【作者】 张显强；

【导师】 孙敏；

【作者基本信息】 西南大学 ， 植物学， 2012， 博士

【摘要】 贵州地处东亚喀斯特发育区中心,喀斯特地区占全省总面积的73.8%,喀斯特地貌分布之广,碳酸盐岩发育厚度之大,在全国独一无二,在世界上也极为罕见。喀斯特石漠化是十地荒漠化的主要类型之一,是人类不合理的经济活动叠加于脆弱生态地质环境所导致的结果。石漠化已严重危及长江、珠江流域的生态安全,所引发的环境问题,如治理和恢复的难度也是世界之最,这对中国西南地区经济社会的可持续发展造成了严重影响。由于我国石漠化的理论研究明显滞后于治理实践,最直接的后果是导致石漠化治理的盲日性和给当地生态环境带来的不确定影响。目前国内外对喀斯特石漠化地区苔藓植物的群落演替规律和生态适应度性研究非常缺乏,这对揭示石漠化地区苔藓植物群落演替机理和制定具体的生态治理措施极为不利。本文采用野外调查和室内模拟实验方法,以贵州强度石漠化区域石头上生长的反叶扭口藓(Barbula fallax Hedw.)和穗枝赤齿藓(Erythrodontium julaceum (Schwaegr.) Par.)为材料,并以广泛分布的土生真藓(Bryum argenteum Hedw.)为参比,探讨贵州石漠化地区石生藓类对干旱环境的生态适应机制,研究结果表明：(1)采用样方法对强度石漠化区域石生环境30个样点150个样方进行了调查,共记录石生藓类9科25属55种。优势科为丛藓科(Pottiaceae)和真藓科(Bryaceae),共17属,41种；优势属为曲柄藓属(Campyulopus)、净口藓属(Gymnostomum)、扭口藓属(Barbula)、真藓属(Bryum)、小石藓属(Weisia)、绢藓属(Entodon)6个属,共30种。区系分布由10个成分组成,其中以温带成分为主,兼以热带亚洲、中国特有和东亚成分。生活型以丛集型和交织型为主,共占总种数的96.4%,平铺型较少。由于喀斯特强度石漠化区域岩石大多为碳酸盐岩,干旱和土壤营养贫瘠导致群落类型以干燥石生苔藓群落占绝对的优势。因此.区域内耐旱的石生藓类得以较好的生长和繁殖,逐渐在岩石表面积累了薄土层,进而改善了岩面局部的温湿环境,在一定程度上为其它植物的殖居创造了条件(2)利用石蜡切片法和显微观察技术,对喀斯特强度石漠化岩面不同小环境的12种石生藓类茎和叶进行形态观察和比较解剖学研究。结果表明：1)不同种类的石生藓类在中肋的有无、导水主细胞的有无、中肋细胞层数及细胞密度、叶片细胞层数和细胞密度、叶表附属物等方面存在显著的差异。12种石生藓类叶片细胞胞壁具不同程度的增厚；穗枝赤齿藓(E.julaceum)叶片无中肋结构,而其余11种皆有明显的中肋结构,真藓科的所有种类中肋突出叶尖形成长短不同的毛尖结构,中肋的有无,反映了对水分吸收和运输方式的不同；除沼生真藓(Bryum knowltonii Barnes.)和真藓(B.argenteum)未见明显的导水主细胞外,其余具中肋结构的石生藓类导水主细胞均较为发达；不同石生藓类中肋厚度和细胞密度、叶片厚度和细胞密度间存在显著的相关性,但中肋厚度与层数相关不显著；叶表面附属物丛藓科所有种类有不同形状和数量的疣,小胞仙鹤藓(Atrichum undulatum (Hedw.) P. Beauv.)有栉片结构,这些叶片附属物的存在是对旱生环境的积极适应。2)12种石生藓类茎的形状、细胞形状、表皮层数及厚度、皮部是否分化及细胞层数、中轴有无和形状以及所占比例等特征因种类不同而存在差异。干旱环境中的藓类茎的解剖结构表现出表皮细胞排列紧密、细胞壁强烈增厚或增厚明显,1-2层不等,以1层居多,较多种类具有向外突起伸长形成多细胞腺体；仅有卷叶丛本藓(Anoectangium thomsonii Mitt.)和反叶扭口藓具内外皮部的分化,外皮部细胞胞壁增厚明显,其余10种藓类无内外皮层的分化或分化极不明显；除小胞仙鹤藓、真藓和反叶扭口藓有明显的中轴分化外,其余8种石生藓类分化极不明显,而短叶小石藓(Weisin semipallida C. Muell.)无中轴的分化。结果说明喀斯特石漠化地区石生藓类对水分吸收和传导以外导水型为主,混合导水型为辅。因此,石生藓类叶片和茎的解剖结构特征能反应所处的旱生环境,具有重要的生态适应意义。(3)比较研究了石漠化地区常见的穗枝赤齿藓、反叶扭口藓和真藓吸水特征和结构对石漠化干旱环境的适应性。结果表明,穗枝赤齿藓和反叶扭口藓的最大持水能力和保水率均大于真藓。3种藓的吸水过程包括外吸水和内吸水,吸水动力学曲线均表现为S型饱和曲线,但吸水特征存在较大差异；穗枝赤齿藓和反叶扭口藓的饱和吸水量相差甚微,但远大于真藓,前两者约为后者的2.5倍；最大总、内、外吸水速度穗枝赤齿藓分别为真藓的3.41倍、2.52倍和3.02倍,反叶扭口藓分别是真藓的2.79倍、2.52倍和3.55倍。茎的解剖学结构显示真藓和反叶扭口藓有明显的中轴,属内导水型藓类,而穗枝赤齿藓无中轴,属外导水型；但严格的内导水型植物不存在,不少植物属于混合导水型,这与环境水分高低有关。因此,中轴的有无并不是导致吸水能力强弱的决定性因素,还与苔藓所处的环境状况、生长型、毛细管系统类型和茎叶结构密切相关。(4)采用-2Mpa PEG-6000模拟干旱胁迫处理石漠化典型的石生藓类穗枝赤齿藓、反叶扭口藓和土生真藓,研究了同一干旱强度下不同时间处理的可溶性糖等4种渗透物质的变化。可溶性糖、还原糖和游离脯氨酸含量随着胁迫强度的增加而不断上升,但游离脯氨酸的积累较微弱；复水后3种物质的含量均比胁迫处理前有不同程度的下降,但都高于对照。可溶性蛋白呈现出先下降,后上升,再下降的趋势,除穗枝赤齿藓略高于对照外,反叶扭口藓和真藓含量均低于对照；复水后,3种藓类的含量均比对照有不同程度的下降。综合4个指标对3种藓类耐旱能力进行评价,种类上渗透调节能力穗枝赤齿藓>反叶扭口藓>真藓,不同渗透调节物质的贡献率是可溶性糖>可溶性蛋白>还原糖>脯氨酸。(5)研究了模拟干旱胁迫和复水条件下3种藓类的抗氧化保护机制。早期3种藓类超氧化酶歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性和类胡萝卜素(Car)含量升高,后期含量下降,表明藓类存在一个对逆境伤害的适应过程,胁迫初期含量增加是抵御干旱的一种适应性反应,后期保护酶和渗调物质含量的降低则是由于持续干旱对藓类造成了伤害。随渗透胁迫的加剧,真藓和反叶扭口藓超氧阴离子(O：)、丙二醉(MDA)旱现出增加-降低-略增加的趋势,而穗枝赤齿藓表现为增加-降低趋势。3种藓类的膜相对透性均呈现出S曲线的变化趋势,均有不同程度的升高,24h后略有下降。因此,水分胁迫早期O2-等活性氧的增加,诱导酶促和非酶促清除系统的启动清除产生的活性氧,随胁迫的加重,活性氧产生超过了抗氧化酶系统的清除能力而造成植物的部分伤害。3种藓类复水均能恢复生理活力,说明后期可通过生理休眠达到逃避极强度的干旱逆境,具有适应干旱胁迫的阶段性反应现象。(6)研究了模拟干旱胁迫和复水对反叶扭口藓、穗枝赤齿藓和真藓叶绿素含量和荧光特性的影响。结果表明,随水分胁迫的增加,叶绿素含量总体呈出先升、后降、再升高的趋势；3种藓类F0、qN上升,Fm、Fv/Fm、Yield、ETR、qP都随干旱胁迫的加剧而下降。复水后各荧光参数在轻中度胁迫下能恢复到正常水平,而重度胁迫较难恢复到对照水平。分析O2-和膜透性与荧光焠灭系数的关系,O2和膜透性随胁迫的增加而伴随qP系数的降低、qN系数的增加，证实胁迫过程中抗氧化防御系统的酶类活性和抗氧化物质含量的变化有关,活性氧的产生超出了植物自身的清除能力而致使体内代谢发生紊乱。水分利用效率(WUE)随胁迫程度的增加而不断下降,3种藓类水分利用效率的大小为：反叶扭口藓>穗枝赤齿藓>真藓,说明反叶扭口藓的耐旱性最强。综上所述,生长在石漠化干旱环境中的石生藓类植物不仅在物种分布、形态结构上具有适应性特征,而且还能通过渗透调节,提高抗氧化酶系统的能力,维持光合机构的稳定等生理生态机制来适应干旱的岩溶环境。本研究结果揭示了喀斯特石漠化地区石生藓类的生态适应机制,可为其他岩溶植物适生机理制研究和石漠化环境治理和生态修复提供理论依据。更多还原

