外源硅缓解基质栽培黄瓜自毒作用的机理研究

The effective alleviation roles of exogenous silicon in plants under both abiotic and biotic stresses, such as insect and disease, salt, drought and heavy metal toxicity, have been investigated. Previous study has proved that exogenous silicon significantly alleviated autotoxicity stress in the process of cucumber seed germination. Based on the result, cucumber used as material, the phenyl carboxylic acid compounds used to simulate autotoxicity stress, the hydroponic experiment would be conducted to study the alleviation role of exogenous silicon in cucumber seedling under autotoxicity stress, and to be better understand effects of exogenous silicon on the dynamic differences of substance metabolism, antioxidative metabolism, photosynthetic physiology response and the ultrastructure of related organs in cucumber seedling under autotoxicity stress. Also, the expression level of genes involved in above metabolism processes would be finally analyzed by RT-PCR. Moreover, the field experiment would be further conducted to study effects of exogenous silicon on root autotoxins accumulation, related enzyme activities of substrate, microbial diversity and root morphology, yield and quality of cucumber. The objective of this project is to reveal the physiological and molecular mechanism of the alleviation role of exogenous silicon in cucumber under autotoxicity stress or substrate continuous cultivation conditions. Therefore, the study would provide theoretical foundation and practical significance for the further study of the silicon’s alleviation mechanism and the recycling of substrate.

外源硅可有效缓解病害、虫害、盐胁迫、干旱胁迫及重金属胁迫等生物和非生物胁迫对作物生长的影响。前期研究证明外源硅可显著缓解自毒物质对黄瓜种子萌发的胁迫作用，在此基础上本研究拟以黄瓜为试材，以苯基羧酸类化合物模拟自毒胁迫条件，通过外源硅处理对水培黄瓜幼苗自毒胁迫缓解试验，明确硅处理下黄瓜幼苗对自毒胁迫后植株内物质代谢、抗氧化代谢和光合生理的响应以及相关组织超微结构的动态差异，并通过RT-PCR技术分析以上代谢过程中关键酶基因的表达量。同时进一步通过田间试验，研究外源硅对基质栽培条件下连作黄瓜根系自毒物质积累、基质相关酶活性、微生物多样性以及根系形态、生理活性、产量和品质等方面的动态影响。揭示外源硅对基质栽培连作条件下黄瓜自毒作用缓解的生理和分子机制。为进一步研究硅对黄瓜连作障碍的缓解机理和栽培基质的循环利用提供理论依据。

以设施蔬菜黄瓜为试验材料，研究了外源硅对肉桂酸（CA）模拟自毒胁迫下黄瓜种子萌发和生理特性，确定了黄瓜种子对肉桂酸自毒作用耐受的浓度阈值（2 mmol·L-1）和最佳的外源硅缓解浓度（3 mmol·L-1），并从生长和生理的角度说明了适宜的外源硅对黄瓜种子的自毒作用有明显缓解作用。采用水培试验，研究不同浓度肉桂酸自毒作用和外源硅对黄瓜幼苗形态指标的影响，确定了黄瓜幼苗对肉桂酸自毒作用耐受的浓度阈值（0.8 mmol·L-1）和最佳外源硅缓解浓度（1.0 mmol·L-1），并从碳代谢、抗氧化酶系统、氮代谢、水分代谢、离子吸收和转录组学等层面，分析了外源硅缓解黄瓜幼苗自毒作用的生理和分子机制。在日光温室中进行连作试验，选取连作黄瓜8年的基质，研究不同浓度外源硅对黄瓜生长（株高、茎粗、叶片数、生物积累量、根系体积及主根长度）和生理（叶绿素含量、脯氨酸含量、丙二醛含量及抗氧化酶活性）的影响，确定了缓解黄瓜连作障碍的最适外源硅浓度（0.75 mmol·L-1），为克服黄瓜基质栽培的连作障碍提供一定的理论依据。发表研究论文29篇，其中SCI 13篇，会议论文4篇；培养博士研究生2名，硕士研究生2名，2名青年教师成为学术骨干。本项目的研究成果揭示了适宜浓度的外源硅缓解黄瓜幼苗自毒作用的机理，为克服设施黄瓜栽培的连作障碍奠定了理论基础，同时大田试验结果为设施黄瓜连作障碍的解决提供了新的解决思路，并为设施黄瓜高产优质栽培技术提供了保障。

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