Phosphorus Utilization Efficiency Research Articles

Nutrient Balance and Nutrient Use Efficiency of Irrigated Pigeon Pea [Cajanus cajan (L.) Millsp.] under Various Integrated Nutrient Management Practices

Aims: To evaluate the nutrient balance and nutrient use efficiency of irrigated pigeon peas under various integrated fertilizers Place and Duration of Study: The field trial was conducted at Instructional Farm (North), Karunya Institute of Technology and Sciences, Coimbatore. Methodology: During the growth phase of the pigeon pea crop, the soil's nitrogen, phosphorus, and potassium levels were monitored to assess their essential nutrient balance. This evaluation was conducted for each treatment, considering the specific nutrient application given to the crop. Additionally, the total quantity of nutrient uptake and the efficiency of nitrogen, phosphorus, and potassium utilization were calculated. Results: Higher availability of nutrients and nutrient uptake at harvest and the maximum values of computed balance and gain values in the nutrient balance studies and agronomic efficiency were observed in the integrated application of 75% RDF + 25% N eq as vermicompost (T2) Conclusion: The integrated application of 75% RDF + 25% N eq as vermicompost (T2) resulted in maximum available nutrients, plant uptake, agronomic efficiency and computed balance nutrient gain.

The effect of phosphorus utilization efficiency on durum wheat cultivars under semi-arid environmental conditions

Faced with the high cost of phosphate fertilisers in several African countries, including Algeria, and in order to better select varieties according to their fertiliser use efficiency, this study was proposed. The goal of the study was to determine how “variety” impacts durum wheat's capacity to utilize phosphorus effectively and to try to pinpoint the agro-morphological factors that contribute to this efficiency so that they can be taken into consideration when choosing which varieties to sow in semi-arid environments. The experimental setup consisted of a split plot with two investigated factors and three repetitions, with the main plot receiving the phosphate treatment while the sub plot receives the variety. The trial set up consisted of 11 durum wheat varieties, which were cultivated over two years successively. The PUE of the fertiliser, provided in 46% triple superphosphate (TSP) granules, and agro-morphological parameters like aerial biomass, plant height, grain yield and yield components were determined. The findings demonstrated that triple superphosphate, a type of phosphorus fertilizer, increases grain yield by between 40 and 60% for all varieties examined as compared to the phosphorus-free control at the average dose employed in this field trial, or 20 kg P2O5.ha-1. This increase in yield is due to an increase: from 20 to 22% in the number of ears per m², 41.5% in the number of grains per ear, and 9% in the average weight of the grain. The PUE is strongly correlated to the yield components (Number of ears per square meter- NEM, Number of grains per ear- NGE, thousand grain weight- TGW and Yield) but also to the height at heading (r=0.86) and dry matter (r=0.85). Phosphorus use efficiency is also strongly correlated to flag leaf length and width as well as leaf area. Also, that genotypes with higher weight of thousand grains (WTG) showed better use of available phosphorus. The principal component analysis (PCA) confirms that the efficiency of phosphorus use by the varieties tested explains a large portion of the variation noted in these varieties. This genetic variation in PUE was associated with plant height and phosphorus content of the sown grains. These results could be of a significant impact in improving rainfed durum wheat productivity in semi-arid areas and preserving the environment as well. Key words: Durum wheat, Phosphorus use efficiency, Plant’s height, Genetic variation, Fertilizers’ reduction

The Rhizosphere Functional Microbial Community: A Key Driver of Phosphorus Utilization Efficiency in Karst Forest Plants

