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The mechanism of salt tolerance in plants had been the focus of plant resistance research in the past years. As the development of biology and application of new fluorescent labeling technologies, determination of intracellular free sodium had been gradually applied to the study of salt tolerance in plants. This review discussed three points as follows: (1) Introduction of three fluorescent indicators of intracellular free sodium: SBFI, Sodium Green and CoroNa Green. SBFI was a kind of fluorescent indicator for excitation ratio measurements, its emission ratio detected at 500 nm when excited at 340/380 nm. Sodium Green and CoroNa Green were fluorescent indicators that lacked a significant shift in emission or excitation wavelength upon binding to Na+. Sodium Green and CoroNa Green could be detected at 532 nm and 516 nm when excited at 507 nm and 492 nm respectively; (2) Compared the advantages and disadvantages of the protocols of loading the fluorescent indicators into cells, including AM esters of the fluorescent probes, acid loading, electroporation and microinjection. A non-invasive loading of acetoxymethyl ester under low temperature was introduced: loading the fluorescent indicator into cells by incubating the cells in solution at 4 °C for 2 h followed by 2 h incubation in the dye-free solution at 20 °C; (3) The measurement of the internal sodium concentration in cells was illustrated. The equation for measurement of fluorescence intensity that lacked a significant shift in emission or excitation wavelength was: [Na+] = Kd(F - Fmin)/(Fmax - F). Fluorescence intensity (F) was targeted fluorescence intensity. Fmin was appropriate mixtures of low Na+, and Fmax was appropriate maximum of high Na+. The equation for measurement of fluorescence intensity ratio was: [Na+] = KdQ(R - Rmin)/(Rmax - R). The ratio of fluorescence intensity (R) was the ration F1/F2 of the fluorescence intensity. Fmin was the ratio of appropriate mixtures of low Na+, and Fmax was the ratio of appropriate maximum of high Na+. [ABSTRACT FROM AUTHOR]

Peptide hormones genes are important in plant growth and development and RALF (rapid alkalinization factor) is one of them. Cruciferae is a big family in Chinese vegetable crops. Polypeptide hormone gene RALFbn was cloned from Brassica campestris (rape) in the authors' previous work. In order to find out the information of RALF homologous genes in Cruciferae vegetable crops, this experiment was done. At this time, the primers were designed according to the sequence of RALFbn gene. The genomic DNAs of 7 important vegetable crops were extracted in advance. The vegetable materials were selected from Brassica, Raphanus, Rorippa and Barbarea and they all belonged to the same family of Cruciferae. Seven sequences homologous to RALF were cloned from the 7 materials from important vegetable crops with the primers designed from RALFbn. Then the 7 DNA sequences together with the RALFbn gene were analyzed. The results showed that all the DNA sequences' open reading frames were about 300 bp long. There was no intron in the 7 genes. The 7 proteins encoded by them were all made by 73 amino acids. All these indicated that the RALF homologous genes were very conservative in the 4 genera of cruciferous species. At the same time , the 7 RALF homologous genes expression analyses were done in four genera in Cruciferae. The result indicated that these genes were not or weakly expressed in root, stem, leaf, inflorescence axis and other vegetative organs, while mainly expressed in reproductive organs, in which, the total amounts of the expression in flower buds and open flowers were generally higher than those in tender siliques. All the expression indicated that the physiological active period of these genes in Cruciferae was in the flower growth period. The system tree was constructed with the 7 RALF homologous genes in the 4 genera of Cruciferae. The NJ tree of RALF homologous genes reflected that RALFbn , Bo-RALFjx and BoRALFzh formed a branch while BjRALFdn4 and BjRALFxlh formed another branch with the rest RALF homologous genes from Raphanus, Rorippa, Barbarea clustered in the same branch. The evolutionary pathway of these RALF homologous genes in a certain extent also reflected the genetic background relationships between these crops. In all , this study enriched the information of the rapid alkalinization factor (RALF) family and expanded the knowledge of the molecular evolution data of Cruciferae. [ABSTRACT FROM AUTHOR]