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生态环境因子对荒漠藻及其结皮生长发育的影响研究
Alternative TitleINFLUENCES OF ENVIRONMENTAL FACTORS ON DESERT ALGAE AND DEVELOPMENTS OF ALGAL CRUSTS
饶本强
Subtype博士
Thesis Advisor刘永定
2009-06-04
Degree Grantor中国科学院水生生物研究所
Place of Conferral水生生物研究所
Keyword生物结皮 荒漠藻 工程化培养 藻结皮发育 露水 沙埋 低温胁迫 干燥-重吸水 盐胁迫 稀土元素
Abstract全球沙漠化日益严重,引起当今国际社会普遍关注。防治沙漠化的方法和手段受到广泛重视。在干旱沙漠区通过人工培植生物结皮以治理沙漠,是值得研究的重要课题。利用荒漠藻进行人工固沙结皮是一种新型的治沙方法,它运用藻类生态、生理学原理和生物结皮理论,将人工藻结皮应用于沙漠化治理实践,并取得了较好的固沙效果,在沙漠化治理中逐步得到应用。本文围绕荒漠人工藻结皮的野外培植与生长发育特性以及影响荒漠藻类及其结皮的环境生态因子进行了一系列研究,主要研究内容有如下几个方面: 1、通过荒漠藻的工程化培养、野外接种和人工藻结皮的形成,研究了人工藻结皮在野外条件下的形态、发育演替、超微结构特征、土壤理化及生物学活性,探讨了人工藻结皮的固沙改土作用及其在沙漠化治理中的可行性。 研究表明,利用荒漠蓝藻接种野外流沙,能够在1-3年内快速生长发育成具有一定厚度和形态的藻结皮,甚至发育成藻-苔藓结皮。结皮的平均厚度达到1.0-5.4mm,呈浅灰色、灰绿色和深黑色,结皮盖度大于70%,植被盖度达60-90%。对人工藻结皮的超微结构研究发现,藻结皮-沙粒土壤中含有丰富的藻丝体。可以观察到大量藻丝体缠绕或黏结着沙粒, 从而实现人工藻结皮的胶结过程,并使结皮具有较高的抗压强度。形成人工藻结皮后,显著改善了流沙土壤的理化特性(含水量、pH、电导率等)、营养状况(碳、氮、磷和有机质含量等)和增加了土壤的生物学活性(微生物数量和土壤酶活性)。 2、在2007年的夏末秋初,于库布齐沙地采用两种蓝藻具鞘微鞘藻和爪哇伪枝藻,经过原种培养和大规模培养后,将两种藻按照10:1和5:1的生物量比例混合接种到野外流沙以形成藻结皮。通过露水测定和藻结皮的生物量测定(叶绿素a含量)以研究二者之间的关系。此外,在实验室条件下通过干燥-重吸水模拟降露来研究露水对藻结皮光系统Ⅱ活性的影响。结果表明,在试验期内,采用绒布-玻璃平板法测定每天平均的降露量为0.154mm,当露水作为唯一的水源时,藻结皮生物量由起始的接种量4.3 微克叶绿素a/平方厘米流沙到5.8-7.3微克叶绿素a/平方厘米藻结皮之间波动。并且由于降雨的发生使藻结皮生物量达到8.2微克叶绿素a/平方厘米藻结皮。研究表明,藻结皮含水量与降露量存在显著差异性(r=0.897 or r=0.882, all P<0.0001),而藻结皮生物量与降露量之间无显著性差异(r=0.246 or r=0.257, all P>0.05)。由此可以推测,露水在调控藻结皮生物量方面可能只具有相对有限的作用,但是降雨可能显著调节藻结皮的生物量。通过在实验室内干藻-重吸水模拟露水研究发现,藻结皮在干燥重吸水过程中大约80%光合活性恢复不受低温和黑暗的影响,仅有20%的光合活性恢复是温度-光照依赖性的。这揭示出露水作为一种暂时性水源对于清晨低温和弱光条件下藻结皮光合活性的恢复具有重要意义。研究还发现,藻结皮沉积露水量大于流沙沉积露水量,而露水在藻结皮的干化过程也要比露水在流沙表面的慢,这与藻结皮特定的土壤结构特性和土壤理化特性密切相关。 3、在野外条件下,沙埋是生物结皮经常遇到的一种环境胁迫。尤其是在藻结皮发育的早期阶段对沙埋胁迫更为敏感。基于此,在库布齐沙地开展了野外沙埋试验来研究沙埋对藻结皮早期生长发育的影响。沙埋处理深度分别为0.5cm,1.0cm,3.0cm和5.0cm。研究表明,随着沙埋时间的延长和沙埋深度的增加,沙埋对蓝藻结皮的胁迫作用愈加明显。沙埋导致蓝藻结皮生物量、胞外多糖和伪枝藻素含量的下降,并减低了结皮的抗压强度。对沙埋结皮进行室内干燥-重吸水试验表明,沙埋对蓝藻结皮的光合活性造成胁迫。研究发现,沙埋对蓝藻结皮生物量、胞外多糖和抗压强度的影响方式有所不同。推测这可能是结皮蓝藻对沙埋胁迫的一种应对机制。值得注意的是,降雨的发生有利于沙埋胁迫下蓝藻结皮生物量和光合活性的恢复,并促进了蓝藻结皮胞外多糖和抗压强度的增加。因此推测,降雨对于蓝藻结皮对抗沙埋胁迫可能具有重要的意义。 4、研究发现,低温胁迫下伪枝藻培养物的叶绿素a含量和光合活性显著降低,而丙二醛和可溶性蛋白质含量明显升高。当2℃低温下加入外源蔗糖和葡萄糖处理时,外源糖对低温胁迫具有一定的缓解作用。研究表明,经过低温10℃适应的伪枝藻骤然降温至2℃时其对低温的耐受性明显提高,表现为叶绿素a和光合活性下降幅度平缓,丙二醛和可溶性蛋白的含量缓慢升高,细胞膜的透性降低,胞外多糖产量大幅度增加。这种低温适应(或称低温锻炼)可能是荒漠藻类耐受寒冬冷胁迫的一种生态适应机制。 结果还表明,外源补加营养盐有利于藻结皮提高对低温的耐受性。研究发现藻结皮在低温黑暗条件下具有较好的生长和光合活性,推测低温黑暗可能对低温光抑制具有较好的修复作用。 5、根据不同饱和溶液所具有的空气湿度不同,分别采用相对湿度为100%、75%、43%和0四种干旱对爪哇伪枝藻和集球藻培养物进行胁迫处理。结果表明,荒漠藻类在干旱胁迫下光合活性显著降低,丙二醛含量和超氧化物酶活性显著升高,过氧化氢酶活性呈现波动性变化,预示着干旱对藻细胞的膜系统和细胞抗氧化系统造成破坏或损害。同时发现在干旱胁迫下细胞可溶性蛋白质和可溶性糖含量增加,这可能是藻体对干旱胁迫的一种保护性反应。采用BG-110培养液对干燥下藻体进行重吸水处理、发现光合活性获得明显恢复。当用外源糖溶液、N-乙酰半胱氨酸和脯氨酸溶液进行重吸水时,光合活性都获得一定程度的恢复。利用敌草隆和氯霉素重吸水时,则显著抑制了藻体的光合活性恢复。 6、研究表明,盐胁迫造成结皮绿藻集球藻生理上的损害,包括生物量和光合活性降低,丙二醛含量和超氧化物酶活性升高以及过氧化氢酶活性的波动。当加入外源蔗糖和胞外多糖,盐胁迫下集球藻的生理活性得到一定程度的恢复。推测生物结皮中绿藻耐受盐胁迫的机制可能是通过两种方式:一是内源调节,包括糖代谢反应加剧,细胞膜系统和抗氧化系统发生应急反应等;二是外源缓解,主要是借助于结皮蓝藻分泌的胞外聚合物或其它糖类来提高绿藻的抗盐性。 7、研究发现,盐处理对伪枝藻具有明显的胁迫效应,表现为生物量和光合活性明显降低,丙二醛含量和超氧化物酶活性升高以及过氧化氢酶活性波动。此外,盐胁迫还造成伪枝藻胞外多糖产量的增加和细胞结构的破坏。采用稀土元素铈处理伪枝藻发现,稀土对伪枝藻的效应表现为低浓度促进和高浓度抑制,而适当浓度的铈有利用缓解盐胁迫效应。
