| Aiming to solve the problem of tree species singleness,especially the deficiency of interstratum plants in the gardening process at saline area of Songnen Plain,several kinds of gardening arbor,shrub and liana,such as Qingshan poplar,Zhongheifang poplar,Xiaohei-14 poplar,Tanguticum nitraia,Shrubby amorpha,Aconiteleaf ampelopsis and Virginia creeper were selected as materials in this papers.These species are typicals species for local conditions and have a potential value in afforestation and planting.By studing their physiological and ecological response under different salt and alkali stress and further discussing on their adaptive ability to such stress,suggestions and advices were given at the view of providing theoretical and practical evidence for landscape plants selection in this inland saline area.The following conclusions were found in this paper.1.Three hybrid poplars'salt and alkali stress experiments divided into field test and laboratory simulation experiment.In the field test,three hybrid poplars'photosynthetic characteristics,growth quantity,root vitality,respiratory capacity and chlorophyll concent were comparatively analyzed.We found that,on the land with a higher salinity,three hybrid poplars' growth were obviously restrained,root respiration and root vitality enhanced,chlorophyll content slightly decreased,Chla/b increased.Comparatively,Qingshan poplar's response to such saline-alkali stress was less.On the same saline-alkali land, Qingshan poplar's photosynthetic capacity was higher than Zhongheifang poplar and Xiaohei-14 poplar. On the saline-alkali land,the Qingshan poplar's photosynthesis rate is slightly lower than that in the control land, which resulted in much higher water use efficiency and chlorophyll use efficiency (36.18%) with respected to other two species.Through reason and efficient utilization of water and chlorophyll,Qingshan poplar thus ensures a higher growth rate,i.e. the average tree height of four-year-old cutting seedings achieved 5.59m.2. The laboratory simulation saline-alkali test at first used 300mmol/L complex salt to treat three hybrid poplars. The result indicates that, Qingshan poplar has a higher salt-tolerance capacity than Zhongheifang poplar and Xiaohei-14 poplar. Furthermore, the experiment of Qingshan poplar under complex saline-alkali stress shows that, when salinity was lower, with the increasing of alkalinity or when alkalinity was lower, with the increasing of salinity, each physiological index's change range of the Qingshan poplar was not obvious. But, with the increasing of salinity and alkalinity, the changes of each index were apparent. Especially when pH was higher than 8.99, the stress with salinity over 200mmol/L greatly influenced the Qingshan poplar, it severely restrained the synthesis of chlorophyll and the accumulation of soluble sugar and proline. Root vitality was obviously restrained. SOD activity significantly decreased. Electrolyte leakage and lipid peroxidation increased rapidly. It can be seen, salt and alkali synergy will result in greater harm to plants. Through statistics analysis, four stress factors linear regression equation was established by pH, salinity, [CO32-] and [HCO3-]. Among the four factors, the influence on Qingshan poplar's physiology in turn were salinity, [CO32-], pH and [HCO3-]. Through field test and laboratory simulation test, confirming among the three hybrid poplar, Qingshan poplar's adaptability to saline-alkali stress is stronger, and it is more suitable for planting in Song-nen plain, and it can be widely used in Songnen saline area landscaping.3.Two kinds of shrubs were popular used in local landscaping greening practies,i.e. Tanguticum nitratia and Shurbby amorpha were tested in this part.This research respectively used complex salt and two kinds of single salt (NaC1 and NaHCO3).Under the complex saline-sakali stress, Tanguticum nitratia's osmotic adjustment substance increased in different degree, Tanguticum nitratia through accumulating osmotic adjustment substance to reduce salt injury. Except chlorophyll content under the combination of alkaline salt was basically stable, other combinations'chlorophyll content was higher than contrast even though under the condition of salinity 400mmol/L. It indicated that saline-aklali stress promoted an increase of chlorophyll content in Tanguticum nitratia. The saline-alkali condition of higher than 300 mmol/L salinity with pH>10.59 was not suitable for the growth of Tanguticum nitratia.4. Under the salt stress, along with the treatment time prolonged and salinity increased, Shrubby amorpha seedlings'membrane permeability increased and the degree of lipid peroxidation aggravated, chlorophyll synthesis was restrained. But Shrubby amorpha could adjust osmotic balance to reduce salt injury by actively accumulating large amount of osmotic adjustment substance such as soluble sugar, soluble protein and proline. At the same salinity, alkaline salt made a heavier damage to Shrubby amorpha than neutral salt. When the salinity of two kinds of salt was 0.8%, Shrubby amorpha still grow at the 9th treatment week, although membrane permeability was larger, the large amount of osmotic adjustment substance in vivo could maintein cell's osmotic balance. But when the salinity higher than 1.1%, Shrubby amorpha could not grow normally, when treating six weeks, leaves completely withered.5. Aconiteleaf ampelopsis and Virginia creeper are all liana plants with good enjoyment and strong resistance, which have a big application potential on city vertival greening in saline area. This reseach used two kinds of single salt (NaC1 and NaHCO3) to treat Aconiteleaf ampelopsis and Virginia creeper, studied on two kinds of liana plant's physiological changes under different salt stress. Under the salt stress, Aconiteleaf ampelopsis resisted injury from salt stress by rapidly accumulating osmotic adjustment substance and enhancing protective enzyme activity. It was difficult for Aconiteleaf ampelopsis to adapt higher salinity stress, and alkaline salt stress made a heavier damage to Aconiteleaf ampelopsis than neutral salt sress. When NaCl salinity was higher than 300mmol/L, NaHCO3 salinity was higher than 200mmol/L, after 12d osmotic adjustment substance content and protective enzyme activity decreased significantly. So the NaCl stress higher than 300mmol/L and the NaHCO3 stress higher than 200mmol/L were not suitable for the growth of Aconiteleaf ampelopsis.6. Along with the treatment time and salinity increased, the electrolyte leakage and MDA content of Virginia creeper increased gradually, soluble sugar and proline content increased, and soluble protein decreased. The adaptability of Virginia creeper to salt stress had a large limitation. When the salinity of NaCl and NaHCO3 was lower than 60mmol/L, its growth were not inhibited obviously. But when the salinity was higher than 90mmol/L, the two kinds of salt remarkably inhibited the growth of Virginia creeper, and alkaline salt's inhibition was bigger. The salinity of 90mmol/L was the threshold of Virginia creeper to tolerant the salt stress.7. During the landscaping process in Songnen saline area, we should according to main saline and alkaline coposition of local soil to study on plants'physiological ecology and biomass ecology under saline-alkali stress, confirming the tolerance liminal value of different plants, and then following it to select suitable arbor, shrub and liana species for severe saline habitats. Through reasonable arrangement of these plants, insist on matching tree species with site, constructing different ecological community, serving for Songnen saline area's ecological garden construction.
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