【作者】 邹丽芸；

【导师】 喻景权；

【作者基本信息】 浙江大学 ， 蔬菜学， 2004， 硕士

【摘要】 目前，随着西瓜生产的产业化、规模化发展，西瓜连作障碍问题日趋严重。许多研究证实自毒作用是导致作物产生连作障碍的主要原因之一。因此，开展西瓜自毒作用机理的研究为西瓜连作障碍问题解决提供十分重要的理论依据。本试验利用活性炭添加与否，研究了西瓜根系分泌物对自身的毒害效果，结果表明西瓜根系分泌物使同茬植株相对电导率增加、膜渗漏增加，根系中总酚含量升高；并降低了体内叶绿素含量，植株光合产物积累减少，最终导致植株根系生长发育不良，影响了西瓜果实的正常膨大。在研究西瓜重茬液对下茬西瓜幼苗生长及其生理生化特性的试验中，结果表明西瓜根系分泌物能改变西瓜幼苗根系中抗氧化酶系统的活性，导致幼苗根系中GPOD活性降低，积累过多的活性氧和MDA，根系发生膜脂过氧化，导致幼苗生物产量下降。重茬液中添加活性炭后，根系分泌物中一些有毒物质被吸附，缓解了西瓜重茬液的自毒作用，保证了西瓜幼苗的正常生长发育。试验研究表明西瓜重茬液含有对下茬西瓜生长具有自毒作用的根系分泌物。重茬液处理的西瓜幼苗根系中PAL活性较高，促进了酚类物质合成，毒害严重，导致西瓜幼苗生长发育受阻；而添加活性炭后，由于活性碳吸附了重茬液中的自毒物质，从而减弱了重茬液的自毒作用，西瓜幼苗根系中PAL活性保持在一个较低的水平，合成的酚类物质及其衍生物减少，降低了西瓜水培液中酚类物质的浓度，使得酚类物质毒害作用降低，幼苗生长受阻现象减轻。 利用西瓜叶、茎、根进行浸提，研究了西瓜不同组织残茬浸提液的生物活性，结果表明西瓜残茬浸提液均具有生长抑制作用。浸提液的作用效果一般表现为低浓度不具有抑制作用，甚至具有促进作用，但随浓度的升高，抑制作用也随之增强。其中西瓜叶、茎浸提液较根浸提液的抑制作用更强，西瓜残茬的自毒作用可能与不同组织有关。不同溶剂浸提残茬所得浸提液对种子萌发的影响不同，其中以水浸提的效果更为显著。利用同一组织浸提液进行西瓜种子生物活性检测表明水浸提液的自毒作用较95％乙醇浸提液的自毒作用强。通过生物活性检测试验验证了西瓜残茬的自毒作用存在。根茬水浸提液和乙醇浸提液的水溶性组分在高浓度时，显著地抑制种子萌发，而低浓度对种子萌发影响不大；而其酸性组分和碱性组分在此浓度范围内几乎不影响莴苣种子萌发数。各组分对莴苣胚根和胚轴生长的抑制作用也随浓度的增加而加强，而以水溶性组分抑制率增加最为显著。因此，根茬浸提液不同组分的抑制活性大小一般表现为水溶性组分>酸性组分)碱性组分。 试验研究水培西瓜营养液残液及活性炭吸附的根系分泌物的生物活性，结果表明西瓜根系分泌物影响了葛芭种子萌发及其胚根或胚轴伸长，并且这种作用效果与浓度有关。西瓜根系分泌物在种植过程中积累，达到一定浓度后才会对西瓜产生自毒作用;随着不断的积累，抑制作用随之增强。不同方法收集的根系分泌物中酸性组分的抑制效果不同。从活性炭浸提出根系分泌物的酸性组分在高浓度具有显著抑制作用，而随浓度下降抑制作用也随之下降;而营养残液中根系分泌物的酸性组分在试验浓缩倍数范围内，其抑制作用效果几乎没有变化。不同方法收集的西瓜根系分泌物的碱性组分都不具有抑制作用或抑制作用较小。水溶性组分对葛芭种子萌发及其胚轴长和胚根长影响最为显著。西瓜根系分泌物的各组分抑制作用大小顺序:水溶性组分>酸性组分>碱性组分或表现为水溶性组分>酸J胜组分或碱性组分。更多还原

【Abstract】 At present, with the development of watermelon industry and regularization of produce, continuous cropping obstacle problem of watermelon is more severe. The primary concern of continuous cropping problems is autotoxicity, and therefore, it is very necessary to study the mechanism of watermelon autotoxicity, to provide highly important theory for resolving continuous cropping problem of watermelon. A number of experiments were carried out. In the first series of experiment, studies were carried out on autotoxicity of root exudates from watermelon plant in a hydroponic system by activated charcoal (AC). The results showed that root exudates of watermelon increased the relative conductivity, which proved that membrane permeability was damaged, the phenols content of roots increased and declined chlorophyll content of watermelon plant, affected the photosynthetic material accumulation, resulting in retardation and inhibition of plant growth. Second set of experiments involved studying the effects of recycled solution in successive cropping with watermelon, the results showed as follows: Through watermelon root exudates, the GPOD activities in roots was low, AOS and MDA content in roots were accumulated, which reflected on root membrane lipid peroxidation, and the abnormal metabolism in watermelon seedlings, which inhibited seedlings growth. Phenylalanine ammonia lyase (PAL) activities of watermelon root were also evidently higher without AC. The higher activities of PAL, resulted in the high rates of phenols synthesis, which were poisonous to seedlings at a certain concentration. Addition of AC, reduced the activities of PAL in roots to a lower degree, and also the amounts of phenols synthesized were reduced. Due to the absorption of AC, autotoxicity of root exudates in recycled solution was alleviated. Autotoxicity of watermelon root exudates was also confirmed.All of the extracted substances from watermelon tissues had inhibitory effects on watermelon and lettuce germination and growth, In general, the inhibitory effects of extracts from the tissues were correlated to their concentrations. At a certain ranges of extracts concentrations, inhibition was increased with the extracts concentration increasing. Under low concentration, the inhibition wasn’t shown, indeed, the promotion was exhibited. With the concentration increasing, the inhibition was enhanced. Inhibitory effects of leaf extracts and stem extracts were more evident than that of root extracts. Autotoxicity of watermelon stubbles correlated to the watermelon extracts components. Extracts with different solvents showed different effects on seeds germination and its growth. In this experiment, two species solvents, distilled water and 95% ethanol were used to test seed bioassay, which extracts with distilled water as a solvent exhibited more inhibitory effects than those of 95% ethanol. The substances extracted from root stubbles were classified into acidic, basic, water soluble parts, respectively, it was proved that all classes or parts of the substances could inhibit the seedlings’ growth and the inhibitory effects were correlative to extracts concentration. Water soluble parts of the extracts with high concentration evidently restrained germination, contrarily, weren’t inhibitory effects on germination. At the test concentrations ranges, lettuce germinations weren’t influenced by acidic part and basic part. Accordingly, inhibition of the parts from root extracts were generally water soluble part >acidic part>basic part in order.Root exudates of watermelon plant were collected from no AC treatment solutionplanted watermelon and extracts of AC, which added into watermelon hydroponic system. The results showed that watermelon root exudates inhibited the growth of lettuce radicle and lettuce hypocotyls, and the inhibitory effects were markedly correlative to concentrations. When the root exudates in the watermelon hydroponic system accumulated to a certain concentration, the inhibitory effects were showed. Therefore whenever, watermelon roo更多还原