Effects Of Salinity Levels Research Articles

The effect of salinity levels on certain physiological groups of microorganisms in irrigated soils of Bukhara region

This article describes some physiological classes of microorganisms (nitrifiers, ammonifiers, and nitrate reducers), their activity, and the variables influencing it in the alluvial soils of irrigated meadows in the Bukhara region.A thorough analysis of the effects of an excess of readily soluble salts in water on ammonifiers, nitrifiers, and nitrate reducers belonging to the physiological group of microorganisms, as well as the influence of soil salinity levels and salt content on these microorganisms, is provided.

Sexual Maturity and Macronutrient Contents in Diopatra sp. (Onuphidae, Polychaeta) Maintained at Different Salinity Levels

Diopatra sp. (Onuphidae, Polychaeta) is an economically important polychaete species commonly used as a fishing bait by local anglers in Cilacap, Central Java Province. Some biological aspects of this local species, however, have not been studied yet. The aim of this research was to see the effect of salinity levels on the sexual maturity and the macronutrient contents of the animals. Diopatra specimens in the present study were collected from the intertidal mangrove habitats of Jeruklegi Village, Cilacap, in sexually immature condition. The worms were then transported to the laboratory and were maintained in containers with four different salinity levels, i.e. 10, 15, 20 and 25 ppt over the next two months. The sexual maturity of the animals were observed based on the presence or absence of coelomic gametes. Proximate analysis was performed to determine macronutrient contents of the animals. The effect of salinity levels on the animals' sexual maturity and macronutrient contents was analyzed using one-way ANOVA. The results showed that salinity levels did not significantly affect the sexual maturity level of Diopatra worms (p > 0.05). Similarly, they did not affect the protein and fat contents, but impacted the carbohydrate content of the animals (p < 0.05). The protein and the fat contents in Diopatra sp., i.e. 41–43% and 6–9%, respectively, met the amount required to be used as shrimp broodstock and fish feeds. While the species has the potential for use in local aquaculture, the annual reproductive cycle as well as the identity of the species, however, require further research.

Functioning of Mosquitofish in Different Bionomics as A Biocontrol Agent to Lower the Population of culex pipiens L. Larvae

The effect of salinity levels, water source and prey density on the predatory efficiency of mosquitofish, Gambusia affinis (Baird and Girard) against the 4th instar larvae of culex pipiens was studied. The salinity levels of 5, 10 and 15% significantly affected the rate of predation of G. affinis. All fishes have died at a salinity level of 15%. However, the predatory efficiency of both males and females was significantly higher at a 5% salinity level than that at 10%, despite fish sex or size. The number of mosquito larvae consumed by a female was higher than male at a 5% salinity level, but the reverse was observed at a salinity level of 10% despite the fish size. The type of water in which mosquito larvae or fish were bred affected the predatory efficiency of G. affinis for both male and female fishes and for all sizes of fish. Distilled water was the highest significant favorable water for predation. The density of mosquito larvae affected the predatory efficiency of G. affinis. Results showed that mosquito larvae at a density level of 40 larvae/200 ml water were the most favorable density for predation by G. affinis despite sex or size of the fish. In general, females were more efficient in predation than males despite fish size or prey density.

Resistance of bacteria isolated from leachate to heavy metals and the removal of Hg by Pseudomonas aeruginosa strain FZ-2 at different salinity levels in a batch biosorption system