Other AbstractThere is a rather common point of view that desertification is becoming increasingly severe in the world. Emphasis on methods and means in control of desertification are widely given. Implanting biological crust with man-made measures at arid sandy zones is an important avenue to control desertification and worthy of being studied. Technology of fixing-sand algal crust is a new method to control desertification, and it adopts ecological, physiological principles on algae and theory of biological crusts. Desert algae were inoculated onto shifting sand for forming fixing-sand algal crust. Fixing-sand algal crust can provide fast, effective and long fixing-sand effects and has been applied to control desertification step by step. In this study, researches on field cultivation and developmental characteristics of man-made algal crusts were conducted, and influences of environmental factors on desert algae and algal crusts were also investigated. The main research results were provided as follows: 1. Morphologic properties, development and succession as well as ultra- structure of man-made algal crusts were examined by means of engineering culture of desert algae, inoculation of algae and cultivation of algal crusts. Based on the above researches, the roles of man-made algal crusts in fixing-sand, improvements of soil characteristics and feasibility of antidesertification were discussed. The results showed that artificial algal crusts came into being after desert cyanobacteria were inoculated onto surface of dunes. The crusts were 1.0-5.4mm in thickness and were grayish, sage green and highly black, and coverage of the crusts over 70% along with coverage of vegetation for 60-90% when artificial algal crusts acquired growth and development during one year and three years. It was showed from observation to ultra-microstructures of algal crusts that artificial algal crust was found to own abundant filamentous forms that could band and felt soil particles by their mechanical force, and simultaneously they exuded polysaccharide to hasten soil aggregation and cement soil particles together, which caused the crusts to bear high compressive strength and maybe contributed to cementation process of artificial algal crusts. All the above research results revealed that man-made algal crusts could not only fix shifting sand dunes, reduced soil erosion by wind or water but also had such ecological functions as changing the physiochemical properties of soils (water contents, pH values and electric conductivity, etc) and affecting soil nutrient circulation (i.e., contents of C, N, P and organic matter), as well as increasing soil biological activities such as soil enzyme activities and amounts of soil microorganisms. 2. The cyanobacteria, Microcoleus vaginatus Gom. and Scytonema javanicum (Kütz.) Born et Flah., were begun with stock cultures and sequential mass cultivations, and then the field experiment was performed by inoculating the inocula onto shifting sand for forming cyanobacterial crust during late summer and autumn of 2007 in Hopq Desert, northwest China. Measurements of dew amount and Chlorophyll a content were carried out in order to evaluate the changes in crust biomass following dew. Also, we determined the activity of photosystemⅡ (PSⅡ) within the crust in the laboratory by simulating the desiccation/rehydration process due to dew. Results showed that the average daily dew amount as measured by the cloth-plate method (CPM) was 0.154 mm during fifty-three days and that the crust biomass fluctuated from initial inoculation of 4.3 μg Chlorophyll a cm-2 sand to 5.8–7.3 μg Chlorophyll a cm-2 crust when dew acted as the sole water source, and reached a peak