Uptake Of Rice Research Articles

Response of soil nitrogen mineralization, nitrification and denitrification to milk vetch (Astragalus sinicus L.) application in a paddy field

We conducted incubation experiments with a paddy soil collected from a long-term field experiment to explore the effect of Chinese milk vetch (Astragalus sinicus L., CMV) application on potential nitrogen (N) denitrification (PDA), nitrification (PNA), mineralization (PNM), soil chemical properties, microbial communities, enzyme activities, yields and nutrient uptake of rice under different fertilization treatments. Five treatments were included: no chemical fertilizers (C0), chemical fertilizers (C100), Chinese milk vetch (M), CMV combined with 100% chemical fertilizers (MC100) and with 80% chemical fertilizers (MC80). Results showed that the M, MC100, and MC80 treatments significantly increased PNM and PNA compared with the C100 treatment (P < 0.05). Meanwhile, the CMV application significantly increased total N, microbial biomass N, and carbon (C) concentrations, the abundances of the bacterial phylum Actinobacteria, and the genera Bradyrhizobium, Mycobacterium, Streptomyces and Reyranella, N-acetyl-glucosaminidase (NAG) activity, yields and N nutrient uptake of rice grain compared with the C100 treatment (P < 0.05). Correlation analyses indicated that grain yield and N uptake of rice, soil total N, microbial biomass C and N, the bacterial phylum Actinobacteria, the genera Bradyrhizobium, Mycobacterium, Streptomyces, Reyranella, and NAG were significantly correlated with PNM under different fertilization regimes, while microbial biomass C and N, Actinobacteria, Bradyrhizobium, and Reyranella were positively related to PNA (P < 0.05). Together, the application of CMV alone or in combination with chemical fertilizers can improve soil properties and rice growth, which may accelerate N mineralization and nitrification in this soil.

Impact of Biochar and Water Regimes on Arsenic Transfer and Uptake in Rice: Insights into Transporter Behaviour and Soil–Plant Dynamics

Impact of Biochar and Water Regimes on Arsenic Transfer and Uptake in Rice: Insights into Transporter Behaviour and Soil–Plant Dynamics

Diversity and transcription of genes involved in respiratory As(V) reduction and As(III) methylation in Japanese paddy soils

BackgroundArsenic (As) metabolism by soil microorganisms has an impact on As geochemical cycling in paddy soils, which in turn affects As uptake in rice. However, little is known about the key microorganisms involved in this process in Japanese paddy soil.ResultsTotal RNA was extracted from Japanese paddy soils with different levels of dissolved As under flooded conditions, and the transcription of As metabolic genes (arrA, ttrA and arsM) was analyzed via a metatranscriptomic approach. The results showed that ttrA was the predominant respiratory arsenate reductase gene transcribed in these soils rather than arrA, suggesting that ttrA contributes to the reductive dissolution of As. The predominant taxa expressing ttrA differed among soils but were mostly associated with genera known for their iron- and/or sulfate-reduction activity. In addition, a wide variety of microorganisms expressed and upregulated arsM approximately 5.0- to 13.2-fold at 9 d compared with 3 d of incubation under flooded conditions in flasks.ConclusionsOur results support the involvement of microbial activity in the geochemical cycling of As in Japanese paddy soils and suggest that ttrA may be one of the key genes involved in the formation of arsenite, an inorganic species taken up by rice.

Involvement of plasma membrane H+-ATPase in the nitrate-nutrition uptake and utilization in indica rice

