Maintaining Membrane Permeability Research Articles

Alternative ergosterol biosynthetic pathways confer antifungal drug resistance in the human pathogens within the Mucor species complex.

The Mucor species complex comprises a variety of opportunistic pathogens known to cause mucormycosis, a potentially lethal fungal infection with limited therapeutic options. The only effective first-line treatments against mucormycosis consist of liposomal formulations of amphotericin B and the triazoles posaconazole and isavuconazole, all of which target components within the ergosterol biosynthetic pathway. This study uncovered M. circinelloides Erg3 and Erg6a as key enzymes to produce ergosterol, a vital constituent of fungal membranes. Absence of any of those enzymes leads to decreased ergosterol and consequently, resistance to ergosterol-binding polyenes such as amphotericin B. Particularly, losing Erg6a function poses a higher threat as the ergosterol pathway is channeled into alternative sterols similar to cholesterol, which maintain membrane permeability. As a result, erg6a mutants survive within the host and disseminate the infection, indicating that Erg6a deficiency may arise during human infections and confer resistance to the most effective treatment against mucormycoses.

Ultra-Low Pressure Filtration Performance in Campus Domestic Waste

This study aims to determine the effect of ultra-low pressure filtration performance on the permeability of clean water and campus domestic waste. Waste treatment can be carried out by applying an ultra-low pressure membrane filtration process with a Gravity Driven Membrane (GDM) system. Ultra-low pressure membrane filtration has less impact on the environment, low energy use, easy operation, high efficiency in removing pathogens, organic matter and turbidity. The filtration was tested using clean water and campus domestic waste as bait with a duration of 30 minutes each for each pressure, starting from a pressure of 1 kPa-10 kPa with a total time of 780 minutes for one sample. At each pressure, a relaxation time will be given for 10 minutes, this is done to maintain membrane permeability. Long-term filtration was carried out for 35 days and every 7 days the domestic waste was replaced without backwashing the membrane. The results of this study indicate that the permeability of clean water decreases due to compaction that occurs along with increasing pressure. Meanwhile, the permeability of campus domestic waste has decreased due to compaction accompanied by pore blockage in the membrane (fouling).

Effects of α-Naphthylacetic Acid on Cadmium Stress and Related Factors of Tomato by Regulation of Gene Expression

Cadmium (Cd) is absorbed and accumulated by crops, and it adversely affects plant growth and development. To explore the effect of exogenous auxin on Cd stress, we applied different concentrations of α-naphthaleneacetic acid (NAA) and the auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) to tomato plants exposed to Cd stress in a hydroponic system. NAA and TIBA at different concentrations were used under Cd stress. Plant growth, root morphology, and auxin distribution were observed. Lipid peroxidation and antioxidant enzyme activities in leaves, cadmiumcontent, and migration coefficient of plants were determined. Transcriptome sequencing and qRT-PCR were used to analyze the differentially expressed genes. Results showed that auxin was concentrated in the leaf veins, stem base, and roots in P5::GUS “Chico III” transgenic tomato, indicating NAA polar transport to the roots and promotion of root growth under Cd stress. Cd was absorbed by the roots and transported to the shoots. It then inhibited plant growth and promoted antioxidant enzyme activities, O2− production, H2O2 accumulation, and membrane lipid peroxidation. Treatment with 0.5 μM NAA improved antioxidant enzyme activities, reduced reactive oxygen, maintained membrane permeability, and decreased malondialdehyde and proline contents. Transcriptome analysis revealed that NAA activated a large number of genes in the roots: 1998 genes were differentially expressed in response to Cd or NAA treatment, and 1736 genes were specifically expressed in response to NAA treatment under Cd stress. Among the differentially expressed genes, tomato metallocarboxypeptidase inhibitor TCMP-2 (2A11) and Solanum lycopersicum heavy metal-associated isoprenylated plant protein (HIPP) 7-like (LOC101264884), which are closely related to plant response to heavy metal stress, may be the key sites of NAA. In conclusion, the NAA-mediated response to Cd stress was closely associated with “defense response” genes in shoots and “oxidoreductase activity, oxidizing metal ions” and “response to auxin” genes in roots.

