Root deformation affects mineral nutrition but not leaf gas exchange and growth of Genipa americana seedlings during the recovery phase after soil flooding

Root deformation (RD) caused by errors in the pricking out process are irreversible and very difficult to detect in container-grown seedlings at the time of planting in the field. The objective of this study was to evaluate the effects of RD on leaf gas exchange, growth, biomass allocation and mineral nutrition of G. americana seedlings during the recovery phase after soil flooding. Four-months-old seedlings, with and without RD, were flooded for 42 days and their recovery was evaluated 28 days after soil drainage. There were no significant interactions between RD and soil flooding for all leaf gas exchange, growth and mineral nutrition after soil drainage, with the exception of leaf P concentrations. In plants with no RD, the P concentration in leaves of non-flooded plants was significantly higher than that of plants with RD. Soil flooding and RD did not influence leaf or root N concentrations or whole-plant N content. RD increased the K concentration in the roots, but not in the leaves. Changes in the nutrient concentrations in leaves and roots indicate that RD may affect physiological performance of seedlings after planting in the field.

Drought and Subsequent Soil Flooding Affect the Growth and Metabolism of Savoy Cabbage

An important factor of current climate change is water availability, with both droughts and flooding becoming more frequent. Effects of individual stresses on plant traits are well studied, although less is known about the impacts of sequences of different stresses. We used savoy cabbage to study the consequences of control conditions (well-watered) versus continuous drought versus drought followed by soil flooding and a potential recovery phase on shoot growth and leaf metabolism. Under continuous drought, plants produced less than half of the shoot biomass compared to controls, but had a >20% higher water use efficiency. In the soil flooding treatment, plants exhibited the poorest growth performance, particularly after the “recovery” phase. The carbon-to-nitrogen ratio was at least twice as high, whereas amino acid concentrations were lowest in leaves of controls compared to stressed plants. Some glucosinolates, characteristic metabolites of Brassicales, showed lower concentrations, especially in plants of the flooding treatment. Stress-specific investment into different amino acids, many of them acting as osmolytes, as well as glucosinolates, indicate that these metabolites play distinct roles in the responses of plants to different water availability conditions. To reduce losses in crop production, we need to understand plant responses to dynamic climate change scenarios.

Understanding a Mechanistic Basis of ABA Involvement in Plant Adaptation to Soil Flooding: The Current Standing

Soil flooding severely impairs agricultural crop production. Plants can cope with flooding conditions by embracing an orchestrated set of morphological adaptations and physiological adjustments that are regulated by the elaborated hormonal signaling network. The most prominent of these hormones is ethylene, which has been firmly established as a critical signal in flooding tolerance. ABA (abscisic acid) is also known as a “stress hormone” that modulates various responses to abiotic stresses; however, its role in flooding tolerance remains much less established. Here, we discuss the progress made in the elucidation of morphological adaptations regulated by ABA and its crosstalk with other phytohormones under flooding conditions in model plants and agriculturally important crops.

Plant growth and nutrient composition in shrub and arbor willows grown in Cu contaminated soil as affected by flooding

Flooding can adversely worsen the metal contaminated soil and plant growth thus, it is crucial to explore the ecophysiological responses of plants upon co-exposure to heavy metals and flooding. Here, the plant growth, photosynthesis, and nutrient elements composition in arbor willow (Salix jiangsuensis ‘J172’) and shrub willow (Salix integra ‘Yizhibi’) were studied using a pot experiment with Cu contaminated soil (239.51 mg∙kg-1) under flooded versus non flooded condition. Salix integra showed larger BCFs than Salix jiangsuensis in both treatments, soil flooding significantly decreased the Cu contents and BCF while obviously increased TF values in both willow species (p < 0.05). Soil flooding markedly enhanced the leaf C:P and N:P ratios, while significantly decreased root C:P and N:P ratios, as compared to non flooded condition. The shrub willow exhibited better tolerance to soil flooding with little alteration in biomass and photosynthetic rate, and showed greater potential of Cu accumulation capacity, even though its total biomass was significantly lower than arbor willow. Our study also helps further understanding the nutrient balance and stoichiometry of willows in Cu contaminated soil and their response to soil flooding, helping the management of Cu-contaminated flooded soils.