Microorganisms play a pivotal role in transforming and making phosphorus (P) available in soil through various mechanisms. However, their specific contributions to alleviating P limitation and enhancing P utilization efficiency in plants within the context of a P-deficient karst ecosystem remains unclear. In this study, eco-stoichiometric methods were employed to evaluate the P utilization efficiency of plants grown in the surveyed karst forest located in Guizhou Province, China. Metagenomic sequencing was utilized to further explore the functional genes and microorganisms involved in soil P cycling. The N:P ratio for 18 out of the 20 surveyed plants exceeded 16, indicating widespread P limitation in karst plants. Among them, plants with high P utilization efficiencies (Nandina domestica Thunb.; Mahonia bodinieri Gagnep.; Pyracantha fortuneana (Maxim.) Li) exhibited higher relative abundances of genes involved in soil P cycling compared to plants with low P utilization efficiencies (Tirpitzia sinensis (Hemsl.) Hallier f.; Albizia kalkora (Roxb.) Prain; Morella rubra Lour.), indicating greater potentials within their rhizosphere microbiomes for soil P transformation. The relative abundance of these functional genes had a significant and positive effect on plant P utilization efficiencies. Structural equation modeling further indicated that microbial P cycling gene abundance directly drove the increase in plant P utilization efficiencies. Specifically, genes involved in soil organic P mineralization (G6PD, suhB, phoD, ppx) and the P uptake and transform system (pstS, pstA, pstB, pstC) contributed to the enhancement of plant P utilization efficiencies. Soil microbial communities involved in P cycling were predominately attributed to Proteobacteria (45.16%–60.02%), Actinobacteria (9.45%–25.23%), and Acidobacteria (5.90%–9.85%), although their contributions varied among different plants. The rhizosphere functional microbial community can thus alleviate P limitation in karst plants, thereby enhancing plant P utilization efficiencies. This study investigated the strong synergism between karst plants and rhizosphere microorganisms and their associated underlying mechanisms from genetic and microbial perspectives.

Root response and phosphorus acquisition under partial distribution of phosphorus and water‐soluble organic matter

AbstractUnderstanding how phosphorus and water‐soluble organic matter (WSOM) from animal manure compost contribute to root development is essential for enhancing phosphorus utilization efficiency under their combined application. This study aims to determine mechanisms underlying root responses and phosphorus acquisition based on the partially varying available phosphorus levels in root zone soil following WSOM. The plant growth test was performed using a specifically designed pot where the root elongation was guided into the soil of different root compartments with either phosphorus combined with WSOM or single phosphorus or WSOM. The results revealed high levels of available phosphorus in the root zone soil of individual plants in the presence of WSOM induced small root weight. Phosphorus concentrations in the root exhibited a negative correlation with root weight. Improved root structure development even in the presence of WSOM induced to increase uptake of phosphorus and other nutrients in the plant. Furthermore, a positive linear relationship was observed between nutrient uptake and aboveground dry weight. These findings provide pioneering experimental evidence demonstrating that root development varies to some extent depending on the level of available phosphorus induced by the combined application of phosphorus and WSOM, even within the root zone soil of individual plants. Given that plant growth varied based on partial root development even when phosphorus and WSOM were combined, this study suggests that implementing appropriate phosphorus fertilizer application while considering the augmented availability of phosphorus via the combined application of animal manure compost can promote root development and nutrient uptake, resulting in improved plant growth.

Phosphorus Utilization Efficiency and Status of Phosphorus Reuse in China from 1990 to 2019

Phosphorus (P) is an essential element for supporting our life and is a non-renewable resource. This study applied dynamic material flow analysis to elucidate the phosphorus flow characteristics in China over the period from 1990–2019. Based on this, we developed a P resource efficiency index system and further explored the potential reasons for the changes in different areas by analyzing the inflow, outflow, and reuse of P in various modules. Results show that the phosphorus utilization efficiency (PUE) in crop planting increased from 63% in 1990 to 72% in 2019, while this figure in feeding livestock increased from 35% in 1990 to 42% in 2019 due to the utilization of straw. The figure in aquaculture remained low at 9% in 2019. The total P amount used for human consumption increased to 2562 Gg in 2019 due to changes in dietary habits, and the overall P recycling rate (PRR) for various human activities jumped to 58% in 2019. Based upon these results, several policy suggestions are proposed from governance, technology, and economic instruments perspectives.

