Physiological And Ecological Characteristics And Transcriptomic Analysis Of Typical Desert Shrubs In Western Ordo

West Ordos is located in the steppe desert region of western my country,and it has the characteristics of desert vegetation with xerophytic shrubs as the dominant species.Its climatic conditions are special,with extremely low temperature in winter and high temperature and aridity in summer,but it has relatively rich species diversity,and there are many rare plants under national key protection,such as Tetraena mongolica,Helianthemum soongoricum,Amygdalus mongolica and Ammopiptanthus mongolicus have the reputation of"refuge" of relict plants,and have become hot spots for research on the adaptation mechanism of desert plants and biodiversity conservation,and have important scientific value.Therefore,in order to explore the physiological and ecological mechanisms of adaptation to arid environment and the similarities and differences in survival strategies of desert shrubs in this region during the long evolution process,this study took six typical desert shrubs as the research objects,and carried out field vegetation surveys,photosynthetic physiological ecology characterization observation and transcriptome sequencing analysis studies.The main findings are as follows:1.The vegetation species composi tion of the West Ordos desert is relatively small,and shrubs and herbs grow alternately,often forming a shrub community type with a single plant as the dominant species.The life forms of desert plants are mainly high-budding plants and annual plants.The geographical components of flora families in the study area were mainly affected by temperate and tropical components,and the geographical components of flora genera were mainly composed of ancient Mediterranean components.2.The physiological and ecological strategies of different desert plants to adapt to the arid environment have commonalities,but there are also some differences.Under drought conditions,desert plants show a trend of decreasing net photosynthetic rate,and most plants have a phenomenon of "photosynthetic lunch break";the electron transfer efficiency of plants generally decreases,and plants mainly use energy for heat dissipation at noon to resist the heat.In the environment,the photosynthetic mechanism of plants is damaged and the carboxylation efficiency is reduced.But Tetraena mongolica showed the opposite trend,which was mainly related to the incomplete development of its leaves in April.Under the influence of drought stress,the five plants of Helianthemum soongoricum,Nitraria tangutorum,Amygdalus mongolica,Ammopiptanthus mongolicus and Zygophyllum xanthoxylon almond showed adaptation strategies of high photosynthesis,low transpiration and high water use efficiency;while Tetraena mongolica showed low photosynthesis,low transpiration and low water use efficiency.3.There were differences in the responses of different shrubs to water changes.In particular,the three species of Zygophyllaceae(Nitraria tangutorum,Zygophyllum xanthoxylon,Tetraena mongolica)were not sensitive to water response.The irrigation treatment experiment of these three plants was set up,and the results showed that the daily average value of net photosynthetic rate of the three plants after irrigation was lower than that before irrigation,but the net photosynthetic rate of the three plants increased at 7:00 am and 9:00 am.It shows that the three plants are under severe drought stress,especially Nitraria tangutorum and Zygophyllum xanthoxylon,and their growth conditions may be in a critical state of severe stress.In addition,Nitraria tangutorum and Zygophyllum xanthoxylon showed a positive strategy of high photosynthesis,low transpiration,and high water use efficiency;while Tetraena mongolica showed a conservative strategy of low photosynthesis,low transpiration,and low water use efficiency.Compared with Nitraria tangutorum and Tetraena mongolica,we speculate Zygophyllum xanthoxylon is a relatively new species.4.The adaptation of desert shrub plants to arid environment is closely related to the molecular regulation mechanism of transcriptional level.Under drought stress,the results of GO and KEGG enrichment analysis of differentially expressed genes in five plants(Nitraria tangutorum,Zygophyllum xanthoxylon,Helianthemum soongoricum,Amygdalus mongolica and Ammopiptanthus mongolicus),showed that the drought stress response of five plants was significantly enriched in the metabolic processes such as hydrolase activity,acting on glycosyl bond and transferase activity,transferring glycosyl,cell wall,starch and sucrose metabolism and plant hormone signal transduction.In this study,NAC,MYB,ZIP,WRKY,AP2/ERF,ERF and other transcription factors were screened,which are widely involved in the drought stress response of desert plants.In addition,five plants drought resistance related genes were screened.The gene function annotation results were related to plant hormone abscisic acid,including abscisic acid response element binding factor and abscisic acid receptor PYR/PYL family.Five plants photosynthetic physiology related genes were screened.The gene function annotation results are related to photosynthesis,including ATP synthase subunit,photosystem I subunit and photosystem II subunit,which can be used as key candidate genes for subsequent gene cloning and function research.In conclusion,this study investigated and analyzed the characteristics of desert vegetation in West Ordos,and compared the physiological,ecological and molecular mechanisms of desert shrubs adapting to arid environment under different drought conditions from different levels such as physiological characteristics and molecular levels.The protection of rare and endangered plants in desert areas and the restoration of vegetation provide reference.