value of approximately 8.2 μg Chlorophyll a cm-2 crust owing to rainfalls. It indicated that there was a highly significant correlation between dew amounts and crust moistures (r=0.897 or r=0.882, all P<0.0001), but not a significant correlation between dew and the biomass (r=0.246 or r=0.257, all P>0.05), and thus concluded that dew might only play a relatively limited role in regulating the crust biomass. Correspondingly, we found that rains significantly facilitated biomass increase of the cyanobacterial crust. Results from the simulative experiment upon rehydration showed that approximately 80% of PSⅡ activity could be achieved within about 50 min after rehydration in the dark and at 5 ◦C, and only about 20% of the activity was light-temperature dependent. This might mean that dew was crucial for cyanobacterial crust to rapidly activate photosynthetic activity during desiccation and rehydration despite low temperatures and weak light before dawn. It also showed in this study that the cyanobacterial crusts could receive and retain more dew than sand, which depended on microclimatic characteristics and soil properties of the crusts. It may be necessary for us to fully understanding the influence of dew on regulating the growth and activity of cyanobacterial crust, and to soundly evaluate the crust’s potential application in fighting desertification because of the available water due to dew. 3. Sand burial is a noticeable environmental disturbance commonly experienced by various types of microbial crusts in the field. The cyanobacterial crusts, existing at early developmental stage of the biotic crusts, are exceedingly susceptible to burial by sand. Therefore, a study campaign was conducted in fields to evaluate the effects of sand burial (burial depth of 0, 0.5, 1, 3 and 5cm) on the crusts in Hopq desert, China. The results showed that sand burial imposed severe stress on the cyanobacteria crusts, such as the reduction of biomass, the restraint of scytonemin synthesis and the damage to PSⅡactivity, as well as the decrease of EPS excretion, etc. Furthermore, in this study the possible mechanisms by which cyanobacterial crusts tolerate burial were fully discussed, and a positive role of rain in the recovery from burial for cyanobacterial crusts was verified. It is necessary for the artificial cyanobacterial crusts to allay burial disturbances by assistants of sand-fixing means in order to ensure their better contribution to desert reclamation. 4. It indicated in this study that chlorophyll a contents and PS Ⅱ activity of S. javanicum were significantly affected by low temperature stress, and MDA content and soluble protein content of the cyanobacterium were distinctly increased due to low temperature. It also found that exterior saccharide played roles in relaxing salt stress to some extent when the saccharide was added into the cultures of S. javanicum. When the temperature was suddenly declined to 2℃, S. javanicum was found to have some tolerance to low temperature after adaptation at the temperature of 10℃. On this condition, the declines of chlorophyll a and PS Ⅱ activity of S. javanicum exhibited slower, and MDA content and soluble protein content increased slowly. At the same time, the osmosis of membrane decreased and the production of EPS increased. This acclimation to low temperature may be an ecological strategy for desert algae to tolerate cold stress. Results from the study showed that tolerance to low temperature was advanced when algal crust was subjected to supplement from nutrition salt. It also indicated that algal crust have better growth and photosystem activity under dark and low temperature, which might mean that the condition both low temperature and dark played some roles in resisting low-light inhibition. 