Utilization of nitrogen by crops is essential for sustainable agriculture. The transport of nitrate (NO3−) across the plasma membrane is a critical gateway for N uptake and subsequent utilization. This process requires proton (H+) coupled cotransport, which is driven by proton motive force, provided by plasma membrane (PM) H+-ATPase. In this report, two indica rice varieties [Meixiangzhan 2 (MXZ) and Jifengyou 1002 (JFY)] in South China were selected and cultivated in hydroponic solution with 0.5 mM or 2.0 mM NO3− as the N source. The JFY exhibited stronger growth with higher biomass than MXZ under both 0.5 mM and 2.0 mM NO3−. PM H+-ATPase activity of JFY roots was significantly higher than that of MXZ. The higher PM H+-ATPase activity in JFY was consistent with a higher abundance of PM H+-ATPase protein and higher transcription levels of OSAs, such as OSA2, OSA7 and OSA8 in roots, OSA3, OSA7 and OSA8 in leaves. The expression of nitrate transporters (OsNRT1;1b, OsNRT2.1, OsNRT2.2, and OsNAR2.1) were also higher in roots or shoots of JFY than those in MXZ. Under 0.5 mM and 2.0 mM NO3−, the NO3− absorption and translocation rate, nitrate content, as well as nitrate reductase (NR) activity were all significantly higher in JFY, as compared to those in MXZ. Taken together, in JFY and MXZ, a higher level of PM H+-ATPase protein and higher activity coupled with greater efficiency in nitrate uptake, translocation and assimilation, suggesting the existence of a close correlation between PM H+-ATPase and nitrate utilization in indica rice. PM H+-ATPase may one of the elite genes that can contribute to nitrate use efficiency in rice.

Co-application of fly ash and zeolite increases N uptake but decreases P uptake and biomass of rice fertilized with fermented liquid manure

ABSTRACT Fermented liquid pig manure (LPM) can be used as a nutrient source to replace synthetic fertilizers (SF). However, concerns remain regarding nitrogen (N) and phosphorus (P) losses from rice (Oryza sativa L.) paddies fertilized with LPM. Fly ash (FA) has a high calcium content (Ca) and zeolite (Z) has a high negative-charge; thus, they can immobilize P and N through the fixation of P with Ca and NH4 + onto negatively charged sites, respectively. This study investigated the effects of the co-application of FA and Z (FAZ) on the nutrient availability and growth of rice fertilized with LPM. Four treatments were evaluated: no input (control), synthetic fertilizer (SF), and LPM at two levels, with or without FAZ application, for 104 days. The pH (pHwater), electrical conductivity (ECwater), N (Nwater), and P (Pwater) concentrations in the ponding water of rice fields were analyzed 18 times during rice growth. The rice biomass and uptake of N and P were measured, and the concentrations of mineral N and available P in soil were determined after harvest. LPM application increased (p < 0.001) N and P availability in the absence of FAZ, leading to rice biomass comparable to that of SF. However, FAZ diminished the fertilization effects of LPM on rice growth. The Nwater decreased by 50% and the rice uptake of N increased by 6% after FAZ application, probably because of the retention of N by Z and its subsequent release. By contrast, FAZ increased (p < 0.001) soluble Pwater (85% for LPMS) and decreased (p = 0.004) P uptake (8%–40%), reducing the rice biomass by 20%–25%. The decreased P uptake is probably due to the strong immobilization of P by FA. Therefore, it is cautioned that P-limitation through immobilization of P by FA under alkaline conditions may hinder rice growth in FAZ-amended paddy fertilized with LPM. An appropriate application rate of FA for improved P nutrition needs to be explored.

Improvement of growth and nutrient uptake of upland rice grown on degraded acid soil with the application of liquid organic fertilizer

This research aimed to determine the effectiveness of several types of liquid organic fertilizer (LOF) derived from plant waste and the dose of P fertilizer on the growth and yield of upland rice on degraded acid soil. The treatments consisted of two factors. The first factor (A) was several types of LOF consisting of A1 (control), A2 (LOF containing isolates of P-solubilizing bacteria), A3 (LOF-banana waste), and A4 (A2+A3). The second factor (B) was fertilizer doses consisting of B1 (50% of the recommended dose of P fertilizer), B2 (75% of the recommended dose of P fertilizer), and B3 (100% of the recommended dose of P fertilizer). The treatment combinations were arranged in a factorial randomized block design with three replications. The research results showed that applying either LOF-banana waste or the mixture of LOF-banana waste and LOF-containing isolates of P-solubilizing bacteria improved plant height, the number of tillers, and N and P uptake by the plant. The rice grain yields among the treatments were not significantly different, but the highest rice grain yield (139.8 g/pot) was obtained at the treatment of the mixture of LOF-P isolate + LOF-banana waste (A2+A3 treatments). The 75% of the recommended dose of P fertilizer was not significantly different from 100% P fertilizer with LOF on growth and yield upland rice and nutrient uptake by the plant.

