Responses Of Seed Storage Substances,Germination And Seedlings Of 7 Dominant Gramineous Plants In Alpine Meadow To Grassland N And P Addition

As the essential element in plant growth process,C,N and P elements has been the hot issues of ecology research,which involved their variation among different levels(individual,population,community)or different functional groups,and influenced by environmental conditions.However,most of these studies have focused on C,N and P allocation of plant roots,stems and leaves,and few have studied the variation of C,N,and P contents in wild plant seeds and their relationship with environmental conditions.In this study,the mature seeds of seven common gramineae species(Poa poophagorum,Poa pachyantha,Deschampsia caespitosa,Agrostis hugoniana,Agrostis trinii,Roegneria nutans,Elymus nutans)from fertilization experiment grassland(nitrogen,phosphorus,nitrogen and phosphorus mixed)in the eastern Qinghai-Tibet Plateau were used to analyze whether the content of seed C,N,P were affected by soil nutrient addition,and whether the germination rate of seeds after six months of storage under room temperature and the morphological parameters of their offspring(plant height,root length,leaf area,biomass,root-shoot ratio,specific leaf area)were influenced by seeds C,N,P variation.This study would provide a theoretical basis for further exploring the response of common plants to environmental changes in alpine meadows,and data reference for the domestication and variety breeding of wild forage.The main results showed that :(1)Plants in fertilized grassland,the seed mass of Agrostis hugoniana and Agrostis trinii decreased significantly;the seed mass of Poa poophagorum,Poa pachyantha and Roegneria nutans increased,especially in nitrogen and phosphorus mixed application plots;Seed mass of Elymus nutans and Deschampsia caespitosa increased only in nitrogen and phosphorus mixed application plots.(2)When N fertilizer was only applied,seeds of Poa poophagorum and Elymus nutans have higher P content and lower C content when higher N is added(N15),the other five plants are all had a higher C,N,P content under control or low N(N5)grassland.(3)When P fertilizer was only applied,there was no uniform trend in the change of C content in seeds,and in the medium and high phosphorus levels(P4,P8),seeds of Poa poophagorum and Poa pachyantha had higher N content,there was no significant difference in the N content of the seeds of Agrostis hugoniana,the other four species had higher N content in the control group.Except for the Elymus nutans,which had the higher seeds P content at the control group,seeds P contents of the other six species were all increased after phosphorus fertilize applied.(4)In N and P mixed fertilized fields,seeds C contens of Poa poophagorum,Agrostis trinii and Roegneria nutans were decreased,while the content of C in other four species was not significantly different.Except that there was no significant difference in P content of the seeds of Poa pachyantha and Agrostis hugoniana under the mixed fertilized grassland of nitrogen and phosphorus,the seeds N and P contents increased,especially from the NP8 plots.(5)From nitrogen applied grassland,the seeds of 7 species all had higher N:P ratios.From phosphorus applied area,it has a larger ratio of C:N.The ratios of C,N and P contents in seeds of all species were in medium level when nitrogen and phosphorus were mixed ferlized.(6)Except that there was no significant difference in seed germination rate of Deschampsia caespitosa,the seeds germination rate of plants from fertilized plots was higher.Among them,the seeds germination rate of Poa pachyantha and Agrostis trinii was the highest,and the seed germination rate of the other four species was the highest in the nitrogen and phosphorus mixed applied grassland.(7)The seed germination ability and seedling growth ability of the 7species are not always limited by the total storage content of seeds.With the increase of seed size,the seed germination rate of Poa poophagorum increased significantly,the root-shoot ratios of Poa pachyantha seedlings increased significantly,the seed germination rate of Agrostis trinii decreased significantly,however the height and biomass of seelding increased significantly.The root length and biomass of Elymus nutans decreased significantly.There was no significant relationship between thegrowth indexes and seed size of Deschampsia caespitosa,Agrostis hugoniana and Roegneria nutans.Although seven species did not show a consistent correlation between seed storage substances and seedling growth-related indicators,but the seedling growth of each species was more or less affected by the differences in the content of seed storage substances,especially N,P contents.(8)Most of the progeny seedlings of Roegneria nutans and Elymus nutans were not significantly different.Fertilization had more or less positive effects on the seed size,germination and growth of progeny seedlings of the other five species.In this study,starting from plant seeds and the growth status of progeny seedlings,With the participation of phosphate fertilizer,it is more helpful for these 7 gramineae species to exhibit excellent seed characteristics.Therefore,it is recommended that in the process of selection of gramineae species in the future,it is better to supplement N and P fertilizers at the same time.