Long-term Waterlogging Research Articles

Will the beneficial properties of plant-growth promoting bacteria be affected by waterlogging predicted in the wake of climate change: A model study

The agricultural sector today is faced with climate change that amplifies extreme climatic events. The use of plant growth promoting bacteria (PGPB) could provide a new approach to increase crop production under these new conditions. In this study, PGPB were isolated from a 5-week pot experiment conducted under greenhouse conditions using cabbage (Brassica oleracea L. var. capitata f. alba) as a model plant. Plants were exposed to either one or two long-term waterlogging events at two different stages of plant development. The results clearly showed that waterlogging leads to changes in the soil microbial community affecting both its overall structure (culturable bacterial fraction) as well as the plant growth promotion (PGP) function provided by the beneficial bacteria to the plant. In general, “the core” of the bacterial community (Bacillus, Pseudomonas, Stenotrophomonas and Peribacillus populations) remained preserved under waterlogged conditions, but shifts in their abundance were observed, with Bacillus, and Pseudomonas proliferating under these conditions. The key to adaptation to waterlogging may lie in “rare” bacterial populations isolated only under certain waterlogging conditions. In our study we identified 11 different genera that can be termed as waterlogging-tolerant. Waterlogging was also shown to induce shifts in the PGP potential, as well as on the structure of a population exhibiting a particular trait, which could eventually lead to either promotion or reduction of plant growth. While the abundances of populations promoting nutrient availability to plants were found to increase after waterlogging, biocontrol protease activity proved to be the trait most sensitive to waterlogging. Enterobacter and Pantoea species were identified as main players in biofilm formation under waterlogging conditions. Waterlogging also appears to trigger the emergence of extremophilic and acidophilic bacteria, aspect important for potential adaptation of soil bacteria to future climate projections, with Bacillus and Pseudomonas showing best potential. Based on all PGP characteristics studied, we selected 11 bacterial isolates belonging to genera Enterobacter, Bacillus, Pseudomonas, Stenotrophomonas, and Pantoea designating them as the most promising bacterial bioinoculants i.e. strains with good potential for future applications in potential waterstress recover of the soil and plants.

Genome-Wide Identification of the DGK Gene Family in Kiwifruit (Actinidia valvata Dunn) and an Expression Analysis of Their Responses to Waterlogging Stress

Diacylglycerol kinase (DGK) is a lipid kinase that phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Based on converting one important signaling molecule (DAG) to another (PA), DGK plays an important role in plant responses to abiotic stress, including waterlogging stress. However, no studies have been reported on the characterization of the DGK gene family in the waterlogging-tolerant kiwifruit germplasm Actinidia valvata Dunn. In this study, we identified 18 AvDGK genes in the A. valvata genome. The phylogenetic analysis showed that AvDGKs can be classified into three clusters, and members within the same cluster have similar domain distributions, exon-intron structures, and conserved motif compositions. The chromosome localization analysis revealed that all AvDGK genes are located across 18 different chromosomes. There were 29 duplicated gene pairs in A. valvata and all had undergone purifying selection during evolution. The promoter cis-element analysis revealed that the cis-elements within AvDGK genes are associated with multiple functions, including phytohormone signal transduction, stress responses, and plant growth and development. The expression pattern analyses indicated that AvDGKs play important roles in fruit development and plant responses to waterlogging stress. The AvDGK gene family in the tetraploid A. valvata genome might promote PA synthesis and subsequent signal transduction both under short- and long-term waterlogging stresses. These results provide information regarding the structural characteristics and potential function of AvDGK genes within A. valvata and lay a fundamental basis for further research into breeding to enhance the kiwifruit’s tolerance to waterlogging stress.

