Flooded Soil Research Articles

Influence of soil drying followed by flooding on micronutrient solubilization

AbstractFlooding is known to solubilize soil nutrients, particularly those associated with redox‐sensitive metals (Fe/Mn). Both soil flooding and drying are becoming more common due to climate change, but it is not clear how soil drying prior to flooding influences nutrient solubilization in soils, compared with flooding of already moist soils. This study was designed to examine how soil drying followed by extended flooding might influence solubilization of micronutrient metals (Fe, Mn, Cu, Co, Zn and Ni). A series of laboratory mesocosm experiments was carried out by flooding samples of two contrasting grassland soils, which had each been either dried (40°C for 10 days) or kept at field moisture conditions (25%, w/w). The flooding of dried soils generally resulted in higher concentrations of the micronutrients (Mn, Co, Ni and Cu) in the water columns relative to their moist‐flooded counterparts. The results demonstrate that the flooding‐induced variations in pH and redox potential influence solubilization of micronutrients in the soils. The mobilization of Co and Ni appeared to be controlled by redox‐driven reductive dissolution of Fe/Mn minerals. This was supported by significant (p < .001) negative correlations between redox and metals: Co (r = −.712), Ni (r = −.784) and the positive correlations between Fe and metals: Co (r = .763) and Ni (r = .714) and between Mn and other metals: Co (r = .909) and Ni (r = .811). However, there were no significant correlations of Zn and Cu with Fe and Mn. The results suggest that soil drying followed by flooding has the potential to promote greater solubilization of soil micronutrients compared with flooding of moist soils, with potential implications for soil fertility and catchment water quality under future changes in weather patterns driven by climate change.

Fate of bisphenol A (BPA) in a flooded soil-rice system

In this study, 14C-tracers were used to investigate the fate of BPA in flooded soil with or without rice plants during a complete growing period. In flooded soil, the dissipation of BPA (half-life 14.8 d) was accompanied by its mineralization (8.4% of the initially applied radioactivity) and the formation of non-extractable residues (NERs) in amounts (79.5%) similar to that formed under oxic conditions. The growth of rice significantly accelerated the dissipation of BPA in flooded soil, resulting in a reduction in both the half-life (5.6 d) and the amount of NERs (35.8%). Two non-polar metabolites were detected both in unplanted and in rice-planted soil. At rice harvest, 57.1% of the radioactivity had accumulated in rice plants, mainly as NERs (54.2%) rather than as extractable radioactivity (2.7%), and mainly in roots (34.5 ± 1.4%), stems (9.4 ± 1.1%), and leaves (8.8 ± 0.6%), with trace amounts in seeds (3.6 ± 0.3%) and seed shells (0.7 ± 0.05%). Our study thus demonstrates that the oxic-anoxic interface stimulates the dissipation of BPA in flooded soil. The link between the releasing of NERs in flooded soil and the uptake of BPA metabolites by rice should be considered in environmental risk assessments of agroecosystems.

Growth and Yield Comparison of Rice Plants Treated with Encapsulated Trichoderma asperellum (UPM 40) in Response to Drought Stress

During low rainfall periods, rice plants often face drought stress, which would significantly affect rice yield. One of the methods to mitigate the problem is incorporating rice plants with fungi such as Trichoderma. This study evaluated the effects of encapsulated Trichoderma asperellum (UPM 40) on the growth and yield of rice plants planted in saturated and flooded soil conditions in response to drought stress. A randomized complete block factorial design was implemented with four replications and two factors. The first factor was encapsulated T. asperellum (UPM 40) concentration of 0 and 5 g. The second factor was the soil condition: saturated and flooded soil. The drought stress was imposed by halting watering during early anthesis for 14 days and resumed afterward. One of the significant interaction effects detected was on the relative water content of rice plants planted in flooded soil conditions and treated with T. asperellum (UPM 40), where the value was 78.51%, higher than the control of 72.09%, which showed the ability of the fungus to help rice plants alleviate detrimental effects of drought stress and delay the onset of adverse effects of drought stress. Thus, it contributed to the crop’s simultaneous improvement in rice yield compared to untreated plants in saturated soil. Applying 5 g encapsulated T. asperellum (UPM 40) to the rice plants would perform best in flooded soil conditions during drought stress.

