【作者】 林霞；

【导师】 李俊清；

【作者基本信息】 北京林业大学 ， 生态学， 2010， 博士

【摘要】 无柄小叶榕(Ficus concinna var. subsessilis)是分布在南亚热带最北缘的高大乔木,作为气候特征的指示植物在生态系统中扮演着关键角色,同时也是造林绿化的优良乡土树种。温州地区有其丰富的古树资源,但存在更新难、病腐严重、资源不断减少等生态退化现象。本文以100a以上的无柄小叶榕古树在温州的资源调查入手,运用主成分分析和非线性典型相关分析等方法定性定量评价现存古榕的资源状况,探讨影响古榕退化的原因；通过研究其种子发芽、种苗生长对生态因子的响应,揭示其生态响应机制,从而为有效保护遗传资源提供理论依据。本研究的主要结果如下：1、古榕存在着更新不良、病腐严重、死亡率增大等严重的生长退化现象。通过主成分分析、单因素方差分析和非线性典型相关分析发现古榕分布的地理位置、古榕历史生长状况、土壤类型对温州古榕资源影响显著,土壤类型、土层厚度、立地条件和树龄等因子对现存古榕生长影响较大,生长在农村的古树生长势明显高于城市、生长在低山与水边的显著高于水泥封地的,300a以上树龄古榕生长状况较100a优。可见古榕退化主要原因是受环境和人为因素的影响。2、无柄小叶榕种子在适宜的温、湿度条件下,播种9d后就开始萌发生出胚根,17d后就可长出第一片真叶。采用25℃温水浸种、500mg/l的赤霉素处理种子、地温达到20℃、腐熟的木屑做播种基质等处理都能够促进无柄小叶榕种子萌发,而盐分胁迫会严重抑制无柄小叶榕种子的萌发。无柄小叶榕果实在自然条件下难以腐烂,种子长时间包裹在干缩的果皮中而失去活力,是无柄小叶榕自然更新差的原因所在。3、无柄小叶榕终年挂果,种子量大,进入结果期至少要达到20年树龄,不适宜的生境会影响榕果的结实率和发芽率,以生活在河边的榕树生长发育为好；土壤类型对其生长影响具有显著性,红壤不是最适宜土壤类型；幼苗生长需要850～1500μmolm-2s-1的光强,而榕树的树冠下光强一般在85～1951μmol m-2s-1之间,这造成古榕树下无更新小苗的重要因素。基质中N的含量与无柄小叶榕的生长存在线性相关性,而P、K的含量对无柄小叶榕的生长发育无明显作用。4、无柄小叶榕受低浓度NaCl胁迫净光合速率(Pn)下降主要是气孔因素引起的,而高浓度NaCl胁迫下,则是由气孔因素和非气孔因素共同起作用的；高浓度NaCl胁迫还通过降低PSⅡ反应中心激发能捕获效率(Fv′／Fm′)和PSⅡ反应中心开放程度从而降低电子传递速率和Pn,还使非光化学猝灭(NPQ)、MDA含量、SOD和POD活性显著上升。这就表明尽管高浓度NaCl胁迫诱导光能耗散机制,但仍不能及时地耗散过剩的激发能,诱导了膜脂过氧化的发生。5、不同苗龄无柄小叶榕抗寒性大小为四年生>三年生>二年生>一年生；受轻度的低温胁迫后,无柄小叶榕植株抗寒性有所提高。降温胁迫过程中,四种不同苗龄无柄小叶榕各项生理生化指标表现趋势基本一致,随着温度的降低,无柄小叶榕叶片细胞膜透性、相对电导率、MDA含量、游离脯氨酸浓度增加,SOD活性、可溶性糖含量和可溶性蛋白含量先增大后降低,POD活性先降低后增加,但不同苗龄无柄小叶榕的各项生理生化指标变化幅度存在差异性,三、四年生明显大于一、二年生植株。更多还原

【Abstract】 Ficus concinna var. subsessilis is an arbor plant distributed in the northernmost south subtropic, which is a kind of excellent afforestation trees. This species is also an important indicator plant of climatic and play an important role in the ecosystem. In this study, we, firstly investigated the resources of the ancient ficus in Wenzhou, which were more than 100 years old. Then, the resource status and the main restricted factors of regeneration were evaluated In order to explore causes of ecological degradation, the effect of nutrition and environmental factors on seed germination and seedling growth were carried out..The present results will help us to conserve the wild germplasm and to enhance the population regeneration of Ficus concinna var.subsessilis. The main results and conclusions of this study were stated as follow:1. Resource investigation suggested that unsuccessful regeneration, rot disease and mortality rate might be the primary ecologically degraded factors to this ficus. Principal Component analysis (PCA),shows that locations, historic growth status and soil type have a great effect on the natural resources of the specie in Wenzhou.Correlation analysis shows that the soil type, soil thickness, locations and tree ages have a significant effect on the growth potential of the species. The growth potential of trees growing in the field was significantly higher than that of in the city, and that of trees growing in hillside or waterside was evidently higher than in cement areas. The main factor threatening to the survival of the ancient trees can be ascribed human activities and the destruction of the habitat..2. Under the appropriate temperature and humidity, seeds taken 9 days to germinate and 17 days to the first leave come out. Soaking in the 25℃water, pretreating by 500 mg/l GA, or 20℃ground temperature, and muck and sawdust as substrates that evidently enhanced seed germination. However, the salt stress did the opposite way. Because rotting of fruits were difficulty under natural conditions, the ability of seed germination significantly declined with increase wrapping in the shrinkage pericarp. We suggest that this factor was the main factor limiting the regeneration rate in the field, although they are fruitful every month each year.3. The tree would take at least 20 years to produce fruits. They can produce numerous fruits and seeds every month each year. The poor conditions will reduce fruit productions and seed germination. Trees growing along the river or rivulet have high fruit productions and seed germination. The soil type had great effect on the tree growth. The soil moisture was the main factors affecting the growth of the species. The optimum light intensity of the seedling stage was from 850μmol m-2s-1 to 1500μmol m-2S-1 However, it was always between 85μmol m-2s-1 and 195μmol m-2s-1 under the canopy, which was another reason limiting regeneration. Nitrogen content in substrate plays an important role in the growth and development of seedlings. Whereas P, K content in substrate had no effect.4. The net photosynthetic rate (Pn) was significantly declined under both the low and high concentration of NaCl. The former condition may be caused by stomatal factors, and the latter one may co-dominate between stomatal factors and non-stomatal factors. In addition high NaCl stress may reduce the excitation energy capture efficiency (Fv’/Fm’) of PSII reaction center, and may restrict the opening degree of PSII reaction center which will restrain the electron transfer rate and Pn and will evidently boost the photochemical quenching (NPQ), MDA content, SOD and POD activity5. The semilethal temperature test showed that the cold resistance of the species from strong to weak was four-year-old trees, three-year-old trees, biennial trees, and annual trees. After prechilling treatment, the cold resistance of the four different ages was improved.In the process of sudden cold resistance, the changes of physiological and biochemical indexes of the four different ages were consistent. Along with the temperature decline, the leaf membrane permeability, relative conductivity, MDA content and free proline increased; the SOD activity, soluble suger and protein content increased first, and decreased later; and the POD activity did the opposite way. Under cold stress, the physiological and biochemical indexes are different by ages. The activity of SOD and POD, soluble sugar and protein content, and free proline content of three or four-year-old seedlings were significantly higher than that of biennial or annual ones.更多还原