Waterlogging Hardening Effect on Transplant Stress Tolerance in Pinus densiflora

Waterlogging induces oxidative damage by accumulation of reactive oxygen species due to stomatal closure. Plants alter their physiological and molecular mechanisms to reduce and adapt to oxidative stress. This mechanism of adaptation to stress, known as hardening, can support future stress tolerance. Pinus densiflora seedlings were grown under waterlogging treatment for three years and then transplanted to another site to identify the waterlogging hardening effect on transplanting. Transcriptome analysis was conducted before and after transplanting, and physiological factors were measured after transplanting. After transplanting, wounding stress is the main cause of transplant stress, and 13 genes related to phenylpropanoid were upregulated for the recovery of wounded roots in waterlogged hardened seedlings. The leaf starch and soluble sugar content of the waterlogged hardened seedlings were 50.3% and 40.5% lower due to the formation of cell walls. However, auxin-related genes were downregulated in waterlogging hardened seedlings, resulting in a lower tendency for height growth in hardened waterlogged seedlings. Waterlogging hardening mitigated transplant stress by wounding more than non-hardening, whereas waterlogging hardening may negatively affect seedling height. Our study provides evidence for the hardening effect of long-term waterlogging on transplanted P. densiflora seedlings.

Molecular mechanism of salinity and waterlogging tolerance in mangrove Kandelia obovata.

Mangrove forests are colloquially referred to as "Earth's kidneys" and serve many important ecological and commercial functions. Salinity and waterlogging stress are the most important abiotic stressors restricting the growth and development of mangroves. Kandelia obovata (K. obovata) is the greatest latitudinally-distributed salt mangrove species in China.Here, morphology and transcriptomics were used to study the response of K. obovata to salt and waterlogging stress. In addition, weighted gene co-expression network analysis of the combined gene expression and phenotypic datasets was used to identify core salinity- and waterlogging-responsive modules. In this study, we observed that both high salinity and waterlogging significantly inhibited growth and development in K. obovata. Notably, growth was negatively correlated with salt concentration and positively correlated with waterlogging duration, and high salinity was significantly more inhibitive than waterlogging. A total of 7, 591 salt-responsive and 228 waterlogging-responsive differentially expressed genes were identified by RNA sequencing. Long-term salt stress was highly correlated with the measured physiological parameters while long-term waterlogging was poorly correlated with these traits. At the same time, 45 salinity-responsive and 16 waterlogging-responsive core genes were identified. All 61 core genes were mainly involved in metabolic and biosynthesis of secondary metabolites pathways. This study provides valuable insight into the molecular mechanisms of salinity and waterlogging tolerance in K. obovata, as well as a useful genetic resource for the improvement of mangrove stress tolerance using molecular breeding techniques.

Exogenous ABA and IAA modulate physiological and hormonal adaptation strategies in Cleistocalyx operculatus and Syzygium jambos under long-term waterlogging conditions

BackgroundThe mechanisms of abscisic acid (ABA) and auxin (IAA) in inducing adventitious root (AR) formation, biomass accumulation, and plant development under long-term waterlogging (LT-WL) conditions are largely unexplored. This study aimed to determine the roles of exogenous application of ABA and IAA in two woody plants (Cleistocalyx operculatus and Syzygium jambos) under LT-WL conditions. A pot experiment was conducted using a complete randomized design with two factors: (i) LT-WL and (ii) application of exogenous phytohormones (ABA and IAA) for 120 d.ResultsResults revealed that exogenous ABA and IAA promoted LT-WL tolerance in both species. In C. operculatus and S. jambos, plant height, the number of blades, leaf area, and fresh shoot weight were increased by exogenous IAA under LT-WL. However, exogenous ABA affected more the adventitious and primary root in C. operculatus compared to S. jambos. LT-WL decreased drastically the photosynthetic activities in both species, but adding moderate amounts of exogenous ABA or IAA protected the photosynthesis apparatus under LT-WL. Exogenous phytohormones at certain levels decreased the superoxide anion level and malondialdehyde accumulation in plants under LT-WL. Also, the increase of the peroxidases and superoxide dismutase activities by exogenous phytohormones was more marked in C. operculatus compared to S. jambos. Meanwhile, the catalase activity was down-regulated in both species by exogenous phytohormones. Exogenous ABA or IAA positively regulated the jasmonic acid content in ARs under LT-WL. Moderate application of exogenous ABA or IAA in plants under LT-WL decreased the ABA content in the leaves. Lower accumulation of IAA and ABA in the leaves of C. operculatus under LT-WL was positively correlated with a decrease in antioxidant activity.ConclusionsLastly, C. operculatus which has greater morphology indexes was more tolerant to waterlogging than S. jambos. Moreover, the adaptive strategies via exogenous ABA were more built around the below-ground biomass indexes particularly in C. operculatus, while exogenous IAA backed the above-ground biomass in both species. Overall, the exogenous hormones applied (spraying or watering) influenced differentially the plant’s responses to LT-WL. The phytohormonal profile of plants exposed to waterlogging stress varied depending on the species’ tolerance level.