Leachate is produced from sanitary landfills containing various pollutants, including heavy metals. This study aimed to determine the resistance of bacteria isolated from non-active sanitary landfill leachate to various heavy metals and the effect of salinity levels on the removal of Hg by the isolated bacterium. Four dominant bacteria from approximately 33 × 1017 colony-forming units per mL identified as Vibrio damsela, Pseudomonas aeruginosa, Pseudomonas stutzeri, and Pseudomonas fluorescens were isolated from non-active sanitary landfill leachate. Heavy metal resistance test was conducted for Hg, Cd, Pb, Mg, Zn, Fe, Mn, and Cu (0–20 mg L− 1). The removal of the most toxic heavy metals by the most resistant bacteria was also determined at different salinity levels, i.e., fresh water (0‰), marginal water (10‰), brackish water (20‰), and saline water (30‰). Results showed that the growth of these bacteria is promoted by Fe, Mn, and Cu, but inhibited by Hg, Cd, Pb, Mg, and Zn. The minimum inhibitory concentration (MIC) of all the bacteria in Fe, Mn, and Cu was > 20 mg L− 1. The MIC of V. damsela was 5 mg L− 1 for Hg and > 20 mg L− 1 for Cd, Pb, Mg, and Zn. For P. aeruginosa, MIC was > 20 mg L− 1 for Cd, Pb, Mg, and Zn and 10 mg L− 1 for Hg. Meanwhile, the MIC of P. stutzeri was > 20 mg L− 1 for Pb, Mg, and Zn and 5 mg L− 1 for Hg and Cd. The MIC of P. fluorescens for Hg, Pb, Mg, and Zn was 5, 5, 15, and 20 mg L− 1, respectively, and that for Cd was > 20 mg L− 1. From the MIC results, Hg is the most toxic heavy metal. In marginal water (10‰), P. aeruginosa FZ-2 removed up to 99.7% Hg compared with that in fresh water (0‰), where it removed only 54% for 72 h. Hence, P. aeruginosa FZ-2 is the most resistant to heavy metals, and saline condition exerts a positive effect on bacteria in removing Hg.

Effects of salinity level on growth performance, feed utilization, and chromatic deformity of the hybrid Red tilapia, Oreochromis niloticus x O. mossambicus

Four different salinities (0, 13, 26, and 39 ppt) were tested to evaluate their effects on growth performance, feed utilization, carcass composition, and chromatic deformity of the hybrid red tilapia (Oreochromis niloticus and O. mossambicus). 204 samples of 97 days post-hatch fingerlings red tilapia were stocked in a glass aquarium filled with 80 liters of water at a stocking rate of 17 fingerlings/ aquarium (0.21fingerlings/L), with an average initial weight of 12.48±0.04 g/fish and three replicates for each treatment. Fingerlings were fed on the experimental diet containing 30.3% protein at a 5% feeding rate, and re-adjusted periodically every10 days. The experimental period was 42 days. The results revealed that the final weight, weight gain, ADG, and SGR values increased significantly (P≤0.05) at the salinity level of 26 ppt, followed by 13 ppt salinity level. The survival % showed that all salinity levels had a high percentage without recording significant differences (P>0.05) between treatments. The best FCR was recorded in a salinity level of 26 ppt with significant differences (P≤0.05) between the treatments. The highest values of PER, PPV, and energy gain were recorded at 26 ppt. Salinity levels significantly influenced dry matter, protein, ether extract, ash, and carcass energy under the investigated salinities. The lowest percent of the chromatic deformity was achieved at salinity 26 ppt. It could be concluded that cultivating hybrid red tilapia in salinity levels between 13 and 26 ppt would significantly improve growth performance and feed utilization and reduce the percentage of fish with chromatic deformity as well.

The Effect of Salinity Levels of irrigation water and Mechanical Damage of Seeds on the Germination and Growth Characteristics of Seedlings of Two Varieties of Bread Wheat (Triticum aestivum L.)

A factorial experiment with completely randomized design (CRD)with three replicates was carried out at agronomy laboratory of the Directorate of seed testing and certification / Branch of Salahaldeen to study the effect of salinity levels of irrigation water )0 ،1.75 and 2 Mm ) and grains affected by the use of mechanical seeds in seed germination and seedling growth for two varieties of wheat bread(IPA99 and Sham 6). The characteristics of germination percentage، speed germination، length of plumule and radical، pure live seed percentage and seed vigor studied. The observed results are as follows :Significant differences are found between cultivars. (IPA99) cultivar gave the highest tolerance to water salinity and seed fracture. However، salinity levels and seed fracture caused a significant decrease in all features. As for interactions، cultivars and seed mechanical damage interactions were significant in all characteristics. While the interactions of varieties and levels of salinity were significant in the characteristics of the speed of germination and length of plumule . Interactions of salinity levels and seed mechanical damage did not reach the significant limit except for the characteristic of the plumule’s length, which reached the highest value at 7.697 cm. At the same time, the triple interactions (cultivars، seed mechanical damage and levels of salinity) were significant except for both germination percentage and pure live seed percentage. The best triple interaction was (IPA99) with 1.75 Mm and undamaged seed, which gave the best values in: germination percentage، length of plumule and radical، pure live seed percentage and seed vigor. The values of the above were as follows: 98.67%، 8.707 cm، 10.01 cm، 94.72، 18.45 respectively.

