Enhanced photochemical efficiency of PSII in Prosopis juliflora suggests contribution to invasion advantage over native C3 xero-halophytes under salt stress.

Chlorophyll a fluorescence parameters related to PSII photochemistry, photoprotection and photoinhibition were investigated in four C3 plant species growing in their natural habitat: Prosopis juliflora ; Abutilon indicum ; Salvadora persica ; and Phragmites karka . This study compared the light reaction responses of P. juliflora , an invasive species, with three native co-existing species, which adapt to varying water deficit and high salt stress. Chlorophyll a fluorescence quenching analyses revealed that P. juliflora had the highest photochemical quantum efficiency and yield, regulated by higher fraction of open reaction centres and reduced photoprotective energy dissipation without compromising the integrity of photosynthetic apparatus due to photoinhibition. Moreover, the elevated values of parameters obtained through polyphasic chlorophyll a fluorescence induction kinetics, which characterise the photochemistry of PSII and electron transport, highlighted the superior performance index of energy conservation in the transition from excitation to the reduction of intersystem electron carriers for P. juliflora compared to other species. Enhanced pigment contents and their stoichiometry in P. juliflora apparently contributed to upregulating fluxes and yields of energy absorbance, trapping and transport. This enhanced photochemistry, along with reduced non-photochemical processes, could explain the proclivity for invasion advantage in P. juliflora across diverse stress conditions.

Utilization of wild Cressa cretica biomass for pectinase production from a halo-thermotolerant bacterium.

Halophytes are the native inhabitants of saline environment. Their biomass can be considered as a potential substrate for the production of microbial enzymes. This study was intended at feasible utilization of a halophytic biomass, Cressia cretica, for pectinase production using a halo- and thermo-tolerant bacterium, Bacillus vallismortis MH 10. The data from fractionation of the C. cretica biomass revealed presence of 17% pectin in this wild biomass. Seven different factors (temperature, agitation, pH, inoculum size, peptone concentration, substrate concentration, and incubation time) affecting pectinase production using C. cretica were assessed through a statistical tool, Plackett-Burman design. Consequently, two significant factors (incubation time and peptone concentration) were optimized using the central composite design. The strain produced 20 IU mL-1 of pectinase after 24 h under optimized conditions. The enzyme production kinetics data also confirmed that 24 h is the most suitable cultivation period for pectinase production. Fourier transform infrared spectroscopy and scanning electron microscopy of C. cretica biomass ascertained utilization of pectin and structural changes after fermentation. The purification of pectinase by using DEAE column yielded specific activity and purification fold of 88.26 IU mg-1 and 3.2, respectively. The purified pectinase had a molecular weight of >65 kDa. This study offers prospects of large-scale production of pectinase by halotolerant strain in the presence of economical and locally grown substrate that makes the enzyme valuable for various industrial operations.

Enzyme Profiling and Identification of Endophytic and Rhizospheric Bacteria Isolated from Arthrocnemum macrostachyum.

Endophytic and rhizospheric bacteria isolated from halophytic plants support their host to survive in hyper-saline soil. These bacteria are also known to produce various enzymes with potential industrial applications. In this study, the endophytic and rhizospheric bacteria were isolated from Arthrocnemum macrostachyum collected from Karachi, Pakistan, and their ability to produce various extracellular enzymes was assessed using commercial and natural substrates. In total, 11 bacterial strains were isolated (four endophytic; seven rhizospheric). Bacillus was found to be the most abundant genus (73%), followed by Glutamicibacter (27%). The isolates including Glutamicibacter endophyticus and Bacillus licheniformis are reported for the first time from A. macrostachyum. All of the isolates were capable of producing at least two of the five industrially important hydrolytic enzymes tested, i.e., xylanase, cellulase, amylase, pectinase, and lipase. Lipase production was found to be highest among the isolates, i.e., up to 18 IU mL-1. Although most of the isolates could grow at a wide range of temperatures (4-55 °C), pH (1-11), and salt concentrations (2-12%), under extreme conditions, very little growth was observed and the optimal growth was recorded between 2% and 6% NaCl, 25 and 45 °C, and 7 and 9 pH. Our results suggest that these isolates could be potential producers of enzymes with several biotechnological applications.

Wild Halophytic Phragmites karka Biomass Saccharification by Bacterial Enzyme Cocktail.

