A technique based on Fourier transform infrared (FT-IR) spectrometry was developed to detect the corresponding changes in chemical composition associated with the rapid changes in sodium and water content in 200 mm NaCl-stressed halophyte ice plants (Mesembryanthemum crystallinum). The changes in glycophyte Arabidopsis stressed with 50 mm NaCl were also examined for comparison. The obtained IR spectra were further processed by deconvolution and curve fitting to examine the chemical nature of the responding sources in the leaves. Using three stages of ice plant leaves, absorption bands corresponding to carbohydrates, cell wall pectin, and proteins were identified, with distinct IR spectra representing each developmental stage. Within 48 h of mild salt stress, the absorption band intensities in the fingerprint region increased continuously in both plants, suggesting that the carbon assimilation was not affected at the early stage of stress. The intensities of ester and amide I absorption bands decreased slightly in Arabidopsis but increased in ice plant, suggesting that the cell expansion and protein synthesis ceased in Arabidopsis but continued in ice plant. In both plants, the shift in amide I absorption band was observed hourly after salt stress, indicating a rapid conformational change of cellular proteins. Analyses of the ratio between major and minor amide I absorption band revealed that ice plant was able to maintain a higher-ordered form of proteins under stress. Furthermore, the changes in protein conformation showed a positive correlation to the leaf sodium contents in ice plant, but not in Arabidopsis.High salinity causes pleiotropic effects in plant growth such as reduced cell expansion, decreased protein synthesis, and accelerated cell death. Soil salinity is one of the major limitations of crop productivity worldwide. Halophytes are native flora of saline environments that have the characteristic to overcome the ion and osmotic imbalance caused by high NaCl concentrations. Halophytes possess a set of unique salt adaptation mechanisms. Through comparisons with glycophytes (nonhalophytes), the mechanisms of salt tolerance in halophytes have been studied at physiological, biochemical, and molecular levels (for review, see Hasegawa et al., 2000). In general, three adaptation strategies are commonly found in halophytes: compartmentation of toxic ions, accumulation of osmolytes, and conservation of water (Bohnert et al., 1995). The main strategy for glycophytes is to control of ion flux into root xylem and as the result, restrict ion movement to the shoot (for review, see Hasegawa et al., 2000).Ice plant (Mesembryanthemum crystallinum) has been used as a halophytic model because the mechanisms of salt tolerance can be induced when the plants reach a certain developmental stage. Although ice plant is not suitable for genetic manipulation, comparisons of the physiological, biochemical, and gene expression changes before and after salt stress has provided useful data. In a time course progression of salt-indu...

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In this paper, the feasibility of applying electroless displacement to prepare silver nanoparticles (AgNPs) on the surface of germanium (Ge) substrate is demonstrated, and the performances of surfaces prepared in this manner for surface-enhanced infrared absorption (SEIRA) spectroscopy are reported. The process used to produce suitable AgNPs for SEIRA by electroless deposition is simple and effective, requiring only pretreatment of the germanium surface with hot air, immersion of the substrate in a dilute solution of silver nitrate, and washing of the resulting plate. To quantify the behavior of AgNPs on a Ge substrate and to optimize the conditions for the preparation of AgNPs on Ge substrates, a monolayer of p-nitrothiophenol (PNTP) was bonded to the surface of the AgNPs by immersion of the plate in a dilute solution of PNTP and measurement of the transmission spectrum. The factors that influenced the formation of AgNPs, and hence the SEIRA signals, included the concentration of AgNO3, the reaction time and the temperature. Results indicated that stronger absorption bands in the SEIRA spectrum of a monolayer of PNTP were obtained if the reaction rate for the displacement of silver ions by Ge was slow. This condition was achieved by keeping the concentration of AgNO3 and the reaction temperature low. Under the optimal conditions found in this work, an enhancement factor of approximately 100 was achieved for commonly used probe molecules in SEIRA measurements.

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The eggs of Mugil cephalus were significantly larger than those of Epinephelus malabaricus, and E. coioides, while those of Sciaenops ocellatus were intermediate between E. coioides and M. cephalus. The distribution density of pores in the egg envelope of S. ocellatus was significantly different from that of E. malabaricus and E. coioides. The micropyle diameters were significantly different in the four species. The ultrastructure of the zona radiata surface, the distribution density of pores and the size of eggs were also useful characters for distinguishing among the four species, but the ultrastructural features of the micropyles were the most important of all for egg identification. 2000 The Fisheries Society of the British Isles