Effects of salinity level on the activity of chloride cell and mucus secreting cell in the gill of the female Shortfin molly, Poecilia mexicana Steindachner, 1863

Ovoviviparous poeciliid fishes have been relatively well studied in the unique reproductive strategy, but their osmoregulatory system largely remains unknown. In this study, we conducted a short-term (7 days) lab experiment to investigate the effect of different salinity levels from 0 (freshwater) to 50 ppt (mesosaline) on the number of chloride cells and mucus secreting cells of female Poecilia mexicana. Chloride cells were found at high density along the epithelial lamellae, whereas mucus secreting cells were also concentrated in the gill raker epithelium. More interestingly, the average density of chloride cells and the mucus secreting cell were significantly increased at high salinity levels (P < 0.05). While further validation by immunohistochemistry is warranted, integrative data from our study suggested that the potential function of the osmoregulatory mechanism/strategy was supported by chloride and mucus secreting cells of female P. mexicana gill.

Partial nitrification performance and microbial community evolution in the membrane bioreactor for saline stream treatment

Effects of salinity level and gradient on partial nitrification performance, sludge properties and microbial activities were investigated using partial nitrification membrane bioreactors (PN-MBRs). PN-MBRs obtained stable nitrite accumulation rate of 91.1% and ammonia removal of 64.8% at 10 g/L NaCl. 10 g/L NaCl obtained higher oxygen uptake rate than 5 g/L, and promoted the differentiation of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria. Salinity increased sludge flocs size, stimulated secretion of extracellular polymeric substances with high carbohydrates contents, but had insignificant impact on sludge settleability and dewaterability. Salt level and gradient were both important for microbial community evolution to salt-tolerant bacteria. PN-MBRs enriched aerobic AOBs (Nitrosomonas and norank_f_Nitrosomonadaceae) and anaerobic AOBs (Candidatus_Kuenenia and Candidatus_Brocadia) for partial nitrification, while salt gradients resulted in different metabolism pathways for nitrification even at the same salinity. Increasing salinity promoted hydroxylamine oxidizer in nitrification process evolving from Candidatus_Kuenenia and Candidatus_Brocadia to aerobic AOBs.

EFFECT OF SALINITY ON PHOTOSYNTHETIC AND ENZYMATIC ACTIVITIES AND TUBERIZATION YIELD IN THE GENOTYPE OF POTATO CULTIVAR AGRIA UNDER IN VITRO CONDITIONS

The aim of this study aimed to investigate the effect of salinity levels on physiological and biochemical properties and tuberization yield of potato, cultivar Agria, in MS culture medium. After preparation and cultivation of tuber, the lateral aerial buds were removed after a few months and cultured in MS medium. After that, healthy samples were prepared and induced at the above-mentioned salinity stress level and transferred to the culture medium. Two weeks later, an air sample was taken, and the physiological and biochemical properties studied in this study (photosynthetic pigments, proline, soluble sugars, anthocyanins, phenolic compounds, and the activity of some antioxidant enzymes) were measured. Finally, salinity stress assessment was evaluated and studied in a fluid environment. The effects of stress on different stages of seedling growth in vitro conditions and the activity of photosynthetic and enzymatic pigments were investigated using spectrophotometric measurements and in accordance with their protocols. Data analysis of variance showed that salinity reduces photosynthetic pigments and salinity to a concentration of 50 mM, it is resistant to the addition of compounds such as soluble sugars, proline and antioxidant activity but at higher concentrations (75 and 100 mM), the plant is likely to be severely damaged due to excessive growth in active oxygen species. Therefore, due to the increase in antioxidant activity, it indicates an increase in the removal of active oxygen species, this feature is often used as an indicator to increase salinity tolerance. Research on the different ecological conditions in Iran, research is needed on other potato cultivars and molecular studies.

