【作者】 石松利；

【导师】 王迎春；

【作者基本信息】 内蒙古大学 ， 植物学， 2009， 博士

【摘要】 四合木（Ttraena mongolica）是蒺藜科（Zygophyllaceae）单种属的古地中海孑遗植物,中国狭域和特有分布种,典型的西鄂尔多斯特有单种属和特有群系,国家二级保护植物,在植物分类、植物区系研究上具有重要科学意义,在防风固沙、水土保持和维持荒漠生态系统功能方面具有重要作用。四合木分布区的生态环境十分脆弱,近年来由于自然环境恶化和人为因素破坏,四合木种群在分布区内破碎化程度逐渐加剧,生境适宜性已明显下降,濒危状况日益严重,对四合木物种保护生物学的研究已引起生物学工作者的广泛关注。因此研究空间上斑块分布区的生境适宜性和四合木的生态适应性具有十分重要的意义,将有助于探索四合木种群的濒危机制,也将为濒危植物保护措施的制定提供科学依据。本论文选取四合木分布区5个不同典型生境为研究样区,以同生境近缘种霸王为对照,通过对种群特征和土壤理化性质（土壤有机质、营养元素和微量元素）的研究,结合野外天然生长状态下不同季节植物水分参数特征、内源激素、抗氧化系统、光合作用、蒸腾作用及水分利用效率等方面特征分析对不同生境四合木抗旱生理生态适应机制及濒危机理进行了系统的研究。研究结果如下:1.研究区不同生境四合木种群密度、盖度、年龄结构存在显著差异,且低山、台地、丘陵种群所处生境有利于四合木幼苗更新和植物生长,其密度和盖度较大,适合建立保护区,应该进一步加强保护;高平原和倾斜平原种群所处生境不利于四合木幼苗更新和植物生长,四合木逐渐被适应性更强的霸王所取代,其密度和盖度较小,四合木有趋于消亡的趋势,应该引起关注。2.研究区四合木根际土壤有机质含量、土壤含水量、营养元素（N、P、K）、微量元素（Fe、Mn、Cu、Zn、Mo、B）含量均较低,pH偏高,体现出贫瘠碱性化的荒漠土壤特点。运用数理统计将5个样地土壤理化性质进行聚类分析,分为两类:低山、台地、丘陵样地为一类（A类）,高平原、倾斜平原为一类（B类）。两类样地土壤理化性质存在一定的差异:低山、台地、丘陵样地（A类）土壤营养元素（N、P、K）和微量元素（Fe、Mn、Cu、Zn的全量和有效量;有效B、有效Mo）、土壤有机质含量及土壤含水量都显著高于B类,而pH值显著低于B类。3.四合木水分参数Ψ_s^sat、Ψ_s^tlp值较低, AWC、V_a/V₀值较高,体现荒漠灌木四合木较强的干旱适应性特点。四合木主要水分参数Ψ_s^sat、Ψ_s^tlp值及ε^max表现为5月>7月>9月,AWC、V_a/V₀表现为5月<7月<9月,四合木耐旱性随5月、7月、9月递增,这种季节变化规律与植物生长发育的节律相吻合即与物候的进程一致。对5个生境四合木进行耐旱性排序,得出倾斜平原、高平原>丘陵>台地>低山,将三个月份5个不同生境四合木水分参数进行聚类。结果和土壤理化性质结果相一致,低山、台地、丘陵四合木为一类（A类）,耐旱性强弱,高平原、倾斜平原四合木为一类（B类）,耐旱性较强。两类样地植物水分参数特征存在一定的差异:三个月份Ψ_s^tlp值、Ψ_s^sat值和AWC值均表现为高平原、倾斜平原四合木显著低于低山、台地、丘陵四合木。不同生境四合木的渗透调节机制不同,倾斜平原和高平原的四合木其体内通过增加细胞质浓度进行渗透调节能力较强(较低的Ψ_s^tlp值和Ψ_s^sat值);而生境为低山、台地和丘陵四合木抗脱水能力较强（较大的AWC值）。4.不同生境四合木体内ABA和GA₃含量均表现为随5月、6月、8月而不断升高,而IAA的含量和ZR的含量均表现为:6月>8月>5月,一方面体现出内源激素对植物生长发育的调控作用,另一方面体现出内源激素在抗逆性中发挥重要作用,干旱胁迫下,IAA和ZR的含量降低,ABA和GA3含量升高,内源激素协同作用促进植物度过不良环境。不同生境条件四合木内源激素存在显著差异:5月份IAA含量表现为在A类样地>B类样地,8月份ABA含量和GA₃含量表现为在A类样地>B类样地。内源激素的综合调控作用是A类样地四合木种群密度和盖度较大的内在原因之一。5.不同生境四合木体内MDA含量均随5月、6月、8月而不断升高,表明随着季节进程加剧叶片受到的过氧化伤害也在不断加剧,而四合木体内抗氧化酶类SOD、POD、CAT、AsA-POD、GR和非酶氧化剂GSH、AsA随5月、6月、8月而不断升高,二者协同作用共同抵抗干旱胁迫诱导的氧化伤害。不同生境四合木的抗氧化系统存在差异性:A类样地受到的膜质过氧化强度相对较低,其体内的抗氧化酶活性和抗氧化剂含量较低;而B类样地四合木根际土壤干旱程度较高,均有提高一定幅度的抗氧化酶活性和抗氧化剂含量以清除干旱导致的氧化伤害的能力。抗氧化系统的调节是四合木对不同生态环境适应的重要生理反应之一。6.对B类样地建群种四合木和近缘种霸王进行比较研究,相同生境下四合木叶片MDA含量均显著高于霸王,膜质过氧化程度高于霸王,抗氧化酶活力和抗氧化剂含量均显著高于霸王,四合木体内ABA、IAA、ZR、GA3含量低于霸王,四合木保持最大膨压和维持最低膨压的水势阈值弱于霸王,耐旱性弱于霸王。说明同生境下霸王竞争有限的环境资源以促进植物生长发育的能力和耐旱性强于四合木,耐受相同程度环境胁迫的能力强于四合木,这些可能是四合木逐渐被霸王取代以及分布局限和濒危的重要内在原因之一。7.自然条件下,四合木和霸王叶片的光合速率、蒸腾速率日进程均呈“双峰”曲线,净光合速率、蒸腾速率峰值分别出现在11:00和15:00,两种植物上午的光合速率、蒸腾速率高于下午。四合木、霸王净光合速率、蒸腾速率具有明显的“午休”现象,而光合速率午间降低的原因主要是由气孔因素即孔导度降低造成的,蒸腾作用的午间降低是旱生植物通过关闭气孔来适应午间高温或防止叶片过度蒸腾失水的一种生态适应对策。PAR和Gs是影响这两种植物光合作用速率和蒸腾速率Tr的最主要因子。二者相比霸王比四合木具有较高的光合速率和水分利用效率,这可能是四合木逐渐被霸王取代以及分布局限和濒危的重要内在原因之一。更多还原

【Abstract】 Tetraena mongolica, monotypic genus of Zygophyllaceae, is the super xerophyte and the relic shrub of Tethys. There is only a small part of them distributing in China. It is a special shrub endemic to the west of Ordos Plateau end its distributed area is very small, belonging to second-class national protected species. It has very important significance both in plant taxonomy and regional system study, and plays an important role as a windbreak, as well as in stabilizing sand and in conserving soil and water. It has also played a very important role in maintaining ecosystem in terms of preventing desertification. But in recent years, the landscape pattern has been fragmented and the habitat has been islanding because of deterioration of the environment and destruction by people. So the plant species has fallen into severe endangered. So the research on the conservation biology of endangered species T. mongolica has been taken great attentions. And analysis on habitat fitness of different population patches in distribution region and ecological adaptability