Plants In Saline Environments Research Articles

Root and Shoot Biomass Growth of Constructed Floating Wetlands Plants in Saline Environments.

Constructed Floating Wetlands (CFWs) are increasingly being used globally in freshwater environments such as urban lakes and ponds to remove pollutants from urban stormwater runoff. However, to date there has been limited research into the use and performance of these systems in saline environments. This study compared the root and shoot biomass growth and nutrient uptake of five different plant species, Chrysopogon zizanioides, Baumea juncea, Isolepis nodosa, Phragmites australis and Sarcocornia quinqueflora, in three different saltwater treatments over a 12-week period. The aim of the study was to identify which of the plant species may be most suitable for use in CFWs in saline environments. Plant nutrient uptake testing revealed that Phragmites australis had the greatest percentage increase (1473–2477%) of Nitrogen mass in the shoots in all treatments. Sarcocornia quinqueflora also had impressive Nitrogen mass increase in saltwater showing an increase of 966% (0.208 ± 0.134 g). This suggests that the use of Phragmites australis and Sarcocornia quinqueflora plants in CFWs installed in saline water bodies, with regular harvesting of the shoot mass, may significantly reduce Nitrogen concentrations in the water. Isolepis nodosa had the greatest percentage increase (112% or 0.018 ± 0.020 g) of Phosphorous mass in the shoots in the saltwater treatment. Baumea juncea had the greatest percentage increase (315% or 0.026 ± 0.012 g) of Phosphorous mass in the roots in the saltwater treatment. This suggests that the use of Isolepis nodosa and Baumea juncea plants in CFWs installed in saline water bodies may significantly reduce Phosphorous concentrations in the water if there was a way to harvest both the shoots above and the roots below the CFWs. The study is continuing, and it is anticipated that more information will be available on CFW plants installed in saline environments in the near future.

Isolation and characterization of halotolerant phosphate-solubilizing microorganisms from saline soils.

Halotolerant phosphate-solubilizing microorganisms (PSMs) capable of producing plant-growth-promoting traits were grown on salt medium containing Ca3(PO4)2 or egg yolk. The number of colonies on plates with Ca3(PO4)2 was higher than that on plates with egg yolk. Further, a total of 42 PSM isolates were purified. The majority were Bacillus spp., while one Providencia rettgeri strain was confirmed, for the first time, as a PSM. All PSMs had a phosphate-solubilizing index (PSI) between 1.1 and 2.58 and a strong capacity for dissolving calcium phosphate between 2.25 and 442 mg·L-1. In contrast, these PSMs were less effective when dissolving aluminum phosphate, ferric phosphate and lecithin. Isolates were also tested for growth-promoting substances. The results showed that all isolates were able to secrete indole-3-acetic acid in amounts ranging from 2.7 to 31.8 mg·L-1 and exopolysaccharide within the range 74.3 and 225.7 mg·L-1. Only 12 siderophore-producing strains with siderophore units of 1.9-42.1% were detected. Among them, ten isolates with solubilization rates greater than 200 mg·L-1 and relatively high NaCl tolerance (1.5M) were classified as candidate PSMs. Eight different organic acids with different contents were detected in the culture filtrates, and propionic and oxalic acids have been proposed as the main mechanisms for solubilization. The ten isolates have the potential for use as bioinoculants to protect plants in saline environments.

Pressure-volume (P-V) curves in Atriplex nummularia Lindl. for evaluation of osmotic adjustment and water status under saline conditions