Phenotypic variation from waterlogging in multiple perennial ryegrass varieties under climate change conditions.

Identifying how various components of climate change will influence ecosystems and vegetation subsistence will be fundamental to mitigate negative effects. Climate change-induced waterlogging is understudied in comparison to temperature and CO2. Grasslands are especially vulnerable through the connection with global food security, with perennial ryegrass dominating many flood-prone pasturelands in North-western Europe. We investigated the effect of long-term waterlogging on phenotypic responses of perennial ryegrass using four common varieties (one diploid and three tetraploid) grown in atmospherically controlled growth chambers during two months of peak growth. The climate treatments compare ambient climatological conditions in North-western Europe to the RCP8.5 climate change scenario in 2050 (+2°C and 550 ppm CO2). At the end of each month multiple phenotypic plant measurements were made, the plants were harvested and then allowed to grow back. Using image analysis and principal component analysis (PCA) methodologies, we assessed how multiple predictors (phenotypic, environmental, genotypic, and temporal) influenced overall plant performance, productivity and phenotypic responses. Long-term waterlogging was found to reduce leaf-color intensity, with younger plants having purple hues indicative of anthocyanins. Plant performance and yield was lower in waterlogged plants, with tetraploid varieties coping better than the diploid one. The climate change treatment was found to reduce color intensities further. Flooding was found to reduce plant productivity via reductions in color pigments and root proliferation. These effects will have negative consequences for global food security brought on by increased frequency of extreme weather events and flooding. Our imaging analysis approach to estimate effects of waterlogging can be incorporated into plant health diagnostics tools via remote sensing and drone-technology.

The biological additives as cey factor on soil moisture dynamics in the context of climate change

In recent years, climate change trends specific to the world's regions have been observed in Lithuania. Droughts and torrential rains are increasingly being recorded, causing long-term waterlogging. As Lithuania is an agrarian country, the horticulture sector is developed. Abundant growers of potatoes, cabbage and other vegetables are counted in years. It is estimated that the consumption of potatoes in Lithuania is more than 96 kg per capita per year. However, potatoes, which are grown by the majority of crop farms, suffer most from frequent natural droughts. To lower droughts influence, farmers can install irrigation systems or use biological additives in the field, such as agroperlite and agrovermiculite. The experiment was conducted at the two experimental farms in Lithuania, growing ‘Vineta’ potatoes. The aim of the study was to determine the dynamics of soil moisture in May-August, when different amounts (effects of different percentages) of biological additives are added to the soil. In 2020, the amount of precipitation varied during the research period. During the whole period in Pupasodis fields precipitation was 234 mm. During observed period, 77% of all decades were drier than perennials (DNs). In Šilavotas fields, it was found that 351.5 mm of precipitation fell during the observed period, which is 164.3 mm more than in the Pupasodis area. The distance between experiment plots was more than 70 km. The study results show that soil temperature correlates with exponential dependence with precipitation. The correlation coefficient r = 0.69, and when assessing the relationship between soil temperature and ambient temperature, a linear dependence and R = 0.5649 were found.

RNA-Seq Reveals Waterlogging-Triggered Root Plasticity in Mungbean Associated with Ethylene and Jasmonic Acid Signal Integrators for Root Regeneration.

