We analyzed photosynthesis parameters, growth indices, pigment accumulation, P content, leaf acid phosphatase activity.

Results

Results demonstrated that T. viride inoculation alleviated inhibition of photosynthesis, reduced leaf acid phosphatase activity, and enhanced growth of C. virgata in the presence of insoluble P sources. Additionally, T. viride inoculation enabled the plants to extract more available P from insoluble P sources, as evidenced by a substantial increase in P content: shoot P content surged by 58.23 to 59.08%, and root P content rose by 55.13 to 55.2%. Biomass P-use efficiency (PUE) declined by 38% upon inoculation with T. viride compared to the non-inoculated insoluble P sources, paralleled by a reduction in photosynthetic P-use efficiency (PPUE) by 26 to 29%. Inoculation under insoluble P sources further triggered a lower allocation to root biomass (25 to 26%) and a higher investment in shoot biomass (74 to 75%). However, its application under low P condition curtailed the growth of C. virgata.

Discussion

Our results suggest that T. viride inoculation represents an innovative approach for plants to acquire available P from insoluble P sources, thereby promoting growth amid environmental P limitations. This insight is crucial for comprehending the synergy among forage grass, P, and T. viride.

Benefits and limits of biological nitrification inhibitors for plant nitrogen uptake and the environment

Plant growth and high yields are secured by intensive use of nitrogen (N) fertilizer, which, however, pollutes the environment, especially when N is in the form of nitrate. Ammonium is oxidized to nitrate by nitrifiers, but roots can release biological nitrification inhibitors (BNIs). Under what conditions does root-exudation of BNIs facilitate nitrogen N uptake and reduce pollution by N loss to the environment? We modeled the spatial-temporal dynamics of nitrifiers, ammonium, nitrate, and BNIs around a root and simulated root N uptake and net rhizosphere N loss over the plant's life cycle. We determined the sensitivity of N uptake and loss to variations in the parameter values, testing a broad range of soil-plant-microbial conditions, including concentrations, diffusion, sorption, nitrification, population growth, and uptake kinetics. An increase in BNI exudation reduces net N loss and, under most conditions, increases plant N uptake. BNIs decrease uptake in the case of (1) low ammonium concentrations, (2) high ammonium adsorption to the soil, (3) rapid nitrate- or slow ammonium uptake by the plant, and (4) a slowly growing or (5) fast-declining nitrifier population. Bactericidal inhibitors facilitate uptake more than bacteriostatic ones. Some nitrification, however, is necessary to maximize uptake by both ammonium and nitrate transporter systems. An increase in BNI exudation should be co-selected with improved ammonium uptake. BNIs can reduce N uptake, which may explain why not all species exude BNIs but have a generally positive effect on the environment by increasing rhizosphere N retention.

Measuring leaf and root functional traits uncovers multidimensionality of plant responses to arbuscular mycorrhizal fungi

PREMISE

While many studies have measured the aboveground responses of plants to mycorrhizal fungi at a single time point, little is known about how plants respond belowground or across time to mycorrhizal symbiosis. By measuring belowground responses and growth over time in many plant species, we create a more complete picture of how mycorrhizal fungi benefit their hosts.

METHODS

We grew 26 prairie plant species with and without mycorrhizal fungi and measured 14 functional traits to assess above- and belowground tissue quality and quantity responses and changes in resource allocation. We used function-valued trait (FVT) modeling to characterize changes in species growth rate when colonized.

RESULTS

While aboveground biomass responses were positive, the response of traits belowground were much more variable. Changes in aboveground biomass accounted for 60.8% of the variation in mycorrhizal responses, supporting the use of aboveground biomass response as the primary response trait. Responses belowground were not associated with aboveground responses and accounted for 18.3% of the variation. Growth responses over time were highly variable across species. Interestingly, none of the measured responses were phylogenetically conserved.