The survival of Atriplex nummularia plants in saline environments is possible mainly due to the presence of salt-accumulating epidermal vesicles. Commonly, destructive methods, such as plant material maceration and subsequent reading in osmometers, are employed in studies on water relations and osmotic adjustment and are inconvenient due to their underestimation of the total water potential inside the cells, which can cause overestimation of an osmotic adjustment that is not present. As a result, methods that preserve leaf structure, such as pressure-volume (P-V) curves, which take into consideration only the salts that compose the symplastic solution, are more adequate. Thus, the main objectives of this study were to evaluate the effect of determination methods of osmotic potential (Ψo) in Atriplex nummularia through destructive and leaf structure-preserving techniques and to determine the water relations of the species under increasing NaCl concentrations. Plants were subjected to daily irrigations, maintaining soil moisture at 80% of field capacity, with solutions of increasing NaCl concentration (0, 0.05, 0.1, 0.2, 0.25 and 0.3 M) for 84 days. Water potential, osmotic potential and osmotic adjustment were determined. In addition, P-V curves were constructed using pressure chambers. Water and osmotic potentials decreased linearly with increasing NaCl concentration in the irrigation solution. The main discrepancies observed were related to the osmotic adjustments determined through maceration and P-V curves. Based on the present research, it was possible to conclude that in studies with species that have salt-accumulating vesicles in the epidermis, such as the plants in the genus Atriplex, constructing P-V curves is more adequate than destructive methods.

Hydraulic redistribution: limitations for plants in saline soils.

Hydraulic redistribution (HR), the movement of water from wet to dry patches in the soil via roots, occurs in different ecosystems and plant species. By extension of the principle that HR is driven by gradients in soil water potential, HR has been proposed to occur for plants in saline soils. Despite the inherent spatial patchiness and salinity gradients in these soils, the lack of direct evidence of HR in response to osmotic gradients prompted us to ask the question: are there physical or physiological constraints to HR for plants in saline environments? We propose that build-up of ions in the root xylem sap and in the leaf apoplast, with the latter resulting in a large predawn disequilibrium of water potential in shoots compared with roots and soil, would both impede HR. We present a conceptual model that illustrates how processes in root systems in heterogeneous salinity with water potential gradients, even if equal to those in non-saline soils, will experience a dampened magnitude of water potential gradients in the soil-plant continuum, minimizing or preventing HR. Finally, we provide an outlook for understanding the relevance of HR for plants in saline environments by addressing key research questions on plant salinity tolerance.

Parental environments and interactions with conspecifics alter salinity tolerance of offspring in the annual Medicago truncatula

Summary Based on expectations of the stress‐gradient hypothesis for conspecific interactions, stress‐sensitive genotypes may be able to persist in stressful environments when positive interactions between individuals occur under stressful environments. Additionally, we test how parental environmental effects alter responses to stress and outcomes of conspecific interactions in stress. While the stress‐gradient hypothesis focuses on plant growth, earlier flowering may provide stress avoidance in short‐lived organisms. We studied responses to soil salinity and conspecific neighbour using genotypes of Medicago truncatula (Fabaceae) originating from saline or non‐saline environments, utilizing seeds from parental plants grown in saline or non‐saline environments. During the early stages of reproduction, we quantified leaf number, as a measure of vegetative growth, and number of flowers, as a measure of early reproduction potential. Based on leaf counts, non‐saline genotypes were better competitors than saline‐origin genotypes and benefited from neighbouring plants in saline environments. This positive interaction was detected only when seeds were matured on parental plants grown in non‐saline environments. Saline‐origin genotypes displayed greater salinity tolerance in early flowering than non‐saline genotypes. Plants with neighbours had greater early flowering, regardless of origin, consistent with facilitative interactions in stressful environments. Transgenerational plastic responses influenced neighbouring plant interactions on plant growth, and results suggest that facilitative interactions may be transient only persisting for one generation. However, earlier flowering of non‐saline genotypes when grown with a neighbouring plant is consistent with facilitative interactions resulting in reproductive benefits in saline environments, if earlier flowering is favoured in saline environments. Synthesis. Adaptation to stressful environments allows tolerant genotypes to persist in these environments. Less appreciated is that stress‐sensitive genotypes lacking such adaptations may persist in stressful environments via positive interactions with other individuals. Thus, positive interactions between individuals may explain the persistence of stress‐sensitive genotypes within a population adapted to stressful environments.