Global climate changes increase the frequency and intensity of heavy precipitation events, which result in flooding or soil waterlogging. One way to overcome these low-oxygen stresses is via modifying the plant root system to improve internal aeration. Here, we used a comparative RNA-seq based transcriptomic approach to elucidate the molecular mechanisms of waterlogging-triggered root plasticity in mungbean (Vigna radiata), a major grain legume cultivated in Asia. Two mungbean varieties with contrasting waterlogging tolerance due to the plasticity of the root system architecture were subjected to short-term and long-term waterlogging. Then, RNA-seq was performed. Genes highly expressed in both genotypes under short-term waterlogging are related to glycolysis and fermentation. Under long-term waterlogging, the expression of these genes was less induced in the tolerant variety, suggesting it had effectively adapted to waterlogging via enhancing root plasticity. Remarkably, under short-term waterlogging, the expression of several transcription factors that serve as integrators for ethylene and jasmonic acid signals controlling root stem cell development was highly upregulated only in the tolerant variety. Sequentially, root development-related genes were more expressed in the tolerant variety under long-term waterlogging. Our findings suggest that ethylene and jasmonic acids may contribute to waterlogging-triggered root plasticity by relaying environmental signals to reprogram root regeneration. This research provides the basis for the breeding and genetic engineering of waterlogging-tolerant crops in the future.

Photosynthetic and Morphological Responses of Sacha Inchi (Plukenetia volubilis L.) to Waterlogging Stress.

Sacha inchi (Plukenetia volubilis L.) is an important oilseed crop that is rich in fatty acids and protein. Climate-change-related stresses, such as chilling, high temperature, and waterlogging can cause severe production loss in this crop. In this study, we investigated the photosynthetic responses of sacha inchi seedlings to short-term waterlogging and their morphological changes after long-term waterlogging stress. Sacha inchi CO2 uptake, stomatal conductance, and transpiration rate are affected by temperature and light intensity. The seedlings had a high CO2 uptake (>10 μmol m−2s−1) during the daytime (08:00 to 15:00), and at 32 and 36 °C. At 32 °C, CO2 uptake peaked at irradiations of 1000 and 1500 µmol m−2s−1, and plants could still perform photosynthesis at high-intensity radiation of 2000–3000 µmol m−2s−1. However, after 5 days of waterlogging (5 DAF) sacha inchi seedlings significantly reduced their photosynthetic ability. The CO2 uptake, stomatal conductance, Fv/Fm, ETR, and qP, etc., of the susceptible genotypes, were significantly decreased and their wilting percentage was higher than 50% at 5 DAF. This led to a higher wilting percentage at 7 days post-recovery. Among the four lines assessed, Line 27 had a high photosynthetic capability and showed the best waterlogging tolerance. We screened many seedlings for long-term waterlogging tolerance and discovered that some seedlings can produce adventitious roots (AR) and survive after two weeks of waterlogging. Hence, AR could be a critical morphological adaptation to waterlogging in this crop. In summary, these results suggest that improvement in waterlogging tolerance has considerable potential for increasing the sustainable production of sacha inchi.

Carbohydrate Assimilation and Translocation Regulate Grain Yield Formation in Wheat Crops (Triticum aestivum L.) under Post-Flowering Waterlogging

In a two-year field study, we quantified the impact of post-flowering soil waterlogging on carbon assimilation and grain yield formation in wheat crops. At anthesis, wheat cultivars YangMai 18 (YM18) and YanNong 19 (YN19) were waterlogged for different durations, i.e., 0 (W0), 3 (W3), 6 (W6) and 9 (W9) days using artificial structures. Changes in leaf physiology, carbon assimilation and biomass production were quantified at 0, 7, 14, and 21 days after anthesis under all treatments. Short-term (W3) waterlogging had no significant effect on wheat crops but W6 and W9 significantly reduced the net photosynthetic rate (Pn), leaf SPAD value, and grain weight of the tested cultivars. Increasing waterlogging duration significantly increased dry matter accumulation in the spike-axis + glumes but reduced dry matter accumulation in grain. Further, the tested cultivars responded significantly variably to W6 and W9. Averaged across two years, YM 18 performed relatively superior to YN19 in response to long-term waterlogging. For example, at 14 days after anthesis, W9 plants of YM18 and YN19 experienced a 17.4% and 23.2% reduction in SPAD and 25.3% and 30.8% reduction in Pn, respectively, compared with their W0 plants. Consequently, YM18 suffered a relatively smaller grain yield loss (i.e., 16.0%) than YN19 (23.4%) under W9. Our study suggests that wheat cultivar YM18 could protect grain development from waterlogging injury by sustaining assimilates supplies to grain under waterlogged environments.