Effects of Biogas Slurry Application on Soil Microbial Communities Structure and Function During Wheat-rice Stubble Period

To reveal the effects of biogas slurry application on soil microbial community structure and function, a soil column experiment was constructed with three treatments[(no N addition, CM; conventional fertilization, SN; biogas slurry addition, SZ)]. The differences in composition, diversity, and structure of bacterial and fungal communities on day 1 and day 21 after soil flooding were evaluated, and their functions were predicted using Illumina high-throughput sequencing technology. The results of the analysis of α diversity showed that the fungal α-diversity indexes of CM, SN, and SZ treatments on day 1 were significantly higher than those on day 21, and there was no significant difference among the three treatments. However, the bacterial Simpson index differed among the three treatments on day 21, with SZ-21 showing a higher Simpson index but lower Chao1 index compared with those of SZ-21. The analysis of bacterial community structure showed that Firmicutes, Chloroflexi, and Actinobacteria in the SN-1 treatment were different from those in the other treatments on day 1, whereas the relative abundance of bacterial phyla in the SZ and SN treatments were similar on day 21. The analysis of fungal community structure showed that the relative abundance of Ascomycota and Zygomycota in the SZ-1 treatment were higher than those in the SN-1 and CM-1 treatments on day 1. The relative abundance of Ascomycota in the SN-21 and SZ-21 treatments were lower, whereas that of Zygomycota were higher compared with that in CM-21. The analysis of NMDS showed that the composition of bacterial and fungal communities in the SN and SZ treatments showed a gradually similar trend. The PICRUSt analysis showed that the function of the soil bacterial community was similar in the CM, SN, and SZ treatments. The FUNGuild function prediction reflected that the main differences in trophic type between the SN-21 and SZ-21 treatments occurred in saprotroph and pathotroph forms. Therefore, biogas slurry addition in the wheat-rice stubble stage could contribute to balancing soil nutrients and maintaining soil ecological function to a certain extent, but there may still be a risk of fungal disease.

The Study of the state of soil cover of the coastal zones of the Caspian Sea, subject to the influence of climatic and anthropogenic factors

This article is dedicated to research of climate impact change and human activity on ecosystems. It is expressed as metals which is called heavy pollution. It covers the coastal territory of northwestern regions of Apsheron. Pollution in the coastal regions of the Caspian Sea with toxic substances, is of great concern, periodic studies of these zones for the presence of heavy metals are necessary. For the first time, a comparative analysis of the content of heavy metals in the territories of the northwestern part of the Absheron was carried out and the hypothetical reasons for their accumulation were presented. The studied soils in the northwestern part of the peninsula were grouped the degree of the density of heavy metals. Zinc (78.62 mg/kg, at a depth of 0–20 sm) copper and cadmium (23.65 mg/kg and 0.92 mg/kg at a depth of 0–20 sm). The concentration of zinc and copper in the northwestern direction of Apsheron by 1.18 and 1.57 times, compared with the allowable norms for clarks. Under the impact of flooding of coastal zones by the waters of the Caspian Sea, the average content of heavy metals, Ni, Cd, Pb in flooded soils at a depth of 0-100 sm increased by 1.7 times.

Effects of soil habitat changes on antibiotic resistance genes and related microbiomes in paddy fields