Identification of ABA-Mediated Genetic and Metabolic Responses to Soil Flooding in Tomato (Solanum lycopersicum L. Mill)

Soil flooding is a compound abiotic stress that alters soil properties and limits atmospheric gas diffusion (O2 and CO2) to the roots. The involvement of abscisic acid (ABA) in the regulation of soil flooding-specific genetic and metabolic responses has been scarcely studied despite its key importance as regulator in other abiotic stress conditions. To attain this objective, wild type and ABA-deficient tomatoes were subjected to short-term (24 h) soil waterlogging. After this period, gas exchange parameters were reduced in the wild type but not in ABA-deficient plants that always had higher E and gs. Transcript and metabolite alterations were more intense in waterlogged tissues, with genotype-specific variations. Waterlogging reduced the ABA levels in the roots while inducing PYR/PYL/RCAR ABA receptors and ABA-dependent transcription factor transcripts, of which induction was less pronounced in the ABA-deficient genotype. Ethylene/O2-dependent genetic responses (ERFVIIs, plant anoxia survival responses, and genes involved in the N-degron pathway) were induced in hypoxic tissues independently of the genotype. Interestingly, genes encoding a nitrate reductase and a phytoglobin involved in NO biosynthesis and scavenging and ERFVII stability were induced in waterlogged tissues, but to a lower extent in ABA-deficient tomato. At the metabolic level, flooding-induced accumulation of Ala was enhanced in ABA-deficient lines following a differential accumulation of Glu and Asp in both hypoxic and aerated tissues, supporting their involvement as sources of oxalacetate to feed the tricarboxylic acid cycle in waterlogged tissues and constituting a potential advantage upon long periods of soil waterlogging. The promoter analysis of upregulated genes indicated that the production of oxalacetate from Asp via Asp oxidase, energy processes such as acetyl-CoA, ATP, and starch biosynthesis, and the lignification process were likely subjected to ABA regulation. Taken together, these data indicate that ABA depletion in waterlogged tissues acts as a positive signal, inducing several specific genetic and metabolic responses to soil flooding.

The effects of waterlogging on the solubility of arsenic and ecotoxicity of soil pore water in non-fertilized and fertilized soils in historical mining sites.

&lt;p&gt;Soil contamination with arsenic in historical mining sites is a matter of considerable environmental concern, as the concentrations of As in those soils are locally as high as thousands mg/kg. Some of soils, particularly those affected in the past by tailings that were released from impoundments, are located in floodplains and used as grasslands. Those lands are periodically flooded, and the frequency and duration of flooding will probably increase in the future with changing climatic conditions. Reducing environment that develops upon soil flooding can cause a release of As from soil solid phase. This is an inherent effect of reductive dissolution of amorphous and crystalline iron hydroxides that are the main hosting components for metalloids. Changing redox conditions affect also the speciation of As in pore water, influencing its toxicity to soil biota. Moreover, soil fertilization with inorganic fertilizers that contain phosphates, or with organic fertilizers such as cattle manure, can accelerate As release from iron hydroxides, mainly via competitive desorption. The effects of all those processes are highly dependent on soil properties and still require a close examination.&lt;/p&gt;&lt;p&gt;Three kinds of soil material, containing up to 8000 mg/kg As, were collected from the tailings-affected floodplain of the Tuj&amp;#261;ca river in Z&amp;#322;oty Stok, a historical As mining centre. A laboratory incubation experiment with fertilized and non-fertilized soils was carried out to examine the changes in As concentrations in soil pore water, as well as to assess pore water ecotoxicity, determined in standard bioassays, including Microtox and Phytotox. Soil flooding resulted in a rapid release of As from soil solid phase. As concentrations in soil pore water in all samples exceeded 10 mg/L after a 2-day incubation, and tended to increase slowly with time. In some cases, after the 270-day incubation, As concentrations in pore water reached several hundred mg/L. Those effects resulted in a very high ecotoxicity of pore water, caused lethal effects to bacteria and springtails, and impeded plant germination. Soil amendment with manure was a factor that significantly enhanced those effects. The factors responsible for various effects that were reported from three soils were discussed.&lt;/p&gt;

Expression of genes related to soil flooding tolerance in soybeans

The flooded environment brings about injuries to soybeans that vary depending on the adaptation ability of the genotype. Oxygen deprivation promotes the induction of the expression of genes related to glycolysis and fermentation pathways to maintain energy metabolism and, in addition to reducing-power consuming processes, act in the formation of adaptive structures and the maintenance of the redox status of the plant. The aim of this work was to evaluate the relative expression of genes related to soil flooding response in two contrasting soybean cultivars. Soybean plants of the sensitive (BRS 154) and tolerant (I27) cultivars at the V1 development stage were submitted to the flooding and control conditions (without flooding) for 0, 24, 48, and 96 hours. The relative expression of genes associated with flooding, including enolase (ENO), alcohol dehydrogenase 1 (ADH1), alanine aminotransferase 2 (ALAT2), hemoglobin 1 (GLB1), LOB41 domain-containing protein (LBD41), xyloglucan endotransglycosylase (XETP) and ascorbate peroxidase (APX2), was evaluated by means of RT-qPCR. The relative expression, in general, increased with flooding, especially in the root tissue. Cultivar I27 responded positively as observed by the expression of the maintenance genes of energy metabolism, structural changes and detoxification, suggesting the presence of three tolerance mechanisms in the flooding response.