【作者】 李茜；

【导师】 张硕新；

【作者基本信息】 西北农林科技大学 ， 生态学， 2011， 博士

【摘要】 我国黄土区生态环境脆弱,水土流失严重。农林复合经营是治理黄土高原的一项主要措施和解决这种恶性循环的有效途径之一。研究农林复合系统中的种间关系,有助于更深层次理解地生态系统结构和功能的稳定性,为探索资源合理和高效的利用方式,及农林复合系统中树种的选择和配置提供理论指导。核桃(Juglans regia L.)是我国重要的经济林树种之一,栽培历史悠久,分布广泛,资源丰富。核桃也是最早发现具有化感作用的植物之一,其自身次生代谢物——核桃醌能抑制其他植物的生长发育。化感作用具有明显的选择性和专一性,核桃虽为典型的化感树种,但只要选择与其相适应、相生的植物,就能充分发挥林药复合种植的各种优势。核桃与一些农作物复合种植模式已初具模式,但到目前为止,鲜见关于核桃与中草药复合种植的研究报道。因此,本研究以渭北黄土区农林复合系统中的主要经济树种核桃为供体,采取生物检测的方法,研究了核桃化感物质对中草药白术、板蓝根、远志和丹参等种子萌发的化感作用潜力及对受体幼苗生长的化感效应,试图阐明核桃化感物质的释放途径以及化感作用对受体植物的作用机理,初步掌握了核桃根际土壤酶活性时间和空间的动态变化规律,探讨了核桃与不同中草药复合种植的可行性,为在生产实践中充分发挥林药复合经营的生态效益和经济效益提供理论依据。主要研究结果如下:1.核桃化感物质对受体植物白术、板蓝根、远志和丹参种子萌发和生长的化感效应既有促进作用,又有抑制作用,也有低浓度促进高浓度抑制的双重浓度效应。核桃的化感效应因核桃叶水浸提液的浓度和受体植物种类的不同而表现出选择性和专一性。2.低质量浓度(5 mg/mL)核桃叶水浸提液对白术幼苗的株高、地径、叶绿素含量、净光合速率及气孔导度的影响表现为促进作用,高质量浓度(100 mg/mL)核桃叶水浸提液对白术幼苗的各项指标表现为抑制作用,即低促高抑的双重浓度效应。3.质量浓度为0.025、0.05、0.1、0.2和0.4 g/mL的核桃叶水浸提液对受体植物白术和板蓝根幼苗叶片的细胞膜透性均有明显的破坏作用,随着质量浓度的增加,对细胞膜的透性增大,细胞内含物外渗,导致细胞电解质渗透率增高。4.核桃化感物质主要的释放途径是地上挥发物和淋溶物,其次为根系分泌物和土壤残体分解。核桃地上部叶水浸提液、地下部根水浸提液和和地上部挥发物对白术、板蓝根、远志和丹参种子萌发、幼苗苗长和幼苗根长的综合效应指数SE为16.77、19.00、12.10和27.25,可知核桃化感作用综合抑制效应为丹参>板蓝根>白术>远志。对4种受体种子萌发、幼苗苗长和幼苗根长的抑制作用综合效应指数SE值依次为7.82、23.94和24.59,可知核桃化感作用对不同受体植物幼生长综合抑制效应依次为幼苗根长>幼苗苗长>种子萌发。5.核桃化感物质抑制了受体植物白术和板蓝根可溶性蛋白质的合成,造成了可溶性糖、PRO和MDA含量的升高以及叶绿素含量的降低,破坏了植物生长的正常代谢水平;同时降低了POD、SOD、CAT等抗氧化酶的活性,打破了植物体内正常的防御系统的平衡,造成了植物体内膜脂过氧化作用程度的加剧,抗胁迫能力减弱,进而对受体植物的生长产生抑制作用。6.渭北黄土区6年生核桃根际土壤的过氧化氢酶、脲酶、磷酸酶和蔗糖酶活性的空间变化随着土层剖面的加深而活性降低,说明土壤中各种酶的活性可能和核桃根系的分泌物有关。随着采样时间的不同,各种土壤酶活性的变化规律不一致,可能是因为核桃根系分泌物的种类和数量以及根系周围的微生物对每种土壤酶的合成影响不同所致。更多还原