The Impact of Various Organic Phosphorus Carriers on the Uptake and Use Efficiency in Barley.

Organic phosphorus (OP) is an essential component of the soil P cycle, which contributes to barley nutrition after its mineralization into inorganic phosphorus (Pi). However, the dynamics of OP utilization in the barley rhizosphere remain unclear. In this study, phytin was screened out from six OP carriers, which could reflect the difference in OP utilization between a P-inefficient genotype Baudin and a P-efficient genotype CN4027. The phosphorus utilization efficiency (PUE), root morphological traits, and expression of genes associated with P utilization were assessed under P deficiency or phytin treatments. P deficiency resulted in a greater root surface area and thicker roots. In barley fed with phytin as a P carrier, the APase activities of CN4027 were 2-3-fold lower than those of Baudin, while the phytase activities of CN4027 were 2-3-fold higher than those of Baudin. The PUE in CN4027 was mainly enhanced by activating phytase to improve the root absorption and utilization of Pi resulting from OP mineralization, while the PUE in Baudin was mainly enhanced by activating APase to improve the shoot reuse capacity. A phosphate transporter gene HvPHT1;8 regulated P transport from the roots to the shoots, while a purple acid phosphatase (PAP) family gene HvPAPhy_b contributed to the reuse of P in barley.

Development of microalgal dual-cultures for enhanced productivity in sewage: An experimental study

Microalgae polycultures can be shown greater productivity than those that characterize monocultures. Nonetheless, rapid and ready identification of optimal microalgae combinations for highly productive polyculture systems remains a challenge. By assessing the corresponding nitrogen and phosphorus utilization efficiencies, this study aimed to identify microalgal combinations that might improve productivity. Ten high-biomass-producing microalgal species in municipal sewage habitats were cultivated in an artificial municipal sewage. Four high-yielding microalgae, which additionally showed complementary nitrogen and phosphorus nutrient utilization preferences, were selected for a subsequent dual-culture experiment. The D41 dual-culture system comprising Pediastrum sp. and Micractinium sp., showed the highest biocrude yield, at 17.5 mg/L/d, which was 13 % and 69 % higher than those of A4 and A1, respectively. Additionally, D41 showed the highest total phosphorus removal rate from artificial sewage, which was 27 % higher than that of Pediastrum sp. monoculture (A4) and 22 % higher than that of the Micractinium sp. monoculture (A1). Therefore, this study demonstrated that, (a) biomass production and nitrogen and phosphorus utilization rates of the constructed microalgae dual-culture systems were higher than those of monocultures, (b) phosphorus was identified as the limiting nutrient for further enhancing microalgae productivity, and (c) the dual-culture system showed intermediate characteristics between those of the constituent monoculture systems, suggesting that microalgae can influence community structure. Through the development of adequate software packages that can integrate microalgae nutrient utilization preference of and microalgae community structure, future research will enable the development of more productive microalgae culture combinations.

Altitudinal variation pattern in Daphniphyllum macropodum leaf traits and influencing environmental factors in Mao'er Mountain, China

