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Tottori University (2012)

Studies on the Salt Tolerance Mechanism of Halophytes Growing in Xinjiang, China


Titre : Studies on the Salt Tolerance Mechanism of Halophytes Growing in Xinjiang, China


Université de soutenance : Tottori University


Progressive soil salinization is a serious issue in worldwide and is a major cause of desertification in arid regions. Extensive degradation of irrigated lands due to salinization poses both environmental and socio-economic problems in Central Asia and northwestern China. To combat soil salinization, various methods have been used. A biological method, phytoremediation, comes into employ to decrease the trend of soil salinization and ameliorate degraded land effectively. A method using native halophytes has drawn attention and been given high priority in several countries. The Xinjiang region of China is very rich in halophyte species. These halophytes might allow the utilization of salt-affected soils. For appropriate and the successful use of halophytes to ameliorate salt-affected soil, it is necessary to determine the mechanism(s) by which halophytes tolerate saline conditions. Therefore, the objective of this study is to gain a precise understanding of the salt-tolerance mechanism of halophytes growing in the Xinjiang region. To achieve this objective, this study conducted field investigations and greenhouse experiments. On the field investigations, the cation concentrations and distributions among plant parts and osmolyte accumulation in leaves were determined in five halophytes (Tamarix hispida, Halocnemum strobilaceum, Kalidium foliatum, Karelinia caspica, and Phragmites australis) growing around Aiding Lake, Xinjiang, China. The responses of Elaeagnus species, a pioneer, multipurpose tree species, to various salinities were examined in greenhouse experiments.
The construction of study was therefore arranged as follows:The first chapter introduces salinization problem in worldwide, rehabilitation methods for salt affected areas, importance of halophytes use as phytoremediation in saline regions and objectives of this study. Chapter II presents the results of a study of the cation content of five halophytes growing under saline conditions, thus providing basic information on the differences in salt-regulation mechanisms among species. Chapter III presents the results of a study of the osmolyte contents of the five halophytes, providing a better understanding of the physiological strategies of halophytes to cope with saline environments. In Chapter IV, the photosynthetic performance of Elaeagnus angustifolia L saplings are discussed to gain a better understanding of the physiological behavior of this species under saline conditions. In chapter V, the salt tolerance and response of different osmolytes to salt stress in Elaeagnus oxycarpa seedlings are discussed to elucidate the salt-tolerance mechanism of this tree species. And finally, main achievements in this study are summarized and ecological applications are offered in the last chapter.


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