RESPONSE OF PEAR SEEDLINGS TO SOME NON-AND MAGNETIZED SALINE IRRIGATION WATER AND HUMIC ACID AND THEIR EFFECT ON GROWTH, LEAF PHYSIOLOGICAL PROPERTIES, LEAF PIGMENTS AND ELEMENTS CONTENTS

This study was conducted during two successive seasons of 2018 and 2019 at El Kanater Horticultural Research Station, Qalyoubeia Government Egypt. The aim of this investigation was to study the effect of salinity levels of non-and magnetized irrigation water alone and in combination with humic acid on one-year-old pear seedlings (Pyrus communis) rootstock. Obtained results revealed that, the two higher concentrations of saline water (1500 and 3000 mg/l) resulted in a gradual significant decreased in all vegetative measurements, dry weights of pear seedling organs, both leaf succulence grade, water potential and leaf content of pigments as well as some leaf elements contents of N, P, K, Mg, Fe, Zn and Mn, Whereas an opposite trends were observed with leaf osmotic pressure, proline content and leaf content of Ca, Na and Cl as compared to the control (270 mg/l –fresh water). On the other hand, seedlings treated with either humic acid or magnetized water were exited significantly an increasing values of vegetative parameters, dry weights of different plant organs, leaf pigments and some macro and micro-nutrients beside Na and Cl as well as both leaf succulence grade and water potential as compared to control (non-magnetized water or non-humic acid) in both seasons of study. The obtained data concluded that the use of magnetized water technique with humic acid applications would be efficiently and safe alternative tool to resolve the problem of irrigating with saline water and to enhance pear rootstock seedlings growth grown under similar conditions of this study.

Aqueous Mercury Removal with Carbonaceous and Iron Sulfide Sorbents and Their Applicability as Thin-Layer Caps in Mercury-Contaminated Estuary Sediment

This study aimed to investigate the Hg removal efficiency of iron sulfide (FeS), sulfurized activated carbon (SAC), and raw activated carbon (AC) sorbents influenced by salinity and dissolved organic matter (DOM), and the effectiveness of these sorbents as thin layer caps on Hg-contaminated sediment remediation via microcosm experiments to decrease the risk of release. In the batch adsorption experiments, FeS showed the greatest Hg2+ removal efficiencies, followed by SAC and AC. The effect of salinity levels on FeS was insignificant. In contrast, the Hg2+ removal efficiency of AC and SAC increased as increasing the salinity levels. The presence of DOM tended to decrease Hg removal efficiency of sorbents. Microcosm studies also showed that FeS had the greatest Hg sorption in both freshwater and estuary water; furthermore, the methylmercury (MeHg) removal ability of sorbents was greater in the freshwater than that in the estuary water. Notably, for the microcosms without capping, the overlying water MeHg in the estuary microcosm (0.14−1.01 ng/L) was far lesser than that in the freshwater microcosms (2.26−11.35 ng/L). Therefore, Hg compounds in the freshwater may be more bioavailable to microorganisms in methylated phase as compared to those in the estuary water. Overall, FeS showed the best Hg removal efficiency, resistance to salinity, and only slightly affected by DOM in aqueous adsorption experiments. Additionally, in the microcosms, AC showed as the best MeHg adsorber that help inhibiting the release of MeHg into overlying and decreasing the risk to the aqueous system.

Salinity tolerance improvement of in vitro propagated Paulownia tomentosa using proline

BackgroundPaulownia tomentosa has been used as an ornamental plant and is still vastly used for this objective and can be utilized for the production of energy, wooden building materials, and paper pulp. The aim was to improve the in vitro propagation ability under salinity stress.MethodologyThis experiment was conducted on Paulownia tomentosa at Tissue Culture Technique Lab., Central Laboratories, Department of Ornamental Plants and Woody Trees, National Research Centre (NRC), Egypt, to examine the micropropagation behavior using different plant growth regulators (BA, Kin, and IBA) and improve the in vitro propagation ability of plant under the effect of salinity levels (500, 1000, 2000, and 4000 ppm) using two concentrations of proline (0.2 and 0.4 g/l).ResultsFor in vitro propagation behavior, the best results for both shooting and rooting behaviors were obtained when MS culture medium was supplemented with BA at 0.2 mg/l, and Kin and IBA at 0.1 mg/l. For the improvement of the in vitro propagation ability under salinity stress, the survival was 100% when the shootlets of Paulownia grown on MS culture medium supplemented with 0.5 g NaCl plus 0.2 or 0.4 g/l proline and 1 g NaCl plus 0.2 g/l proline which were similar to control treatment.ConclusionMicropropagation ability of Paulownia tomentosa under salinity stress was optimized when the explants were cultured on MS medium supplemented with BA at 0.2 mg/l, and Kin and IBA at 0.1 mg/l using proline at 0.2 g/l. This study will help the producers to cultivate Paulownia trees in saline soils up to 1000 ppm such as some new lands which are not suitable for growing other crops.