Analyzing the pattern of altitudinal variation in the leaf traits and their networks of a particular tree species of similar age and its influencing factors could contribute to understanding the impacts of environmental factors on leaf traits and excluding the interference of genetic factors. We investigated the stomatal, structural, chemical, and vein traits of Daphniphyllum macropodum leaves in middle-aged forests, following the altitudinal gradient (1100, 1500, and 1900 m) on Mao'er Mountain. The objectives of this study were to reveal patterns in leaf trait and leaf trait networks variation, the life strategy of the tree species, and the major environmental factors affecting the altitudinal variations. The results showed that leaf area, specific leaf area, leaf thickness, leaf dry matter content, chlorophyll content, nitrogen content, phosphorus content, C:N, C:P, vein density, and vein diameter varied significantly across altitudes. Mean annual temperature and total radiation explained 42.1% and 16.2% of leaf-trait variation, respectively. They served as key environmental factors driving the altitudinal variation in leaf traits. Mean annual temperature exhibited the greatest influence on leaf area (R2=0.73), and total radiation exerted the most prominent effect on leaf thickness (R2=0.72). Both relationships were significantly positive. D. macropodum exhibited low leaf nitrogen and phosphorus at the low altitude of 1100 m, and the overall and local trait networks were loose, adopting a conservative resource strategy. At the medium altitude of 1500 m, leaf nutrient contents were relatively high. The overall network of leaf traits was tightly connected and local network was loose. By enhancing the dependency among leaf traits, and improving phosphorus utilization efficiency, D. macropodum could cope with competition in deciduous forests and adopt resource acquisition strategies. Further, at the highest altitude of 1900 m, D. macropodum had relatively large leaf thickness, chlorophyll content, and leaf dry matter content, but relatively small leaf area. The local network connections were tight while the overall network looseness, indicating a resource conserving strategy. The trade-off relationship between C:P and leaf phosphorus content was closely related to phosphorus use efficiency, and its variation was an important indicator for identifying life strategies of D. macropodum in different altitudes.

Impact of Phosphogypsum Application on Fungal Community Structure and Soil Health in Saline–Alkali-Affected Paddy Fields

Modifying saline–alkali soil is crucial for ensuring food security and expanding arable land. Microorganisms play a key role in driving various biochemical processes in agricultural ecosystems. However, limited information exists on the changes in the microbial community and soil structure in soda saline-alkali soil under modified conditions. In this study, we examined the changes in soil physicochemical properties of saline–alkali soil altered by rice planting alone and by combined application of phosphogypsum in the Songnen Plain. The results demonstrated that phosphogypsum significantly improved the soil’s physicochemical properties; it notably reduced salinity and alkalinity while enhancing nutrient structure. Additionally, the utilization efficiency of carbon (C), nitrogen (N), and phosphorus (P) increased. Fungal community diversity also significantly improved, influenced mainly by soil water content (SWC), total organic carbon (TOC), soil organic matter (SOM), total nitrogen (TN) and sodium ion (Na+). TOC, SOM, TN, ESP, and Na+ served as the primary drivers affecting the fungal community. Our findings indicate that combining rice planting with phosphogypsum application effectively modifies saline–alkali soil, regulates fungal community structure, and enhances long-term soil health. Furthermore, the beneficial effects of phosphogypsum on saline–alkali soil persist for persists for several years, largely owing to its role in promoting microbial community growth.

Soil and foliar Si fertilization alters elemental stoichiometry and increases yield of sugarcane cultivars

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L−1 in soil during planting; sodium silicate spray at 40 mmol L−1 on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha−1) in stalk yield, 9.0% (12 Mg ha−1) in total recoverable sugar, and 20% (4 Mg ha−1) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality.

Silicon-phosphorus pathway mitigates heavy metal stress by buffering rhizosphere acidification