Applying Boron Fertilizer at Different Growth Stages Promotes Boron Uptake and Productivity in Rice

Boron (B) is an essential micronutrient for plant growth and yield. We investigated the optimal growth stage for B fertilizer application for to improve rice production. The study was conducted using a 2 × 4 factorial design in a randomized complete block during the rainy season of 2022. We utilized two premium Thai rice varieties Khao Dawk Mali 105 (KDML105) and Pathum Thani 1 (PTT1), and four soil B fertilizer treatments: a control (no B application), B application at the tillering stage, B application at the flowering stage, and B application at both the tillering and flowering stages. The results showed that the application of B fertilizer at the flowering stage and at both the tillering and flowering stages increased grain yield by 25.0% and 34.0% in KDML105, respectively. In contrast, the grain yield of PTT1 did not show a response to B application. The increased grain yield in KDML105 was attributed to an increased number of panicles per plant and a higher filled grain rate, which was due to the elevated B concentration in all plant parts and the total B uptake, particularly when B was applied at the flowering and tillering stages. Notably, B application increased the fertilized grain rates and reduced the proportion of unfertilized grains, a phenomenon that corrected with the increased B concentration across all plant parts. The total B uptake ranged from 5.11 to 15.85 mg/m2 in KDML105 and from 8.37 to 24.26 mg/m2 in PTT1, with the highest total B uptake observed when B was applied at both the tillering and flowering stages for both rice varieties.

Impact of nitrogen and potassium management on growth, nutrient uptake and nutrient use efficiency of rice under semi dry condition

The current study was aimed to search effect of nitrogen doses and time of application on performance of semi dry rice. The field experiment was conducted at College of Agriculture,(V. C. Farm), Mandya, University of Agricultural Sciences, Bengaluru during kharif 2019 and 2020, which comes under Southern Dry Zone of Karnataka (Zone-VI) to study the response of semi dry rice on growth and nutrient use efficiency under two doses of nitrogen and potassium doses (100% RDNK, 125%RDNK) as main treatments and seven time of application as sub treatments.The result revealed that higher SPAD meter reading (37.77) and nutrient uptake (77.90, 27.98 and 24.14 kg ha-1)was seen in 125% RDNK and higher nitrogen and potassium use efficiency was observed in 100%RDNK (49.30, and 98.59 kg kg-1 nutrient applied respectively). Where as in split application, higher SPAD meter reading (38.90), nutrient uptake (81.82, 29.57 and 25.35kg ha-1)and nutrient use efficiency (49.86, 11.33 and 99.73 kg kg-1 nutrient applied respectively) was recorded in N at 4 splits as, 25% each at sowing, early tillering, tillering and panicle initiation, K at 2 splits (50% at basal and 50% at panicle initiation) compared to rest of the application. Hence application of application of 125% RDNK, N at 4 splits as, 25% each at sowing, early tillering, tillering and panicle initiation, K at 2 splits (50% at basal and 50% at panicle initiation) is the appropriate time for rice production Southern Dry Zone of Karnataka.

Effect of Integrated nutrient management practices on nutrient uptake, yield and quality of improved black kavuni rice variety (CO57)

The rising demand for high-quality rice and rice products motivates farmers to produce traditional rice varieties. Rice production needs to be substantially increased with suitable nutrient management practices to meet the demand. Hence, the present study was carried out to evaluate the influence of integrated nutrient management practices on nutrient yield and quality of improved black kavuni rice. The research was conducted during the Early kar (April-August 2023) and Late samba (September - January 2023-24) seasons in a randomized block design (RBD) with three replications and twelve treatments consisting of N in equivalent basis with organic manure and inorganic fertilizers and one control. Based on an N equivalent basis, the required quantity of inorganic fertilizer, farmyard manure (FYM), vermicompost (VC) and poultry manure (PM) were applied to rice. Observations on nutrient uptake, yield and quality were recorded, and the data were analyzed using LSD at a 5% probability level for significance differences. The results revealed that higher nutrient uptake, yield and quality parameters of rice were recorded with 50% recommended dose of nitrogen through inorganic fertilizer + 50% recommended dose of nitrogen through VC + foliar spray of 0.5% ZnSO4 &amp; 1% FeSO4 at tillering, panicle initiation (PI) and flowering stage (T11).

