Effects of drought and moisture stress on the growth and ecophysiological traits of Schima superba seedlings.

Changes in rainfall patterns are important environmental factors affecting plant growth, especially when larger precipitation events and prolonged drought periods occur in subtropical regions. There are many studies on how drought reduces plant biomass through drought-sensitive functional traits, but how excess water affects plant growth and ecophysiology is still poorly understood. Therefore, a greenhouse experiment was conducted on Schima superba (Theaceae), a dominant tree species in subtropical forests and commonly used in forestry, in a closed chamber under control (25% soil water content (SWC) as in local forests), drought stress (D, 15% SWC) and moisture stress (W, 35% SWC). Plant growth and ecophysiological traits related to morphology, leaf gas exchange, water potential and structural traits were measured. Compared to control, S. suberba under dry conditions significantly decreased its aboveground biomass, photosynthetic rate (A), leaf water potential and nitrogen use efficiency, but increased intrinsic water use efficiency, root to shoot ratio and specific root length. S. superba under wet conditions also significantly decreased its total biomass, aboveground biomass and specific root length, while W had no effect on A and leaf water potential. Our results indicate that S. superba shows a decrease in carbon gain under drought stress, but less response under wet conditions. This emphasizes the need to consider the strength and frequency of rainfall pattern changes in future studies because rainfall may either alleviate or intensify the effects of drought stress depending on the moisture level, thus suitable water conditions is important for better management of this tree species in subtropical China.

Role of PGPR on the physiology of sunflower irrigated with produced water containing high total dissolved solids (TDS) and its residual effects on soil fertility.

The present study was conducted to evaluate the bioremediation potential of plant growth-promoting rhizobacteria (PGPR) PGPR isolates from high total dissolved solids (TDS) bearing produced water on the water quality, soil physicochemical properties and growth and physiology of sunflower irrigated with high TDS bearing produced water having salinity level 130 times higher above seawater and also containing traces of oil and grease. Seeds of sunflower hybrid Parsun 3 were soaked for 3-4 h prior to sowing in 72 h old culture of PGPR strains W1 and W2 isolated from high TDS bearing polluted water. The control plants were irrigated with 90% diluted TDS water supplemented with 5 ml LB media. Whereas, the inoculated plants were irrigated with 90% diluted TDS water supplemented with 5 ml PGPR inocula.in LB media. The plants were grown under natural conditions. The 16S rRNA sequence analyses identified the isolate W1 bearing 100% similarity with the plant growth-promoting rhizobacteria (PGPR) Ralstonia pickettii and W2 bearing 99.7% similarity with Brevibacillus invocatus. Both the isolate were catalase and oxidase positive. The Ralstonia pickettii and Brevibacillus invocatus treatments decreased the EC and TDS values significantly such that the EC and TDS values of 90% diluted TDS water were 29 times and 19 times higher than tap water. Sodium adsorption ratio (SAR), organic matter, nitrogen, potassium, magnesium and carbon content were 1.96, 1.10, 2.28 1.20, 6.63 and 1.00 times greater than control in the rhizosphere soil of Ralstonia pickettii inoculated plants irrigated with high TDS bearing water There were significant increases in plant growth, sugar, flavonoids and phenolics, chlorophyll b, total chlorophyll, carotenoids content and activities of superoxide dismutase, catalase and peroxidase in plants inoculated with Ralstonia pickettii and Brevibacillus invocatus. The flavonoids, phenolics and proline contents were 0.54, 0.72 and 0.30 times higher in Ralstonia pickettii inoculated plants. Shoot/root dry weight ratio was about (50%) lower than control in Ralstonia pickettii and Brevibacillus invocatus treatments. Ralstonia pickettii was more effective than Brevibacillus invocatus to combat oxidative and osmotic stresses. It is inferred that the high TDS bearing produced water from oil factory harbor Plant growth-promoting rhizobacteria (PGPR) having the potential to combat high salinity stress in plants when used as bioinoculant. The broth culture containing the bacteria may be supplemented with the saline water used for irrigation as it provides nutrients for the growth and proliferation of bacteria present in the saline water and hence the synergistic action of bacterial inocula with the indigenous bacteria present in saline water may better alleviate osmotic and oxidative stresses of plants encountered under salinity stress. The residual effect of Ralstonia pickettii on organic matter and Ca, Mg, K and P content of the rhizosphere soil was notably higher for succeeding crops. Novelty statement This is the first report demonstrating that rhizobacteria can proliferate in water containing salinity higher above seawater in addition to oil grease and TSS. Their efficiency to reduce TDS can be augmented by an exogenous supply of LB broth culture of PGPR isolated from the polluted water. These indigenous rhizobacteria when used as bioinoculant on the plant can act as plant growth promoters as well as bioremediation of salinity effects.

