Study On The Allelopathic Substances And Their Mechanism Of Action In Two Plants With Allelopathic Effect

Allelopathic is widely present in agricultural production,as a kind of interspecific relationship between plants,allelopathic will affect the growth and development of crops and physiological and biochemical metabolism processes,bringing many problems to agricultural practice,such as self-toxicity,continuous cropping disorders,etc.,and the study of allelopathic is an effective way to solve these problems.Gossypium hirsutum and Hippophae rhamnoides are important economic crops in China,and play critical roles in national economy.In recent years,with the long-term and large-scale cultivation,the continuous cropping of Gossypium hirsutum and the premature aging of Hippophae rhamnoides are increasingly prominent,leading to reduced crop yield,quality,and serious economic losses,consequently hindering the stable and sustainable development of environment of agroecosystem.It is an effective way to ensure the sustainable development of Gossypium hirsutum and Hippophae rhamnoides production by elucidating the causes of continuous cropping obstacles and premature senescence and to find corresponding countermeasures.Previously studies have found that Gossypium hirsutum and Hippophae rhamnoides release allelopathic substances into the environment to produce allelopathic effects,which affect the growth and development of their own and other crops,and cause continuous cropping disorders and premature senescence.However,there is still a lack of systematic studies on allelopathic substances,and the mechanisms for functioning of allelopathic substances remain unknown.In this study,the root of Gossypium hirsutum and Hippophae rhamnoides were used as research materials.The allelopathic effects of allelopathic substances of several common model plants were studied by means of exogenous addition.The allelopathic mechanism of allelopathic substances was investigated by analyzing the effects of allelopathic substances on plant growth and development,chlorophyll content,root activity and enzyme activity.The above research provides scientific explanations for the obstacles of continuous cropping of Gossypium hirsutum and the premature senility of Hippophae rhamnoides,which has important theoretical significance and practical reference value for guiding the operation and management of continuous cropping,intercropping and agricultural complex ecosystem.The main results of this study are as follows:(1)Separation,identification and mechanism study of allelopathic substances in the root of Gossypium hirsutum:18 compounds were isolated and identified from Gossypium hirsutum through systematic separation,extraction and structure identification.Compounds 1-12 are semi-gossypol compounds,which are the main chemical components.Two of them were new structural compounds that had not been reported,and three compounds were isolated from Gossypium hirsutum for the first time.The allelopathic effects of four representative hemigossypol compounds were studied using wheat and lettuce as receptors.The results showed that these hemigossypol compounds had potent allelopathic activities,which could inhibit the seed gemination of wheat and lettuce,and inhibit the growth and development of above-ground and underground portion of plants.The structure-activity relationship showed that the presence of aldehyde group could improve the allelopathic activity of hemigossypol.The allelopathic mechanism study showed that semi-gossyphenol 6 could significantly reduce the relative content of chlorophyll and root activity in wheat.In addition,it also reduced the activity of superoxide dismutase(SOD)and increased the content of malondialdehyde(MDA),resulting in oxidative stress on plants and damage the membrane lipid structure of plant cells.(2)Isolation,identification and mechanism study of allelochemicals of Hippophae rhamnoides:14 compounds were isolated and identified from the root of Hippophae rhamnoides through systematic isolation,extraction and structural identification,among which 9 triterpenoids were the main chemical components;The allelopathic effects of three representative triterpenes were studied by using wheat and lettuce as receptors.The results showed that these triterpenes had good allelopathic activities,which could inhibit the seed germination of wheat and lettuce,and inhibited the growth and development of above-ground and underground parts of plants.Allelopathic mechanism studies showed that triterpenoid 1 could significantly reduce the relative content of chlorophyll and root activity in wheat.In addition,it can also reduce the activity of SOD and increase the content of MDA,resulting in oxidative stress on plants and damage the membrane lipid structure of plant cells.In conclusion,semi-gossypol substances in Gossypium hirsutum can produce allelopathic effects by affecting plant photosynthesis,nutrient element transport,water absorption and enzyme activity,thus inhibiting plant growth and development.Triterpenoids in Hippophae rhamnoides can inhibit the growth of recipient plants by affecting photosynthesis,nutrient element transport,water absorption and enzyme activity.It provides a reference for the study of the resource utilization of cotton and sea buckthorn and the allelopathic effect of other crops.