Insights from a 19-year field study: optimizing long-term nutrient supply strategies for enhanced crop productivity and nutritional security in rice–wheat systems

What nutrient supply options can ensure maximum productivity and optimize the nutrient uptake of rice–wheat system (R-W system)? an experiment started in the year 1998 (19-year-old) to examine the impact of optimal nutrient supply (NS) strategies to maximize crop productivity and nutritional security in R-W system. To determine the best nutrient management strategies (BNMS), seven different NS methods were tested. These included (organic and mineral fertilizers), as well as combinations such as integrated plant nutrition system (IPNS), IPNS + B (berseem), and IPNS + C (cowpea), with the aim of enhancing the productivity and nutrient absorption of R-W system. Results showed that rice grain yield notably wide-ranging from 1.61 to 5.81 t ha−1 under different NS options and highest rice grain yield (mean of 19 years) was observed at IPNS + C (5.81 t ha−1), which was at par with IPNS (5.79 t ha−1), STCR (soil test crop response) (5.76 t ha−1) and IPNS + B (5.67 t ha−1) followed by 100% recommended dose fertilizer NPK (4.41 t ha−1), which equality with OF (organic farming) (4.04 t ha−1) and lowest was recorded in control plot (1.61 t ha−1). Wheat grain yield varied significantly from 1.43 to 5.86 t ha−1 under different NS options. The highest yield (mean of 19 years) was observed in treatments IPNS + B (5.86 t ha−1), IPNS (5.77 t ha−1), IPNS + C (5.48 t ha−1), and STCR (5.45 t ha−1), followed by OF at 4.49 t ha−1, NPK at 3.76 t ha−1, with the lowest in the control plot at 1.43 t ha−1. Additionally, total phosphorus and sulfur accumulation in rice (grain: 8.41 to 39.09 kg ha−1; straw: 6.02 to 23.54 kg ha−1) varied significantly across nutrient supply treatments. Overall, adoption of IPNS integration with legumes (IPNS + B and IPNS + C), can significantly improve productivity and nutrient accumulation in R-W systems. Incorporating legumes into farming practices is advised for sustained productivity and nutritional benefits.

The transcription factor OsNAC5 regulates cadmium accumulation in rice

Cadmium (Cd) is a hazardous heavy metal that threatens human health through the consumption of contaminated rice. To mitigate Cd accumulation in rice grains, it is crucial to reduce Cd uptake. Nevertheless, the transcriptional mechanisms governing Cd uptake in rice remain largely unknown. This research identifies the transcription factor OsNAC5 in Oryza sativa as a positive regulator of the Cd transporter gene OsNRAMP1, thereby influencing Cd uptake. OsNAC5 is predominantly expressed in the roots, resides in the nucleus, and is upregulated by Cd-induced hydrogen peroxide (H2O2). Knocking out OsNAC5 results in lower Cd concentrations in both shoots and roots and heightens sensitivity to Cd. The expression of OsNRAMP1, enhanced by Cd stress, is dependent on OsNAC5. OsNAC5 binds to "CATGTG" motifs in the OsNRAMP1 promoter, activating its expression. The loss of OsNAC5 function leads to reduced Cd accumulation in rice grains. Our findings provide insights into the transcriptional regulation of Cd stress response in rice and propose biotechnological strategies to lower Cd uptake in crops.

Synergistic mitigation of cadmium stress in rice (Oryza sativa L.) through combined selenium, calcium, and magnesium supplementation.