Developing Functional Relationships between Soil Waterlogging and Corn Shoot and Root Growth and Development.

Short- and long-term waterlogging conditions impact crop growth and development, preventing crops from reaching their true genetic potential. Two experiments were conducted using a pot-culture facility to better understand soil waterlogging impacts on corn growth and development. Two corn hybrids were grown in 2017 and 2018 under ambient sunlight and temperature conditions. Waterlogging durations of 0, 2, 4, 6, 8, 10, 12, and 14 days were imposed at the V2 growth stage. Morphological (growth and development) and pigment estimation data were collected 15 days after treatments were imposed, 23 days after sowing. As waterlogging was imposed, soil oxygen rapidly decreased until reaching zero in about 8–10 days; upon the termination of the treatments, the oxygen levels recovered to the level of the 0 days treatment within 2 days. Whole-plant dry weight declined as the waterlogging duration increased, and after 2 days of waterlogging, a 44% and 27% decline was observed in experiments 1 and 2, respectively. Leaf area and root volume showed an exponential decay similar to the leaf and root dry weight. Leaf number and plant height were the least sensitive measured parameters and decreased linearly in both experiments. Root forks were the most sensitive parameter after 14 days of waterlogging in both experiments, declining by 83% and 80% in experiments 1 and 2, respectively. The data from this study improve our understanding of how corn plants react to increasing durations of waterlogging. In addition, the functional relationships generated from this study could enhance current corn simulation models for field applications.

Waterlogging-Stress-Responsive LncRNAs, Their Regulatory Relationships with miRNAs and Target Genes in Cucumber (Cucumis sativus L.)

Low oxygen level is a phenomenon often occurring during the cucumber cultivation period. Genes involved in adaptations to stress can be regulated by non-coding RNA. The aim was the identification of long non-coding RNAs (lncRNAs) involved in the response to long-term waterlogging stress in two cucumber haploid lines, i.e., DH2 (waterlogging tolerant—WL-T) and DH4 (waterlogging sensitive—WL-S). Plants, at the juvenile stage, were waterlogged for 7 days (non-primed, 1xH), and after a 14-day recovery period, plants were stressed again for another 7 days (primed, 2xH). Roots were collected for high-throughput RNA sequencing. Implementation of the bioinformatic pipeline made it possible to determine specific lncRNAs for non-primed and primed plants of both accessions, highlighting differential responses to hypoxia stress. In total, 3738 lncRNA molecules were identified. The highest number (1476) of unique lncRNAs was determined for non-primed WL-S plants. Seventy-one lncRNAs were depicted as potentially being involved in acquiring tolerance to hypoxia in cucumber. Understanding the mechanism of gene regulation under long-term waterlogging by lncRNAs and their interactions with miRNAs provides sufficient information in terms of adaptation to the oxygen deprivation in cucumber. To the best of our knowledge, this is the first report concerning the role of lncRNAs in the regulation of long-term waterlogging tolerance by priming application in cucumber.

Can the native faunal communities be restored from removal of invasive plants in coastal ecosystems? A global meta-analysis.

