The Physical Defense Traits Of Leaves And Fatty Acid Of Seeds And Seedlings Of Lauraceae

The interaction between plants and herbivores has always been a hot topic in ecological research.With the continuous development of molecular systematics,new research directions for solving plant defense problems are proposed.Lauraceae is an ancient branch of angiosperms,and its phylogenetic relationship has been clearly studied so far.Therefore,it is an ideal group for studying the plant defense.The survival of seeds and seedlings is a key factor determining the structure of tropical forest communities.However,little is known about the defense strategies of plants in the two critical life history stages of seeds and seedlings in the existing studies.In this study,the defense traits of Lauraceae species at different stages were taken as the research object,and the leaf physical defense traits of 92 Lauraceae species at the mature stage in the common garden were used to explore the trend of Lauraceae plant leaves during the evolution process.The function of fatty acids in plants is not only to store nutrients,but also to defense.We investigated three Lauraceae species: Persea americana,Machilus chrysotricha and Machilus yunnanensis.The changes of fatty acid contents in different parts of three Lauraceae species at the seed stage,germination stage,hypocotyl stage and true leaf stage were studied to explore the trends of defense substances in plant seeds and seedlings.The main results of this study are as follows:(1)The physical defense traits of Lauraceae leaves were more affected by environment than phylogenetic factors during evolution.Phylogenetic signals were not detected for all function traits of leaves.(2)The evolutionary trend of the physical defense traits of Lauraceae plant leaves indicated that the plant leaves tended to evolve towards the smaller,softer and higher C content leaves in the evolution process.(3)The defense strategies of the seed coat and cotyledon of a plant are different.C16-18 fatty acids account for the majority of the components in the the seed coat and cotyledon of four species.C16:0 was the main component in the seed coat,while C18:2was the main component in the cotyledon.(4)The fatty acid content in most seeds of plants tended to decrease with time.This paper believes that there are trade-offs during the growth and development of plants,and the defense strategies of plants in different stages are different.