Response Of Seed Storage Content To Soil N And P Addition And Its Effect On Early Growth Of Plants

Seed germination and early seedling are the most fragile and critical stages in the life cycle of plants.During the period from seed imbibition to radicle breaking through the testa and germ protruding from the ground,a series of orderly physiological and biochemical reactions and morphological changes will take place.The substances and energy required for this process all come from the nutrients stored in the seeds.Although many studies have paid attention to the responses of seed storage contents to environmental conditions and their effects on germination and early growth of seedlings,most of them regard seed storage contents as a whole(measured by seed size).Little attention was focused on the variation in seed storage components and its effect on the early life history stages of plants.Different storage contents play different roles in seed germination and early seedling growth,and their compositional differences may lead plants to adopt different seed germination and seedling growth strategies,which in turn affect subsequent population regeneration and community construction.Comparing and studying the differences,variation laws of seed storage composition among different species and their effects on the early stages of plant life history can provide a deep understanding of plant evolutionary pathways and adaptive mechanisms,and promote the development of seed ecology,it will also provide a theoretical basis for the construction of community.The content of stored substances in seeds is affected by various environmental conditions(such as temperature,drought,precipitation,shading,soil nutrients,etc.).Among the environmental factors,the soil,which is the substrate for plant growth and development,provides plants with necessary mineral elements and water,which directly affects the growth and reproduction of plants.Therefore,in this study,seven typical wild grass(Elymus nutans,Roegneria nutans,Poa poiphagorum,Poa pachyantha,Agrostis hugoniana,Agrostis vinealis and Deschampsia cespitosa)seeds from the long-term nitrogen and phosphorus addition sample of alpine meadow on the northeastern edge of the Qinghai-Tibet Plateau were used to test the variation in seed several storage contents of plants from different nitrogen and phosphorus addition grassland,its role to the seed germinability and seedling early growth by seed depletion,through determination of seed storage contents,germination experiments and monitoring seedling growth.The main findings are as follows:(1)The contents of different storages in the seeds varied among species from grassland with different nutrient addition.Overall,there were significant inter-species differences in seed size,seed soluble carbohydrate,soluble protein,starch and lipid content of the seven species.When the parental plants growed in grassland with nutrient addition,the soluble protein content in seeds of the seven species increased;the starch content of Agrostis vinealis and Deschampsia cespitosa decreased significantly while it increased significantly in two Poa annua L seeds,the starch content of other species did not change significantly under nutrient addition;the seed lipid content increased significantly in Poa poiphagorum,Poa pachyantha and Elymus nutans under nutrients addition but it was decreased in Roegneria nutans and Agrostis vinealis,the changes of the lipid content in the seeds of Agrostis hugoniana and Deschampsia cespitosa were not consistent under the addition of different parental nutrients;in addition,the seed size of Elymus nutans,Poa poiphagorum and Deschampsia cespitosa was significantly increased by the addition of parental nutrients while there was no significant change in Roegneria nutans,Poa pachyantha and Agrostis hugoniana.(2)When the parental plants growed in grassland with nutrient addition,seed germination percentage and germination rate of seven species were increased significantly,while the germination start time was significantly shortened.GP was significantly negatively correlated with the lipid content of seeds,but was always positively correlated with the contents of soluble carbohydrates and soluble protein;GR was significantly negatively correlated with the lipid content too,and significantly positively correlated with the other stored substances and seed size.Seeds with higher lipid content germinated later,while seeds with higher soluble carbohydrates,soluble protein and starch germinated earlier.(3)The relative growth rate and absolute growth rate of the progeny seedlings of the other six species showed significant differences among groups in the early growth stage except Agrostis hugoniana.Partial correlation analysis showed that the relative growth rate(RGR)of seedlings had no significant correlation with seed size,lipid and starch content,but had a weak negative correlation with soluble carbohydrate and soluble protein content;the absolute growth rate(AGR)of seedling growth was always positively correlated with seed soluble carbohydrate,soluble protein and starch content and seed size,while there was a weak negative correlation with seed lipid content.Here,the results showed that as an environmental factor of seed development,soil N and P addition affected seed size and contents of various storage content,which varied with species and fertilization type.Meanwhile,seeds with higher contents of soluble protein,soluble carbohydrate and starch germinated earlier and faster.The seeds with high fat content germinated later and had lower germination rate.In the process of seedling growth,the absolute biomass accumulation rate of seedling growth was significantly positively correlated with soluble carbohydrate,soluble protein and starch content of seeds,but was weakly negatively correlated with fat content before Before the seedlings are fully leafed.This study revealed the effects of seed storage variation on seedling growth of seven wild grassland plants from different parental nutrient additions,which provided a theoretical basis for studying the performance of plant life history strategy in the whole regeneration under different ecological environment.