Improvement of permeation flux by evaluating the effects of coagulated-humic acids flocs and pH during coagulation-microfiltration hybrid process for water treatment: Performance, fouling modeling, specific energy consumption, and processes comparison

The objective of this study is to analyze the relation between flocs shape and the permeation flux stability in a pilot-scale Coagulation/Flocculation-Microfiltration hybrid process for humic acids removal from water under different coagulant dose and pH values. Besides, the treatment performance was examined. The results showed that at pH 7.1 and polychloride of aluminum coagulant of 10−1 mmol Al.L−1, coagulation/flocculation was effective in maintaining membrane permeability flux. Also, UV254, TOC, and turbidity removal efficiencies were almost ≥ 90%. In addition, this condition proved a potent effect on residual aluminum control and specific energy consumption, where they were, respectively, 0.0852 kWh.m−3 and 20 µg.L−1. Furthermore, humic acids fouling using four Hermia mechanisms (individual and combined) was modeled. Complete pores blocking and cake filtration appeared to be the major mechanisms of microfiltration membrane fouling. Finally, this hybrid process was compared with the most used technologies for the humic acids removal from water. It was concluded that the former process is more reliable, efficient, and cost-effective.

Molecularly Imprinted Affinity Membrane: A Review.

A molecularly imprinted affinity membrane (MIAM) can perform separation with high selectivity due to its unique molecular recognition introduced from the molecular-printing technique. In this way, a MIAM is able to separate a specific or targeted molecule from a mixture. In addition, it is possible to achieve high selectivity while maintaining membrane permeability. Various methods have been developed to produce a MIAM with high selectivity and productivity, with their respective advantages and disadvantages. In this paper, the MIAM is reviewed comprehensively, from the fundamentals of the affinity membrane to its applications. First, the development of a MIAM and various preparation methods are presented. Then, applications of MIAMs in sensor, metal ion separation, and organic compound separation are discussed. The last part of the review discusses the outlook of MIAMs for future development.

The Role of the Two-Component System PhoP/PhoQ in Intrinsic Resistance of Yersinia enterocolitica to Polymyxin.

Polymyxin is the “last resort” of antibiotics. The self-induced resistance to polymyxin in Gram-negative bacteria could be mediated by lipopolysaccharide (LPS) modification, which is regulated by the two-component system, PhoP/PhoQ. Yersinia enterocolitica is a common foodborne pathogen. However, PhoP/PhoQ has not been thoroughly studied in Y. enterocolitica. In this study, the functions of PhoP/PhoQ in Y. enterocolitica intrinsic resistance were investigated. The resistance of Y. enterocolitica was found to decrease with the deletion of PhoP/PhoQ. Further, PhoP/PhoQ was found to play an important role in maintaining membrane permeability, intercellular metabolism, and reducing membrane depolarization. Based on subsequent studies, the binding ability of polymyxin to Y. enterocolitica was decreased by the modification of LPS with structures, such as L-Ara4N and palmitate. Analysis of the gene transcription levels revealed that the LPS modification genes, pagP and arn operon, were downregulated with the deletion of PhoP/PhoQ in Y. enterocolitica during exposure to polymyxin. In addition, pmrA, pmrB, and eptA were downregulated in the mutants compared with the wild-type strain. Such findings demonstrate that PhoP/PhoQ contributes to the intrinsic resistance of Y. enterocolitica toward polymyxins. LPS modification with L-Ara4N or palmitate is mainly responsible for the resistance of Y. enterocolitica to polymyxins. The transcription of genes related to LPS modification and PmrA/PmrB can be both affected by PhoP/PhoQ in Y. enterocolitica. This study adds to current knowledge regarding the role of PhoP/PhoQ in intrinsic resistance of Y. enterocolitica to polymyxin.