Heavy metal pollution threatens food security, and rhizosphere acidification will increase the bioavailability of heavy metals. As a beneficial element in plants, silicon can relieve heavy metal stress. However, less attention has been paid to its effects on plant rhizosphere processes. Here, we show that for Japonica (Nipponbare and Oochikara) and Indica (Jinzao 47) rice cultivars, the degree of root acidification was significantly reduced after silicon uptake, and the total organic carbon, citric acid, and malic acid concentrations in rice root exudates were significantly reduced. We further confirmed the results by q-PCR that the expressions of proton pump and organic acid secretion genes were down-regulated by 35–61 % after silicon treatment. Intriguingly, phosphorus allocation, an intensively studied mechanism of rhizosphere acidification, was altered by silicon treatment. Specifically, among total phosphorus in rice seedlings, the soluble proportion increased from 52.0 % to 61.7 %, while cell wall phosphorus decreased from 48.0 % to 32.3 %. Additionally, silicon-mediated alleviation of rhizosphere acidification has positive effects on relieving heavy metal stress. Simulation revealed that low acidification of the nutrient solution resulted in a decrease in bioavailable heavy metal concentrations, thereby reducing rice uptake. We further confirmed that the impediment of rhizosphere acidification led to free-state Cr3+ in solutions decreasing by 43 % and contributed up to 63 % of silicon's mitigation of Cr(III) stress. Overall, we propose a novel mechanism in which silicon reduces heavy metal absorption by increasing plant soluble phosphorus concentration and buffering rhizosphere acidification. This paper provides a unique insight into the role of silicon in plants and, more importantly, a theoretical reference for the rational application of silicon fertilizer to improve phosphorus utilization efficiency, alleviate heavy metal stress, and balance soil pH.

Invasive Wedelia trilobata Performs Better Than Its Native Congener in Various Forms of Phosphorous in Different Growth Stages.

At present, many hypotheses have been proposed to explain the mechanism of alien plants' successful invasion; the resource fluctuations hypothesis indicates that nutrient availability is a main abiotic factor driving the invasion of alien plants. Higher phosphorus utilization and absorption efficiency might be one of the important reasons for alien plants successful invasion. Wedelia trilobata, one of the notorious invasive weeds in China, possesses a strong ability to continue their development under infertile habitats. In this study, firstly, W. trilobata and its native congener, W. chinensis, were grown in various phosphorus forms to test their absorption efficiency of phosphorus. Secondly, the different responses of W. trilobata and W. chinensis to the insoluble phosphorus in three growth stages (at 30, 60, and 150 days cultivation) were also tested. The results showed that the growth rate, root morphology, and phosphorus absorption efficiency of W. trilobata under various insoluble, organic, or low phosphorus conditions were significantly higher than that of W. chinensis. During the short-term cultivation period (30 d), the growth of W. trilobata under insoluble and low phosphorus treatments had no significant difference, and the growth of W. trilobata in insoluble phosphorus treatment also had no significant effect in long-term cultivation (60 and 150 d). However, the growth of W. chinensis in each period under the conditions of insoluble and low phosphorus was significantly inhibited throughout these three growth stages. Therefore, invasive W. trilobata had a higher phosphorus utilization efficiency than its native congener. This study could explain how invasive W. trilobata performs under nutrient-poor habitats, while also providing favorable evidence for the resource fluctuations hypothesis.

Regulating method of microbial driving the phosphorus bioavailability in factory composting

Phosphorus bioavailability is essential for assessing compost quality. However, the effects of microbial and environmental factors on potentially active phosphorus (H2O-P + NaHCO3-Pi) in factory compost have not been investigated. The findings indicated that chicken manure had significantly higher available phosphorus (AP) and H2O-P + NaHCO3-Pi throughout the composting process than kitchen waste (P < 0.05). Chicken manure compost also exhibited higher α-microbial diversity. Novibacillus, Marinococcaceae and Bacillales were the core bacteria involved in bioavailable phosphorus conversion in both composts. The core bacteria in kitchen waste compost had a broader range of phosphorus metabolism functions. Moreover, moisture and pH were the key environmental factors that significantly influenced the bioavailable phosphorus (P < 0.05). These findings provide a scientific foundation for regulating the composting process and improving phosphorus utilization efficiency.

Comparative Transcriptome Analysis Reveals Key Genes and Pathways Associated with Phosphate-Sensitive Behaviors in Cunninghamia lanceolata (Lamb.) Hook.