Rice is susceptible to cadmium (Cd) accumulation, which poses a threat to human health. Traditional methods for mitigating moderately contaminated soils can be impractical or prohibitively expensive, necessitating innovative approaches to reduce Cd uptake in rice. Nutrient management has emerged as a promising solution by leveraging the antagonistic interactions between nutrients and cadmium. However, the research on the synergistic effects of multiple nutrients on Cd toxicity in rice is limited. To address this limitation, pot experiments was utilized to investigate the combined effects of selenium (Se), calcium (Ca), and magnesium (Mg) denoted as (SeCM) on Cd uptake and translocation in rice. The synergistic application of SeCM reduced grain Cd levels by 55.0%, surpassing the individual effects of Se (42.1%) and CM (40.5%), and bringing Cd content below the safe consumption limits. SeCM treatment exhibited multiple beneficial effects: it decreased malondialdehyde (MDA) levels, enhanced catalase (CAT), peroxidase (POD) and glutathione (GSH) enzyme activities, limited Cd translocation from roots to shoots, promoted iron plaque formation, and reduced Cd transfer from soil to iron plaque and subsequently to rice grains. Correlation analysis revealed strong negative relationships between rice Cd content, Cd translocation factors, and the translocation factors of selenium, calcium, and magnesium. These findings suggest that selenium, calcium, and magnesium collaboratively mitigate Cd toxicity through antagonistic and competitive interactions. These nutrients enhance the uptake of beneficial elements, while competitively inhibiting the translocation and accumulation of Cd in rice plants. SeCM application offers a promising strategy for producing nutrient-rich, and Cd-safe rice in contaminated soils.

The Impact of Integrated Weed Management Practices on Nutrient Uptake in Rice (Oryza sativa L.)

The study investigated the impact of integrated weed management practices on nutrient uptake in rice (Oryza sativa L.) and weeds at 90 days after transplanting (DAT) over the 2022 and 2023 growing seasons at the Crop Research Centre (CRC) farm of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut. Various weed control strategies, including the application of pre-emergence and post-emergence herbicides combined with manual weeding, were evaluated for their effectiveness in enhancing the uptake of essential nutrients such as nitrogen (N), phosphorus (P), and potassium (K) by rice, while also reducing nutrient loss to weeds. Among the strategies tested, the combination of Pyrazosulfuron at 150 g active ingredient per hectare (a.i. ha⁻¹) as a pre-emergence herbicide and Penoxsulam at 22 g a.i. ha⁻¹ as a post-emergence herbicide, supplemented with one manual weeding at 40 DAT, proved to be the most effective. This approach resulted in the highest nutrient uptake by rice and the lowest nutrient uptake by weeds. In this treatment, nitrogen uptake in the rice grains reached 62.7 kg per hectare in 2022 and 67.4 kg per hectare in 2023, significantly outperforming other treatments. The weed-free treatment, which involved complete weed eradication, also demonstrated high nutrient absorption, highlighting the importance of thorough weed control for optimal rice growth. Conversely, the untreated weedy check, where no weed control was implemented, led to the highest nutrient uptake by weeds, severely limiting the availability of nutrients for the rice crop. Manual weeding alone, without the use of herbicides, showed moderate effectiveness but was less efficient compared to the integrated approach combining herbicides and hand weeding.

Effects of different phosphorus and potassium supply on the root architecture, phosphorus and potassium uptake, and utilization efficiency of hydroponic rice

Phosphorus (P) and potassium (K) affect seedling growth, root configuration, and nutrient uptake in hydroponic rice, but there are few studies on all growth stages of rice. The purpose of this experiment was to determine the response characteristics of root morphology, plant physiology, and P and K uptake and utilization efficiency to different supplies of P and K. Two local conventional rice varieties (Shennong 265 and Liaojing 294) were used as experimental materials across four treatments, including HPHK (sufficient P and K supply), HPLK (sufficient P supply under low K levels), LPHK (sufficient K supply under low P levels) and LPLK (low P and K levels) in a hydroponic setting. The results showed that HPHK and HPLK significantly decreased the acid phosphatase activity of leaves and roots from full heading to filling stages when compared to LPHK and LPLK. Sufficient supply of P or K significantly increased the accumulation of P and K (aboveground, leaves, stem sheath, and whole plant) and root morphological parameters (root length, root surface area, total root volume, and tips) during major growth stages when compared to LP or LK levels. HPHK was significantly higher than other treatments in terms of dry weight and the root activity at the main growth stage, P and K uptake rates in nutrient solutions at various stages, related P and K efficiency at the maturity stage, yield, effective panicle number, and grain number per panicle. In addition, the effect of HPHK on the above indexes were significantly greater than those of single sufficient supply of P or K. In conclusion, HPHK can improve plant configuration, increase plant P and K absorption and root activity, and increase rice yield and related P and K utilization efficiency.