【Abstract】 Guizhou Province is located in the center of the karst area in East Asia. The total karst area accounts for73.8%of the province, hence there are large areas of karst in China. Karst rocky desertification is one major type in desertification, which is under irrational human impact on the vulnerable eco-geo-environment. In this process, the vulnerable eco-geo-environment serves as its base, violent human impaction as its driving force, devolution of bearing capability of the land is the essence, and the appearing of landscape similar to desert is the sign. Rocky desertification has threatened seriously the ecological safety of the Yangtze River, Pearl River Basin. However, it is very difficult to handle the environmental problems in karst regions and hard to recover and governance if once deteriorated. Therefore, rock desertification has been severely restricted the sustained development in southwest China. Meanwhile, theoretical researches of Rocky Desertification has lagged far behind comprehensive improvement of karst areas in China. This leads to the blindness of controlling rocky desertification and the uncertainty to local ecological environment. It is very important for the recovery of the degradation of the karst ecosystem and reconstruction for the in-depth study about moss community succession law and adaptability. Lack of such researches is extremely detrimental to reveal mechanism of community succession and development of specific ecological management measures. In this study, Barbula fallax Hedw. and Erythrodontium julaceum (Schwaegr.) Par. the saxicolous mosses grow in the regions of rock desertification in Guizhou were determined via a combination of field investigation and laboratory experiments. Furthermore, of Bryum argenteum Hedw., a widely distributed to soil mosses, as the reference was also investigated, especially in the physiological ecology of rocky desertification in drought environments adaptive mechanisms. These results provide the theoretical proofs for the study of karst plant on adapt mechanisms and rocky desertification environment governance. These results in detail were shown as follows:(1) Sampling methods are adopted to investigate30sample plot150small quadrat in the aquatic environment of intense rocky desertification area and record saxicolous mosses9families and25genera and55species. Dominant families are Pottiaceae and Bryaceae, a total of17genera,41species. Dominant generas are Campyulopus, Gymnostomum, Barbula, Weisia, Entodon, a total of6families and30kinds. The flora of saxicolous mosses have10ingredients are mainly distributed in tropical Asia, and unique to China and East Asian. Life forms are chiefly Turfs and Wefts, the total number of species in96.4%, less Mats. Because Karst rocky desertification area rocks are mostly carbonate rocks, barren environment of the drought and soil nutrition results in an absolute advantage of Bryo-xero-petrophytia. The saxicolous mosses drought tolerance in the region, therefore, is of good growth and reproduction, and there gradually accumulates in the rock surface with a thin layer. Thus, it improves the local rock surface temperature and humidity environment, and ranks to create, a certain extent, the conditions for the colonization of other plants.