The changes of paddy soil habitat profoundly affect the structure and function of soil microorganisms, but how this process drives the growth and spread of manure- derived antibiotic resistance genes (ARGs) after entering the soil is unclear. Herein, this study explored the environmental fate and behavior of various ARGs in the paddy soil during rice growth period. Results showed that most ARG abundances in flooded soil was lower than that in non-flooded soil during rice growth (decreased by 33.4 %). And soil dry-wet alternation altered microbial community structure in paddy field (P < 0.05), showing that Actinobacteria and Firmicutes increased in proportion under non-flooded conditions, and Chloroflexi, Proteobacteria and Acidobacteria evolved into the dominant groups in flooded soil. Meanwhile, the correlation between ARGs and bacterial communities was stronger than that with mobile genetic elements (MGEs) in both flooded and non-flooded paddy soils. Furthermore, soil properties, especially oxidation reduction potential (ORP), were proved to be an essential factor in regulating the variability of ARGs in the whole rice growth stage by structural equation model, with a direct influence (λ = 0.38, P < 0.05), following by similar effects of bacterial communities and MGEs (λ = 0.36, P < 0.05; λ = 0.29, P < 0.05). This study demonstrated that soil dry-wet alternation effectively reduced the proliferation and dissemination of most ARGs in paddy fields, providing a novel agronomic measure for pollution control of antibiotic resistance in farmland ecosystem.

An integrated metagenomic model to uncover the cooperation between microbes and magnetic biochar during microplastics degradation in paddy soil

The free radicals released from the advanced oxidation processes can enhance microplastics degradation, however, the existence of microbes acting synergistically in this process is still uncertain. In this study, magnetic biochar was used to initiate the advanced oxidation process in flooded soil. paddy soil was contaminated with polyethylene and polyvinyl chloride microplastics in a long-term incubation experiment, and subsequently subjected to bioremediation with biochar or magnetic biochar. After incubation, the total organic matter present in the samples containing polyvinyl chloride or polyethylene, and treated with magnetic biochar, significantly increased compared to the control. In the same samples there was an accumulation of “UVA humic” and “protein/phenol-like” substances. The integrated metagenomic investigation revealed that the relative abundance of some key genes involved in fatty acids degradation and in dehalogenation changed in different treatments. Results from genome-centric investigation suggest that a Nocardioides species can cooperate with magnetic biochar in the degradation of microplastics. In addition, a species assigned to the Rhizobium taxon was identified as a candidate in the dehalogenation and in the benzoate metabolism. Overall, our results suggest that cooperation between magnetic biochar and some microbial species involved in microplastic degradation is relevant in determining the fate of microplastics in soil.

Monitoring of the mining waste neutralization facility of LW Bogdanka

Investing in renewable energy sources bringing direct profits from unattractive areas is one of the most advantageous ways of wastelands revitalization. In the case of post-mining dumps, it is realized by using photovoltaics and wind turbines. Analyzes showed that the greatest benefits can be acquired from photovoltaic farms, mainly due to the simplicity of their design and principles of operation, as well as the quick return on investment - up to 7 years. The construction of wind turbines is more complicated. Despite the favorable conditions of the mining dumps (elevated areas, which are located mainly away from residential buildings), the construction of the turbine requires more effort in designing and installation work, mainly due to the necessity of building the foundations. Methods for revitalizing mine dumps by installing renewable energy systems have some limitations due to periodicity of operation (time of day, season), weather conditions (wind speed, temperature), expensive energy storage, etc. For this reason, real-time monitoring of climatic conditions is required. The following parameters are monitored: the average available solar energy (important for the assessment of the efficiency of photovoltaic cells), speed and direction of the wind (which affects the efficiency of wind turbines), changes in groundwater level (risk of flooding and periodic soil softening), soil and air temperature (air – affects the choice of the method of revitalization, soil – affects the preservation of soil) and dust concentration, which affects the degree of contamination of the photovoltaic modules and thus the efficiency of the photovoltaic (PV) power plant. The presentation includes interesting data that was obtained during the tests.

