KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 荒漠区齿肋赤藓(Syntrichia caninervis Mitt)对微生境差异的生态与生理生化适应性 | |
| 尹本丰 | |
| Subtype | 硕士 |
| Thesis Advisor | 张元明 |
| 2015 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 植物学 |
| Keyword | 生物土壤结皮 种群密度 光合 抗氧化酶 渗透调节物质 积雪 古尔班通古特沙漠 |
| Abstract | 齿肋赤藓(Syntrichia caninervis Mitt)广泛分布于世界干旱和半干旱荒漠地区，是典型的耐旱藓类。同时，齿肋赤藓也是古尔班通古特沙漠生物土壤结皮中的优势藓类植物，能够在多种微生境下良好生长，对荒漠生态系统稳定性与功能多样性具有重要作用。荒漠藓类植物叶片仅具一层细胞，对环境条件的变化十分敏感。古尔班通古特沙漠夏季炎热干燥，冬、春季降雪频繁，并能形成稳定的积雪层。然而，藓类植物如何适应这种夏季极端高温干燥、冬季极端低温以及早春地表反复冻融交替过程等环境的剧烈变化，相关的研究还鲜见报道。本研究探讨了不同微生境下(活灌丛下、枯死灌丛、裸露地、人为去除灌丛和遮阴)齿肋赤藓在不同时期(初冬降雪前后、积雪期、融雪期、春季干燥期和夏季高温干燥期)对光照和水热变化的生理生化及生态响应，为了解荒漠苔藓对极端环境的适应机制提供重要依据。 不同生境间齿肋赤藓种群与形态存在显著差异。对于不同微生境下齿肋赤藓纯群而言，齿肋赤藓的总生物量与单株生物量呈灌丛下 > 死灌丛 > 裸露地的趋势，而种群密度则完全相反。不同微生境下齿肋赤藓在株高、毛尖长度/叶长、叶倾角、毛尖及中肋疣状突起长度、不同叶部位疣密度、疣状突起的排布等方面均存在明显差异。活灌丛下齿肋赤藓的株高显著高于枯死灌丛，裸露地最低；相反，裸露地齿肋赤藓的毛尖长度/叶长、毛尖及中肋疣长度均显著高于活灌丛，但叶倾角显著低于其他两生境。 不同生境间齿肋赤藓光合活性的差异明显。不同时期齿肋赤藓表现出不同的光合活性，在冬季极端低温和夏季高温干燥环境下齿肋赤藓通过失水进入休眠状态，而在初冬和春季的积雪融化时齿肋赤藓能快速恢复荧光活性。同时，灌丛的存在在一定程度上增加了灌丛下齿肋赤藓恢复活性的机会，延长光合活性时间。研究表明灌丛下齿肋赤藓的最大光化学效率(Fv/Fm)显著高于裸露地和死灌丛，但实际光化学效率(Y(II))差异不显著。人为去除灌丛使齿肋赤藓的Fv/Fm和Y(II)均显著降低。 不同生境间齿肋赤藓渗透调节物质存在显著差异。在夏冬的极端高低温和春季中期的干旱条件下，齿肋赤藓的可溶性糖含量均显著高于水热相对适中的初冬和春季融雪期，但可溶性蛋白的变化与之相反。与可溶性糖相比，齿肋赤藓植株体内脯氨酸含量对低温的响应相对较弱，其在夏季高温干燥和春季中期的干旱条件下含量更高。同时，不同微生境下齿肋赤藓可溶性蛋白在不同时期均表现为灌丛下 > 死灌丛 > 裸露地。而脯氨酸和可溶性糖含量在不同时期却表现各异，在干燥和高温环境下表现为灌丛下显著低于死灌丛和裸露地，在低温湿润环境下呈相反趋势。而在冬季积雪期和春季积雪融化期，灌丛下齿肋赤藓较裸露地拥有更高的可溶性糖含量。 不同生境显著影响齿肋赤藓抗氧化酶的活性。冬季的极端低温、春季中期的极端干燥和夏季的炎热干燥环境下齿肋赤藓植株的丙二醛(MDA)含量显著高于初冬和春季融雪期，过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD) 3种保护酶的活性也呈相同趋势。除春季融雪早期灌丛下植株的MDA含量高于死灌丛和裸露地外，其余各时期灌丛下齿肋赤藓植株的MDA含量及所有时期的3种保护酶活性均显著低于裸露地。灌丛的去除可导致植株体内MDA大幅升高并显著高于其他生境，但其保护酶活性与裸露地无显著差异。裸露地齿肋赤藓在所有时期较其他生境均具有较高的保护酶活性，体现了前者具有更强的耐胁迫特性。 综上所述，活灌丛能为荒漠齿肋赤藓创造更好的水分、光照等生长条件，灌丛的枯死和去除均不利于齿肋赤藓的生长和存活。较活灌丛，裸露地的齿肋赤藓对高温、高光强和低含水量表现出更高的形态与生理耐受性。 |
| Other Abstract | As a typical drought-tolerant moss, Syntrichia caninervis Mitt is widely spread across many semi-arid and arid regions worldwide. As one of the dominant species in the moss crusts, Syntrichia caninervis Mitt grows well at different microhabitats of the Gurbantunggut Desert, a cold northern desert in Central Asia. The presence of crusts can roughen the soil surface, while affecting nutrient cycling, soil stability and hydrological processes of soil surface. With its leaves of only a layer of cells, Syntrichia caninervis Mitt is very sensitive to changes of its growing environments. Compared to other desert ecosystems, the Gurbantunggut Desert is extremely hot and drought during summer, being stable snow cover because of frequent and abundant snowin spring and winter. However, how it successfully adapts to the extreme hot and drought environments in summer and the alternative freezing – thawing cycles of soil surface in spring and keeps activity in such dramatically changing environments have not been well explained. This paper is to explore how Syntrichia caninervis Mitt changes in physiological, biochemical and ecological aspects to adapt to different desert microhabitats. There were significant differences in morphology between different habitats. For pure populations of Syntrichia caninervis Mitt in different habitats, the population biomass and individual biomass are higher in live shrub canopy than dead shrub and bare land. On the contrary, the density of population appeared an opposite trend compared with the biomass: bare land > dead shrub > live shrub. In addition, we found significant differences in the height of plant, the ratio of hair point length to leaf length, the leaf inclination angles, the length of papillae in hair point and coast, the density of the papillae in the leaf and its arrangement mode in different habitats by using the electron and optical microscope. The height of Syntrichia caninervis Mitt showed significantly decreasing trends from live shrub to dead shrub to bare land. And the ratio of hair point length to leaf length, the leaf inclination angles, the length of papillae in hair point and coast in bare land were higher than those under live shrub. The density of the papillae in the leaf and its arrangement mode in different habitats may be affected by both water and light. At the same time, the leaf inclination angels of Syntrichia caninervis Mitt which live in bare land were lower than live in other habitats. The lower leaf inclination angles may provide a greater photosynthesis area for these moss living at bare land. It is obvious that the chlorophyll fluorescence activity was different among three habitats. Our study