(2)Through paraffin wax section and microscopic observation, the study of comparative anatomy and morphology are as for12saxicolous mosses stems and leaves in different environments of karst rock desertification. The results showed that:1) There is a significant difference among different types of saxicolous mosses such as the absence or presence of hydrome cells, the numbers of cell layer and the density of the costae, leaf cell layers and cell density, the numbers of laminal cell layer, and some of them have attachment on surface, etc. The saxicolous mosses under dry conditions often have thickened laminal cell-walls on the surfaces, Erythrodontium julaceum (Schwaegr) Par has no costa structure, while the remaining11kinds have obvious costa structure. As for all types of Bryaceae have different hair points of prominent forms. The absence of costa reflects on the different water absorption and modes of transport; except the Bryum knowltonii Barnes and Bryum argenteum Hedw, there is no apparent Hydrome chief cell. The Hydrome chief cell with saxicolous mosses of the costa structure is more developed; different saxicolous mosses class in the costa thickness and cell density between leaf thickness and cell density exists a significant correlation, but the costa is not significantly related to the thickness of layers; attachment on surface have varied kinds of different shape and number of papillae. Atrichum undulatum (Hedw.) P. Beauv. has lamellae structure and the existence of these attachment on surface has positive adaptation to the dry conditions.2) The stems of12saxicolous mosses species were of different types among stem shape, cell shape, the layers numbers of epidermisand the thickness, the differentiation and layers of cortex, the existence or inexistence and the scale of the mainaxis of stems varied highly. The tightly arrayed epidermis in their stem, the distinctly thickened cellwalls in epidermis were found in xeric saxicolous mosses, the majority of one cell-layer. More types are outward protruding extension and form cells glands; only Anoectangium thomsonii Mitt. and Barbula fallax has inner cortex or external cortex as well as the thickened cell walls of external cortex. The remaining10species of mosses have no differentiation of the inner and external cortex. The Bryum argenteum, Atrichum undulatum and Barbula fallax with the mainaxis of differentiation, the differentiation of the remaining8species saxicolous mosses is not very obvious. However, the mainaxis of Weisin semipallida C. Muell. has not differentiation, which indicates that the Karst Areas of saxicolous mosses on water uptake and conduction are the ectohydric based and mixohydric supplemented. Therefore, the anatomical structure of the saxicolous mosses leaves and stems in the xerophytic environment has important ecological significance of adaptation.