of endemic species T. mongolica are of great significance. It will help to seek after the danger mechanism and offer science base for establishing the safeguard. Then five T. mongolica populations in different habitats （upland, hill tableland, high plain and terrace） and its congener species Zygophyllum xanthoxylon in the same condition were selected as our research objects. Through analyze the soil physical and chemical characters, combining with research on aspects of eco-physiology characters with season including water parameters characters, endogenous phytohormone, enzymatic antioxidant system, photosynthesis and water use efficiency responses, researches on eco-physiological adaptation mechanism of T. mongolica Maxim in different habitats to drought condition and endangering mechanism was carried out. The results are as follows:1.There was a significant difference in density, coverage, width-class and age-class structures of T. mongolica populations in different habitats. The habitats of Upland, hill and tableland population were fit for seedlings rebirthing and plants growth, and the density and coverage in these three populations were significantly higher than that of high plain and terrace populations. The habitats of these three populations is fit to establish nature preservation zone and shoud be given more effective way to conservation. But the habitats of high plain and terrace populations were not fit for seedlings rebirthing and plants growth. T. mongolica in these two populations has been replaced by Z. xanthoxylon that has stronger adaptability and will die out. So the habitats of these two populations should be given more attention.2. The content of organic matter, nutritional elements （N、P、K）,micro-element （Fe、Mn、Cu、Zn、Mo、B） was very low, but the pH was high. This embodied the bad condition of barren soil and alkalization in desert. The physical and chemical index of soil in T. mongolica were cluster analyzed and T. mongolica population in five habitats were classified into two groups: upland, hill and tableland populations （group A） and high plain and terrace populations （group B）. The content of organic matter, nutritional elements （N、P、K） in the group A was significantly higher than that in group B. The total content of micro- elements Fe、Mn、Cu Zn in soil is higher in the group A than in group B. The available content of six kinds of micro-element such as Fe、Mn、Cu、Zn Mo、B indicates the same results as above.3. T.mongolica is of lowΨ_s^sat，lowΨ_s^tlp , high AWC and high V_a/V₀, which shows that T.mongolica is of strong ability of drought tolerance. The seasonal change ofΨ_s^sat、Ψ_s^tlpandε^max showed May > July > September. And the AWC、V_a/V₀ showed May < July < September. The drought tolerance of T.mongolica continuously enhanced with season. This seasonal change is response to the phonological rhythm of plant. The ordination analysis for drought tolerance of T. mongolica in upland, hill,tableland, high plain, terrace was finished. The level of drought-tolerance among the five habitats above decreased in the following order: high plain and terrace>upland> tableland>hill. Based on three measurements of water parameters of T. mongolica in five habitats in P-V curves, the cluster analysis of drought tolerance of T. mongolica was finished. T. mongolica in five habitats can be classified into two groups: upland, hill and tableland is one group, high plain and terrace is the other group. The variance analysis showed that three measurements ofΨ_s^sat、Ψ_s^tlp and AWC of T.mongolica in high plain and terrace is lower than that of upland, hill