The Chloride Conductance Inhibitor NS3623 Enhances the Activity of a Non-selective Cation Channel in Hyperpolarizing Conditions

Handbooks of physiology state that the strategy adopted by red blood cells (RBCs) to preserve cell volume is to maintain membrane permeability for cations at its minimum. However, enhanced cation permeability can be measured and observed in specific physiological and pathophysiological situations such as in vivo senescence, storage at low temperature, sickle cell anemia and many other genetic defects affecting transporters, membrane or cytoskeletal proteins. Among cation pathways, cation channels are able to dissipate rapidly the gradients that are built and maintained by the sodium and calcium pumps. These situations are very well-documented but a mechanistic understanding of complex electrophysiological events underlying ion transports is still lacking. In addition, non-selective cation (NSC) channels present in the RBC membrane have proven difficult to molecular identification and functional characterization. For instance, NSC channel activity can be elicited by Low Ionic Strength conditions (LIS): the associated change in membrane potential triggers its opening in a voltage dependent manner. But, whereas this depolarizing media produces a spectacular activation of NSC channel, Gárdos channel-evoked hyperpolarization's have been shown to induce sodium entry through a pathway thought to be conductive and termed Pcat. Using the CCCP method, which allows to follow fast changes in membrane potential, we show here (i) that hyperpolarization elicited by Gárdos channel activation triggers sodium entry through a conductive pathway, (ii) that chloride conductance inhibition unveils such conductive cationic conductance, (iii) that the use of the specific chloride conductance inhibitor NS3623 (a derivative of Neurosearch compound NS1652), at concentrations above what is needed for full anion channel block, potentiates the non-selective cation conductance. These results indicate that a non-selective cation channel is likely activated by the changes in the driving force for cations rather than a voltage dependence mechanism per se.

Effect of CPPU on postharvest attributes of Chinese flowering cabbage during storage

Chinese flowering cabbage is an important cultivated leafy vegetable. Experiments were conducted to test the effect of exogenous application of N-phenyl-N-(2-chloro-4-pyridyl) urea (CPPU) as a cytokinin analogue on postharvest attributes of Chinese flowering cabbage during storage at low temperature. The results revealed that CPPU treatment significantly delayed the de-greening of Chinese flowering cabbage. The treatment reduced the H2O2 accumulation, O2.− production rate and malondialdehyde content, maintained membrane permeability and delayed the decrease in the contents of total unsaturated fatty acids. Meanwhile, the deficiency of energy status referred to the ATP level and energy charge in relation to the expressions of energy-related genes of Chinese flowering cabbage was slowed down after CPPU treatment. Furthermore, the decreases in the contents of chlorophylls, the transcript levels of chlorophyll catabolic genes BrPAO1, BrPPH1, BrSGR1 and BrNYC1 and senescence associated genes BrSAG12 and BrSAG19 were markedly suppressed. These results exhibited that exogenous application of CPPU efficiently retarded the oxidative damage of membrane integrity, helped to maintain the energy status, slowed down the rapid degradation of chlorophylls and, thus, delayed the leaf senescence of Chinese flowering cabbage during storage, which suggested that the application of CPPU might be as a postharvest handling for quality maintenance and shelf life extension of leafy vegetables.

An energy-efficient membrane rotating biological contactor for wastewater treatment

Membrane filtration exhibits excellent separation performance for water and wastewater treatment but is still limited by the membrane fouling. This study presents a novel membrane rotating biological contactor (MRBC) that combines a conventional rotating biological contactor (RBC) with membrane filtration. MRBC combines conventional RBC with the membrane filtration placed in between two adjacent rotating disks to offer inherent control over membrane fouling. The disks rotations provide some degree of foulant removal, maintain membrane permeability, and potentially save a substantial amount of energy. The biological and hydraulic performance of MRBC was compared with a series of RBC and external membrane filtration (RBC + ME) where the membrane is treated as a post-treatment unit. Results show that the MRBC enhances not only the biological performance but also offers advantages for inherent membrane fouling control through the rotation of the disk. Membrane fouling control primarily originates from the enhanced shear rate from higher disk rotation and minimum membrane-to-disk gap. The hydraulic performance is 92.4% higher than literature, which further enhanced at smaller membrane-to-disk gaps and higher disk rotations. The highest steady-state permeability of 297 L/(m2.h.bar) and 288 L/(m2.h.bar) results at 40 rpm disk rotational speed and 0.5 cm membrane-to-disk gap, respectively. A projected full-scale MRBC consumes 0.18 kWh/m3 permeate, one-fourth of the energy for the referenced MBR system thanks to the active role of disks rotation for membrane fouling control which eliminates the need of extensive aeration like in the traditional MBRs. MRBC offers a promising alternative for traditional wastewater treatment as a low energy foot-print process, which is in line with the requirements of sustainable development and promotes the development of cleaner production.

