The Studies On Salt Tolerance Of 15 Landscape Plant Species

Saline soil, a kind of agro type with widespread distribution and an important soil resource, which is in the proportion of 25% to the land total area, amounts to approximately 10 hundreds million ha. The salt and harmful ions in saline land limited the plant growth, Causes the majority of plants to be unable the normal growth. Now, the improvements of saline soil have been a cosmopolitan problem. In recent years, the scholars proposed let biology adapt environment, breeding salt-tolerance plant to use and improve the saline soil. To improve saline soil by using salt-tolerance plant is a mode that centers on recovering vegetation. It can improve bad ecological environment in the area of saline soil and advance the soil fertility. So we can impulse development by using these plants. It can bring out great ecological and economic effects. Usually, the plants used to green the saline land are divided into two kinds: the local halophytes and the landscape plants have certain salt tolerance. But at present, the varieties of plants are used in the city are unitary and the resources of high value are deficient. Those factors have restricted the city's construction of the greening system.In a pot experiment with the nutritional medium made by seaside-alkali soil, this paper studied the salt tolerance of 15 landscape plants. The 15 kind of plants were divide into 2 batches to plant: (1) Forsythia suspense (Thunb.) Vahl, Rosa chinensis Jacq., Osmanthus fragrans cv. Semperflo, Ligustrum vicaryi Ait, Sabina procumbens (Endl.) Iwata et Kusaka, Cedrus deodara (Roxb.)G and Pinus tabulaeformis Carr., the salt stress level is: 0.91 g/kg, 2.3g/kg, 4.6 g/kg, 4.9 g/kg, 5.8 g/kg, 8.7 g/kg, 12.7 g/kg; (2) Aesculus chinensis Bunge., Liriodendron chinense (Hemsl.) Sarg., Chaenomeles speciosa (Sweet) Nakai., Osmanthus fragrans var. thunbergii Makino, Albizzia julibrissin Durazz., Edgeworthia chrysantha Lindl., Celtis sinensis Pers. and Sapindus mukorossi Gaertn, The salt stress level is: 0.91 g/kg, 1.3 g/kg, 2.1 g/kg, 3.8 g/kg, 5.7 g/kg, 9.4 g/kg, 10.2 g/kg.After 3 months of treatment, determined the plants' growth performance, survival rate; 2 grow indicators: height growth, and seem basal diameter; 2 physiological indexes: chlorophyll content and the relative water content; 4 photosynthesis index: net photosynthetic rate, stomatal conductance, intercellular CO₂ and the transpiration speed. And used the "Index of salinity tolerance" method to carry on the evaluation to plant's salt tolerance in the expectation of selecting more landscape plants have certain salt-tolerance. The ecological benefits and landscape effects of urban greening will be materialized. This study takes theories to biology improvement of saline land and exploitation and use of saline soil resources, also builds the foundation for the further selective breeding work.The mainly conclusions as follow:1. Under the big awning shallow seas and tidelands earth bonsai condition, along with the salinity density ascension, 15 kinds of landscape plants' survival rate and the growth state has all come under the varying degree influence. Height growth, seem basal diameter, chlorophyll content, the relative water content, the net photosynthetic rate and stomatal conductance change all follows: the salinity is higher; the determination value is smaller, suppression phenomenon more obvious. The suppression degree different has the obvious difference because of the floristic component. Intercellular CO₂ assumes the trend of escalation along with the soil salinity ascension; But the transpiration speed, changes not identically along with the soil salinity change.2. According to this experimental goal and the union actual situation, we choice the survival threshold value, unified the growth state of plants to determine the salt tolerance of the 15 landscape plants. According to this standard, the salt tolerance of these experimental plants is: (1) Forsythia suspense, Rosa chinensis and Osmanthus fragrans cv. Semperflo are light-degree salt tolerance plants, can grow well in the salty soil not higher than 4.6g/kg. Ligustrum vicaryi grows well in the salty soil not higher than 4.9g/kg. Cedrus deodara grows well in the salty soil not higher than 5.8g/kg. Pinus tabulaeformis grows well in the salty soil not higher than 12.7g/kg. Sabina procumbens is of high salt tolerance, can grow in 12.7g/kg salty soil. (2) Edgeworthia chrysantha Lindl. and Liriodendron chinense (Hemsl.) Sarg. can grow well in the salty soil which is not higher than 1.32g/kg; while Celtis sinensis Pers. and Albizzia julibrissin Durazz. are light-degree salt tolerance plants, only can grow well in the salty soil not higher than 2.21g/kg; Chaenomeles speciosa (Sweet) Nakai., Osmanthus fragrans var. thunbergii Makino and Sapindus mukorossi Gaertn. grow well in the salty soil not higher than 3.84g/kg. The seedling of Aesculus chinensis can grow in the salty soil not higher than 5.68g/kg., which displays well for the second batch of species.3. Using the "Index of salinity tolerance" method to evaluate the salt tolerance of these two batch of plants, its order respectively is: (1) Osmanthus fragrans cv. Semperflo