Tuzluluk Stresi altında Lathyrus sativus L.'nin Çimlenme ve Büyümesini İyileştirmede, Salisilik Asit ile Tohum Priming Uygulaması

Increasing the ability of crops to maintain growth and productivity under saline conditions is of paramount importance. The effect of salicylic acid (SA) priming on germination and physiological traits of Lathyrus sativus under salinity stress was studied in a factorial experiment based on a completely randomized design. The experimental treatments composed of SA at three levels (0, 0.1, and 0.2 mM) and NaCl salinity at three levels (0, 50, and 100 mM). The effect of salinity level and SA priming was significant on all recorded factors, except from final germination percentage. As salinity level increased, all germination and physiological traits declined compared with control, whereas the mean germination time and percentage of cell death were increased. Moreover, as salinity was intensified, the Hill reaction was decreased significantly. Salinity exhibited the strongest effects at NaCl rate of 100 mM. Seed priming with SA increased germination speed index, reduced mean germination time, and increased leaf relative water content, seedling fresh and dry weight compared with plants from non-primed seeds. Seedling vigor index was increased by 23.4% in primed seeds with 0.2 mM SA. SA priming especially at 0.2 mM rate increased the Hill reaction rate and reduced percentage of cell death. SA priming could be regarded as a practical approach to improve germination traits, seedling growth, and physiological traits of Lathyrus sativus L. under salinity stress conditions.

GERMINATION AND SEEDLING GROWTH OF SILYBUM MARIANUM AS A MEDICINAL PLANT UNDER SALINITY STRESS

Milk thistle (Silybum marianum) is used as a medicinal plant in the treatment of liver diseases. In order to investigate germination and seedling growth in S. marianum subjected to NaCl, a three replicated experiment was carried out in a randomized complete block design in the laboratory of Gorgan University of Agricultural Sciences and Natural Resources. Treatments included seven salinity levels (50, 75, 100, 125, 150, 175 and 200 mM) and a control (distilled water). Germination percentage (GP), mean germination time (MGT), seed-ling vigour index (SVI), shoot, root and seedling weight were measured. The effect of salinity levels was significant on GP, SVI, MGT and seedling weight and length (p ≤ 0.01). However, the NaCl concentration effect was not significant on shoot : root length ratio and or shoot : root weight ratios. Results showed that germination decreased when salinity increased, while MGT increased. MGT was 1.75 times higher than in the control at the highest salt concentration. MGT difference was not significant between 75 mM NaCl and con-trol, while it dramatically increased by increasing the NaCl concentration from 150 to 200 mM NaCl. Reduc-tion slope and salt tolerance index (STI) were estimated for germination (0.54 and 231.9) and seedling stage (0.24 and 237.4). According to the results, milk thistle could be considered as a valuable medicinal plant in fairly salinized areas.

Effects of salinity level on the survival, growth, feed utilization, carcass composition, haematological and serum biochemical changes of juvenile Meagre (Argyrosomus regius) (Asso, 1801) grown in ground saltwater

A study was performed to examine the effects of salinity on water quality, fish performance, carcass composition and haemato-biochemical parameters in juvenile meagre, Argyrosomus regius. Fish (5.0 g) were stocked in fibreglass tanks at four salinity levels: 8‰, 16‰, 24‰ and 32‰, and fed a pelleted diet (47/17 protein/lipid) for 56 days. Results indicated that the growth, feed utilization, carcass composition and haemato-biochemical parameters of meagre gradually improved with the increase in salinity up to 24‰ and then significantly (p ≤ .05) decreased at 32‰. The survival per cent showed a significant decrease when A. regius exposed to 8‰ salinity. An improvement with 32%, 47% and 34.1% of FCR, protein productive value and energy utilization was detected at 24‰ compared with 8‰ salinity respectively. The highest content of protein and the lowest of lipids were recorded in fish carcass at 24‰ compared with the opposite trend at 8‰ salinity. The 24‰ salinity treatment exhibited the highest value of haemoglobin (4.9 g/dl) and the lowest ratio (0.73) of albumin/globulin. The serum total protein, albumin and globulin were significantly higher at 24‰ and 32‰ salinity than those at 8‰ and 16‰ salinity groups. These findings indicate that 24‰ salinity level might be the best for meagre.