Effect of scrubbing by NaClO backwashing on membrane fouling in anammox MBR

NaClO based chemically enhanced backwash (CEB) is often administered to maintain membrane permeability during the operation of MBR. However, the effect and working mechanism of NaClO concentrations in CEB were rarely investigated. The current investigation examined the changes in membrane resistance, permeate production and membrane morphology with or without CEB in an anammox MBR to reveal the scrubbing effect of different NaClO concentrations (0–596 mg/L). Good cleaning effect indicated by membrane fouling rate of 1.98–2.26 kPa/day and membrane permeate production of 80–88 L was observed when NaClO concentration of 149–596 mg/L was used. The best cleaning effect was observed when 298 mg/L of NaClO was used. To explore the mechanism of CEB action, backwashing foulants were also analyzed. Insoluble EPS transformed into soluble forms like S-EPS or SMP after the sludge was exposed to NaClO. The NaClO based CEB removed 112–675 mg of polysaccharide (PS)/m2 in foulants at NaClO concentration of 149–596 mg/L, which was significantly higher than the value obtained by pure water (35 mg PS/m2). The possible mechanisms behind the detachment of soluble PS seemed as oxidation and sterilization by NaClO. The current investigation provides useful guidelines on NaClO concentrations applied during CEB for anammox MBR.

Flexible Cleaning Regimes Promote Membrane Permeability

Maintain membrane permeability by selecting an efficient cleaning approach based on critical fouling dynamics and source water characteristics, with further reassessment as needed.

Investigating the significance of coagulation kinetics on maintaining membrane permeability in an MBR following reactive coagulant dosing

In this study, the impact of kinetically controlled floc growth on sustaining membrane permeability following reactive coagulant dosing was determined using a model particle system. Floc formation was indicated to comprise of two stages following coagulant addition: (i) an initial destabilisation phase which encouraged complexation of protein and polysaccharide; and (ii) entrapment of the coarse model particles (3µm Firefli™ microspheres) in the polymeric complex during the floc growth phase. Floc growth was characterised by an expected time lag as with conventional flocculation systems and biopolymer aggregation was kinetically favoured. When coagulant was dosed during the filtration cycle, the intermediate biopolymer aggregates (comprised of protein and polysaccharide) were preferentially transported toward the membrane increasing fouling. However, when coagulant was dosed at the onset of filtration, membrane fouling was constrained. It is asserted that by dosing at the onset of filtration: (i) early development of biopolymer aggregation is initiated which inhibits transport of the individual biopolymers to the membrane; and (ii) by dosing coagulant in the absence of a developed polarised layer, formation of biopolymer complexes local to the membrane is obviated. However, when dosing coagulant at the onset of filtration, only limited floc growth occurred which can be explained by the low applied wall shear rate and the absence of a ‘polarised’ region which ostensibly promoted floc growth when coagulant was dosed mid-filtration. Based on results from the model particle system studied, it is proposed that reactive coagulant dosing is best undertaken when: (i) filtration is stopped; (ii) modest shear is applied within the bioreactor to promote coagulant dispersion; and (iii) sufficient contact time is allowed to promote floc growth before commencement of filtration.