CONCLUSIONS

Mycorrhizal fungi increase plant growth in most scenarios, but the effects of these fungi belowground and across time are more complicated. This study highlights how differences in plant allocation priorities might affect how they utilize the benefits from mycorrhizal fungi. Identifying and characterizing these differences is a key step to understanding the effects of mycorrhizal mutualisms on whole plant physiology.

Tryptophan regulates sorghum root growth and enhances low nitrogen tolerance

Over evolutionary time, plants have developed sophisticated regulatory mechanisms to adapt to fluctuating nitrogen (N) environments, ensuring that their growth is balanced with their responses to N stress. This study explored the potential of L-tryptophan (Trp) in regulating sorghum root growth under conditions of N limitation. Here, two distinct sorghum genotypes (low-N tolerance 398B and low-N sensitive CS3541) were utilized for investigating effect of low-N stress on root morphology and conducting a comparative transcriptomics analysis. Our foundings indicated that 398B exhibited longer roots, greater root dry weights, and a higher Trp content compared to CS3541 under low-N conditions. Furthermore, transcriptome analysis revealed substantial differences in gene expression profiles related to Trp pathway and carbon (C) and N metabolism pathways between the two genotypes. Additional experiments were conducted to assess the effects of exogenous Trp treatment on the interplay between sorghum root growth and low-N tolerance. Our observations showed that Trp-treated plants developed longer root and had elevated levels of Trp and IAA under low-N conditons. Concurrently, these plants demonstrated stronger physiological activities in C and N metabolism when subjected to low-N stress. These results underscored the pivotal role of Trp on root growth and low-N stress responses by balancing IAA levels and C and N metabolism. This study not only deepens our understanding of how plants maintain growth plasticity during environmental stress but also provides valuable insights into the availability of amino acid in crops, which could be instrumental in developing strategies for promoting crop resilience to N deficiency.

Rejuvenating potato growth and yield in challenging semiarid and saline sandy Cholistan: harnessing PGPB-coated N and P application strategies

BACKGROUND

Potato serves as a major non-cereal food crop and income source for small-scale growers in Punjab, Pakistan. Unfortunately, improper fertilization practices have led to low crop yields, worsened by challenging environmental conditions and poor groundwater quality in the Cholistan region. To address this, we conducted an experiment to assess the impact of two fertilizer application approaches on potato cv. Barna using plant growth-promoting bacteria (PGPB) coated biofertilizers. The first approach, termed conventional fertilizer application (CFA), involved four split applications of PGPB-coated fertilizers at a rate of 100:75 kg acre-1 (N and P). The second, modified fertilizer application (MFA), employed nine split applications at a rate of 80:40 kg acre-1.

RESULTS

The MFA approach significantly improved various plant attributes compared to the CFA. This included increased plant height (28%), stem number (45%), leaf count (46%), leaf area index (36%), leaf thickness (three-folds), chlorophyll content (53%), quantum yield of photosystem II (45%), photosynthetically active radiations (56%), electrochromic shift (5.6%), proton flux (24.6%), proton conductivity (71%), linear electron flow (72%), photosynthetic rate (35%), water use efficiency (76%), and substomatal CO2 (two-folds), and lowered non-photochemical quenching (56%), non-regulatory energy dissipation (33%), transpiration rate (59%), and stomatal conductance (70%). Additionally, the MFA approach resulted in higher tuber production per plant (21%), average tuber weight (21.9%), tuber diameter (24.5%), total tuber yield (29.1%), marketable yield (22.7%), seed-grade yield (9%), specific gravity (9.6%), and soluble solids (7.1%). It also reduced undesirable factors like goli and downgrade yields by 57.6% and 98.8%, respectively. Furthermore, plants under the MFA approach exhibited enhanced nitrogen (27.8%) and phosphorus uptake (40.6%), with improved N (26.1%) and P uptake efficiency (43.7%) compared to the CFA approach.

CONCLUSION

The use of PGPB-coated N and P fertilizers with a higher number of splits at a lower rate significantly boosts potato production in the alkaline sandy soils of Cholistan.