5. Two desert algae, S. javanicum and Palmellococcus sp. were respectively subjected to desiccation under four relative humidity of 100%、75%、43% and 0 based on differences of air humidity owned by different saturated solutions. Results from this study indicated that PSⅡ activity decreased significantly due to the desiccation stress, and MDA content and SOD activity greatly increased along with the fluctuation of CAT activity when the desert alga were exposed to desiccation, which might signify some damages to membrane system and antioxidant system when the desert algae subjected to desiccation stress. It also indicated that the contents of soluble protein and soluble saccharide were increased when the algae were exposed to desiccation, which might represent a safeguard reaction to desiccation. PSⅡ activity obtained great recover when the desert algae were rehydrated by BG-110 medium, and recover in PSⅡ activity were also acquired when rehydrated by means of the solutions of saccharid, NAC and Pro. While PSⅡ activity was evidently inhibited by additions of DCMU and CMP during rehydration. 6. It indicated in the study that Palmellococcus sp. was damaged in physiological activities when exposed to salt stress, such as declines of PS Ⅱ activity, increases of MDA content and SOD activity, as well as fluctuation of CAT activity. Physiological activities of the green algae were recovered due to the additions of exterior sucrose and EPS when the algae were subjected to salt stress. It may be conclude that there are two ways of resisting salt stress for the species of green algae within biotic crusts. On the one hand, it is endogenesis regulation such as metabolic intensification of saccharide, emergent reactions from membrane system and antioxidant system. On the other hand, green algae in crusts may increase their resistance to salt stress by means of excretion of EPS and other saccharide from cyanobacteria within biotic crusts. 7. It also showed that the similar effects of salt stress on Scytonema javanicum were found when the cyanobacterium was subjected to salt stress, such as declines of PS Ⅱ activity, increases of MDA content and SOD activity, as well as fluctuation of CAT activity. Moreover, the damages of ultrastructure and the increase of EPS production in Scytonema javanicum were observed due to salt stress. Results indicated in the study that the lanthanon, Ce, was found to promote growth and activity of Scytonema javanicum in low concentration of Ce, while inhibition effects occurred in high concentration of Ce, and moderate concentration of Ce availed to relax the salt stress effects on Scytonema javanicum.
Pages187
Language中文
Document Type学位论文
Identifierhttp://ir.ihb.ac.cn/handle/342005/12432
Collection学位论文
Recommended Citation
GB/T 7714
饶本强. 生态环境因子对荒漠藻及其结皮生长发育的影响研究[D]. 水生生物研究所. 中国科学院水生生物研究所,2009.
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