| Pinus sylvestris var. sylvestriformis，which belongs to Pinus in Pinaceae is evergreen trees.It was originated in Changbai mountain in Jilin, China, and belong to national key protectedspecies. The pine tree as a typical tall evergreen tree, and there is obvious advantages in theconstruction of urban landscaping. Due to the large area soil salinization in urban, the salttolerance degree of the pine tree is great important for its can be fully used. But the research ofsalt tolerance has never been reported, and the scientific problem of salt tolerance needs to besolved urgently. So the research object of this dissertation is the biennial the pine tree seeding inthe soil salt simulation experiment. The growth conditions and physiological changes of theseeding under the salt (Na2CO3and NaCl) stress of different concentration and ratio wereobserved and determined into the year growth cycle in pots containing soil. The salt resistanceand salt tolerance of the seeding were discussed and evaluated using the fuzzy membershipfunction and the related research of plant salt tolerance thresholds. The results are as follows:1. With the increase of salt concentration, the plant heigh and stem diameter of the seedinghas present a downward trend under the various salt stress. The seeding was appear significantinjury or death, when the concentration of Na2CO3, NaCl and compound salt stress are morethan4.5g/kg,3.0g/kg and4.5g/kg, respectively. In addition, the seeding leaves was yellowingfrom the leaf base to tip under Na2CO3salt stress. But form the leaf tip to base under NaCl saltstress.2. Under three kinds of salt stress, the chlorophyll content of seeding leaves showedgradually decreased with the increase of salt concentration. The three kinds of organicosmoregulation substances(soluble sugar, protein and proline)were higher than the control. Withthe extension of stress time，the cell membrane permeability of the low salt treatment wasincreased slowly and it is significantly higher under relatively high salt concentration. In themeantime, the MDA content of seeding leaves was gradually rise with the increase of saltconcentration and the extension of stress time. The superoxide (SOD) and peroxidase (POD)activities in the seeding leaves were increased in the early stage. But the SOD and PODactivities were obvious dropped in high salt stress with the extension of stress time.3. The influences of the chlorophyll, soluble sugar and protein, proline, cell membranepermeability, MDA and SOD, POD in the seeding leaves were reached a significant level (or avery significant level) under the concentration of salt stress. But it was not significant under the different kinds of salt. In addition, the salt stress impact on cell membrane permeability andMDA were more apparent than other physiological indexes.4. The comparison results showed that the stress of compound salt was lighter than singlesalt, and the NaCl salt stress was more serious than the Na2CO3. This study concluded that thesalt tolerance threshold of seeding under NaCl, Na2CO3and compound salt stress were4.5～6.0g/kg,3.0～4.5g/kg and4.5～6.0g/kg, respectively. After comprehensive analysis anddiscussion, to deduce the salt tolerance threshold of the pine tree seeding was about4.5g/kg.In conclusion, the pine tree seeding can be to grow normally in the soil which is less than3.0g/kg, and it showed some salt resistance. When the soil salt content is more than3.0g/kg,the growth and physiological characteristics of the seeding were obvious influenced by saltstress. The stress performance of compound salt was lighter than single salt in the pine treeseeding, but the NaCl salt was more serious than the Na2CO3salt. In addition, the salt tolerancethreshold of the pine tree seeding was about4.5g/kg. |
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