Sodium (Na+) homeostasis and salt tolerance of plants

Soil and water salinity substantially constrain crop and biomass production. Research over the last two plus decades, facilitated by advances in molecular genetics and biotechnology, and with genetic model systems, has identified genes involved in salt acclimation or adaptation and linked these to critical mechanisms and processes. A case in point is present understanding of critical transport determinants that facilitate intra- and intercellular Na+ homeostasis of plants in saline environments predominated by NaCl. Pumps in the plasma membrane (H+-ATPase), and the tonoplast (H+-ATPase) and H+ pyrophosphatases (AVP1) generate proton electrochemical gradients necessary to energize Na+ efflux to the apoplast and influx into vacuoles, respectively. The plasma membrane Na+/H+ antiporter SOS1 is responsible for apoplastic efflux, and NHX type Na+/H+ antiporters for vacuolar and endosomal compartmentalization. Ca2+ext reduces passive intracellular Na+ influx cells by decreasing Na+ transport through high affinity K+ uptake systems and what are presumed to be nonselective cation channels, and activating, through the SOS signal pathway, the SOS1 plasma membrane Na+/H+ antiporter. Moreover, there is greater understanding about how cellular transport systems functionally integrate to facilitate tissue and organismal Na+ homeostasis. Notable in this process are HKT1 Na+ transporters, which regulate Na+ loading into the root xylem, limiting flux to and accumulation in the shoot. This review will summarize ion transport systems that facilitate plant Na+ homeostasis. Halophyte and glycophyte salinity responses and transport determinant function are compared and contrasted. The potential of halophytes as genetic resources for unique alleles or loci of transport protein genes and transcriptional and post-transcriptional regulation of transport protein function are discussed in the context of crop salt tolerance.

Cultivation of medicinal and aromatic plants in saline environments.

Abstract In the last few decades there has been probably more interest in drugs obtained from plant sources than at any time in history because of success with antibiotics, and other plant drugs showing encouraging results in controlling serious diseases such as cancerous tumours and acting as stimulants and contraceptives, controlling cardiac arrests, and in the treatment of rheumatoid arthritis and several other ailments. With an increase in population and decrease in per capita available arable land (particularly in developing countries), it has become very difficult to find fertile land for cultivation of medicinal and aromatic plants (MAPs). The results reported in this review clearly indicate that cultivation of MAPs on degraded lands through biosaline agriculture is feasible and profitable. Experiments have been conducted in arid regions of the Indian subcontinent growing various MAPs on salt-affected lands and irrigating them judiciously with saline water. Several medicinal species (such as Plantago ovata , Aloe vera , Catharanthus roseus , Cassia angustifolia , Withania somnifera , Asparagus racemosus , Emblica officinalis , Terminalia arjuna , Azadirachta indica , Lepidium latifolium , etc.) and aromatic species (such as Cymbopogon flexuosus , Cymbopogon martinii , Vetiveria zizanioides , Matricaria chamomilla , Mentha arvensis , Pandanus odoratissimus , etc.) can successfully be cultivated on moderate alkaline/saline soils using saline irrigation, showing their potential. There are plenty of salt-tolerant species found in nature that can easily be domesticated to improve economic gains. Attempts should be made to educate the farming community about the practicalities of growing these plants and to create market avenues for procurement of these products. Scientists must develop more salt-tolerant and productive cultivars. These will not only provide better economic returns but also help in ameliorating the saline environment.

Characterization of Salt Overly Sensitive 1 (SOS1) gene homoeologs in quinoa (Chenopodium quinoa Willd.)

