Allelopathy Effect Of Corn Straw Decomposed Liquid And Isolation And Identification Of Typical Allelochemicals

China is the largest country of renewable energy material output in the world,producing700million ton straw every year.Heilongjiang Province is an important strategic base of grain security in China and playing an important role in protecting our country grain security. As to allelopathic effects after straw returning in Heilongjiang Province,our countries have carried out research on the subject.In North China,corn straws returning largely year by year have shown significantly effect on the growth and development of wheat and soil ecosystems under the cropping system of wheat-corn double cropping.In the farmland ecosystem of Heilongjiang Province,it is unclear that whether corn long-term cropping generating autotoxic effects or existing positive effects.This paper explores the impact of different time decomposing corn straw decomposition liquid on corn seed germination and seedling growth and development,to determine allelopathic effects of corn straw returning,identifying allelochemicals,aiming to reveal the response mechanism of corn straw returning, in order to improve the theory and technology of corn straw returning,optimizing the use of straw,avoiding negative effects of straw returning and providing a theoretical basis for optimizing cultivation system,.This paper regarded corn as the research object, on the basis of previous research, setting several different corn straw decomposition time(0,60,120,180,240,300,360d), after the extracting decomposed liquid, setting into five concentration (0.5,0.25,0.125,0.0625,0.03125gDW/ml), with water as controls, researching the effect on seed germination, and using potted ways to explore the effect on corn seedling growth and development. By measuring germination index, seedling agronomic traits, chlorophyll fluorescence parameters, protective enzyme activity, MDA content and endogenous hormone contents in leaves, combining the LC-MS analysis of allelopathic ingredients in decomposing liquid, forming the main results as follows:Straw decomposed liquid affects seed germination.Under the same decomposing days, compared with the control, with the increasing of decomposing liquid concentration, seed germination decreased, germination time delay, radicle and hypocotyl growth was inhibited.showing a certain degree of concentration effect, the lowest rate of seed germination is under the treatment of0.5gDW/ml.Under the same concentration, as decomposing prolonged germination reduced first and then rise, in the treatment of60d decomposing liquid, seed germination is the lowest, by inhibitory effect the most obvious, with the extension of decomposing time, the inhibitory effect reduced.Straw decomposed liquid affect the growth of corn seedlings.After watering decomposed liquids, with growth stage propulsion, all treatment plant height, leaf area, plant fresh and dry weight increased with decomposing concentration decreases, all indicators under60d decomposed liquids of0.5gDW/ml concentrations treatment is the lowest.Under the same concentration, with the increase of decomposing days, the indicators shown trend of reduced firstly and then increased. Under60d decomposing liquid treatment, all indicators is the lowest, then gradually increased.Indicates that short-term decomposing have adverse effect on seedling growth, with the extension of decomposing time, this negative effect started to diminish or disappear.Straw decomposed liquid affect leaf physiological, chlorophyll content, fluorescence parameters, some enzymatic activity, metabolic and balance of hormones in leaves.This study shows that a shorter time decomposed straw decomposing liquid, can cause chlorophyll content and Fv/Fm decreased, Fo increased, thereby weakening the photosynthetic capacity, and also generated stress, to make SOD and POD activity decreased, MDA content increased, affecting membrane osmotic adjustment. Furthermore decomposing liquid will result in the plant endogenous hormones metabolic disordered, leading to IAA、GA、ZR accumulated in a great amount, affecting normal hormone balance, suppressed plant growth, and also generated a lot of ABA, accelerating plant senescence.Decomposition in the soil after the straw returning is an extremely complex process, the effect on succeeding crop growth and development of allelopathy chemical generated after decomposed is resulted by interaction of a variety of allelopathy chemicals.Currently about the action mechanism of allelopathy chemicals to succeeding crop is unclear, and it is urgent to discover the molecular mechanism.