Detection of salinity stress in soilless tomato based on crop reflectance

Salinity is one of the most serious abiotic factors limiting the productivity of agricultural crops, with adverse effects on germination, plant water relation and crop yield. Until recently, salinity stress management techniques were based on electric conductivity measurements that indicate the salinity level in the root zone or destructive sampling methods, something difficult to realise in real time. Hyperspectral sensing is a non-destructive sensing technology that can be used to extract information from a target object based on spectral data. In the present work, the effect of salinity level on leaf reflectance measured by a portable hyperspectral sensor (ASD Inc.) is studied. For this purpose tomato plants were cultivated under two levels of salinity (electrical conductivity: 2.7 and 5 dS m(‑1)). Plant spectral data were transformed into vegetation indices to define the physiological status of the crop. The results of the study are promising and show that hyperspectral sensors could be used for early salinity stress detection.

Salt-Stress Induced Protein Pattern Related to Seed Germination Indices in Lemon Balm (Melissa officinalis L.)

Salinity is one of the major environmental stress factors that cause many adverse effects on growth and productivity of plants. The objective of the present study was to investigate the effects of salinity levels on seed germination indices and protein patterns in Melissa offcinalis seedlings. An experiment was carried out based on randomized complete block design with five concentrations of NaCl and four replicates with sand medium. The results indicated that salt stress had negative effects on the seed germination percentage (GP), mean germination time (MGT) and germination rate (GR), primary shoot and root length, as well as the protein content. After two days of salt exposure, the lowest (0%) GP was obtained for seeds treated with 12 dSm-1 salinity, as compared to the control (48.5%). Although, high salinity levels delayed seed germination, but during the experimental period GP increased and no significant differences were observed among the treatments in terms of GP after two weeks. The highest MGT (4.97 days) was obtained for plants stressed with 12 dSm-1 salinity level, as compared to the control (1.89 days). Analysis of the protein bands revealed that salinity suppressed the expression of two proteins with the size of 45 (Y1), and 40 kDa (Y2) and protein of 60 kDa (D1) was down-regulated. Also, the synthesis of four proteins of 70 (X1), 30 (X2), 25 (X3), and 20 kDa (X4) was induced in the seedlings under salinity stress. The changes in protein pattern under salinity stress indicated that the synthesis of new proteins may be associated to the stress specific proteins.

Salt stress affects germination, seedling growth and physiological responses differentially in eggplant cultivars (Solanum melongena L.)

Abstract Salinity tolerance levels and physiological changes were evaluated in four eggplant cultivars ( Solanum melongena L.). Seeds and seedlings were exposed to increasing salinity levels. In vitro germination kinetics and young seedling growth divided the cultivars in a sensitive and a tolerant group. ‘Adriatica’ and ‘Black Beauty’ supported only moderate salt stress up to 40 mM NaCl while the tolerance level of ‘Bonica’ and ‘Galine’ was up to 80 mM NaCl. Effects of salinity levels (0, 20, 40, 80 and 160 mM of NaCl) were also tested in a greenhouse experiment. Increasing NaCl concentration increased strongly the levels of proline, malondialdehyde and soluble carbohydrates in the leaves of ‘Adriatica’ and ‘Black Beauty’. In contrast, ‘Bonica’ and ‘Galine’ showed a decrease in soluble carbohydrates and a significant increase in starch under saline stress. The midday leaf water potential (ψ l ) and leaf osmotic potential (ψ π ) were significantly affected in sensitive cultivars and remained quite stable in tolerant cultivars under salt stress. Leaf Na + and Cl − content was higher in sensitive than in tolerant cultivars. The leaf K + , Ca 2+ and Mg 2+ contents were reduced under salt stress in sensitive cultivars. Under increasing salinity ‘Bonica’ and ‘Galine’ combine low leaf Na + accumulation with a high plant tolerance index (PTI) thus maintaining a normal level of growth, while ‘Adriatica’ and ‘Black Beauty’ accumulate significantly higher concentrations of leaf Na + and fail to maintain a normal level of growth from 80 mM NaCl on.

