【作者】 王霞；

【导师】 赵长明；

【作者基本信息】 兰州大学 ， 生态学， 2013， 硕士

【摘要】 多倍化是驱动植物进化的主要力量,自然界中约30%-70%的开花植物经历过一次或多次多倍化过程,研究表明由于基因的加倍,植物表现出与其亲本形态以及生理特征方面的差异,另外多倍体与其二倍体植物在生境上存在着明显分化。本文以青藏高原及其周边分布的二倍体和四倍体青甘韭为材料,通过野外移栽种植于同质生境中,首先测定了二倍体和四倍体青甘韭在形态特征方面的差异以此来探讨基因加倍之后的表型特征,然后利用Li-6400便携式光合仪测定了二倍体和四倍体青甘韭叶片在不同光照强度、CO2浓度与温度处理下的气体交换特征,旨在探讨不同倍性青甘韭叶片气体交换特征对光照、CO2浓度和温度的响应差异,阐明四倍体青甘韭适应高原低温、低CO2分压、温度变幅大等恶劣生境的光合生理生态机制,进而为揭示多倍化引起植物生境分化的生理生态机制提供理论依据及数据支撑。研究结果如下：(1)四倍体青甘韭单株叶面积明显高于二倍体植株,但其单株冠幅和单株高度却都低于二倍体植株,这种基因加倍之后,并未表现出超亲模式可能主要是由于四倍体分布在青藏高原较高海拔地区,导致植株矮化的结果。气孔数据显示,四倍体青甘韭气孔大于二倍体,表明更有利于其在低CO2分压条件下吸收C02。四倍体青甘韭单花体积和总花序体积均大于二倍体,表现出基因加倍的优势,但其花期长度短于二倍体,且结实率低于二倍体,表明不同倍性青甘韭繁殖特征(花体积与花期和结实率)间存在着权衡关系。(2)二倍体和四倍体青甘韭叶绿素含量差异不显著,但四倍体植株类黄酮含量高于二倍体,有利于其适应青藏高原高海拔地区较强的紫外辐射。(3)二倍体和四倍体青甘韭净光合速率(Pn)对光强(PAR)的响应能力差别不显著,可能由于叶绿素含量变化不明显造成的；但净光合速率对CO2浓度响应曲线表明,四倍体最大净光合速率(P max)、最大羧化效率(V cmax)、电子传递速率(Jmax)和丙糖磷酸利用率(TPU)都显著高于二倍体,进而有利于四倍体在较低C02分压的高海拔生境生存；同时,四倍体青甘韭的最适温度下最大净光合速率(Pmax)和最适温度(Top1)均明显低于二倍体,且在相对低温条件下四倍体青甘韭叶片气体交换参数明显高于二倍体,以及四倍体青甘韭对温度变化的敏感度较小。综上结果表明,四倍体青甘韭通过其二倍体加倍后,四倍体青甘韭无论形态特征还是光合生理特征更能适应低温、低CO2分压和较大温度变幅的不稳定生境,有助于其在青藏高原高海拔极端环境中分布、生长和生存,具有更大的扩散和进化优势。更多还原

【Abstract】 Polyploidy is a major force of driving plant evolution, even about30%-70%of flowering plants have experienced one or more times polyploidization process in nature. Compared with their dioploid parents, due to the doubling of the gene, the polyploidy plants offen showed differences in the morphological and physiological characteristics, and occupied the different habitats. In order to study the ecophysiological mechanisms of photosynthesis in habitats’ differentiation of polyploid, we used the diploid and tetraploid Allium przewalskianum Regel which distributedin the Qinghai-Tibet Plateau as the test materials. Firstly, in order to study the morphological effects of gene doubling for A. przewalskianum, the growth and phenotypic characteristics of diploid and tetraploidy were measured; Then, the gas exchange parameters of tetraploid and diploid A. przewalskianum under different photosynthetic photon flux density, CO2concentration and temperature treatments were measured with the portable photosynthesis system(Li-6400) to investigate the differences of gas exchange characteristics between different ploidy of A. przewalskianum. Lastly, all the above goals were to clarify the photosynthesis-related ecophysiological characteristics of tetraploid A. przewalskianum to adapt to alpine harsh habitats, and provide a theoretical basis and/or data support for the habitat differentiation of polyploid in nature. The results of this thesis are as follows:(1) The data of morphological characteristics of diploid and tetraploid A. przewalskianum showed that the tetraploid leaf area per plant was significantly higher than its ancestral diploid, while its canopies and height of single plant were lower than its diploid. Therefore, there is no transgressive characteristics of tetraploid plants in phenotypic traits after gene doubling, which main reason may be the tetraploid distributed in high altitude areas of Qinghai-Tibet Plateau and resulted the plant in dwarf. Stomatal data showed that the stomatal sizes of tetraploid plant were greater than its diploid, which could be help to taking in more CO2in the low CO2partial pressure conditions. The volumes of single flower and in florescence of tetraploid plant were greater than its diploid, shown the advantage of gene doubling. However, the flowering length and seed setting rate were on the contrary, which showed there were the trade-offs among some reproductive traits in different ploidy plants.(2) There is no significant difference between the chlorophyll content of diploid and tetraploid plants, but the content of tetraploid flavonoids was higher than its diploid, these changes could help the tetraploid plants adapt to the strong ultraviolet radiation in high-altitude areas of the Qinghai-Tibet Plateau.(3) The response of net photosynthetic rate (Pn) to photosynthetic photon flux density (PAR) had no distinct differences in leaves of diploid and tetraploid A. przewalskianum. It may be because the chlorophyll content had no difference between diploid and tetraploid. Meanwhile, the response of photosynthetic rate (Pn) to intercellular CO2concentration (Ci) in leaves of diploid and tetraploid A.przewalskianum showed that the maximum net photosynthetic rate (Pmax), carboxylation efficiency (Vcmax), electron transport rate (Jmax) and triose phosphate utilization (TPU) of tetraploid plants were higher than its diploid. Then, high carbon dioxide utilization efficiency makes tetraploid plants adapt to the lower partial pressure of CO2. In addition, the responsive curves of photosynthetic rate (Pn) to different temperatures in A. przewalskianum indicated that the leaf gas exchange parameters of tetraploid plants were significantly higher than its diploid both at a specific temperature and in the same temperature fluctuation, then the sensitivity to temperature changes of tetraploid plants was lower than its diploid.In summary, we conclude that the tetraploid A. przewalskianum has obvious advantages both at the morphological and photosynthetic characteristics after gene doubling, which could help it adapt to the low temperature, lower partial pressure of CO2, and large unstable temperature habitats, contributing to its distribution, growth and survival in the high-altitude extreme environments.更多还原