【作者】 朱文杰；

【导师】 陈欣；

【作者基本信息】 浙江大学 ， 生态学， 2011， 硕士

【摘要】 化感作用普遍存在于自然界,是一种重要的生态机制,是植物防御进化的组成部分,也是某些植物为了提高自身竞争能力的一种化学手段。外来植物的入侵过程往往伴随着强烈的化感作用。加拿大一枝黄花(Solidago canadensis L.)是上世纪30年代入侵我国东南沿海地区的典型入侵植物。大量研究表明,加拿大一枝黄花可以通过化感作用加强其竞争优势。但加拿大一枝黄花对入侵地土传病原菌的化感作用迄今鲜有报导。本文通过培养皿、原位实验以及野外模拟实验研究分析了不同浓度加拿大一枝黄花根系提取物、分泌到土壤中的化感物质对终极腐霉菌(Pythium ultimum)、立枯丝核菌(Rhizoctonia solani)的抑制效应。并通过实验室受控实验,研究化感物质在土壤中积累所受到土壤生物的影响。主要取得以下结果：1加拿大一枝黄花提取液对土传病菌菌落生长的影响不同浓度的加拿大一枝黄花根状茎与根系提取物,对琼脂培养基上生长的土传病原菌菌落生长有抑制作用。提取物浓度越大,对病原菌的抑制效果越强。2加拿大一枝黄花化感物质对植物幼苗得病率的影响两种土传病原菌都能使番茄或紫花苜蓿幼苗得病。加拿大一枝黄花提取液或砂培中原位释放的化感物质,都能显著降低幼苗得病率。化感物质浓度越大,得病率越低。但本地植物鸡眼草根系分泌物对得病率无影响。野外采集的土壤,加拿大一枝黄花根际土壤种植的番茄幼苗得病率显著低于鸡眼草根际土壤种植番茄幼苗的得病率。3加拿大一枝黄花化感物质对植物幼苗死亡率的影响化感提取物与病原菌都能提高番茄种子的死亡率。土壤未接菌处理,提取物各浓度水平处理对番茄种子萌发都有化感抑制效应。化感效应引起的番茄种子死亡率升高,并随化感物浓度升高而升高。与只接种病原菌但不添加加拿大一枝黄花根状茎与根系提取物处理对照相比,接种后同时加入不同浓度的加拿大一枝黄花根状茎与根系提取物能不同程度地降低指示植物(番茄幼苗)的死亡率,表明加拿大一枝黄花根状茎与根系提取物可以抑制两种土传病原菌的致病活性,抑制效果随着提取物浓度的升高而增强。加拿大一枝黄花根系分泌到体外的化感物质对土传病原菌的致病活性也有抑制作用,能降低番茄幼苗死亡率,但本地植物鸡眼草(Kummerowia striata)根系分泌物却无化感作用。随着加拿大一枝黄花密度逐渐升高,在砂培中检测到总皂苷、总黄酮、总多酚3种化感物质含量也不断升高。土壤接种土传病原菌后,本地植物紫花苜蓿(Medicago sativa)的死亡率也随着化感物质浓度升高而降低。野外采集的土壤,加拿大一枝黄花根际土壤种植的番茄幼苗死亡率显著低于鸡眼草根际土壤种植番茄幼苗的死亡率。4土壤生物对化感物质积累的影响野外模拟加拿大一枝黄花入侵过程,入侵过程中土壤中化感物质浓度升高,化感物质对终极腐霉菌有抑制作用。化感物积累的同时受到土壤微生物的影响。灭菌土壤中化感物质降解速度迟缓,而未灭菌土壤中三种主要化感物质降解迅速。在加入化感提取物第8d总皂苷只存留55%左右,总黄酮存留26%,总多酚存留17%。更多还原

【Abstract】 Allelopathy is a common phenomenon in nature, and is an important ecological mechanism for plants. It is an part of the evolution of plant defense, but also a chemical means for some plants to improve their competitive ability. Strong allelopathy often accompanied by the invasion progress of exotic plants. Canada goldenrod (Solidago canadensis L.) is a typical invasive plant in southeastern coastal areas of China. Currently a large number of studies have shown that Solidago canadensis could’enhance the competitive advantage by allelopathy. However, at present there is no study about allelopathy of invasive S. canadensis on soil-borne pathogens. In this paper, I design Petri dish experiment, in situ simulation experiments and field studies to study the effects of different concentrations of root extracts of S. canadensis, also the effects of allelochemicals secreted into the soil on the Pythium ultimum and Rhizoctonia solani. At last, I studied whether the accumulation of allelochemicals in the soil affected by soil microbes. Main results obtained from these experiments are as follows:1 Effects on growth of colonies of two species of Soil-borne pathogensRhizome and root extracts of S. canadensis at different concentrations could inhibit the colony growth on agar medium. The higher concentrations of the extracts, the stronger the inhibitory effects.2 Effects on damping-off rates of seedlingsBoth two species of pathogens could cause diseases on M. sativa and tomato seedlings. Extracts or roots exudates of S. canadensis can inhibit activity of these pathogens. The inhibitory effects increase with the increasing of allelochemicals concentrations. Roots exudates of K. striata has no effects on pathogenic activity. Rhizospheric soil of S. canadensis could decrease damping-off rates of tomato seedlings contast to rhizosphere soil of K. striata. 3 Effects on mortality rates of seedlingsBoth extracts and soil-borne pathogens could increase the mortality rate of tomato seedlings. The mortality caused by allelopathy increases with the concentration of extracts. Contrast to only-pathogens treatment, the rhizome and root extract of S. canadensis at different concentrations could decrease the mortality rates of tomato seedlings, that is it could inhibit activity of soil-borne pathogens. The inhibitory effects increase with the higher concentrations of rhizome and root extract. The allelochemicals of S. canadensis secreted into sands can also inhibit the activity of soil-borne pathogens. They can decrease the mortality rate of tomato seedlings. But the roots exudates of Kummerowia striata have no allelopathic effects on these two species of soil-bome pathogens. Concentrations of three kinds of allelochemicals (total saponins, total flavonoids and total polyphenols) in sands culture become higher with increasing of the density of S. canadensis. When the sands inoculated with soil-borne pathogens, the mortality rate of native plant Medicago sativa L. decreases, because of the increasing concentrations of allelochemicals. Rhizosphere soil of S. canadensis has allelopathic effects, but rhizosphere soil of K. striata has no allelopathic effects on tomato seedlings.4 Effects of soil microbes on accumulation of allelochemicalsIn field experiment, during the invasion progress of S. canadensis, concentrations of allelochemicals in soil increase, and the allelochemicals can inhibit the activity of Pythium ultimum. The accumulation of allelochemicals are affected by soil microbes. The allelochemicals degrade slowly in sterilized soil, but degrade quickly in unsterileized soil. After 8 days of addition extracts of S. canadensis into soil that never planting this invasive species, total saponin retained only about 55%, total flavonoid retained only about 26%, total polyphenols retained only about 17%.更多还原