Effect of pH and Salinity on Polarization Behavior of Cathodically Protected HY80 Steel, Inconel 625 and Nickel-Aluminum Bronze in Mexican Gulf Seawater

Metal structures submerged in seawater are subject to corrosion. Corrosion protection is usually implemented by applying negative potentials between -0.8 and -1.0 V vs Ag/AgCl reference electrode [1]. At these potentials, anodic metal dissolution is expected to be suppressed, and the typical dominant reactions that govern electron transfer on the protected surface in seawater are oxygen reduction reaction (ORR) and hydrogen evolution from water. The ORR in basic environments (pH~ 8.4) result in the generation of hydroxyl ions, eliciting an increase in the carbonate (CO3 2-) ions from the carbonate buffer system. When concentrations of CO3 2- and OH- near the electrode surface become sufficient to exceed solubility constants of CaCO3 and Mg(OH)2 compounds, they precipitate on the surface, decreasing the electroactive surface area, and making cathodic protection more efficient [2]. Formation of calcareous deposits on metal alloys is affected by applied potential, DO level, salinity, pH and temperature. Although the influence of DO, pH and temperature on the formation of calcareous deposits have been previously reported [3-5], the effect of salinity level has been overlooked. The effect of pH has been explored only minimally for a limited range of pH (usually ~ 7). Here, we explore polarization behavior of three cathodically protected alloys (Inconel 625, HY 80 Steel, and C-632 Nickel-Aluminum Bronze used in marine environment as a function of seawater salinity and pH. Electrochemical experiments were conducted in a three-electrode electrochemical cell (BioLogic, Inc). Freshly polished coupons of three different alloys served as working electrodes (WEs), while platinum mesh and Ag/AgCl in 3M NaCl (BioLogic, Inc) were used as a counter and reference electrodes, respectively. WEs held at -1.0 V were immersed into 0.5, 3.5 or 35 ppt seawater for 24 h, and polarization curves were recorded at 0.6 V/h prior and following the potential hold. Acetic acid, MES and MOPS organic buffers (Sigma Andrich) were used for maintaining pH levels of 5, 6, and 7, respectively. Seawater from Mexican Gulf was collected at Key West, FL. The influence of salinity and pH on polarization behavior of HY 80 steel is shown in Figures 1 and 2, respectively. The presentation will discuss the reasoning behind the changes in HY 80 Steel, Inconel 625 and C-632 Nickel-Aluminum Bronze polarization behavior under different environmental conditions.

On the use of spectral reflectance indices to assess agro‐morphological traits of wheat plants grown under simulated saline field conditions

AbstractSuccessful breeding of plants for salinity stress tolerance requires realistic growing conditions and fast, non‐destructive evaluation techniques for phenotypic traits associated with salinity tolerance. In this study, we used subsurface water retention technique (SWRT) as a growing condition and spectral measurements as an evaluation method to assess different agro‐morphological traits of salt‐tolerant (Sakha 93) and salt‐sensitive (Sakha 61) wheat genotypes under three salinity levels (control, 60, and 120 mm NaCl). The effects of salinity on agro‐morphological traits were evaluated and related with forty‐five published vegetation‐ and water‐spectral reflectance indices (SRIs) taken at both the heading and grain milk growth stages for each salinity level, genotype, and growth stage. In general, the agro‐morphological traits gradually decreased as salinity levels increased; however, the reduction in these traits was more pronounced in Sakha 61 than in Sakha 93. The effect of salinity levels and their interaction with genotypes on the SRIs was only evident at the grain milk stage. The performance of the spectral reflectance indices depicted that the closest associations with agro‐morphological traits depended on salinity level, degree of salt tolerance of the genotypes, and growth stage. The SRI‐based vegetative indices correlated better with growth and yield of Sakha 93 than SRI‐based water indices and vice versa for Sakha 61. The SRI‐based vegetative and water indices are effective for assessment of agro‐morphological traits at early growth stages under high salinity level. The functional relationship between grain yield per hectare and the best SRIs was linear for the high salinity level and Sakha 61; however, the quadratic model was found to best fit this relationship for the control, moderate salinity level, and Sakha 93. The overall results indicate that the usefulness of the SRIs for assessment of traits associated with salinity tolerance is limited to salinity level and growth stage.