Research on flood sediments and rainstorm events in Huangtuwa, Northern Shaanxi

The research purpose of this paper is to reveal the relationship between flood deposits, rainfall and flooding in the Loess Plateau over the last 50 years. The research in this paper is of great significance as it reveals the torrential flood events and soil erosion in the central region of the Loess Plateau. Through grading analysis and 137Cs content determination of a closed lake sedimentary profile formed by landslide-blocked rivers in middle part of Loess Plateau, Zizhou County, Shaanxi Province, the age of the sedimentary formation in the section, as well as the rainstorm events and changes of soil erosion since 1954 are studied. The results show that the sediment particle size composition in the study section is fine, mainly comprising of coarse silt, while the content of sand particles (&amp;gt;100 μm) is very low. The changes in137Cs content show that the sedimentary layer at a depth of 280–210 cm in the research profile was formed between 1954 and 1964, while the deep sedimentary layer at 210–70 cm was formed between 1965 and 1986 and the sedimentary layer above 70 cm depth was formed between 1987 and 2011. In total, 20 coarse particle layers (particle size &amp;gt;50 μm) were deposited in the lake between 1954 and 2011. The sedimentation timing of the 20 coarse particle layers was basically consistent with the timing of rainstorm events (daily rainfall ≥60 mm) in the study area, indicating that the coarse particle sediments in the lake represent rainstorm events. Soil erosion was stronger between 1954 and 1985 and was weaker after 1986.

Effect of N and P fertigation on fruit yield and quality of kinnow

The effects of N and P fertigation on productivity and quality of kinnow mandarin were investigated in southwestern part of Punjab at the Regional Research Station, Abohar of Punjab Agricultural University, Ludhiana, Punjab during 2018–2020. Different combinations of the recommended dose (RD) of N and P, viz. 100, 75, and 50% were applied in equal splits at 5 stages of kinnow trees (February–October) and compared with conventional flood irrigation plus soil fertilization. The results showed that fertigation resulted in higher nutrient uptake, total leaf chlorophyll content, and vital physiological processes as compared to conventional practices. Tree volume under fertigation was about 29% higher than conventional practices. The data also revealed a significantly higher fruit set (20.13%), fruit weight (168.6 g), and fruit size (7.68 cm) as compared to flood irrigation plus soil fertilization. Fruit yield was about 33% higher in fertigated trees over flood irrigation and soil fertilization. Further, fruit quality parameters especially in terms of per cent juice, TSS-acid ratio, and ascorbic acid concentration were also superior in fertigated trees. In addition, fertigation resulted in a higher proportion of economic fruit grades over conventional flood irrigation and soil fertilization. The results suggest that fertigation @75% of N and P of recommended dose exhibited higher growth and productivity of kinnow mandarin, saving 25% N and P usage with better grade andhigher quality of kinnow.

Effects of simulated acid rain and carbon-rich water on mercury mobilization in soils amended with aluminum-based drinking water treatment residuals

Mercury (Hg) contamination in soils is of concern because of its known adverse effects on ecosystem functions and human health. Research on how to reduce Hg contamination in soil is still needed, mainly because of the difficulties in remediating Hg-contaminated soils while minimizing adverse effects on treated systems. We investigated the potential of a waste substrate, aluminum (Al)-based drinking water treatment residuals (Al-WTRs), as a low-cost sorbent for immobilizing the mobile fraction of Hg in contaminated soils using column leaching studies. Because of the known role of acidic deposition and dissolved organic matter on the environmental cycling of Hg, columns packed with Hg-contaminated alluvial soils collected from the watershed of Poplar Creek in Tennessee of USA were leached using either the synthetic precipitation leaching procedure (SPLP) to simulate the effects of acid rain or low pH dissolved organic carbon (DOC) rich river water (Suwannee River water, pH 4.20) to mimic soil flooding events with DOC-rich waters. The results show that, for soils with very high mobile Hg fractions, control columns without Al-WTR leached with the SPLP solution retained only 51% of total-Hg, which was significantly less (p ​< ​0.05) than in the Al-WTR treated soil columns (up to 80%). Leaching with DOC-rich river water (53.3 ​mg ​C/L) decreased the sorption capacity of Al-WTR. Using waters with increasing DOC concentrations (from 5.33 to 40 ​mg ​C/L) resulted in the removal of 63% of the initial mass of Hg in the control columns compared to 22–29% in the columns amended with 2 and 5% Al-WTR. Overall, Al-WTR can immobilize Hg under extreme leachability conditions and should be considered as a potential sorbent for in situ remediation of Hg-contaminated soils. However, further studies are needed on the fate of Al-WTR-immobilized Hg.