Proteins homologous to aquaporins of higher plants in the freshwater alga Ulothrix zonata (Ulotrichales, Chlorophyta)

The green filamentous alga Ulothrix zonata inhabits Lake Baikal and overgrows the underside of hummocky ice during winter and spring. To clarify physiological adaptations of U. zonata to low temperature and the potential contribution of membrane water permeabilities, the expression level of aquaporins from a winter population growing under the lake ice and in interstitial water was compared with that of benthic summer and autumn populations of algae by immuno-detection using an anti-maize PIP1 (plasma membrane intrinsic protein) antiserum. Algal, and in particular Ulvophycean, transcriptome sequences are only partially available and this higher plant-specific PIP1 epitope has not been detected so far in available genomic datasets. PIP1 expression levels were highest in the ice population and the rise in water temperature during summer was correlated with a drop in PIP1 amounts, which slightly increased again in autumn. ITS2 rDNA (internally transcribed spacer region 2) sequences revealed conspecificity of the ice and summer populations. The difference in PIP1 aquaporin expression suggests adaptation of the algae to changing environments by maintaining membrane permeability at low temperatures. Our study shows that the ice population of U. zonata inhabiting Lake Baikal is a unique subject for studying physiological and biochemical adaptation mechanisms of freshwater extremophiles.

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Objectives Because of the great diversity of human lipid species, discerning meaningful patterns in lipidomic data has proven daunting. Considering the function of lipid classes in maintaining cell membrane permeability and viscosity provides a tool to bring order to the chaos of lipidomic studies. Methods Literature search. Results Compared to controls, a decreased phosphatidyl choline (PC) to phophatidyl ethanolamine (PE) ratio is seen in preeclampsia, cold adaptation, and essential fatty acid deficiency lipidomics. Because PC tends to aggregate in a relatively impermeable lamellar pattern and PE in a more permeable hexagonal pattern, the altered sphingolipid ratios in these diseases may be interpreted as homeostatic responses to maintain membrane permeability. Cold adaptation occurs by remodeling phospholipids to reduce membrane stiffness. Lipids alter membrane flexibility in predictable ways: long-chain saturated fatty acids and trans fatty acids stiffen cell membranes, monounsaturated and medium-chain saturated fatty acids maintain moderate membrane viscosity, and polyunsaturated fatty acids increase membrane flexibility. Pulse wave velocity demonstrates that women with preeclampsia have significantly increased vascular stiffness, correlating positively with severity of disease. Dietary trans fatty acids are preferentially integrated into the sn-1 position of PCs, which contain PUFA at the sn-2 position; a rise in PC PUFAs is noted with diets enriched in trans fatty acids. Using metabolomics biomarkers, to predict preeclampsia in early pregnancy, long-chain PUFAs were found to be significantly increased in women destined to develop preeclampsia later in pregnancy compared to pregnant women who did not, therefore increasing the unsaturation index, a pattern similar to that of cold adaptation, but not found in essential fatty acid deficiency. Increased unsaturation index is positively correlated with increased oxidative stress, a known pathological element in preeclampsia. Conclusions Considering the effects of lipid species on membrane viscosity and permeability offers a novel means to interpret lipidomic studies. Disclosures N.R. Hart: None.

Simultaneous alkali supplementation and fouling mitigation in membrane bioreactors by on-line NaOH backwashing

In this study, we took advantage of the conventionally used physical backwashing and chemical cleaning methods to develop an on-line maintenance cleaning method using the NaOH solution (0.01mol/L, pH around 12) as the backwashing agent in a membrane bioreactor (MBR) operated at two imposed fluxes (6.5 and 13L/(m2·h) (LMH)). The results indicate that NaOH backwashing had little adverse effect on biological nutrient removal, and the pH in the MBR reactor remained at stable and acceptable levels (6.6–7.8) because of the alkali consumption by the nitrification process and the buffering role of the mixed liquor. Importantly, the NaOH backwashing significantly slowed the increased rates of total fouling (50% and 69% for 6.5 and 13 LMH, respectively) and irreversible fouling (40% and 50% for 6.5 and 13 LMH, respectively) compared with the pure water backwashing. Off-line backwashing tests indicate that NaOH backwashing enhanced the detachment of biopolymers from the surface of fouled membranes due to the co-occurrence of hydraulic actions and chemical alterations. The characterizations by scanning electron microscopy (SEM) indicate that both backwashing methods increased the size of membrane pores. Nevertheless, the Fourier transform-infrared spectrometry (FTIR) of membranes indicates that the long-term exposure to the NaOH solution did not change the chemical structure of membranes. This study suggests that on-line NaOH backwashing could not only maintain membrane permeability but also simultaneously supply alkali to bioreactors to ultimately facilitate the operation of MBRs.