【Abstract】 The ecological environment of Loess area of China is fragile, and soil erosion is serious. Agroforestry is one of the main measures to control the Loess Plateau and is an effective way to resolve this vicious circle. Researches on the relationship between species of Agroforestry will help us understand the deeper structure and function of ecosystem stability, explore the rational and efficient resource use patterns, and provide theoretical guidance for agroforestry systems selection and configuration.Walnut (Juglans regia L.) is an important economic tree species in China, it has long history of cultivation, widely distribution and abundant resources. Walnut is the first plant we found that has allelopathy, its secondary metabolite-Juglone can inhibit the growth of other plants. Allelopathy is obvious selectivity and specificity, walnut tree is the typical allelopathic plant, but as long as we choose suitable plants intercropping with walnut, agroforestry will be able to give full play of the advantages grown. For a long time walnut and some crops have been applied for intercropping, however so far there are few reports on intercropping patterns between walnut and Chinese medicinal plants. Therefore, Bioassay methods were used to probe into the walnut allelopathic effect on Chinese medicinal plants Atractylodes macrocephalak, Isatis tinctoria, Polygala tenuifolia and Salvia miltiorrhiza. The objectives were to clarify the main allelopathic substance releasing routes of walnut and allelopathy function mechanism on different receptor plants, to understand the time and spatial change rule of the enzyme activities in rhizosphere soil of walnut, to discuss the feasibility of intercropping between the Chinese medicinal plants and walnut, and to provide a theoretical basis for maximizing the ecological and economic benefits of agroforestry. The main results are as follows:1. Allelochemicals of walnut had promote effects, inhibit effects and double concentration effects on A. macrocephalak, I. tinctoria, P. tenuifolia and S. miltiorrhiza, there exsited different effects with concentration of walnut leaf extracts and receptor plant species, so allelopathic effects exhibited different selectivity and specificity.2. Low concentration (5 mg/mL) of walnut leaf aqueous extract could stimulate the stem length, root collar diameter, chlorophyll content, net photosynthetic rate and stomatal conductance of I. tinctoria, high concentration (100 mg/mL) of walnut leaf aqueous extract inhibited the stem length, root collar diameter, chlorophyll content, net photosynthetic rate and stomatal conductance, therefore, the receptor showed the double effects of concentration.3. Concentration of 0.025, 0.05, 0.1, 0.2 and 0.4 g/mL walnut leaf aqueous extract had obvious damaging effect on the cell membrane permeability of receptor A. macrocephala and I. tinctoria. When the concentration increased, the cell membrane permeability increased, cell inclusions extravasated, resulting in increasing the conductance rate of extracellular osmose fluid.4. The main allelopathic substance releasing routes of walnut were volatile matter aboveground and eluvial matter of walnut, next were root exudates and plant debris decoposition underground. The synthetic effects (SE) of allelopathic substance releasing routes of walnut on different receptor plant were: the SE of A. macrocephalak was 16.77, the SE of I. tinctoria 19.00, the SE of P. tenuifoli 12.10 and the SE of S. miltiorrhiza 27.25 respectively, i.e., the synthetic inhibitory effect of S. miltiorrhiza>that of I. tinctoria>that of A. macrocephalak>that of P. tenuifolia. The synthetic effects of seed germination, shoots length and roots length on four different receptor plants were: the SE of seed germination was 7.82, the SE of shoot length 23.94 and the SE of root length 24.59 respectively, that is the synthetic inhibitory effect of root length>that of shoots length>that ofseed germination.5. Walnut allelochemicals inhibited the receptor plants’(I. tinctoria and A. macrocephalak) soluble protein synthesis, resulting in increasing soluble sugars, PRO and MDA content and decreasing chlorophyll content, and destroying the normal metabolism of plant growth; simultaneously, reducing the POD, SOD, CAT and other antioxidant enzymes activity, breaking the balance of normal defense system, weakening the resistance, and inhibiting the receptor plants growth.6. In the Loess area, the catalase, urease, phosphatase and saccharase activities in rhizosphere soil of 6 years old walnut decreased with the depth of spatial profile, indicated that the soil enzymes activities may be related with the root secretion. Along with sampling time’s difference, variation rules of different soil enzyme activities were inconsistent, this was because of rhizosphere of the walnut secretion types and quantity, and microorganism that displayed the different functions to each kind of soil enzyme’s synthesis.更多还原