and tableland. There are difference in osmotic adjustment mechanism among five different habitats. T. mongolica in high plain and terrace is of stronger ability of osmosis adjustment by improving the concentration of cellular solute, but T. mongolica in upland, hill and tableland is of stronger ability of holding water （high AWC）.4. The change trend of ABA and GA3 in the five populations were distinct and regulative in the whole growthing season , i.g. August>June>May. Similarly, the content of IAA and ZR embodys distinct regulative changes, i.g. June> August>May. On the one hand, this proved IAA and ZR content decreased but ABA and GA3 increased under drought stress. On the other hand, this embodied interrelated relationships between endogenous phytohormone and plants growth . ABA played an important role as a signal under drought stress. The content of IAA in May, ABA and GA3 in August in group A were significantly higher than that in group B. The condition of endogenous phytohormone is adapted with its habitats, which plays an important role in plants growth and development.5. The seasonal change of MDA content showed August>June>May, which embodied the memberane lipid peroxidation became stronger. Both the activity and amount of five detected enzymatic antioxidant system SOD、POD、CAT、AsA-POD、GR and antioxidant AsA、GSH were increased significantly with the season, which mutually regulated to promote the growth of T.mongolica. The Enzymatic antioxidant systems have difference in five habitats. The memberane lipid peroxidation of growp A were lower than group B. The activity and amount of antioxidant system were lower than group A. It may be suggested that enzymatic antioxidant play a key role as one of the adaptation mechanism of T.mongolica in different habitats.6. Compared T.mongolica with its its congener species Z. xanthoxylon in group B, The MDA content of T.mongolica were higher which embody the memberane lipid peroxidation were higher than Z.xanthoxylon to eliminate the oxidation damage. The content of endogenous phytohormone ABA、IAA、ZR、GA₃ were lower. T.mongolica has lower ability of maintaining large turgor and low water potential , which embody lower ability of drought tolerance than Z. xanthoxylon. This explained that the ability of Z.xanthoxylon competing limited entironment resource to promote plant growth and drought tolerance, were higher than T.mongolica. These are reasons why T. mongolica has been replaced by Z.xanthoxylon and narrow distributing and endangering.7. Under wild conditions, Analysis on a series of physiological and ecological characteristics of photosynthesis of T. mongolica and Z.xanthoxylon during the growth season shows that the daily change pattern of net photosynthetic rate （Pn） and transpiration rate （Tr） of two plants can be expressed as a two-peak curve. The Pn and Tr reache the maximum at 11:00 and 15:00, Also the Pn and Tr were higher in the morning than in the afternoon. The decline of Pn and Tr of two plants in the noon were observed. The reasons of Pn decline were mainly caused by stomatal limitation. And the decline of Tr were a ecological adaptation way by closing down the stomatal to adapt high temperature in the noon. Correlation analysis and regression analysis showed the photosynthetic active radiation （PAR） and the stomatal conductance （Gs） are the two most influential factors on the Pn and Tr. Compared with T.mongolica, Z. xanthoxylon had higher Tr and water use efficiency （WUE）, which may be an important reason why why T. mongolica has been replaced by Z.xanthoxylon and narrow distributing and endangering.更多还原