Coastal ecosystems worldwide are being threatened by invasive plants in the context of global changes. However, how invasive plants influence native faunal communities and whether native faunal communities can recover following the invader removals/controls across global coastal ecosystems are still poorly understood. Here, we present the first global meta-analysis to quantify the impacts of Spartina species invasions on coastal faunal communities and further to evaluate the outcomes of Spartina species removals on faunal community recovery based on 74 independent studies. We found that invasive Spartina species generally decreased the biodiversity (e.g., species richness), but increased coastal faunal abundance (e.g., individual number) and fitness (e.g., biomass), though the effect on abundance was insignificant. The pattern of influence was strongly dependent on habitat types, faunal taxa, trophic levels, and feeding types. Specifically, Spartina species invasion of mudflats caused greater impacts than invasion of vegetated habitats. Insects and birds at higher trophic levels were strongly affected by invasive Spartina, indicating that invasive plant effects can cascade upward along the food chain. Additionally, impacts of Spartina invasions were more obvious on food specialists such as herbivores and carnivores. Furthermore, our analyses revealed that invader removals were overall beneficial for native faunal communities to recover from the displacement caused by Spartina invasions, but this recovery process depended on specific removal measure and time. For example, the long-term waterlogging had strong negative impacts on faunal recovery, so it should not be encouraged. Our findings suggest that invasive plants could have contrasting effects on functional responses of native faunal communities. Although invasive plant removals could restore native faunal communities, future functional restorations of invaded ecosystems should take the legacy effects of invasive species on native communities into account. These findings provide insightful implications for future scientific controls of invasive species and ecosystem restoration under intensifying global changes.

Oxygenated Compound Fertilizer Improved Rice Yield by Empowering Soil Aeration

ABSTRACT Poor soil aeration is a limiting factor that influences rice (Oryza sativa L.) growth. Oxygenated compound fertilizer (OCF) is a vital strategy to address this challenge by improving soil aeration. Three kinds of newly developed fertilizers amended with different amounts of calcium peroxide (OCF1, OCF2, and OCF3) were prepared by mixing nutrients and other additive materials. Using waterlogging (WL), micro-bubble aerated water irrigation (MBWI), and fertilization of calcium peroxide for four times (FCP) as check, effects on soil aeration, physiological characteristics, and yield of rice with two rice varieties (Q681 and EK1) were examined in a pot culture. The results showed that OCF achieved a higher soil Eh and dissolved oxygen at the main growth stages and had higher nitrification intensity with lower de-nitrification intensity at tiller stage and full heading stage compared to WL/MBWI/FCP. Compared to WL/MBWI/FCP, OCF3 has 5–76% higher soil NH4 +-N and 0–33% higher soil NO3 –N, respectively. OCF3 increased the photosynthesis rate, stomatal conductance, and transpiration rate by more than 11%, 21%, and 7% compared to WL, respectively. OCF3 improved 1.07 times of rice yield than WL and has more than 29–58% rice yield than MBWI/FCP. OCF3 kept good soil aeration with long periods, being low price and user-friendly, and could be especially useful in paddy soil under long-term waterlogging.

Long-Term Waterlogging as Factor Contributing to Hypoxia Stress Tolerance Enhancement in Cucumber: Comparative Transcriptome Analysis of Waterlogging Sensitive and Tolerant Accessions.

Waterlogging (WL), excess water in the soil, is a phenomenon often occurring during plant cultivation causing low oxygen levels (hypoxia) in the soil. The aim of this study was to identify candidate genes involved in long-term waterlogging tolerance in cucumber using RNA sequencing. Here, we also determined how waterlogging pre-treatment (priming) influenced long-term memory in WL tolerant (WL-T) and WL sensitive (WL-S) i.e., DH2 and DH4 accessions, respectively. This work uncovered various differentially expressed genes (DEGs) activated in the long-term recovery in both accessions. De novo assembly generated 36,712 transcripts with an average length of 2236 bp. The results revealed that long-term waterlogging had divergent impacts on gene expression in WL-T DH2 and WL-S DH4 cucumber accessions: after 7 days of waterlogging, more DEGs in comparison to control conditions were identified in WL-S DH4 (8927) than in WL-T DH2 (5957). Additionally, 11,619 and 5007 DEGs were identified after a second waterlogging treatment in the WL-S and WL-T accessions, respectively. We identified genes associated with WL in cucumber that were especially related to enhanced glycolysis, adventitious roots development, and amino acid metabolism. qRT-PCR assay for hypoxia marker genes i.e., alcohol dehydrogenase (adh), 1-aminocyclopropane-1-carboxylate oxidase (aco) and long chain acyl-CoA synthetase 6 (lacs6) confirmed differences in response to waterlogging stress between sensitive and tolerant cucumbers and effectiveness of priming to enhance stress tolerance.

