| Soil salinity is an important factor affecting agricultural production and ecological environment, the proportion of arable land becoming less and less with the development of industry and the increase of population. So improving the crop resistance to adversity has become an important problem to the future sustainable development of agriculture and environmental management. Given the erosion of large areas of land and increased salinity stress experienced by numerous plants worldwide, soil salinity has become a global problem. Soil salinity, a major abiotic stress that affects germination, crop growth, and productivity, is a common adverse environmental factor. Soil salinity affects plant growth, the global geographic distribution of vegetation, and medicinal plant yields. Soil salinity is a long-term using of water for irrigation contains some insoluble salts or excessive use of fertilizers. The original soil and water for production formation of the facilities secondary soil salinity, unreasonable fertilization, unconscionable cropping patterns are the important factors in the soil salinity. It is a significant problem to the scientists to let the crops growth normally in the salinity habitats and obtain a certain yield.Coptis chinensis Franch. is a well-known traditional Chinese medicinal plant belonging to the medically and economically important of genus Coptis family Ranunculaceae with other name like "weilian","chuanhuanglian","jizhualian", and so on. It is widely distributed in the province of Sichuan, Chongqing, Hunan, Hubei. Shizhu is the main producing areas in Chongqing. The active ingredient berberine in the root of C. chinensis with distinctive therapeutic effectiveness make it of great medicinal value. In the long-term cultivation process, due to the limitations of single fertilization methods and the areas of cultivated land, the physical and chemical properties of soil has large changes. In recent years, more and more research had fund that variety of exogenous chemicals can induce plants to improve the salt tolerance under salt stress. In this study, seeds and seedlings of C. chinensis were used to research the specific role of exogenous substances under salinity stress. The5-aminolevulinic acid (ALA), nitric oxide (NO) donor sodium nitroprusside (SNP), carbon monoxide (CO) donor hematin, spermidine (Spd) and salicylic acid (SA) were applied to study the effects to the seed germination, photosynthetic characteristics of seedlings, chlorophyll fluorescence characteristics, lipid peroxidation, antioxidant enzyme machinery, permeability protection substances, secondary metabolites of C. chinensis seeds and seedlings. The main results of this study as follows:1. Seed germination indices, such as Gv, Gr, Gi, and Vi, of C. chinensis were inhibited with different degrees under different concentrations of NaCl. The treatment with lower NaCl concentration dose not show an obviously change compared with the control. When the concentration of NaCl got50mmol·L-1, the germination indices reflected the same trend and showed an obvious inhibition with the improvement of the concentration. When the concentration got400mmol·L-1, every indices became to zero and this result means the germination was inhibited completely. With the treatments of different exogenous substances, every index improved with different degrees. Every exogenous substance with different concentrations got an appropriate concentration finally.2. The Chi content of C. chinensis seedling leaves treated under different concentrations of NaCl stress were inhibited with different degrees and yielded lower concentrations than the control. Chi a, Chi b, and total Chi concentrations decreased with similar tendencies following treatment days. Chi a/b has the trend of increased first and then decreased in the early days of treatment, and decreased with the treatment days. The change of Car/Chl (a+b) shown a tendency of decrease in the whole process of treatment. This result shown that the injury of salinity stress to Chi a was more severe compared with Chi b, the stress to total Chi was more obvious to Car. The content of different pigments, the level of Chi a/b were all improved and the level was Car/Chl a+b decreased with the treatments of different exogenous substances. The result indicated that exogenous substances increased the content of total Chi and the level improved more significant to Car.3. The level of Pn, Gs, and Tr of C. chinensis seedlings were all decreased with the treatment days and the increased concentrations of NaCl under salinity stress, and the value of Ci increased with the opposite tendency. These results indicate that the main influencing factor to the decreasing net photosynthetic rate of C. chinensis is non-stomatal factors. After treated with different exogenous substances, the Pn, Gs, and Tr were all increased with different degrees, and the level of Ci was decreased. Among the different concentrations in the same exogenous substance has a appropriate concentration. It indicated that exogenous substances have a positive effect of to maintain normal photosynthesis and the higher activity of photosynthetical system of C. chinensis. 