Mitigation effects of glycinebetaine on oxidative stress and some key growth parameters of maize exposed to salt stress

The aim of the current study was to investigate the effects of glycinebetaine (GB) on oxidative stress and some key growth parameters in maize (Zea mays L. 'DK 647 F1') grown under saline conditions. Maize seedlings were grown in pots containing perlite. The experiment was designed in a 2 × 2 factorial arrangement with 2 levels (0 and 100 mM) of sodium chloride (NaCl) and 2 levels (25 and 50 mM) of GB sprayed onto leaves of maize seedlings. Saline stress caused a considerable decline in total dry matter, chlorophyll content, relative water content (RWC), peroxidase (POD; EC. 1.11.1.7), and catalase (CAT; EC. 1.11.1.6); however, it increased proline, polyphenol oxidase (PPO; 1.10.3.1), and electrolyte leakage. Foliar application of both GB doses mitigated the deleterious effects of salinity stress to variable extents on the key growth parameters tested. As expected, sodium (Na^+) concentrations were higher in the tissues of plants grown under saline conditions, and the GB treatments significantly reduced Na^+ concentration in the plant tissues. Salinity stress reduced both calcium (Ca^{2+}) and potassium (K^+) in the leaves, and GB treatments increased concentrations of both elements in plant tissues; however, their levels were still lower than control values. In particular, foliar application of 50 mM GB mitigated some of the deleterious effects of salt stress by improving proline, Ca^{2+}, and K^+ levels and maintaining membrane permeability.

Silicon-induced changes in growth, ionic composition, water relations, chlorophyll contents and membrane permeability in two salt-stressed wheat genotypes

We investigated the effect of exogenously applied silicon (Si) on the growth and physiological attributes of wheat grown under sodium chloride salinity stress in two independent experiments. In the first experiment, two wheat genotypes SARC-3 (salt tolerant) and Auqab 2000 (salt sensitive) were grown in nutrient solution containing 0 and 100 mM sodium chloride supplemented with 2 mM Si or not. Salinity stress substantially reduced shoot and root dry matter in both genotypes; nonetheless, reduction in shoot dry weight was (2.6-fold) lower in SARC-3 than in Auqab 2000 (5-fold). Application of Si increased shoot and root dry weight and plant water contents in both normal and saline conditions. Shoot Na+ and Na+:K+ ratio also decreased with Si application under stress conditions. In the second experiment, both genotypes were grown in normal nutrient solution with and without 2 mM Si. After 12 days, seedlings were transferred to 1-l plastic pots and 150 mM sodium chloride salinity stress was imposed for 10 days to all pots. Shoot growth, chlorophyll content and membrane permeability were improved by Si application. Improved growth of salt-stressed wheat by Si application was mainly attributed to improved plant water contents in shoots, chlorophyll content, decreased Na+ and increased K+ concentrations in shoots as well as maintained membrane permeability.

RESPONSES OF SOME ENZYMES AND KEY GROWTH PARAMETERS OF SALT-STRESSED MAIZE PLANTS TO FOLIAR AND SEED APPLICATIONS OF KINETIN AND INDOLE ACETIC ACID