Role of calcium nutrition in plant Physiology: Advances in research and insights into acidic soil conditions - A comprehensive review

Plant mineral nutrition has immense significance for crop productivity and human well-being. Soil acidity plays a major role in determining the nutrient availability that influences plant growth. The importance of calcium (Ca) in biological processes, such as signaling, metabolism, and cell growth, underlines its critical role in plant growth and development. This review focuses on soil acidification, a gradual process resulting from cation leaching, fertilizer utilization, and drainage issues. Soil acidification significantly hampers global crop production by modifying nutrient accessibility. In acidic soils, essential nutrients, such as nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and Ca become less accessible, establishing a correlation between soil pH and plant nutrition. Cutting-edge Ca nutrition technologies, including nanotechnology, genetic engineering, and genome sequencing, offer the potential to deliver Ca and reduce the reliance on conventional soluble fertilizers. These fertilizers not only contribute to environmental contamination but also impose economic burdens on farmers. Nanotechnology can enhance nutrient uptake, and Ca nanoparticles improve nutrient absorption and release. Genetic engineering enables the cultivation of acid-tolerant crop varieties by manipulating Ca-related genes. High-throughput technologies such as next-generation sequencing and microarrays aid in identifying the microbial structures, functions, and biosynthetic pathways involved in managing plant nutritional stress. The ultimate goal is to shed light on the importance of Ca, problems associated with soil acidity, and potential of emerging technologies to enhance crop production while minimizing the environmental impact and economic burden on farmers.

Rhizospheric Precipitation of Manganese by Phosphate: A Novel Strategy to Enhance Mn Tolerance in the Hyperaccumulator Phytolacca americana

Manganese (Mn) exclusion in the Mn hyperaccumulator pokeweed (Phytolacca americana L.) was investigated. Hydroponic experiments were carried out to observe the responses of pokeweeds continually exposed to high levels of Mn. In this study, crystals were observed to appear firstly on the root hair, and soon after, more crystals appeared on the root surface, and crystals of Mn phosphate were observed to appear on the root surface in a time sequence negatively correlated with the number of leaves treated with 5 mM Mn. Crystals were identified via phase analysis of X-ray diffraction and element analysis, and these white insoluble crystals were identified using XRD to be Mn phosphate, with the molecular formula (Mn,Fe)3(PO4)2·4H2O. The nutrient solution pH increased from 4.5 to about 5.6 before the crystals appeared. Mn phosphate crystals appeared in all solutions except those without phosphate and emerged earlier in the solutions containing no Fe. Compared with control group, pokeweed accumulated much more Mn in the leaves when treated without phosphate or Fe. The present study suggests that pokeweed can exclude Mn by means of rhizosphere precipitation by phosphate to form Mn phosphate crystals that accumulate on the root surface. Although the detailed mechanism requires further investigation, this study provides the first direct evidence of a novel strategy to inhibit Mn uptake in the roots of a hyperaccumulator in a P-enriched environment.

The Growth-Inhibitory Effect of Increased Planting Density Can Be Reduced by Abscisic Acid-Degrading Bacteria

High-density planting can increase crop productivity per unit area of cultivated land. However, the application of this technology is limited by the inhibition of plant growth in the presence of neighbors, which is not only due to their competition for resources but is also caused by growth regulators. Specifically, the abscisic acid (ABA) accumulated in plants under increased density of planting has been shown to inhibit their growth. The goal of the present study was to test the hypothesis that bacteria capable of degrading ABA can reduce the growth inhibitory effect of competition among plants by reducing concentration of this hormone in plants and their environment. Lettuce plants were grown both individually and three per pot; the rhizosphere was inoculated with a strain of Pseudomonas plecoglossicida 2.4-D capable of degrading ABA. Plant growth was recorded in parallel with immunoassaying ABA concentration in the pots and plants. The presence of neighbors indeed inhibited the growth of non-inoculated lettuce plants. Bacterial inoculation positively affected the growth of grouped plants, reducing the negative effects of competition. The bacteria-induced increase in the mass of competing plants was greater than that in the single ones. ABA concentration was increased by the presence of neighbors both in soil and plant shoots associated with the inhibition of plant growth, but accumulation of this hormone as well as inhibition of the growth of grouped plants was prevented by bacteria. The results confirm the role of ABA in the response of plants to the presence of competitors as well as the possibility of reducing the negative effect of competition on plant productivity with the help of bacteria capable of degrading this hormone.