Elucidating the morpho-physiological adaptations and molecular responses under long-term waterlogging stress in maize through gene expression analysis

Waterlogging stress in maize is one of the emerging abiotic stresses in the current climate change scenario. To gain insights in transcriptional reprogramming during late hours of waterlogging stress under field conditions, we aimed to elucidate the transcriptional and anatomical changes in two contrasting maize inbreds viz. I110 (susceptible) and I172 (tolerant). Waterlogging stress reduced dry matter translocations from leaves and stems to ears, resulting in a lack of sink capacity and inadequate grain filling in I110, thus decreased the grain yield drastically. The development of aerenchyma cells within 48 h in I172 enabled hypoxia tolerance. The upregulation of alanine aminotransferase, ubiquitin activating enzyme E1, putative mitogen activated protein kinase and pyruvate kinase in I172 suggested that genes involved in protein degradation, signal transduction and carbon metabolism provided adaptive mechanisms during waterlogging. Overexpression of alcohol dehydrogenase, sucrose synthase, aspartate aminotransferase, NADP dependent malic enzyme and many miRNA targets in I110 indicated that more oxygen and energy consumption might have shortened plant survival during long-term waterlogging exposure. To the best of our knowledge, this is the first report of transcript profiling at late stage (24−96 h) of waterlogging stress under field conditions and provides new visions to understand the molecular basis of waterlogging tolerance in maize.

Spatial water calendar: An illustrative workbook for adaptive transformation

In this paper, concepts for deploying climate resilient design in deltaic regions which encounter environmental challenges are explored. Today, most deltas experience persistent flooding and long-term waterlogging which adversely affects the livelihood of its inhabitants. A new approach was formulated to rethink design and planning pedagogies in the discipline of landscape architecture at Delft University of Technology, to visualize open-ended spatial transformations involving both the landscape architect and the inhabitants over longer periods of time. The graduates proposed flexible spatial frameworks that integrate time and people1. This results in design interventions that do not rely on a fixed plan, but rather propose and visualize a process using a ‘water calendar’ as the driving force. The spatial water calendar is a chart that helps to represent time linked to space and water which can be useful to enumerate, elucidate, and determine time-based fluctuations in a landscape and make decisions accordingly. The idea was prompted by ancient calendars that were based on the rhythm of seasons – a method which farmers often used. However, the spatial water calendar also integrates other processes which are influenced by water, focussing specifically on the spatial impact, thereby becoming a design tool for landscape architects. The calendar developed in the Circular Water Stories lab is an open-ended framework stirred by a sequence of spatial drawings showing the temporal and social processes in relation to human-made interventions, resulting in spatial transformations through time and scale. Because working with a calendar is highly participatory in nature, the spatial water calendar will be more meaningful in vulnerable geographies2 where there is still a strong connection between people and landscape. Nevertheless, in other parts of the world, we imagine that this approach also opens new possibilities for landscape architects to engage with dynamic sites.

Arabidopsis phenotyping reveals the importance of alcohol dehydrogenase and pyruvate decarboxylase for aerobic plant growth

Alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) are key to the establishment of the fermentative metabolism in plants during oxygen shortage. Most of the evidence that both ADH and PDC are required for plant tolerance to hypoxia comes from experiments performed by limiting oxygen in the environment, such as by exposing plants to gaseous hypoxia or to waterlogging or submergence. However, recent experiments have shown that hypoxic niches might exist in plants grown in aerobic conditions. Here, we investigated the importance of ADH and PDC for plant growth and development under aerobic conditions, long-term waterlogging and short-term submergence. Data were collected after optimizing the software associated with a commercially-available phenotyping instrument, to circumvent problems in separation of plants and background pixels based on colour features, which is not applicable for low-oxygen stressed plants due to the low colour contrast of leaves with the brownish soil. The results showed that the growth penalty associated with the lack of functional ADH1 or both PDC1 and PDC2 is greater under aerobic conditions than in hypoxia, highlighting the importance of fermentative metabolism in plants grown under normal, aerobic conditions.