Biofuel derived from halophytic biomass is getting attention owing to the concerns of energy versus food crisis. The disadvantages associated with edible bioenergy resources necessitate the need to explore new feedstocks for sustainable biofuel production. In this study, biomass from locally available abundant halophytes (Panicum antidotale, Phragmites karka, Halopyrum mucronatum, and Desmostachya bipinnata) was screened for saccharification by an enzyme cocktail composed of cellulase, xylanase, and pectinase from Brevibacillus borstelensis UE10 and UE27, Bacillus aestuarii UE25, Aneurinibacillus thermoaerophilus UE1, and Bacillus vallismortis MH 1. Two types of pretreatment, i.e., with dilute acid and freeze-thaw, were independently applied to the halophytic biomass. Saccharification of acid-pretreated P. karka biomass yielded maximum reducing sugars (9 mg g-1) as compared to other plants. Thus, the factors (temperature, pH, substrate concentration, and enzyme units) affecting its saccharification were optimized using central composite design. This statistical model predicted 49.8 mg g-1 of reducing sugars that was comparable to the experimental value (40 mg g-1). Scanning electron microscopy and Fourier-transform infrared spectroscopy showed significant structural changes after pretreatment and saccharification. Therefore, halophytes growing in saline, arid, and semi-arid regions can be promising alternative sources for bioenergy production.

Differences in photosynthetic syndromes of four halophytic marsh grasses in Pakistan.

Salt-tolerant grasses of warm sub-tropical ecosystems differ in their distribution patterns with respect to salinity and moisture regimes. Experiments were conducted on CO2 fixation and light harvesting processes of four halophytic C4 grasses grown under different levels of salinity (0, 200 and 400 mM NaCl) under ambient environmental conditions. Two species were from a high saline coastal marsh (Aeluropus lagopoides and Sporobolus tremulus) and two were from a moderate saline sub-coastal draw-down tidal marsh (Paspalum paspalodes and Paspalidium geminatum). Analyses of the carbon isotope ratios of leaf biomass in plants indicated that carbon assimilation was occurring by C4 photosynthesis in all species during growth under varying levels of salinity. In the coastal species, with increasing salinity, there was a parallel decrease in rates of CO2 fixation (A), transpiration (E) and stomatal conductance (g s), with no effect on water use efficiency (WUE). These species were adapted for photoprotection by an increase in the Mehler reaction with an increase in activity of PSII/CO2 fixed accompanied by high levels of antioxidant enzymes, superoxide dismutase and ascorbate peroxidase. The sub-coastal species P. paspalodes and P. geminatum had high levels of carotenoid pigments and non-photochemical quenching by the xanthophyll cycle.

Effects of salinity and ascorbic acid on growth, water status and antioxidant system in a perennial halophyte.

Salinity causes oxidative stress in plants by enhancing production of reactive oxygen species, so that an efficient antioxidant system, of which ascorbic acid (AsA) is a key component, is an essential requirement of tolerance. However, antioxidant responses of plants to salinity vary considerably among species. Limonium stocksii is a sub-tropical halophyte found in the coastal marshes from Gujarat (India) to Karachi (Pakistan) but little information exists on its salt resistance. In order to investigate the role of AsA in tolerance, 2-month-old plants were treated with 0 (control), 300 (moderate) and 600 (high) mM NaCl for 30 days with or without exogenous application of AsA (20 mM) or distilled water. Shoot growth of unsprayed plants at moderate salinity was similar to that of controls while at high salinity growth was inhibited substantially. Sap osmolality, AsA concentrations and activities of AsA-dependant antioxidant enzymes increased with increasing salinity. Water spray resulted in some improvement in growth, indicating that the growth promotion by exogenous treatments could partly be attributed to water. However, exogenous application of AsA on plants grown under saline conditions improved growth and AsA dependent antioxidant enzymes more than the water control treatment. Our data show that AsA-dependent antioxidant enzymes play an important role in salinity tolerance of L. stocksii.

Excreting and non-excreting grasses exhibit different salt resistance strategies.

The combination of traits that makes a plant successful under saline conditions varies with the type of plant and its interaction with the environmental conditions. Knowledge about the contribution of these traits towards salt resistance in grasses has great potential for improving the salt resistance of conventional crops. We attempted to identify differential adaptive response patterns of salt-excreting versus non-excreting grasses. More specifically, we studied the growth, osmotic, ionic and nutrient (carbon/nitrogen) relations of two salt-excreting (Aeluropus lagopoides and Sporobolus tremulus) and two non-excreting (Paspalum paspalodes and Paspalidium geminatum) perennial C4 grasses under non-saline and saline (0, 200 and 400 mM NaCl) conditions. Growth and relative growth rate decreased under saline conditions in the order P. geminatum > S. tremulus = A. lagopoides > P. paspalodes. The root-to-shoot biomass allocation was unaffected in salt-excreting grasses, increased in P. paspalodes but decreased in P. geminatum. Salt-excreting grasses had a higher shoot/root Na(+) ratio than non-excreting grasses. K(+), Ca(2+) and Mg(2+) homoeostasis remained undisturbed among test grasses possibly through improved ion selectivity with rising substrate salinity. Salt-excreting grasses increased leaf succulence, decreased ψs and xylem pressure potential, and accumulated proline and glycinebetaine with increasing salinity. Higher salt resistance of P. paspalodes could be attributed to lower Na(+) uptake, higher nitrogen-use efficiency and higher water-use efficiency among the test species. However, P. geminatum was unable to cope with salt-induced physiological drought. More information is required to adequately document the differential strategies of salt resistance in salt-excreting and non-excreting grasses.