Hybrid integrated PDMS microfluidics with a silica capillary.

To harness the properties of both PDMS and silica, we have demonstrated hybrid integrated PDMS microfluidic systems with fused silica capillaries. The hybrid integrated PDMS microfluidics and silica capillary (iPSC) modules exhibit a novel architecture and method for leakage free CE sample injection merely requiring a single high voltage source and one pair of electrodes. The use of the iPSC device is based on a modular approach which allows the capillary to be reused extensively whilst replacing the attached fluidic module for different experiments. Integrating fused silica capillaries with PDMS microfluidic modules allows the direct application of a wide variety of well established conventional CE protocols for separations of complex analytes. Furthermore it bears the potential for facile coupling to standard electro-spray ionization mass spectrometry (ESI-MS), letting users focus on the sample analysis rather than the development of new separation protocols. The fabrication of the iPSC module consists of a simple and quick three-step method that submerges a fused silica capillary in PDMS prepolymer. After cross linking the prepolymer and punching the inlets, the iPSC module layer can be mounted onto a microfluidic device for CE separation.

Reactive deposition of nano-films in deep polymeric microcavities.

We report the controlled diffusion of gas-phase high-reactivity chemical species into long polymeric microcavities to form glass-like, low-permeability barrier films on the interior surfaces of the microcavities. Reactive species created from fragmentation of O(2) and hexamethyldisiloxane (HMDSO) in a radio-frequency (RF) plasma environment are allowed to diffuse into the microcavities of polydimethylsiloxane (PDMS), where surface reactions lead to the formation of an effective, glass-like thin-film barrier. Reactive species including silicon radicals and elemental oxygen maintain their reactivity for sufficient times (up to 7000 s) and survive the random diffusional walk through the microcavities to form glass barriers as much as 65 mm from the cavity entrance. The barrier thickness and the growth length can be controlled by the reaction time and chamber operating pressure. Increasing the cross sectional area of the cavity inlet and/or decreasing the mean free path was found to increase the thickness of the barrier film. Optical emission spectroscopic analysis was used to characterize the reactive fragments formed from HMDSO, and energy-dispersive X-ray analysis revealed that the barrier composition is consistent with oxides of silicon (SiO(x)). Formed inside PDMS microcavities, the glass barrier blocks the penetration or absorption of small molecules such as rhodamine B (RhB) and biotin, and also resists permeation of organic solvents such as toluene, preventing the PDMS microfluidic structures from swelling and deforming. Moreover, formation of glass-like thin films in PDMS microcavities enhances the stability of electroosmotic flow (EOF) relative to uncoated PDMS devices, in which EOF instabilities are significant; this enables separation by electrophoresis with reproducibility (relative standard deviation 3%, n = 5) and baseline peak resolution (R:1.3) comparable to that obtained in conventional fused-silica capillaries.

Calibration of migration times of variable salinity samples with internal standards in capillary electrophoresis.

A practical approach is presented for identifying the analyte peaks stacked by transient ITP (TITP) in samples of uncontrolled salinity. For TITP with chloride ions acting as the leading electrolyte, the effect of matrix chloride of an unknown concentration was calibrated using multiple internal standards to predict the migration times of weakly acidic anionic analytes behaving as strong electrolytes to an accuracy of over 99.9%. The calibration equations for the migration time of an analyte are given as a function of the migration times of internal standards using the mobilities of the relevant ions as parameters. The effects of matrix chloride and various separation conditions such as the temperature, plug length, ionic strength, and pH of the BGE were completely eliminated from the calibration equations. In addition, the actual mobilities, determined for a standard saline sample under the working conditions, were used, and thus, there was no need to conduct supplementary experiments to determine the absolute mobilities at infinite dilution. The internal standards were dyes, which were easily identified in an auxiliary channel monitoring the absorbance at a longer wavelength. For five standard saline matrices containing 100-300 mM NaCl at intervals of 50 mM, the mean absolute error (MAE) in migration times calibrated with two internal standards was 0.4 s (n=5x13). For an electropherogram of a real standard reference urine sample, peaks of spiked analytes were identified with an MAE of 0.9 s (n=13) without conductivity normalizing or desalting of the sample.

Transient isotachophoresis of highly saline trace metals under strong electroosmotic flow conditions.