Cadmium distribution in rice: Understanding the role of plant nodes and growth stages

Cadmium (Cd) contamination in farmland poses a significant threat to food security in staple crops, especially rice. Using a mix of hydroponic and soil culture methods, stable isotope tracers, and advanced analytical techniques, this study elucidated the mechanisms of Cd uptake, translocation, and accumulation in rice throughout different growth stages. Despite a notable linear correlation between soil DTPA (diethylene-triaminepentaacetic acid)-Cd and the total Cd concentration of rice, our findings showed that the influence of soil Cd level on the proportion of Cd in grain was negligible. The study highlighted the dynamic response of Cd distribution within plant nodes to changes in DTPA-extractable Cd. Heading stage (HS) and mature stage (MS) were critical for Cd uptake and upward transport in rice, and the contribution of Cd absorption in brown rice was 28.61% and 40.16%, respectively. Moreover, the distribution of Cd in nodes showed how important nodes are for controlling and redistributing Cd in rice. In the HS, the lower node had a function in re-transporting, whereas in the MS, there was a considerable redistribution of Cd in the upper node.These insights can help us understand rice Cd dynamics and develop agronomic techniques and rice cultivars that minimize Cd accumulation.

Uptake and Accumulation of Cobalt Is Mediated by OsNramp5 in Rice.

Cobalt (Co) contamination in soils potentially affects human health through the food chain. Although rice (Oryza sativa) as a staple food is a major dietary source of human Co intake, it is poorly understood how Co is taken up by the roots and accumulated in rice grain. In this study, we physiologically characterized Co accumulation and identified the transporter for Co2+ uptake in rice. A dose-dependent experiment showed that Co mainly accumulated in rice roots. Further analysis with LA-ICP-MS showed Co deposited in most tissue of the roots, including exodermis, endodermis and stele region. Co accumulation analysis using mutants defective in divalent cation uptake showed that Co2+ uptake in rice is mediated by the Mn2+/Cd2+/Pb2+ transporter OsNramp5, rather than OsIRT1 for Fe2+ and OsZIP9 for Zn2+. Knockout of OsNramp5 enhanced tolerance to Co toxicity. Heterologous expression of OsNramp5 showed transport activity for Co2+ in Saccharomyces cerevisiae. Co2+ uptake was inhibited by either Mn2+ or Cd2+ supply. At the reproductive stage, the Co concentration in the straw and grains of the OsNramp5 knockout lines was decreased by 41%-48% and 28%-36%, respectively, compared with that of the wild-type rice. The expression level of OsNramp5 in the roots was not affected by Co2+. Taken together, our results indicate that OsNramp5 is a major transporter for Co2+ uptake in rice, which ultimately mediates Co accumulation in the grains.

Effect of Chinese Milk Vetch on Zinc Content and Zinc Absorption of Rice in Purple Tidal Mud Soil

Rice is a staple food crop that feeds billions globally. Addressing Zn deficiency in rice is crucial for improving nutrition and food security. Zn deficiency in rice is a widespread issue, especially in purple tidal mud substrates, which often exhibit low Zn availability. The objective of this two-year pot study was to explore the relationship between Zn content, yield components, and Zn absorption in rice grown in purple tidal mud substrate with varying amounts of Chinese milk vetch (Astragalus sinicus L.) incorporation. The experimental design consisted of seven treatments: an unfertilized control, a Chinese milk vetch control, a chemical fertilizer control, and four treatment variations incorporating Chinese milk vetch alongside chemical fertilizer applications. The results indicated that planting and applying Chinese milk vetch improved the grain yield of rice in purple tidal mud substrate, and the yield increased with higher levels of Chinese milk vetch applied. The increased grain yield resulted in higher Zn absorption in rice grains. The application of Chinese milk vetch, both solely and in combination with chemical fertilizers, had varying effects on zinc uptake and grain zinc formation efficiency in early and late rice, with the control and low-level Chinese milk vetch treatments generally exhibiting the highest performance across the two-year period. By introducing Chinese milkvetch following the use of chemical fertilizers, the Zn content in rice grains increased starting from the second year. The treatment with Chinese milkvetch applied at a rate of 2.25 t/hm2 showed the best results in increasing the Zn content in rice grains. The increase in Zn content and Zn uptake by the rice plants gave rise to a lowering of the DTPA-extractable Zn content in the purple tidal mud substrate. Sole Chinese milk vetch application and using Chinese milk vetch following chemical fertilizer application both increased Zn content extracted by DTPA in purple tidal mud substrate.