The influence of genes regulating transmembrane transport of Na+ on the salt resistance of Aeluropus lagopoides.

Plantlets of Aeluropus lagopoides (Linn.) Trin. Ex Thw. were grown at different NaCl concentrations (26, 167, 373 and 747mM) for 3, 7 and 15 days; their growth, osmotic adjustment, gas exchange, ion compartmentalisation and expression of various genes related to Na+ flux was studied. Plantlets showed optimal growth in non-saline (control; 26mM NaCl) solutions, whereas CO2/H2O gas exchange, leaf water concentration and water use efficiency decreased under all salinity treatments, accompanied by increased leaf senescence, root ash, sodium content and leaf osmolality. A decrease in malondialdehyde (MDA) content with time was correlated with Na+ accumulation in the leaf apoplast and a concomitant increase in Na+ secretion rate. A. lagopoides accumulated a higher concentration of Na+ in root than in leaf vacuoles, corresponding with higher expression of V-NHX and lower expression of PM-NHX in root than leaf tissue. It appears that V-ATPase plays a vital role during Na+ transport by producing an electromotive force, driving ion transport. Leaf calcium increased with increasing salinity, with more rapid accumulation at high salinity than at low salinity, indicating a possible involvement of Ca2+ in maintaining K+:Na+ ratio. Our results suggest that A. lagopoides successfully compartmentalised Na+ at salinities up to 373mM NaCl by upregulating the gene expression of membrane linked transport proteins (V-NHX and PM-NHX). At higher salinity (747mM NaCl), a reduction in the expression of V-NHX and PM-NHX in leaves without any change in the rate of salt secretion, is a possible cause of the toxicity of NaCl.

Continuous renal replacement therapy.

Acute renal failure refers to sudden deterioration in biochemical and physiological functioning of kidneys and often associated with multi organ failure. Continuous renal replacement therapy (CRRT) holds special significance for the treatment of renal failure due to a variety of factors. It is believed that CRRT helps in restoration of acid-base imbalances and electrolyte abnormalities. Along with that, with gradual solute removal, it ensures haemodynamic stability and prevents the risk of cerebral oedema in neurosurgery patients. Besides this, several studies have supported that CRRT enables practitioners to adjust drug dosages and prevent drug accumulation and overdose. In addition, gradual removal of solutes and metabolic waste products helps to clear inflammatory mediators and ensure adequate nutrition for patients and lead to improved renal recovery. Therefore, this article will discuss the different treatment modalities that encompass CRRT and explore the indications and advantages of CRRT in acute renal failure.

Light, salinity, and temperature effects on the seed germination of perennial grasses.

The germination requirements of four perennial halophytic grasses, Aeluropus lagopoides, Halopyrum mucronatum, Sporobolus ioclados, and Urochondra setulosa, were studied under control conditions in the laboratory. Treatments included two light levels (12 : 12 h light : dark period and 24-h dark environment), six salinity concentrations (0, 100, 200, 300, 400, and 500 mmol/L NaCl), and four temperature regimes (fluctuating day : night temperature regimes of 10° : 20°, 15° : 25°, 20° : 30° and 25° : 35°C), using a completely randomized block design. Best seed germination of all grasses was obtained in a distilled water control. Increase in salinity progressively inhibited germination of all species. For example, few seeds of H. mucronatum germinated above 300 mmol/L NaCl, while seeds of the other grasses germinated in up to 500 mmol/L NaCl. Optimal temperature regime for germination for all species was 20° : 30°C both for light- and dark-germinated seeds. At higher temperatures differences between light and dark treatments were not significant. Absence of light had no effect on the seed germination of U. setulosa and H. mucronatum; however, germination was lower in all salinity treatments. In the case of A. lagopoides, absence of light substantially inhibited the germination both in control and saline conditions. The light effect was marked in the case of S. ioclados, which showed very low germination in the absence of light both under saline and nonsaline conditions.