The study examined the effects of kinetin (KIN) and indoleacetic acid (IAA) applied as seed treatment or sprayed on leaves of salinity stressed plants. Five -week old maize (Zea mays L. cv. ‘DK 647 F1’) plants were grown in pots containing peat and perlite in 1:1 (v/v) mixture. Different treatments used were: 1) control (nutrient solution alone), 2) salt stress [100 mM sodium chloride (NaCl)], 3) 100 mM NaCl and 1 mM kinetin (KIN), 4) 100 mM NaCl and 2 mM KIN, 5) 100 mM NaCl and 1 mM indole acetic acid (IAA), 6) 100 mM NaCl and 2 mM IAA, 7) 100 mM NaCl and 25 mg L−1 KIN and 8) 100 mM NaCl and 25 mg L−1 IAA. In treatments 7 and 8 application was to the seeds, for treatments 3-6 it was applied to foliage. The seeds were soaked in KIN or IAA solution for 12 h. Salt stress reduced the total dry matter, chlorophyll content, and relative water content (RWC), but increased proline accumulation, activities of superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1) and electrolyte leakage. Both foliar applications of KIN and IAA treatments overcame to variable extents the adverse effects of NaCl stress on the above mentioned physiological parameters. However, seed treatments with KIN or IAA did not improve salinity tolerance in maize plants. Furthermore, foliar application or seed treatments with KIN and IAA reduced the activities of antioxidant enzymes in the salt stressed-plants. Salt stress lowered some macronutrient concentrations [calcium (Ca) and potassium (K) in leaves and roots, phosphorus (P) in roots] but foliar application of both KIN and IAA increased Ca in both leaves and roots and P in leaves. Foliar application of IAA increased K concentrations in leaves of the salt-stressed plants. Foliar application of KIN and IAA, especially at 2 mM concentration, counteracted some of the adverse effects of NaCl salinity by causing the accumulation of proline and essential inorganic nutrients as well as by maintaining membrane permeability.

Effect of foliar applied kinetin and indole acetic acid on maize plants grown under saline conditions

This study examined the effects of kinetin (KIN) and indoleacetic acid (IAA) sprayed on the leaves of salinity- stressed maize (Zea mays L. cv., DK 647 F1) plants grown in field conditions. Salt stress was created by adding 100 mM NaCl to the irrigation water through a drip irrigation system during the irrigation schedule. Kinetin (KIN), indole acetic acid (IAA), and their combinations were sprayed foliarly. Salt stress (S) reduced the total dry matter, grain yield, chlorophyll content, and relative water content (RWC), but increased electrolyte leakage and proline accumulation in the maize plants. Foliar applications of both KIN and IAA treatments overcame to variable extents the adverse effects of NaCl stress on the earlier mentioned physiological parameters. However, the combination of KIN plus IAA did not improve salinity tolerance in maize plants. Salt stress increased Na + concentration, and reduced those of Ca 2+ and K + in the leaves of maize plants. Foliar application of both KIN and IAA significantly reduced Na + concentration and increased those of Ca 2+ and K + . Foliar application of KIN and IAA, especially at 2 mM, counteracted some of the salt induced adverse effects by enhancing essential inorganic nutrients as well as by maintaining membrane permeability.

Silicon alleviates salt stress, decreases malondialdehyde content and affects petal color of salt-stressed cut rose (Rosa xhybrida L.) Hot Lady

A greenhouse experiment was conducted to investigate the effects of different levels of silicon (Si) application on cut rose (Rosa xhybrida L.) ‘Hot Lady’ under two levels of salt stress. Four Si concentrations (0, 50, 100 and 150 ppm) as Si were combined with a 25 mM NaCl (EC ≈ 3.8) level in the nutrient solution supplied to the plants. Addition of Si partially maintained membrane permeability but only fully restored it to control levels in the Si50 and Si100 treatments. 150 ppm Si with or without NaCl could not alleviate or decrease cell wall damages. Inclusion of Si significantly reduced malondialdehyde content and chlorophyll content of salt-stressed plants in all treatments except that of 150 ppm. Maximum chlorophyll content was noticed when 50 ppm Si was supplied. Addition of 50 ppm Si increased the flower number in both plants grown under salinity and unstressed conditions. However, no significant difference was observed between 100 and 50 ppm Si accompanying with NaCl. Plants treated with NaCl alone showed a reduction in plant leaf area, while the reduction in plants treated with NaCl plus 50 and 100 ppm Si were like control and other unstressed plants. Key words: CIELAB, cut rose, ion leakage, malondialdehyde, salt stress, silicon.