多岐苏铁和叉叶苏铁的引种驯化及其生态适应性研究

The distribution area of a species is not necessarily the optimum area for its growth and species restricted distribution range may be only due to the geographic obstacle. Both the endangered species-Cycas multipinnata and C. bifida have narrow distribution, and it is not clear the adaptation of the two species to various environmental factors. Introduction and acclimation is an important strategy for the conservation of germplasm. C. multipinnata and C. bifida were previously introduced to Kunming. Although the seedlings survive, their adaptation to environment of the introduced area is not clear. The preliminary work showed that cold acclimation could increase the freezing tolerance of the two species, however, the mechanisms are not clear. In the present study, the variation in the ecological adaptation of C.multipinnata and C. bifida with the introduced period is analyzed by measuring photosynthesis, root vigor and architecture, and other physiochemical characteristics. The mechanisms of cold-acclimation-induced freezing tolerance, the adaptation of the two species to various environmental factors and combination of cold and drought stress are analyzed by measuring photosynthesis, osmotic substance, hormone content, membrane lipid composition, key gene or protein expression and other physiochemical characteristics. The results can provide theoretical basis for the endangered mechanisms, germplasm conservation, introduction and cultivation of C.multipinnata and C. bifida.

物种的分布区未必是其生长发育最适宜的地区，同样物种的局限分布可能仅仅是地理障碍的结果。濒危物种多歧苏铁和叉叶苏铁分布区域狭窄，其对各种生态因子的适应性尚不清楚。引种驯化是种质资源保存的有效措施，前期在昆明对多歧苏铁和叉叶苏铁进行了引种，植株虽成活但其对引种地的适应性还不清楚；前期工作发现冷驯可以提高多歧苏铁和叉叶苏铁的抗冻性，但其机理尚不清楚。本研究通过对光合特性，根系活力及构型等生理生化和形态指标的跟踪测定，分析多歧苏铁和叉叶苏铁的生态适应性随引种时间的变化。通过对光合特性、渗透调节物质、激素含量、膜脂组成、关键基因或蛋白表达等的测定，分析冷驯对提高其抗冻性的生理生化和分子机制；多歧苏铁和叉叶苏铁对温度和光照等生态因子的适应性及其机制；多歧苏铁和叉叶苏铁对低温和干旱复合胁迫的适应性及其机制。通过综合分析，可为揭示两种苏铁的濒危机制，种质保存和引种栽培提供理论依据。

多歧苏铁和叉叶苏铁均已处于极危状态。引种驯化是物种保护的重要策略，但多歧苏铁和叉叶苏铁的生态适应性及驯化生物学方面的研究尚无报道。本项目揭示了多歧苏铁和叉叶苏铁引种昆明后的适应性，冷驯对其抗冻性的影响及机理以及极端温度，干旱及复合胁迫对其生理和代谢的影响。多歧苏铁和叉叶苏铁引种昆明后，其植株死亡率逐年降低且珊瑚根产生率呈逐年上升趋势。多歧苏铁比叉叶苏铁抗冻性强，其低温半致死温度分别为-1.86℃和 -0.15℃，4℃冷驯7d和16d后均可提高2种苏铁的抗冻性，但其涉及的生理生化机制有所不同。对多歧苏铁进行的分子生物学实验结果表明，冷驯7d 和16d引起许多基因的差异表达，涉及脂肪酸去饱和酶等基因。高温干旱比低温干旱复合胁迫对多歧苏铁的光合等生理生化特性影响更大。低温干旱复合胁迫比低温或干旱对叉叶苏铁的光合等生理生化特性影响更大。攀枝花苏铁的低温半致死温度为-2.02℃，比叉叶苏铁的抗冻性更强。低温下，攀枝花苏铁比叉叶苏铁受到的氧化胁迫程度低，光合活性受到的影响小。抗热性方面，多歧苏铁>叉叶苏铁>攀枝花苏铁，3种苏铁在各类脂质的含量，碳酰链长度及不饱和度方面呈现出不同的变化。研究结果可为以上苏铁的引种驯化及濒危机制提供科学依据。