【作者】 包艳丽；

【导师】 刘左军；

【作者基本信息】 兰州理工大学 ， 生物化学与分子生物学， 2011， 硕士

【摘要】 干旱和盐碱化是人类面临的世界性问题,也是制约生物结皮中荒漠藻类生长的主要环境因子。特别是我国西北干旱半干旱地区,随着水资源的日益缺乏,干旱和土壤盐碱化已成为该地区结皮演替和生态环境的严重威胁。本研究通过对青藏高原东缘沙化区生物结皮中荒漠藻类的野外考察、采样和实验室的培养,对该沙化区中藻类的抗旱性进行了详细的研究和综合性的评价,从而为筛选出抗旱性强的藻种奠定了基础。主要研究结果如下:1.渗透调节与脯氨酸、可溶性蛋白含量的变化。随着PEG渗透胁迫强度的增大,四种藻种体内游离脯氨酸的含量和可溶性蛋白的含量都呈现出先上升后下降的趋势。藻种一和藻种二体内游离脯氨酸的含量和可溶性蛋白的含量分别在20%PEG和30%PEG渗透胁迫下最高,藻种三体内游离脯氨酸的含量和可溶性蛋白的含量都在30%PEG渗透胁迫下最高,藻种四体内游离脯氨酸的含量和可溶性蛋白的含量都在10%PEG渗透胁迫下最高。增加幅度越大,渗透调节能力越强,则抗旱性就越强。通过对比发现四种藻种中,藻种三体内的游离脯氨酸含量和可溶性蛋白的含量增加幅度最大,渗透调节能力最强,其抗旱性也最强,藻种四的渗透调节能力最弱,其抗旱性最弱。2.膜透性与丙二醛含量的变化。藻种一在10%PEG渗透胁迫下体内丙二醛的含量最高,藻种二、藻种三、藻种四在40%PEG渗透胁迫下体内丙二醛的含量最高,且膜透性与MDA的质量摩尔浓度在水分胁迫处理的过程中增幅最大,这说明干旱胁迫在10%PEG和40%PEG渗透胁迫条件下分别对藻种一和藻种二、三、四膜系统的伤害最大,膜脂过氧化程度最大,其抗旱性最弱;在20%PEG和30%PEG渗透胁迫条件下,藻种二、藻种三和藻种四体内的MDA质量摩尔浓度较小,膜透性较小,其抗干旱的能力较强,而藻种一随着渗透胁迫强度的增强,藻种一体内的MDA质量摩尔浓度呈现下降的趋势。通过对比发现藻种一在水分胁迫下,细胞膜的透性最小,膜脂过氧化程度最低,对藻种膜系统的伤害最小,其抗旱性最强。3.保护酶活性的变化。藻种一SOD和CAT的活性分别在30%PEG和20%PEG时最高,藻种二和藻种三SOD和CAT的活性都在20%PEG时最高,而藻种四SOD和CAT的活性在10%PEG时最高,说明藻种一、二、三消除氧自由基的能力较藻种四强,能够减轻活性氧自由基对藻种膜系统的伤害,使藻种表现出较强的抗旱性,藻种四的抗旱性较弱。随着PEG胁迫强度的增大,四种藻种SOD和CAT的酶活力降低,膜脂过氧化进一步加重,致使O₂-、H₂O₂过多积累,使藻种体内的保护酶体系在维护膜的稳定性和清除自由基上不能够充分发挥作用,也不能够积极地消除氧自由基对藻种膜系统的伤害,从而导致藻种较弱的抗旱性。对比四种藻种体内SOD和CAT的活性变化,发现藻种一较其他三种藻种有着较强的抗干旱能力。更多还原

【Abstract】 Drought and salinity are not only global problems, but also the major environmental factors limiting the growth of biological desert crust algae. With the growing shortage of fresh water resources, drought and soil salinity have been threatening the development of crust succession and the environment in the arid and semi-arid areas of northwest China particularly.In this study, drought resistance of desert algal crusts in the eastern margin desert region of Tibetan Plateau was researched by field studies, sampling and laboratory cultivation, so as to filter out the algae species which have strong drought resistance. The main results were showed as follows:1. The changes of osmotic adjustment, proline and soluble protein content. With the increased intensity of PEG osmotic stress,free proline content and soluble protein content of the four algae species increased and then emerged in a downward trend.Free proline content and soluble protein content of the first and the second algal species is the highest in 20% PEG and 30% PEG osmotic stress respective, the third algal species has the highest content in30% PEG osmotic stress and the forth algal species in 10% PEG osmotic stress. The rate of increase is greater, the osmotic adjustment is stronger, so the drought resistance is stronger also. By comparing the four algal species, it found that the increase of free proline content and soluble protein content of the third algae species is the highest, the osmotic adjustment is the strongest, so the drought resistance is also the strongest, osmotic adjustment ability of the forth algae is the weakest, so its drought resistance is the weakest.2. The change of membrane permeability and MDA content. the MDA content of the first algae species is the higest in 10% PEG osmotic stress,while the second, third and forth species have the highest MDA content in 40% PEG osmotic stress, the membrane permeability and the MDA molar mass concentration increased obviously during the treatment of water stress,indicating that the membrane systems of the first algal species have maximal damage in 10% PEG, while the second, the third and the forth algal species have maximal damage in 30% PEG osmotic conditions, the lipid peroxidation is the highest respectively, so the drought resistance is the weakest.In 20% PEG and 30% PEG osmotic stress conditions, the second, third and forth algal species have lower MDA molar mass concentration and membrane permeability, so they have higher drought resistance. With the increasing intensity of PEG osmotic stress,theMDA content of the first algae species showed a downward trend. By comparing the four algal species, it found that the membrane permeability and the lipid peroxidation of the first algal species is the weakest, so it has the highest drought resistance.3. The change of protective enzyme activities .The first algae species has the highest CAT and SOD activities in 30% PEG and 20% PEGrespectively, the second and the third algae species have the highest SOD and CAT activities in 20% PEG,while the forth algae species in 10% PEG, indicating that the first, the second and the third algae species have higher ability to eliminate oxygen free radicals than the forth algae species, it can reduce the damage to the membrane system of algae species,so that the three algae species have stronger drought resistance, the forth algae species has lower drought resistance. With the increase of PEG stress intensity,SOD and CAT enzyme activities of the four algae species aredecreased, lipid peroxidation is further increased,resulting in O₂-, H₂O₂ excessive accumulation, and the protective enzyme systems of the four algae species are not able to fully play their role inmaintaining membrane stability and removing oxygen free radicals actively,which result in weaker drought resistance of the four algae species. By comparing SOD and CAT enzyme activities of the four algal species, it found the first algae species has the highest drought resistance.更多还原