(3) In this study, a theoretical foundation for the interest of recovering and administering the environments of rock-desertification ecology was provided by compared with the adaptability to habitat heterogeneity in rocky desertification environments among Eiythrodontium julaceum, Barbula fallax and Bryum argenteum. The results show that, firstly, E. julaceum and B. fallax are more than B. argenteum in the capacity of holding maximal water and also in the rate of preserving natural water. Secondly, the water-uptaking processes of the three mosses are outer water uptake and inner water uptake. Although the three species had the same dynamic curve of the S type saturated water content, they had considerably different dynamic properties. Little difference was found in the amount of water saturated by E. julaceum and B. fallax. However, the amount of saturated water in E. julaceum and B. fallax were about2.5times of that in the silver B. Argenteum. The amount of saturated water and the maximal rates of water uptake, inner as well as outer water uptake in E. julaceum were3.41,2.52and3.02times than those of B. argenteum, respectively. Similar results were also found in B. fallax. Furthermore, the stem cross-section structure of three mosses showed that B. argenteum and B. fallax had the obvious conducting strand and belonged to endohydric mosses. In contrast, E. julaceum owned no conducting strand and belonged to the part of the ectohydric. Strictly, the structure of endohydric and ectohydric in mosses is not the decisive factor of water absorption capability, which has close relationship with many aspects including growth form, type of capillary system and microstructure of stem and leaf positive correlations.(4)-2Mpa PEG-6000is adopted to simulate drought treatment on typical karst rocky desertification Erythrodontium julaceum and Barbula fallax of saxicolous mosses, and native Bryum argenteum, and the study touches on changes of four kinds of osmolytes in different time to deal with the same intensity material. With the increase of the stress time, the soluble sugar, reducing sugar and free proline is rising, but the accumulation of free proline is weaker; after rewatering three kinds of substances decreased in varying degrees, but it is higher than the control. Soluble protein shows a first decreased and then increased, and then a downward trend. In addition to the Erythrodontium julaceum is slightly higher than the control Barbula fallax, Bryum argenteum content is lower than the control; after rewatering, the content of the three kinds of mosses in the control decreased in varying degrees. Based on the four indicators to evaluate the drought tolerance of the three kinds of mosses, osmotic adjustment ability on the type of ear branches is like: Erythrodontium julaceum> Barbula fallax> Bryum argenteum, while the contribution rate of different osmolytes is soluble sugar> soluble protein> reducing sugar> proline.