Cunninghamia lanceolate (Lamb.) Hook. (Chinese fir) is one of the most important wood-producing species, supplying ~20% of commercial timber by plantations in China. However, the genetic potential of the bred variety is limited by soil degrading in the long term and requiring continuous replanting, and especially the shortage and supply of active and efficient phosphorus. Recently, great attention has been paid to the genotypic variation in phosphorus conversion and utilization efficiency by tree breeders. In this study, the morphological characteristics were used to evaluate the Chinese fir clonal Pi-efficiency stress. A Pi-tolerant clone and a Pi-sensitive clone were selected for RNA sequencing, respectively. In addition, gene function annotation and weighted correlation network analysis (WGCNA) were performed. A total of 60 hub genes were selected, combining phosphate accumulation under Pi-deficiency stress. We also used RNA-seq data to analyze the differences in the response of Pi-sensitive clones and Pi-tolerant clones to Pi-deficiency stress, and real-time quantitative polymerase chain reaction (RT-PCR) analyses were used to test the validity of transcriptome data. The present study provided new insights into the molecular mechanisms of Pi-efficient utilization in Chinese fir clones.

Comparative physiological and proteomic response to phosphate deficiency between two wheat genotypes differing in phosphorus utilization efficiency

Genetic variation in phosphorus utilization efficiency (PUE) widely exists among wheat genotypes. However, the underlying mechanisms are still unclear. Two contrasting wheat genotypes, Heng4399 (H4399) and Tanmai98 (TM98), were screened out from 17 bread wheat genotypes based on shoot soluble phosphate (Pi) concentrations. The TM98 had a significantly higher PUE than the H4399, especially under Pi deficiency. The induction of genes in the PHR1-centered Pi signaling pathway was significantly higher in TM98 than in H4399. Collectively, through a label-free quantitative proteomic analysis, 2110 high-confidence proteins were identified in shoots of the two wheat genotypes. Among them, 244 and 133 proteins were differentially accumulated under Pi deficiency in H4399 and TM98, respectively. The abundance of proteins related to nitrogen and phosphorus metabolic processes, small molecule metabolic process, and carboxylic acid metabolic process weas significantly affected by Pi deficiency in the shoots of the two genotypes. The abundance of proteins in energy metabolism, especially photosynthesis, was decreased by Pi deficiency in the shoots of H4399. Inversely, the PUE-efficient genotype TM98 could maintain protein abundance in energy metabolism. Moreover, the proteins involved in pyruvate metabolism, glutathione metabolism, and sulfolipid biosynthesis were significantly accumulated in TM98, which probably contributed to its high PUE. SignificanceImproving the PUE of wheat is urgent and crucial for sustainable agriculture. Genetic variation among wheat genotypes provides materials for exploring the underlying mechanisms for high PUE. This study selected two wheat genotypes with contrasting PUE to reveal the differences in the physiological and proteomic responses to phosphate deficiency. The PUE-efficiency genotype TM98 greatly induced the expression of genes in the PHR1-centered Pi signaling pathway. Subsequently, the TM98 could maintain the abundance of proteins related to energy metabolism and enhance the abundance of proteins involved in pyruvate metabolism, glutathione metabolism, and sulfolipid biosynthesis to increase PUE under Pi deficiency. The differentially expressed genes or proteins between the genotypes with contrasting PUE would provide potential and basis for breeding wheat varieties with improved phosphorus use efficiency.

Biochemical and Molecular Responses Underlying the Contrasting Phosphorus Use Efficiency in Ryegrass Cultivars.

