Effects Of Salt Stress On Photosynthesis And Salt Tolerance Estimate Of Pinus Silvestris L.

Pinus silvestris L., an adaptability precious salt-tolerance variety, could grow on the saline-alkali soil (Cl- 0.213%, SO42- 0.606%, Na+ 0.419%). A study on introduction of Pinus silvestris L. is necessary to be carried out in order to enriching genetic resources of Pinus silvestris L., selecting excellent species, and providing crossing parents in China.In a pot experiment made by saline-alkali soil, this paper studied the salt-tolerance of 7 introduced Pinus silvestris L. provenances and 2 Pinus sylvestris var. mongolica domestic ones. The 9 kind of 2-year-old seedlings were divide into 2 batches to plant:(1) Hal, Ha2,754, 17330, N8,11,17274, DAXINGANLING, HONGHUAERJI, the salt stress level is 0.5% and control. After salt treatment,2 grow indicators, height growth and stem basal diameter, were determined on the 10th,30th,45th,60th day. Net photosynthetic rate (Pn) measured on the 2nd, 20th,50th day and Fv/Fm measured on the 5th,30th,50th day. (2) Hal, Ha2, the salt stress level is 0.25%,0.5%,1.0% and control. After salt treatment, diurnal variation of 9 photosynthesis indexes was measured on the 25th day. Photosynthesis physiological indexes and Light responsive curve measured on the 2nd,20th,50th day and chlorophyll fluorescence parameters measured on the 5th,30th,60th day. The mainly conclusions as follow:1. Four indexes, relative variable ratio of height growth, basal diameter, Pn and Fv/Fm were used to evaluate the salt tolerance of 7 introduced Pinus silvestris L. provenances and 2 Pinus sylvestris var. mongolica domestic ones, its order is:Hal>Ha2>17330 and 11>754>N8> 17274>HONGHUAERJI>DAXINGANLING.7 introduced Pinus silvestris L. provenances have stronger tolerance to salt stress than those of 2 domestic ones (HONGHUAERJI and DAXINGANLING), tolerance to salt stress of Hal and Ha2 was superior.2. According to the results of Pn, Gs, Ci, Tr, Vpdl, Ls, WUE and CE, descended Pn under salt stress of Hal and Ha2 has both concentration effects and time effects. It denoted the main factor inhibiting Pn of Hal is stomatal control. The factor inhibiting Pn of Ha2 to short-time salt stress is stomatal control, and that to long-time salt stress is stomata and non-stomatal control. Regression analysis results showed that effects of salt stress on photosynthetic ecological factors of Hal order is CE>Ci>Gs> WUE>Ls> Vpdl, and that of Ha2 is Ci>CE >LS>GS>Tr>WUE.3. According to the results of diurnal variation of Pn, Gs, Ci, Tr, Vpdl, Ls, WUE, LUE and CE, the Pn diurnal variation curves of Hal under 0.25%, CK together with 0.5%,1% salt stress is single-peak, two-peak and waves respectively. Ecological factors orders of Hal under CK, 0.25%,0.5% and 1% salt treatments respectively is RH>Ci>Ca>Ta>Gs>Vpdl, RH>Tr>Ci >Ca>Ta>PAR, Ta>RH>Vpdl>Ci>PAR, Ci>Ca>GS. The Pn diurnal variation curves of Hal under CK together with 0.25%,0.5% together with 1% salt stress is single-peak and two-peak respectively. Ecological factors orders of Hal under CK,0.25%,0.5% and 1% salt treatments respectively is Ci>Vpdl>RH>Tr>Ca>Gs, Vpdl>Ta>RH>Ci>PAR>T, Ca>Ci >PAR>Tr>Ta, Tr>Ci>PAR>Ca>Ta>RH.4. The light response curves fitting results showed that model 5 were better than the others. Descended AQYand LSP might be important factors resulting in the decrease of Pn.5. According to the results of Fv/Fm, Fv'/Fm',ΦPSⅡ, PhiCO2, qP, qN, ETR, under salt stress, the statistics analysis of Hal showed a significant negative correlation between salinity and Fv/Fm, Fv'/Fm',ΦPSⅡ, ETR, PhiCO2, a significant positive correlation between salinity and qN, but a non-significant negative correlation between salinity and qP. The reaction center inactivation, reducing electrons transport rate and hampering photosynthetic electron transfer might be important factors resulting in the decrease Pn of Hal. The statistics analysis of Ha2 showed a significant negative correlation between salinity and Fv/Fm, Fv'/Fm',ΦPSⅡ, ETR, qp, PhiCO2, a significant positive correlation between salinity and qN. The reaction center inactivation, reducing quantum yield corresponding to CO2 assimilation rate might be important factors resulting in the decrease Pn of Ha2.Under salt stress, photosynthesis was inhibited in varying degrees. The Ha2 value of decreased Pn and Pmax, daily average of WUE, LUE, CE, damage of the reaction center were greater than those of Hal. Overall, the salt tolerance of Hal is superior to Ha2.