Phosphorus deficiency alters root length, acid phosphatase activity, organic acids, and metabolites in root exudates of soybean cultivars

Phosphorus (P) deficiency alters the root morphological and physiological traits of plants. This study investigates how soybean cultivars with varying low-P tolerance values respond to different P levels in hydroponic culture by assessing alterations in root length, acid phosphatase activity, organic acid exudation, and metabolites in root exudates. Three low-P-tolerant cultivars ('Maetsue,' 'Kurotome,' and 'Fukuyutaka') and three low-P-sensitive cultivars ('Ihhon,' 'Chizuka,' and 'Komuta') were grown under 0 (P0) and 258 μM P (P8) for 7 and 14 days after transplantation (DAT). Low-P-tolerant cultivars increased root length by 31% and 119%, which was lower than the 62% and 144% increases in sensitive cultivars under P0 compared to P8 at 7 and 14 DAT, respectively. Acid phosphatase activity in low-P-tolerant cultivars exceeded that in sensitive cultivars by 5.2-fold and 2.0-fold at 7 and 14 DAT. Root exudates from each cultivar revealed 177 metabolites, with higher organic acid exudation in low-P-tolerant than sensitive cultivars under P0. Low-P-tolerant cultivars increased concentrations of specific metabolites (oxalate, GABA, quinate, citrate, AMP, 4-pyridoxate, and CMP), distinguishing them from low-P-sensitive cultivars under P0. The top five metabolomic pathways (purine metabolism, arginine and proline metabolism, TCA cycle, glyoxylate and dicarboxylate metabolism, alanine, aspartate, and glutamate metabolism) were more pronounced in low-P-tolerant cultivars at 14 DAT. These findings indicate that increasing root length was not an adaptation strategy under P deficiency; instead, tolerant cultivars exhibit enhanced root physiological traits, including increased acid phosphatase activity, organic acid exudation, specific metabolite release, and accelerated metabolic pathways under P deficiency.

Nitrogen Journey in Plants: From Uptake to Metabolism, Stress Response, and Microbe Interaction

Plants uptake and assimilate nitrogen from the soil in the form of nitrate, ammonium ions, and available amino acids from organic sources. Plant nitrate and ammonium transporters are responsible for nitrate and ammonium translocation from the soil into the roots. The unique structure of these transporters determines the specificity of each transporter, and structural analyses reveal the mechanisms by which these transporters function. Following absorption, the nitrogen metabolism pathway incorporates the nitrogen into organic compounds via glutamine synthetase and glutamate synthase that convert ammonium ions into glutamine and glutamate. Different isoforms of glutamine synthetase and glutamate synthase exist, enabling plants to fine-tune nitrogen metabolism based on environmental cues. Under stressful conditions, nitric oxide has been found to enhance plant survival under drought stress. Furthermore, the interaction between salinity stress and nitrogen availability in plants has been studied, with nitric oxide identified as a potential mediator of responses to salt stress. Conversely, excessive use of nitrate fertilizers can lead to health and environmental issues. Therefore, alternative strategies, such as establishing nitrogen fixation in plants through diazotrophic microbiota, have been explored to reduce reliance on synthetic fertilizers. Ultimately, genomics can identify new genes related to nitrogen fixation, which could be harnessed to improve plant productivity.