Salt tolerance is an agronomically important trait that affects plant species around the globe. The Salt Overly Sensitive 1 (SOS1) gene encodes a plasma membrane Na+/H+ antiporter that plays an important role in germination and growth of plants in saline environments. Quinoa (Chenopodium quinoa Willd.) is a halophytic, allotetraploid grain crop of the family Amaranthaceae with impressive nutritional content and an increasing worldwide market. Many quinoa varieties have considerable salt tolerance, and research suggests quinoa may utilize novel mechanisms to confer salt tolerance. Here we report the cloning and characterization of two homoeologous SOS1 loci (cqSOS1A and cqSOS1B) from C. quinoa, including full-length cDNA sequences, genomic sequences, relative expression levels, fluorescent in situ hybridization (FISH) analysis, and a phylogenetic analysis of SOS1 genes from 13 plant taxa. The cqSOS1A and cqSOS1B genes each span 23 exons spread over 3477 bp and 3486 bp of coding sequence, respectively. These sequences share a high level of similarity with SOS1 homologs of other species and contain two conserved domains, a Nhap cation-antiporter domain and a cyclic-nucleotide binding domain. Genomic sequence analysis of two BAC clones (98 357 bp and 132 770 bp) containing the homoeologous SOS1 genes suggests possible conservation of synteny across the C. quinoa sub-genomes. This report represents the first molecular characterization of salt-tolerance genes in a halophytic species in the Amaranthaceae as well as the first comparative analysis of coding and non-coding DNA sequences of the two homoeologous genomes of C. quinoa.

Prophylactively parking sodium in the plant

Prophylactively parking sodium in the plant

Interactions between growth, Cl− and Na+ uptake, and water relations of plants in saline environments. I. Slightly vacuolated cells

Abstract. Slightly vacuolated cells, i.e. microalgae and meristematic cells of vascular plants, maintain low Cl− and Na+ concentrations even when exposed to a highly saline environment. The factors regulating the internal ion concentration are the relative rate of volume expansion, the membrane permeability to ions, the electrical potential, and the active ion fluxes.For ion species which are not actively transported, a formula is developed which relates the internal concentration to the rate of expansion of cell volume, the permeability of membranes to that ion, and the electrical potential. For example, when the external concentration of Cl− is high, and Cl− influx is probably mainly passive, the formula predicts that rapid growth keeps the internal Cl− concentration lower than that in a non‐growing cell with the same electrical potential; this effect is substantial if the plasmalemma has a low permeability to Cl−.For ion species which are actively transported, the rate of pumping must be considered. For instance Na+ concentrations are kept low mainly by an efficient Na+ extrusion pump which works against the electric field across the membrane. The requirement for Na+ extrusion is related to the external Na+ concentration, the rate of expansion of cell volume, the membrane permeability, and the electrical potential. It is possible that microalgae have a more positive electrical potential than many other plant cells; if so, requirements for high rates of active Na+ extrusion will be lower. The required rates of Na+ extrusion are lower during rapid growth, provided that the permeability of the plasmalemma to Na+ is low.The energy required for the regulation of Cl− and Na+ concentrations is low, especially in rapidly expanding cells where Na+ extrusion requires only 1–2% of the energy normally produced in respiration. The exclusion of these ions, however, must be accompanied by the synthesis of enough organic compounds to provide adequate osmotic solutes for the increases in volume accompanying growth. This process reduces the substrates available for respiration and synthesis of cell constituents, but the reduction is not prohibitively large—even for cells growing in 750 mol m−3 NaCl, the carbohydrate accumulated as osmotic solute is only 10% of that consumed in respiration.

Interactions between growth, uptake of Cl− and Na+, and water relations of plants in saline environments. II. Highly vacuolated cells

Abstract. In a highly saline environment high rates of ion uptake are required to generate sufficient osmotic pressure to maintain the turgor that is needed for the continued growth of plants. We estimate the rates of net uptake of Cl− and Na+ required by growing cells to sustain cell expansion at an external NaCl concentration of 500 mol m−3. We also estimate the ion fluxes required to regulate turgor of expanding and fully expanded cells during diurnal changes in transpiration. Passive fluxes could contribute significantly to osmotic regulation, but active fluxes are still essential and would consume a substantial amount of energy. We discuss whether a limitation to growth at high salinity would arise from lack of energy, or from insufficient capacity for ion uptake. There is insufficient evidence to choose between these possibilities.

Plants in Saline Environments

Plants in Saline Environments