4. The indices, such as maximum fluorescence (Fm), potential maximum photochemical efficiency (Fv/Fm), potential photochemical efficiency (Fv/Fo), photochemical efficiency (Fv'/Fm'), actual photochemical efficiency ((DPSII), and photochemical quench coefficient (qP), electronic transfer rate (PCR), photochemistry rate (ETR), and absorbed light in photochemistry energy (P) were all significantly decreased with NaCl stress compared with the control, the values of these parameters increased with the number of treatment days, while the minimal fluorescence (Fo), non-photochemical quenching coefficient (NPQ), antenna heat dissipation (D), excess energy (E) were all increased. These results indicate that the primary light energy conversion efficiency of PSII was significantly inhibited under salinity stress and the PSII response centre is damaged by photooxidation and photoinhibition. The energy absorbed by the PS II antenna pigments to the photochemical energy reduced and the part that dissipated with the form of fluorescent improved. The number of PSII open centres and the original electronic receptor QAs decreased. With the treatments of different exogenous substances, the level of Fm,Fv/Fm,Fv/Fo,ΦPSⅡ,Fv'/Fm, qP,ETR,PCR, and P were all improved significantly, the level of Fo,NPQ,E和1D were all decreased. The photosystem, by increasing non-radiative heat dissipation, could consume the excessive light energy absorbed by PSII. Consequently, the PSII response centre is protected from damage by photooxidation and photoinhibition for absorbing excess light energy and the salinity stress-induced damage to C. chinensis had been alleviated.5. An age-dependent increase in TBARS concentration, H2O2content, LOX activity, production rate of O2-, and the relative conductivity were all observed in leaves subjected to NaCl-only treatment. The level of plasma membrane peroxidation was decreased with five different exogenous substances, the TBARS concentration, H2O2content, the production rate of O2-, and the relative conductivity were all decreased significantly. ALA, SNP, and Hematin treatments decreased the LOX activity significantly. The effects of Spd and SA treatments to the LOX activity were not significantly. This might due to the form alleviating the membrane peroxidation was different to other three substances.6. NaCl treatments with lower and medium concentrations made the SOD activity of C. chinensis leaves increased significantly in the early and mid, and decreased in the late period of treatment. The SOD activity decreased with higher concentration of NaCl treatments has a continuing trend. This may be the defense function of the SOD has reached its limitation and adjusted by other modes. POD activity gradually increased with the increase of NaCl concentration in the early period and the treatments with lower and medium concentrations in the mid and late period were also increased, while the higher concentration showed a decreasing trend. The lower and medium concentrations of NaCl treatments increased the CAT activity and the higher concentration showed a trend that increased first and then decreased. In the late period of the NaCl treatment, CAT activity got the minimum. APX activity in the initial period of salinity stress was significantly increased, and the low and mid concentrations of NaCl treatment showing a trend of increasing first and then decreasing. The higher concentration of NaCl treatment shown a continuous decline trend. GR activity in the whole process of the low concentration of NaCl treatment has a rising trend, and showing a continuous decrease trend with the higher concentration. Medium concentrations treatment made a trend that increasing first and then decreasing. The application of exogenous substances in different treatment periods to C. chinensis improved the activities of SOD, POD, CAT, and APX and GR effectively. This can form a more effective antioxidant system and remove the accumulated lipid peroxidation reactive oxygen species in order to ease the oxidation of the target.7. The content of soluble sugars has a increasing trend in the early and mid period of treatment, while in the late period, the content of soluble sugars decreased. The content of free proline increased in the whole process of the treatment. The soluble protein has the increasing tendency in the early period of treatment with the increase of NaCl concentrations, and the content has a decreasing trend with different degrees with the treatment time. Total flavones content increased with the treatment times and has no significant in the mid and late period of the treatment. The content of berberine hydrochloride increased with the lower concentration of NaCl, while the content decreased in the higher NaCl concentration. The application of exogenous substances in different treatment periods to C. chinensis increased the content of soluble sugars, free proline, soluble protein, and berberine hydrochloride. Total flavones content also has a improvement, but there is no significant difference between different concentrations.8. In the process of C. chinensis treated with different exogenous substance under salinity stress, the time that got the optimum result of every indices has a slightly different, while the optimum concentration to every indices was the same. The seeds of C. chinensis treated with different exogenous substance got the optimum concentration were as follows:ALA (10mg-L-1), SNP (0.1mmol·L-1),Hematin(0.5μmol·L-1),Spd (0.25mmol·L-1),SA (10mg·L-1).The seedlings of C. chinensis treated with different exogenous substance got the optimum concentration were as follows:ALA (50mg·L-1),SNP (0.25mmol·L-1),Hematin (2.0μmol·L-1),Spd (0.50mmol·L-1), SA (50mg·L-1)...
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