(5) The research focuses on the antioxidant protection mechanism of three species of saxicolous mosses by PEG-6000simulated drought stress and rewatering conditions. In the early period, the contents of three kinds of mosses superoxide dismutase dismutase (SOD), catalase (CAT), peroxidase (POD) activity and carotenoids (Car) content increased, and at late declined. This shows that the mosses have an adaptation-injury process. The increasing stress in the initial period reacts to resist drought, but later to reduce self-inflicted injury. When osmotic stress intensifies, Biyum argenteum and Barbula fallax superoxide anion (O2-), malondialdehyde (MDA) show the increase-lower-slightly increasing trend. However, the Erythrodontium julaceum performs increase-reduce trend. As for the relative permeability of membrane, three kinds of mosses were shown a trend of the S-curve and increased in varying degrees. There is a slight decline after24hours. Therefore, the increases in drought stress early O2-and other reactive oxygen species (ROS) induce enzymatic and non-enzymatic scavenging system to start to clear ROS. With the aggravation of stress, ROS exceeds the scavenging capacity of the antioxidant enzyme system so as to injury plant. The rewatering of three kinds of moss can restore physical vitality, and it instructs that physiological dormancy in later period can help to escape the very intensity of the response from drought stress because of the reaction phenomenon adapted to drought stress phase.(6) The study of drought and rewatering on the Barbula fallax, Erythrodontium julaceum, Bryum argenteum chlorophyll content and fluorescence characteristics. The results showed that under the increase of drought stress, total chlorophyll content was the first rose and then dropped, and then the tendency to increase. F0and qN of three kinds of mosses was increased while the Fm, Fv/Fm, Yield, ETR and qP are decline with drought stress. Fluorescence parameters after rewatering can be restored to normal levels in mild to moderate stress, and severe stress is more difficult to return to the control level. Analysis of the relationship among O2-and membrane permeability fluorescence quenching shows that O2-and membrane permeability with stress increased accompany by qP coefficient lower and qN increased in the coefficient. It confirms that the activity of enzymes of antioxidant defense system in the stress process relates to the changes of anti-oxidation material content. The production of ROS is beyond the plant clearance resulting in the vivo metabolic disorder. Water use efficiency (WUE) decreased continuously with the increased stress in WUE. The most drought tolerance is the Barbula fallax>Erythrodontium julaceum>Bryum argenteum.In summary, the saxicolous mosses grown in the karst dry enviroment have not only certain features and morphology of adaptations from the distribution of moss species, but also adapt to changes of the physiological and ecological mechanisms in karst environments by adjusting osmotic and improving the ability of the antioxidant enzyme system to maintain the stability of photosynthetic apparatus.更多还原