Iron oxidation coupled with nitrate reduction affects the acetate-assimilating microbial community structure elucidated by stable isotope probing in flooded paddy soil

Acetate is an abundant carbon source that can trigger microbial redox processes in anoxic environments, thereby affecting the microbial community structure, function, and associated element cycling. Here, we investigated the acetate-assimilating microbial community, especially the key microorganisms involved in nitrate-dependent Fe(II) oxidation that are closely associated with soil redox processes in flooded soil. In the present study, DNA-stable isotope probing (DNA-SIP) with labeled acetate (13C) as a carbon source was applied to examine the acetate-assimilating communities associated with nitrate-dependent Fe(II) oxidation. The results showed that NO3− was rapidly reduced in the treatments with NO3− and NO3− + Fe(II). Fe(II) oxidation occurred quickly only in the presence of NO3−. In the treatments with acetate only, the predominant 13C-labeled genera such as Geobacter, Azospira, Azospirillum, Ideonella, and Desulfovibrionia were probably involved in acetate oxidation coupled with the redox processes of NO3−, Fe(III) and SO42− reduction, which are the most important electron acceptors in flooded soils. The addition of NO3− and Fe(II) significantly affected the acetate-assimilating microbial community from the original soil. The enriched genera in 13C heavy fractions were associated with Pseudogulbenkiania, Azospira, Zoogloea, Azoarcus, and Bdellovibrio dominated in the treatments with NO3− and Fe(II). In the treatments with NO3− only, Zoogloea, Azospira, Azoarcus, and Geothrix were the dominant genera. Given the different genera with enrichments in 13C-heavy fractions in different treatments, Zoogloea and Pseudogulbenkiania were identified as key microorganisms associated with NO3− reduction and nitrate-dependent Fe(II) oxidation, respectively. These findings suggest the importance of Zoogloea and Pseudogulbenkiania for C, Fe, and N biogeochemistry and indicate that Fe and N cycling have a great impact on soil biogeochemistry processes.

The efficacy of conservation practices in reducing floods and improving water quality

Conservation practices such as crop rotation, filter strips, and constructed wetlands are nature-based approaches intended to safeguard natural resources in agricultural landscapes. In this study, we reviewed the literature on how conservation practices, both at watershed and field scales, have been proven to subdue flood peaks, surface runoff, soil erosion, sediment transport, and nutrient loss. We classified different conservation practices based on the mode of their application (i.e., in-field, edge-of-field, and structural practices) and described what prior research efforts have concluded about the efficacy of different practices. At the field scale, practices such as reduced or no-till farming, grassed waterways, and creation of wetlands significantly reduced the peak flow. Similarly, water quality was improved with implementation of conservation practices such as using cover crops, filter strips, and managing residue and tillage. The assessment of conservation practices across the literature was found to be challenging as different conservation practices showed a similar response, thus making it complex to assess the individual effect. A wide range of challenges related to the data, modeling/analysis, and management aspects of conservation practices were identified, and recommendations were provided to overcome these challenges.

Oxidative compensation mechanism of Fe-S synergetic inhibition of Cd activity in paddy field during flooding and drainage

It is known that the transformation of Fe and S forms in soil affects the migration and activity of Cd, but the coordinated regulation of Cd activity by Fe and S under different redox conditions is still unclear. Here, Diffusive gradients in thin films (DGT), an in-situ monitoring technique, is used to explore the difference of the regulation of Cd activity in paddy fields with ferrihydrite (FH) and ferrihydrite coprecipitated by sulfate (FH-S) under the flooding and drainage conditions. The addition of FH-S and FH significantly reduced the activity of Cd (Dissolved, Exchanged, and CDGT-Cd). Compared with pure FH, the adsorption extent of Cd in FH was enhanced by increasing concentrations of SO42− (i.e., S/Fe ratio), which is attributed to the decrease in the crystallinity of FH by sulfate. During soil flooding, the addition of FH-S promoted the production of metal sulfide (CdS and FeS/FeS2). The activity of Cd increased after drainage, while the FH-S treatment groups delayed the release of Cd. After 30 days of drainage, the concentration of Cd in FH-S treatment groups decreased by 28.9–44.1 % compared with the control group. The fresh FeS/FeS2 is not the main adsorbent for fixing Cd, and due to the existence of oxidation compensation mechanism, the preferential oxidation of FeS/FeS2 delays the release of Cd in the drainage stage. Our study shed new light on the mechanism of Fe-S synergistic regulation of Cd and remediation of Cd-contaminated soils.