Improving plant ability to acquire and efficiently utilize phosphorus (P) is a promising approach for developing sustainable pasture production. This study aimed to identify ryegrass cultivars with contrasting P use efficiency, and to assess their associated biochemical and molecular responses. Nine ryegrass cultivars were hydroponically grown under optimal (0.1 mM) or P-deficient (0.01 mM) conditions, and P uptake, dry biomass, phosphorus acquisition efficiency (PAE) and phosphorus utilization efficiency (PUE) were evaluated. Accordingly, two cultivars with high PAE but low PUE (Ansa and Stellar), and two cultivars with low PAE and high PUE (24Seven and Extreme) were selected to analyze the activity and gene expression of acid phosphatases (APases), as well as the transcript levels of P transporters. Our results showed that ryegrass cultivars with high PAE were mainly influenced by root-related responses, including the expression of genes codifying for the P transporter LpPHT1;4, purple acid phosphatase LpPAP1 and APase activity. Moreover, the traits that contributed greatly to enhanced PUE were the expression of LpPHT1;1/4 and LpPHO1;2, and the APase activity in shoots. These outcomes could be useful to evaluate and develop cultivars with high P-use efficiency, thus contributing to improve the management of P in grassland systems.

Assessing phosphorus efficiency and tolerance in maize genotypes with contrasting root systems at the early growth stage using the semi‐hydroponic phenotyping system

AbstractBackgroundDevelopment of an evaluation tool to determine genotypic variation in phosphorus (P) utilization efficiency is essential to ensure crop productivity and farmers’ income under low P environments.AimsThis study aimed to develop an evaluation tool to determine genotypic variation in low‐P tolerance and P use efficiency under low P environments.MethodsRoot response and P efficiency traits in 20 maize genotypes with contrasting root systems were assessed 32 days after transplanting into the semi‐hydroponic root phenotyping system under low P (10 µM) or optimal P (200 µM) supply.ResultsCompared to optimal P, low P supply increased root‐to‐shoot biomass ratio by 48.7% (shoot dry weight decreased by 20.0% and root dry weight increased by 20.6%). Low P supply increased total root length by 17.8% but decreased primary root depth, with no significant change in lateral root number across all genotypes. Low P stress enhanced P utilization efficiency. Based on genotypic variation and correlations among the 17 measured plant traits in response to low P stress, nine traits were converted to low‐P tolerance coefficients (LPTC), compressed by principal component analysis. The three principal component scores were extracted for hierarchical cluster analysis and classified the 20 genotypes into three groups with different P efficiency, including two P‐efficient genotypes and nine P‐inefficient genotypes.ConclusionsThe study demonstrated genotypic variation in response to low P stress. The P‐efficient genotypes with higher LPTC values better adapted to low P environments by adjusting root architecture and re‐distributing P and biomass in plant organs. The systematic cluster analysis using selected traits and their LPTC values can be used as an evaluation tool in assessing P efficiency among the genotypes.

Transcription factor OsNAC016 negatively regulates phosphate-starvation response in rice

Phosphate (Pi), the main form of inorganic phosphorus that can be absorbed by plants, is one of the most limiting macro-nutrients in plants. However, the underlying molecular mechanism determining how plants sense external Pi levels and reprogram transcriptional and adaptive responses is incompletely understood. At present, few rice NAC members have been reported to be involved in the signaling pathways of Pi homeostasis in plants. Here, our research demonstrated that OsNAC016, a Pi-starvation responsive gene in rice, was regulated by PHOSPHATE STARVATION RESPONSE protein 1 (OsPHR1) and OsPHR4. Under Pi-starvation stress, the root growth of OsNAC016-overexpression lines was inhibited more severely, and overexpression plants had lower Pi content than wild type, while osnac016 mutant was hyposensitive to Pi starvation, indicating that OsNAC016 negatively modulates rice Pi-starvation response. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) analysis and transient transactivation assays indicated that OsNAC016 could activate the SPX-domain-containing protein 2 (OsSPX2) gene through binding to its promoter. Further, we found that Pi starvation enhanced OsNAC016 binding to the OsSPX2 promoter, thus strongly promoting OsSPX2 expression. At the same time, Pi starvation induced OsNAC016 protein accumulation in plants. Moreover, similar to OsSPX2, OsNAC016 negatively regulates leaf inclination by repressing the cell elongation in lamina joint in rice under Pi-starvation stress. Together, our findings demonstrate that OsNAC016 negatively regulates rice phosphate-starvation response and leaf inclination by activating OsSPX2 expression under Pi-starvation conditions. These data provide a strategy to create smart crops with ideal shoot architecture and high phosphorus utilization efficiency.