Influence of management practices on water-related grain yield determinants

Adequate management of N supply, plant density, row spacing, and soil cover has proved useful for increasing grain yields and/or grain yield stability of rainfed crops over the years. We review the impact of these management practices on grain yield water-related determinants: seasonal crop evapotranspiration (ET) and water use efficiency for grain production per unit of evapotranspired water during the growing season (WUEG,ET,s). We highlight a large number of conflicting results for the impact of management on ET and expose the complexity of the ET response to environmental factors. We analyse the influence of management practices on WUEG,ET,s in terms of the three main processes controlling it: (i) the proportion of transpiration in ET (T/ET), (ii) transpiration efficiency for shoot biomass production (TEB), and (iii) the harvest index. We directly relate the impact of management practices on T/ET to their effect on crop light interception and provide evidence that management practices significantly influence TEB. To optimize WUEG,ET,s, management practices should favor soil water availability during critical periods for seed set, thereby improving the harvest index. The need to improve the performance of existing crop growth models for the prediction of water-related grain yield determinants under different management practices is also discussed.

Phosphorus Plays Key Roles in Regulating Plants' Physiological Responses to Abiotic Stresses

Phosphorus (P), an essential macronutrient, plays a pivotal role in the growth and development of plants. However, the limited availability of phosphorus in soil presents significant challenges for crop productivity, especially when plants are subjected to abiotic stresses such as drought, salinity and extreme temperatures. Unraveling the intricate mechanisms through which phosphorus participates in the physiological responses of plants to abiotic stresses is essential to ensure the sustainability of agricultural production systems. This review aims to analyze the influence of phosphorus supply on various aspects of plant growth and plant development under hostile environmental conditions, with a special emphasis on stomatal development and operation. Furthermore, we discuss recently discovered genes associated with P-dependent stress regulation and evaluate the feasibility of implementing P-based agricultural practices to mitigate the adverse effects of abiotic stress. Our objective is to provide molecular and physiological insights into the role of P in regulating plants' tolerance to abiotic stresses, underscoring the significance of efficient P use strategies for agricultural sustainability. The potential benefits and limitations of P-based strategies and future research directions are also discussed.

Silicon, by promoting a homeostatic balance of C:N:P and nutrient use efficiency, attenuates K deficiency, favoring sustainable bean cultivation

BACKGROUND

In many regions of the world, K is being depleted from soils due to agricultural intensification a lack of accessibility, and the high cost of K. Thus, there is an urgent need for a sustainable strategy for crops in this environment. Si is an option for mitigating stress due to nutritional deficiency. However, the underlying effects of Si in mitigating K deficiency C:N:P homeostasis still remains unknown for bean plants. This is a species of great worldwide importance. Thus, this study aims to evaluate whether i) K deficiency modifies the homeostatic balance of C, N and P, and, if so, ii) Si supply can reduce damage caused to nutritional stoichiometry, nutrient use efficiency, and production of dry mass in bean plants.

RESULTS

K deficiency caused a reduction in the stoichiometric ratios C:N, C:P, and P:Si in shoots and C:N, C:P, C:Si, N:Si, and P:Si in roots, resulting in a decrease in K content and use efficiency and reducing biomass production. The application of Si in K-deficient plants modified the ratios C:N, C:Si, N:P, N:Si, and P:Si in shoots and C:N, C:P, C:Si, N:Si, N:P, and P:Si in roots, increasing the K content and efficiency, reducing the loss of biomass. In bean plants with K sufficiency, Si also changed the stoichiometric ratios C:N, C:P, C:Si, N:P, N:Si, and P:Si in shoots and C:N, C:Si, N:Si, and P:Si in roots, increasing K content only in roots and the use efficiency of C and P in shoots and C, N, and P in roots, increasing the biomass production only in roots.

CONCLUSION

K deficiency causes damage to the C:N:P homeostatic balance, reducing the efficiency of nutrient use and biomass production. However, Si is a viable alternative to attenuate these nutritional damages, favoring bean growth. The future perspective is that the use of Si in agriculture in underdeveloped economies with restrictions on the use of K will constitute a sustainable strategy to increase food security.