Photosynthetic traits and plant–water relations of two apple cultivars grown as bi-leader trees under long-term waterlogging conditions

Waterlogging has been one of the major problems in plant cultivation worldwide. As its frequency and severity are increasing in the era of climate change, waterlogging tolerance of fruit cultivars is an important factor that should be considered before plantation. In this study, we investigated leaf morphological traits, photosynthetic responses, and plant–water relations of the two most popular apple cultivars in Korea, Hongro (medium maturing) and Fuji (late maturing), under long-term waterlogging conditions. Experimental bi-leader trees grafted on a single M.9 rootstock were subjected to two irrigation regimes (well-irrigated and waterlogged) for 75 days. Waterlogging stress adversely affected most of the morphological, physiological, and anatomical characteristics as well as the plant–water relations in both cultivars; the negative effects of waterlogging were more pronounced in Hongro than in Fuji. Both cultivars experienced a significant decrease in leaf size, whereas leaf length was reduced significantly in Hongro and leaf width in Fuji. Predawn leaf water potential (ΨPD) decreased with waterlogging, but midday leaf water potential (ΨMD) was more significantly decreased in Hongro than in Fuji under waterlogging. Net photosynthetic rate (Pn) and stomatal conductance (gs) were significantly reduced in both cultivars; the reduction was greater in Hongro than in Fuji. A more pronounced reduction in vessel density, vessel diameter, and stomatal density (Sd) was observed in Hongro than in Fuji, resulting in greater reduction in daily sap flow and hydraulic conductivity in Hongro than in Fuji. These results indicate that Fuji was better adapted to waterlogging, as indicated by fewer changes in morphological, physiological, and anatomical responses when compared with those of Hongro. Our data suggest that the lower reduction in vessel density, vessel area, and vessel diameter in the Fuji cultivar under waterlogging are major factors that improve plant–water relations and photosynthetic performance, which in turn determine the leaf morphological characteristics and vegetative growth under prolonged waterlogging.

Defining the waterlogging tolerance of Ornithopus spp. for the temperate pasture zone of southern Australia

Increasing the area sown to Ornithopus spp. (serradella) can reduce overall fertiliser requirements in Australian permanent pastures owing to their greater nutrient-acquisition efficiency than that of more widely used pasture legumes such as Trifolium spp. However, uncertainty regarding waterlogging tolerance of Ornithopus spp. may restrict their adoption in the high-rainfall zone of southern Australia. The waterlogging tolerance of cultivars and accessions of three species of Ornithopus (O. compressus, O. sativus and O. pinnatus) was determined by comparing root and shoot growth of plants in deoxygenated, stagnant agar nutrient solution (simulated waterlogging) with growth in aerated nutrient solution. The responses were benchmarked against the known waterlogging-tolerant pasture legume Trifolium michelianum. All Ornithopus cultivars were highly impacted by the deoxygenated stagnant treatment, including those of the anecdotally waterlogging-tolerant O. pinnatus. The 14-day stagnant treatment reduced root dry mass by 32–62% and relative growth rate (RGR) of roots by 36–73%. At the same time, root porosity increased from 1.4% to 8.8%. Following a 14-day recovery period, during which plants were returned to aerated nutrient solution, Ornithopus spp. failed to increase their shoot RGR (particularly for O. sativus cultivars); however, root RGR returned to that of the aerated controls. The stagnant conditions inhibited transport of potassium (K+) to the shoots in all species, as evidenced by lower shoot tissue K+ concentrations, with O. compressus and O. sativus most adversely affected (45% and 48% of the tissue concentration of aerated control plants). We conclude that the suggested area for Ornithopus spp. adaptation should not preclude areas of high rainfall because they have root adaptations that would assist them in coping with transient water excess; however, soil types and surface profiles conducive to long-term waterlogging should be avoided to negate significant productivity losses.