Improving radish phosphorus utilization efficiency and inhibiting Cd and Pb uptake by using heavy metal-immobilizing and phosphate-solubilizing bacteria

Phosphate-solubilizing bacteria play a key role in increasing plant growth as potential suppliers of soluble phosphorus and have great potential for the remediation of heavy metal-polluted soils. However, the soil and microbiological mechanisms by which phosphate-solubilizing bacteria prevent heavy metal absorption in radish have not been adequately studied. Here, the mechanisms of phosphorus solubilization, Cd and Pb immobilization, and the inhibition of heavy metal absorption by phosphate-solubilizing bacteria were studied in radish through solution adsorption and pot experiments. Two phosphate-solubilizing bacteria with high Cd and Pb removal rates (46.9–97.12 %), Klebsiella sp. M2 and Kluyvera sp. M8, were isolated. The soluble phosphorus content released by strains M2 and M8 was 265–277 mg L−1, achieved by secreting oxalic acid, ascorbic acid, citric acid, and succinic acid in an inorganic phosphorus medium containing 3 mg L−1 Cd and 5 mg L−1 Pb. Furthermore, these two functional strains induced the formation of Pb2(PO4)2, Cd(PO3)2, Fe2Pb3(PO4)2, CdS, and PbS precipitates that immobilized Cd and Pb in the solution. In general, strains M2 and M8 inhibited the absorption of Cd and Pb by radish by the following mechanisms: i) bacterial cell wall adsorption, ii) induction of Pb2(PO4)2, Cd(PO3)2, Fe2Pb3(PO4)2, CdS, and PbS precipitation in the solution/soil, iii) increases in the Ca2P and FeP contents in the radish rhizosphere, and iv) the promotion of bacterial community enrichment toward phosphorus-solubilizing and plant growth-promoting properties (Ramlibacter, Enterobacter, Bacillus, Gemmatimonas, and Lysinibacillusin) in the radish rhizosphere. These results provide bacterial resources and technical approaches to heavy metal pollution amelioration and efficient phosphorus fertilizer use in farmland.

Genetic Variation for Traits Related to Phosphorus Use Efficiency in Vigna Species

Phosphorus (P) is a major limiting nutrient reducing crop yields especially in weathered soils of the subtropics and tropics. P exhibits poor mobility and availability to plants in soil. To overcome P deficiency in soil, phosphatic fertilizers are added. Global phosphate rock reserves are finite, and the addition of phosphatic fertilizers is not financially and ecologically sustainable. Mungbean (Vigna radiata (L.) Wilczek) is important grain legume for nutritional security. Attempts are being made to develop mungbean varieties with better P-use efficiency through enhanced P uptake and utilization. In the present study, 327 accessions of 18 Vigna species were examined for inter- and intra-specific variation for traits related to phosphorus uptake and utilization efficiency under hydroponic conditions at two levels of phosphorus. Significant species-specific variation was recorded for studied traits. Among the studied Vigna species, mungbean exhibited higher phosphorus use efficiency. Seven mungbean genotypes (IC 251950, IC 585931, V1002532AG, IC 371653, IC 331615, V1001400AG, and V1000532BG) were found to be promising for both PupE and PutiE. Using mean and standard deviation as criteria, mungbean genotypes identified with high phosphorus-use efficiency include IC 25950 and IC 583664. Mungbean genotypes KPS 1546, IC 277060, IC 697141, IC 343440, and Pusa 0831 were identified based on the stress tolerance index as genotypes that performed better under P stress. Cultivated species revealed higher PUE in comparison withwild forms. The most promising genotype identified from this study for PUE can be used as a parent for the development of a mapping population of mungbean for understanding genetics of PUE under a low-phosphorus environment.