showed that Syntrichia caninervis Mitt were different in chlorophyll fluorescence activity in different periods. Syntrichia caninervis Mitt would be inactivated due to dehydration in extreme environment during summer and winter. However, the melt of snow in the early winter and spring could provide water for the bryophytes, and facilitate the recovery of photosynthesis activity. Meanwhile, Syntrichia caninervis Mitt in different microhabitats also showed differences in photosynthesis. Rainfall can be gathered under shrub, and its low-temperature effect under shrub could also reduce the loss of the surface water. These effects of shrub may increase the chances for the bryophytes to restore the activity, and extends the time of photosynthesis to a certain extent. On the contrary, those bryophytes which live in the bare land or in the dead shrub areas are more sensitive to warming events during winter than in the live shrub areas. The activity of Fv/Fm in bryophytes under the shrub canopy appeared significantly higher than that of bare land. But for the value of Y(II), there are no significant differences among the three microhabitats. Removal of shrub would significantly reduce the values of Fv/Fm and Y(II) of Syntrichia caninervis Mitt. Although the shade can increase the Fv/Fm to some extent, no significant effects were found in Y(II). Osmoregulatory substances were significantly affected by microhabitats. The result showed that the content of soluble sugar was higher in summer and winter, or in middle spring, when it was extremely hot or very drought, than in early winter and early spring when snow were melting. But the changes of soluble proteins were the opposite. The response of proline content of Syntrichia caninervis Mitt was weaker compared with the soluble sugar in low temperature environment, but it would be stronger while the plant was faced with drought. The contents of soluble proteins for all periods in three microhabitats were highest under live shrub, then were under the dead shrub and bare land. However, the contents of proline and soluble sugar were affected by microhabitats, periods and their interactions. The values under live shrub would be high while the environment was severe (such as higher temperature or drought). On the contrary, the contents of them would be an opposite trend when the temperature became low or the water supply was sufficient. Different habitats significantly affected antioxidant enzyme activity of Syntrichia caninervis Mitt. The extremely low temperature in winter, severe drought in middle spring and extremely higher temperature or drought in summer would significantly enhance the content of malondialdehyde (MDA) of Syntrichia caninervis Mitt than the snowmelt periods in early winter and early spring. Meanwhile, its catalase (CAT) activity, peroxides (POD) activity, superoxide dismutase (SOD) and other antioxidant enzyme activity also showed a similar trend with the content of MDA. Except the snowmelt periods in early spring, the content of MDA was higher under live shrub than under bare land. In other periods, the content of MDA and three kinds of antioxidant enzyme activity were significantly lower under live shrub than under bare land. Removal of shrub would significantly increase the content of MDA of Syntrichia caninervis Mitt. And the activities of three antioxidant enzyme were higher under bare land than under live shrub in all periods. This may indicate that the bryophytes living on bare land may have stronger tolerance to stress than those living under shrub canopy. In summary, Syntrichia caninervis Mitt could change the density of population, the biomass, and the ratio of hair point length to leaf length, the leaf inclination angles, the length of papillae in hair point and coast, the density of the papillae in the leaf and it arrangement mode to adapt to extreme environments. In physiology, Syntrichia caninervis Mitt could fasten the recovery of its chlorophyll fluorescence activity when snowmelt occurred in early winter and spring. Our study showed that Syntrichia caninervis Mitt could accumulate soluble sugars, proline and antioxidant enzymes in response to extreme temperature or water stress. |
| Subject Area | 植物学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/14680 |
| Collection | 研究系统_荒漠环境研究室 |
| Affiliation | 中科院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 尹本丰. 荒漠区齿肋赤藓(Syntrichia caninervis Mitt)对微生境差异的生态与生理生化适应性[D]. 北京. 中国科学院大学,2015. |
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