Transient isotachophoresis (TITP) is usually performed under low-electroosmotic flow (EOF) conditions using a coated capillary or a low pH background electrolyte. We used a bare fused-silica capillary for TITP stacking of anionic complexes of some heavy metals under high-EOF conditions (pH 9.0). The sample component chloride as a leading electrolyte induced stacking by an isotachophoretic mechanism and the complexing agent 4-(2-pyridylazo) resorcinol (PAR) acted as a terminating electrolyte. The optimized background electrolyte was composed of 150 mM N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 127 mM triethylamine, and 0.1 mM PAR at pH 9.0. The strong EOF at pH 9.0 pulled the analytes against their mobilities toward the outlet side, allowing a separation in the normal polarity mode. The stacking efficiency, reproducibility, analysis time, and sample loading capacity in coated and bare capillaries were compared. The stacking efficiency and reproducibility were higher and the analysis time was shorter in the coated capillary. However, a larger volume of a sample could be injected in the bare capillary to achieve detection limits comparable to those for the coated one without compromising the resolution between the analyte peaks. The limits of detection (S/N = 3) were in the sub-ppb range for the selected metals (Fe2+, 0.3 ppb; Ni2+, 0.16 ppb; and Zn2+, 0.8 ppb) in a standard saline sample with 250 mM NaCl matrix. The proposed method was successfully applied to the analysis of reference urine samples and human urine samples.

Large-volume stacking in capillary electrophoresis using pH hysteresis of the electroosmotic flow in a bare fused-silica capillary.

For large-volume stacking with the electroosmotic flow pump (LVSEP) in capillary electrophoresis of anionic analytes it is required that the electroosmotic mobility (EOM) should be smaller than the magnitudes of the effective mobilities of the analytes. When a fused-silica capillary is treated with an acidic solution, the silanoate group on the silica surface is neutralized to silanol and the EOM is suppressed. Due to the slow deprotonation equilibrium of the silanol group at an intermediate pH, this reduced EOM can be retained during a number of electrophoresis runs. Using a bare fused-silica capillary preconditioned with 0.01 M HCl, successful LVSEP at pH 6.0 was achieved for weakly acidic compounds with two orders of magnitude enhancements in the concentration sensitivity. The repeatability in migration times of ten analytes stacked by LVSEP in a single day was excellent with the relative standard deviation (RSD) less than 1% (n = 6). The day-to-day repeatability was also excellent with RSD less than 3% (n = 3 x 6) when the capillary was preconditioned each day.

Capillary electrophoresis of trace metals in highly saline physiological sample matrices.

Trace metal ions in highly saline samples such as urine were determined with capillary electrophoresis (CE) without desalting or off-line preconcentration. By mixing with a dye, 4-(2-pyridylazo) resorcinol (PAR), the metal ions were converted into anionic complexes having strong absorbance near 500 nm. A large volume of the metal-PAR complex sample solution injected into a coated capillary was stacked isotachophoretically and separated under a reverse potential. The salt anion (chloride) and PAR in the sample matrix acted as the leading and terminating electrolytes, respectively. In a sample containing a 250 mM NaCl matrix, more than 400-fold enhancement in the absorbance detector response was realized compared to the normal CE injection mode. Combination of the dye complexation and isotachophoretic stacking provided excellent detection limits (S/N = 3) for three trace metal ions in the low ppb range (Fe(2+), 0.7 ppb, Ni(2+), 0.4 ppb; Zn(2+), 1.2 ppb) with absorbance detection. The migration time reproducibility was excellent (relative standard deviations: standard samples < 1%, urine samples approximately 1%). The proposed method is convenient and fast, and the sample analysis can be completed within 20 min.

Dual stacking of unbuffered saline samples, transient isotachophoresis plus induced pH junction focusing.

A dual stacking mechanism based on transient isotachophoresis (TITP) and induced pH junction focusing is demonstrated as a means to increase the concentration sensitivity in capillary electrophoresis of highly saline samples. When stacking was carried out with an unbuffered saline sample of fluorescein between two zones of low mobility background electrolyte at high pH under an electric field of reverse polarity, two transient peaks at both boundaries of the sample zone were observed. One peak at the rear boundary could be inferred as a transient isotachophoretic stacked zone. Through computer simulations of an unbuffered sample with a high concentration of sodium chloride, we showed that the fast moving zones of sodium and chloride ions induced pH changes at both boundaries to satisfy the electroneutrality condition and that the peak at the front boundary was due to the induced pH junction. To verify the pH changes, an indicator, thymol blue, was added to an NaCl solution and the color changes under an electric field were observed. The proposed mechanism was supported by observing the dual stacking procedure for an unbuffered sample of 4-nitrophenol and measuring additional sensitivity enhancements by dual stacking for ten weakly acidic compounds. For the ten analytes including nucleoside phosphates, every dual stacking of an unbuffered sample exhibited an additional enhancement up to 86% larger than that of usual transient isotachophoresis of the corresponding buffered sample without loss of separation efficiency and reproducibility. Therefore, it would be useful to skip over buffering in sample preparation for TITP, contrary to the general recommendation.