The Adaptive Strategies Of Xerophil Seeds Along A Moisture Gradient In North China

Although there is a large of arid or semi-arid area and abundant plant source in North China,the globle warm and environment change made so many xerophil species face to huge challenges of unfavorable environment,especially,water stress. Seeds have an important role that the only link from one year to the next also the terminal and start of the plant as an organ of reproduction.Thus,seeds adaptable ability under unfavorable conditions could directly influence population stability, population quantity,plant diversity and community structure.In previous study,the ability of plant resist-drought almost focuses on plant foot,corm and leaf,except seed, especially,large number kinds of plant species is not report.For this reason,we investigate the physiology and morphology's characteristics of different seeds which distributed in different regions in northern China under different water condition,to find out the important mechanism and strategies of adapted environment to protect population stability andplant diversity.First of all,we tested the germination and water uptake rate of 47 species typical xerophil seeds grow up in north China from 20 families,38 genuses under sufficient water and different Grads water stress by high-molecular-weight polyethylene glycol(PEG6000).The results show that Xerophil seeds from the same habitat exhibited similar patterns in response to water stress.Xerophil seeds from arid community were stronger in germination and imbibition than that from other two communities under serious water stress,whereas Xerophil seeds from humid community were sensitive to any degree of water stress.Namely,the seeds live in arid habitat possessed high germination and quickly water uptake in sufficient water or any degree of water stress,but the others grow up in humid habitat shown significant difference which germination and water uptake well under sufficient water but inhibited even if slight water stress.Secondly,we use the SEM photography of 47 xerophil seeds and combine with the data about rainfall of last 20 years in China to conclude that community-specific morphological traits displaying by seed coats were consistent with the pattern of water availability in different habitat.Arid(annual rainfall<200mm) species displayed complex and rough seed coats,while humid (annual rainfall>600mm) species exhibited simple and glossy seed coats.In contrast,semi-arid species showed transitive morphology of seed coats between arid and humid species.Thirdly,the elements of arid seed coats have high Ca,while the humid seed coats have high K.In our research,we study the differences of seeds physiology and morphology and conclude that seed live in hungriness shown short period of imbibitions,strong ability of germination and complicated seed coat,contrarily this,seed live in humid region shown long period of imbibitions,weak ability of germination and simple seed coat.We can sum up this phenomenon is "the convergence in same habitat and difference in different habitats",mean that selectivity between environment and seeds, and the different of seed adaptive ability to environment.Our result shown that seeds live in same water condition has similar traits on physiology and morphology; different traits appeared among different rainfall region;but all seeds have adaptive traits in each habitat.Namely,in the long process of phylogeny,seeds ensure its development and production by migrated to more suitable moisture or developed superior traits to adapt environment,when the environment has changed.This is the general adaptive strategies to different water condition.Additionally,we specially tested seeds antioxidant enzyme and protein of Hedysarum scoparium under drought stress or recover condition,and the Peganum harmala characteristics of seed traits and communities distribution to find out the mechanism of resist-drought.Our research on seeds adaptive strategies to different water condition will supply a new thought and role to study the selectivity and adaption of seeds to other environments(i.e.temperature,light,soil).Also,it's an important supplement to research of plant adaptive strategies to environment.