Alleviation of cadmium uptake in rice (Oryza sativa L.) by iron plaque on the root surface generated by Providencia manganoxydans via Fe(II) oxidation.

Iron plaque is believed to be effective in reducing the accumulation of heavy metals in rice. In this work, a known soil-derived Mn(II)-oxidizing bacterium, LLDRA6, which represents the type strain of Providencia manganoxydans, was employed to investigate the feasibility of decreasing cadmium (Cd) accumulation in rice by promoting the formation of iron plaque on the root surface. Firstly, the Fe(II) oxidation ability of LLDRA6 was evaluated using various techniques including Fourier Transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, phenanthroline photometry, and FeS gel-stabilized gradient assays. Subsequently, the formation of iron plaque on the root surface by LLDRA6 was investigated under hydroponic and pot conditions. Finally, Cd concentrations were examined in rice with and without iron plaque through pot and paddy-field tests. The results showed that LLDRA6 played an efficient role in the formation of iron plaque on seedling roots under hydroponic conditions, generating 44.87 and 36.72g kg- 1 of iron plaque on the roots of Huazhan and TP309, respectively. In pot experiments, LLDRA6 produced iron plaque exclusively in the presence of Fe(II). Otherwise, it solely generated biofilm on the root surface. Together with Fe(II), LLDRA6 effectively reduced the concentrations of Cd in Huazhan roots, straws and grains by 25%, 46% and 44%, respectively. This combination also demonstrated a significant decrease in the Cd concentrations of TP309 roots, straws and grains by 20%, 52% and 44%, respectively. The data from the Cd translocation factor indicate that obstruction of Cd translocation by iron plaque predominantly occurred during the root-to-straw stage. In paddy-field tests, the Cd concentrations of grains harvested from the combination treatment of LLDRA6 and Fe(II) exhibited a decline ranging from 40 to 53%, which fell below the maximum acceptable value for Cd in rice grains (0.2mg kg- 1) as per the China national standard for food security (GB2762-2017). Meanwhile, the relevant phenotypic traits regarding the yield were not adversely affected. These findings have demonstrated that LLDRA6 can impede the uptake of Cd by rice in Cd-contaminated soils through the formation of iron plaque on roots, thus providing a promising safe Cd-barrier for rice production.

Nitrogen Uptake and Use Efficiency of Aerobic Rice as Affected by Different Nitrogen Management: A Review

Nitrogen Uptake and Use Efficiency of Aerobic Rice as Affected by Different Nitrogen Management: A Review

Hexavalent chromium uptake in rice (Oryza sativa L.) mediated by sulfate and phosphate transporters OsSultr1;2 and OsPht1;1

Chromium (Cr) soil contamination is a critical global environmental concern, with hexavalent chromium (Cr[VI]) being especially perilous due to its high mobility, bioavailability, and phytotoxicity. This poses a significant threat to the cultivation of crops, particularly rice, where the mechanisms of Cr(VI) absorption remain largely unexplored. This study uncovered a competitive interaction between Cr(VI) and essential nutrients—sulfate and phosphate during the uptake process. Notably, deficiencies in sulfate and phosphate were associated with a marked increase in Cr(VI) accumulation in rice, reaching up to 76.5 % and 77.7 %, respectively. Employing q-PCR, this study identified significant up-regulation of the sulfate transporter gene, OsSultr1;2, and the phosphate transporter gene, OsPht1;1, in response to Cr(VI) stress. Genetic knockout studies have confirmed the crucial role of OsSultr1;2 in Cr(VI) uptake, with its deletion leading to a 36.1 % to 69.6 % decrease in Cr uptake by rice roots. Similarly, the knockout of OsPht1;1 resulted in an 18.1 % to 25.7 % decrease in root Cr accumulation. These findings highlight the key role of the sulfate transporter OsSultr1;2 in Cr(VI) uptake, with phosphate transporters also contributing significantly to the process. These insights are valuable for developing rice varieties with reduced Cr(VI) accumulation, ensuring the safety of rice grain production.