| The one-year seeding of Alnus formosana has been study on in this paper. Based on the determination of the seeding`s kinds of indexes of hysio-biochemical and photosynthetic characteristics under the different NaCl treatments.the the physiological, biochemical and photosynthetic response mechanism of Alnus formosana seedling in salt stress environment were analyzed, moreover, their salt-damage mechanism was researched. The aim was to provide theoretical basis for developing of Alnus formosana in inshore beach.Under salt stress,the chla content,chlb content,chl content and carotenoids content of the seedling presented degressive trend as a whole along with the salt density and the time increase, and the fall range of chla content was more than chla`s.Stress for 30 days ,each treatment `s total chlorophyll content respectively fallen 12%,16.4%,27% and 28.2% than the comparison ,and respectively fallen 20.1%,40%,42.2% with the time increase. The effects of pigment content of seedling reached significant level respectively under different salt stress.The content of MDA of the seedling presented increasing trend as a whole along with the salt density and the time increase.The rise was not obvious under 0.1%(g/kg.DW)NaCl concentration treatment,it content was 1.32 times as much as the comparison content; while the content of MDA reduced slightly under 0.1% NaCl concentration treatment with decreased by 17.72%; but significantly increase under high NaCl concentrations(0.4%.0.6%) treatment,they were respectively 3.29,3.85 times more than the comparison. The effects of MDA content of seedling reached significant level respectively under different salt stress.The content of Pro of seedling decreased at first and increased subsequently as a whole along with the salt density increase. The Pro content of 0.1% and 0.2% NaCl concentration treatment were respectively fallen 21.96%, 33.59% than the comparison content; while it content of 0.4% and 0.6% NaCl concentration treatment were respectively risen 93.28%, 110.59%. It significantly increase under 0.1%, 0.2% NaCl concentration treatment with the time increase, and reached significant level respectively with the comparison..The activity of SOD of the seedling increased as a whole along with the density respectively content increase. Stress for a month , the activety of SOD of each NaCl concentration treatment were respectively 2.23,2.64,3.78 and 4.01 times as much as the comparison`s,and all reached significant level rspectively with the comparison .The activity of SOD decreased with the time increase, and also reached significant level rspectively with the comparison.Under salt stress, the MDA content of the seedling reached extremely significant negative correlation with the chl content (-0.89**), and the Pro content reached significant positive correlation with the activity of SOD (0.79*).The others indexes of the seedling were independent.The diurnal course of Pn of the seedling presented"diauxie curve"under 0.1%, 0.2% NaCl concentration treatment, and were consistent with the comparison, while presented"gradually declined line"under 0.4%, 0.6% NaCl concentration treatment. The diumal course of Tr and the diumal course of Gs presented the same trend. The net photosynthetic rate gradually decreased with NaCl concentration and time increasing.It denoted the main factor inhibiting Pn is non-stomatal control.The response of photosynthesis to light of leaf all presented a quadratic curves under different salt concentration treatment. Under normal circumstances, Alnus formosana `s max net photosynthetic rate is 6.87 CO2μmol.m-2.s-1, and had high light saturation point (1060.29μmol.m-2.s-1) and AQY(0.063μmol.m-2.s-1),low light compensation point (4.28μmol.m-2.s-1).The max net photosynthetic rate,LCP,LSP,AQY were presented degressive trend as a whole along with the salt density and the time increase, and the fall range of LSP was more than LCP.Salt stress reduced the seedling`s adaptability of optical encironment.The response of photosynthesis to CO2 of leaf all presented a quadratic curves under different salt concentration treatment.The net photosynthetic rate after stabilizing show CK>0.1%>0.2%.0.4%.0.6%.Under normal circumstances, the CCP of Alnus formosana is 57.11μmol.m-2.s-1 and the ACE is 0.0253μmol.m-2.s-1.Under salt stress,the ACE of the seedling had decreased and the CCP had increased.To some extent,enhancing CO2 concentration may enhance Pn.Salinity had significant impact on the chlorophyll fluorescence of the seedling leaves. During the experiments, it showed a declining trend for Fo with NaCl concentration increasing. Fv/Fm, Fv/Fo, Fm and Yield declined, but NPQ is first increased and then decreased.Salt stress had inhibition the function of PSII,obstruct the photosynthetic electronic transfer, reduce the original conversion efficiency of PSII, restrain the photosynthesis of the seedling. |
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