| Polyamines (PAs) are small polycationic ubiquitous aliphatic nitrogen compounds, which is produced during nitrogen metabolism. putrescine (Put), spermidine (Spd) and spermine(Spm) are the most abundant PAs in plants. They are involved in various physiologically processes, stabilization of membrane and scavenging of free radicals, regulation of ion balance and integral role under different environmental stress conditions. Nitraria sibirica pall. is strong shrub and halophyte which is a species of Nitraria genus in the Zygophyllaceae, Nitraria sibirica pall. spread in Northwest China's desert region and maintain a balance in the desert ecosystem. we study endogenous the content of spermine, spermidine contents and growth index of Nitraria s. test-tube plantlets under NaCl stress as well as CHA on the basis of established tissue culture and rapid propagation of system Nitraria s. then we explore the role of polyamines in the real halophytes under NaCl stress.The results are as follows:1. Established RP-HPLC chromatography determination PAs in Nitraria s. can apply to halophytes', this method is highly sensitive. Mobile phase: methanol-water=60:40, flowrate:0.8ml/min, wavelength:230nm, temperature:25℃2. Free putrescine content of Nitraria s. test-tube plantlets is not shown since it was below the sensitivity of our detection system, it suggests that Spd and Spm could serve as valuable protection countermeasure against salt stress but not Put in halophyte3. Salt stress (50,200mmol·L-1NaCl) significantly affects PAs contents which are varied widely with different stress time. Under the salt treatment, content of Spd is significantly lower than the control group, especially under 200mmol·L-1NaCl. plantets may adjust the total PAs by changing content of Spd to avoid damaging to plants because of accumulation too much. The growth of Nitraria s. are optimal at the concentration of 50mmol·L-1NaCl,200mmol·L-1NaCl inhibites the test-tube plantlets growth, content of Spd at 30d under 0 and 50mmol·L-1NaCl is the highest, Respectively is 1.17 times and 1.28 times comparison to 15d. different content of Spd in different stages of growth may indicate Spd relation to growth.15d-30d, content of Spm has changed significantly by salt stress, which suggests that Spm may be related to early growth of Nitraria s. response to salt stress.4. Polyamines are determined in roots, stems and leaves under salt stress, PAs in leaves are more sensitive to salt stress, polyamine is inhibited in stems and roots only under high salt stress. Content of Spd in roots is inhibited under high salt stress, then in shoots and leaves, Spm content in roots is not inhibited, salt mainly affects the content of ground parts.5.Applying exogenous (Cyclohexylamine, CHA) to culture medium, content of Spd significantly lower than 50mmol·L-1NaCl treatment group, even lower than 200mmol·L-1NaCl treatment group, in leaves is significantly decreased, chlorophyll synthesis are inhibited and conductivity value increases. These results suggest that contents of Polyamines too high or too low may be bad to the growth of Nitraria s.According to our study and previous research reports, it is indicated free Spd and Spm play an important role in the protection of plants against salt stress by osmosis-regulating substance, maintaining cation balance and regulation of intracellular pH. PAs are in line with the idea that polyamine are biochemical indicators of long-term salt stress, At the same time, in plant growth and development, they also play an important role. The inhibitor of synthesis of PAs will increase the salt stress damage, so the PAs are of great significance in salt tolerance of plants.
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