Arbuscular mycorrhizal fungi and endophytic fungi differentially modulate polyamines or proline of peach in response to soil flooding

Symbiotic fungi are involved in plant flooding tolerance, while the underlying mechanism is not yet known. Since polyamines and proline are also associated with stress tolerance, it is hypothesized that the enhancement of stress resistance by symbiotic fungi is associated with changes in polyamines (PAs) and/or proline. The aim of this study was to analyze the effect of inoculation with Funneliformis mosseae and Serendipita indica on growth, polyamine and its metabolism, and proline and its metabolism in peach (Prunus persica) under flooded conditions. Two-week flooding did not affect root colonization frequence of F. mosseae, while it promoted root colonization frequence of S. indica. Inoculated plants with F. mosseae and S. indica maintained relatively higher growth rates of peach under flooding than those of uninoculated plants. F. mosseae promoted root ornithine levels and arginine decarboxylase and ornithine decarboxylase activities under flooding, which promoted putrescine (Put), cadaverine (Cad) and spermidine (Spd) levels. Conversely, S. indica inhibited levels of arginine, ornithine, and agmatine and arginine decarboxylase activities, thus decreasing PAs under flooding. PAs were negatively correlated with expressions of polyamine uptake transporter 1 (PUT1) and PUT4 in peach. Transporters of polyamine (TPO) of F. mosseae and S. indica were regulated by flooding, of which FmTPO1 was positively correlated with Put, Cad, and Spd, along with a positive correlation of Spd with SiTPO1, SiTPO2, and SiTPO4. Under flooding, F. mosseae inhibited proline, while S. indica increased proline, correlated with Δ1-pyrroline-5-carboxylate synthetase 2 expressions. It thus was concluded that F. mosseae modulated polyamine accumulation while S. indica induced proline accumulation to tolerate flooding.

Efecto de dos niveles de inundación sobre crecimiento y parámetros fisiológicos en porta-injertos de durazno “Nemared”

While peach tree is very sensitive to waterlogging, there are no works on the effect of the flooding over only part of its root system. The objective of this work was to investigate physiological and growth responses of Nemared rootstock to partial flooding of roots. Treatments were performed for 6-days: control trees, half-flooded, and fully-flooded. Both flooding treatments negatively affected the vegetative growth, stomatal conductance, chlorophyll content and leaf water potential. The response observed in the half-flooded treatment was intermediate between the control and fully-flooded treatment. The fastest response of stomatal conductance to soil flooding, before differences among treatments in leaf water potential were perceived, suggested that there should be a stomatal closure mechanism that responds to a signal that arises from flooded roots. The importance of this work, lies in showing the negative effects of unnoticed and partial floods, frequently occurring in peach trees.

Type-specific quantification of particulate methane monooxygenase gene of methane-oxidizing bacteria at the oxic-anoxic interface of a surface paddy soil by digital PCR.

Aerobic methane-oxidizing bacteria (MOB) play an important role in mitigating methane emissions from paddy fields. In this study, we developed a differential quantification method for the copy number of pmoA genes of type Ia, Ib, and IIa MOB in paddy field soil using chip-based digital PCR. Three probes specific to the pmoA of type Ia, Ib, and IIa MOB worked well in digital PCR quantification when genomic DNA of MOB isolates and PCR-amplified DNA fragments of pmoA were examined as templates. When pmoA genes in the surface soil layer of a flooded paddy were quantified by digital PCR, the copy numbers of type Ia, Ib, and IIa MOB were 105 -106 , 105 -106 , and 107 copies g-1 dry soil, respectively, with the highest values in the top 0-2-mm soil layer. Especially, the copy numbers of type Ia and Ib MOB increased by 240% and 380% at the top layer after soil flooding, suggesting that the soil circumstances at the oxic-anoxic interfaces were more preferential for growth of type I MOB than type II MOB. Thus, type I MOB likely play an important role in the methane consumption at the surface paddy soil.

The barrier to radial oxygen loss protects roots against hydrogen sulphide intrusion and its toxic effect.

The root barrier to radial O2 loss (ROL) is a key root trait preventing O2 loss from roots to anoxic soils thereby enabling root growth into anoxic, flooded soils. We hypothesized that the ROL barrier can also prevent intrusion of hydrogen sulphide (H2 S), a potent phytotoxin in flooded soils. Using H2 S and O2 sensitive microsensors, we measured the apparent permeance to H2 S of rice roots, tested whether restricted H2 S intrusion reduced its adverse effects on root respiration, and if H2 S could induce the formation of a ROL barrier. The ROL barrier reduced apparent permeance to H2 S by almost 99%, greatly restricting H2 S intrusion. The ROL barrier acted as a shield towards H2 S; O2 consumption in roots with a ROL barrier remained unaffected at high H2 S concentration (500 μM), compared to a 67% decline in roots without a barrier. Importantly, low H2 S concentrations induced the formation of a ROL barrier. In conclusion, the ROL barrier plays a key role in protecting against H2 S intrusion, and H2 S can act as an environmental signalling molecule for the induction of the barrier. The study demonstrates the multiple functions of the suberized/lignified outer part of the rice root beyond that of restricting ROL.

The Impact of Carbohydrate Management on Coleoptile Elongation in Anaerobically Germinating Seeds of Rice (Oryza sativa L.) under Light and Dark Cycles

The ability of rice to elongate coleoptiles under oxygen deprivation is a determinant of anaerobic germination tolerance, critical for successful direct seeding. Most studies on anaerobic coleoptile elongation have been performed under constant darkness or in flooded soils because a drilling method was the primary approach for direct seeding of rice. However, aerial seeding is becoming popular, in which seeds which land on flooded soils are exposed to light during the daytime. Here, we investigated physiological mechanisms underlying anaerobic elongation of coleoptiles under light and dark cycles. This study identified two novel varieties, LG and L202, enabling the development of long coleoptiles under oxygen limitation, comparable to well-characterized varieties with strong anaerobic germination tolerance. Germination experiments using these two tolerant and two intolerant varieties, including Takanari and IR64, revealed that light and dark cycles increased coleoptile length in LG, Takanari, and IR64 relative to constant darkness. Interestingly, even in intolerant lines, dramatic starch breakdown and soluble carbohydrate accumulation occurred under oxygen limitation. However, intolerant lines were more susceptible to a representative soluble sugar, glucose, than tolerant lines under oxygen deprivation, suggesting that coleoptile growth can be inhibited in intolerant lines due to hypersensitivity to soluble sugars accumulated in anaerobically germinating seeds.

Exploring the Potential of Multiomics and Other Integrative Approaches for Improving Waterlogging Tolerance in Plants.

Soil flooding has emerged as a serious threat to modern agriculture due to the rapid global warming and climate change, resulting in catastrophic crop damage and yield losses. The most detrimental effects of waterlogging in plants are hypoxia, decreased nutrient uptake, photosynthesis inhibition, energy crisis, and microbiome alterations, all of which result in plant death. Although significant advancement has been made in mitigating waterlogging stress, it remains largely enigmatic how plants perceive flood signals and translate them for their adaptive responses at a molecular level. With the advent of multiomics, there has been significant progress in understanding and decoding the intricacy of how plants respond to different stressors which have paved the way towards the development of climate-resistant smart crops. In this review, we have provided the overview of the effect of waterlogging in plants, signaling (calcium, reactive oxygen species, nitric oxide, hormones), and adaptive responses. Secondly, we discussed an insight into past, present, and future prospects of waterlogging tolerance focusing on conventional breeding, transgenic, multiomics, and gene-editing approaches. In addition, we have also highlighted the importance of panomics for developing waterlogging-tolerant cultivars. Furthermore, we have discussed the role of high-throughput phenotyping in the screening of complex waterlogging-tolerant traits. Finally, we addressed the current challenges and future perspectives of waterlogging signal perception and transduction in plants, which warrants future investigation.