Effects Of Nutriment Transfer In Cotyledon On Seed Dispersal And Seedling Establishment

Many plants rely on rodents to disperse the seeds,germinate and build seedlings in suitable environments to achieve population regeneration.However,the interaction between rodents and the plants is often complicated,on the one hand,plants rely on rodents to disperse the seeds;on the other hand,they need to protect rodents from over-predation.In order to adapt to the fierce external environment,there evolved many germination phenotypes among different plant species: some plant seeds exhibit no dormancy and germinate immediately at or even before seed fall,and some plant seeds germinate undergo a period of dormancy.Seed germination means the change of nutritional resources in the seed,so the germination trait of seeds is also one critical factor influencing dispersal and establishment of seeds.In this study,we conducted germination experiment,regermination experiment after cotyledon removal,seed release and bury experiment in the field and enclosures of Quercus variabilis,Q.acutissima,Q.serrate and Cyclobalanopsis glauca seeds with different germination traits,to test the effects of seeds germination trait on seed dispersion and seedling establishment.The main results are as follows:1.The seeds of Q.variabilis and Q.serrate germinated in autumn,rapidly producing robust taproots,and the seeds of Q.acutissima and C.glauca dormant.During the germination of Q.variabilis and Q.serrate seeds,nutrition transfer from cotyledon to the robust taproot rapidly,and cotyledon dry mass of both seeds decreased by more than 45% within 55 days after planting.2.In the enclosures,with the exception of N.confucianus,the other the four sympatric rodents preferred to eat acorns of Q.variabilis and Q.serrate rather than those of Q.acutissima and C.glauca;larderhoarding N.fulvescens and N.confucianus preferred to larder-hoard Q.variabilis and Q.serrate nuts;whereas scatterhoarding L.edwardsi,A.draco and A.chevrieri tended to scatter-hoard Q.acutissima and C.glauca nuts.This indicates that sympatric rodents have different selection preferences for seeds with different germination traits.3.In the field,the dispersal speed of Q.variabilis seeds with non-dormant trait more slowly than dormant Q.acutissima,but the dispersal speed of Q.serrate seeds with non-dormant trait faster than dormant C.glauca.Seeds germination traits have no significant effect on rate of hoard and eat after seed dispersal.The rate of seedlings of Q.variabilis and Q.serrate with non-dormant trait is higher than that of dormant Q.acutissima and C.glauca seeds.4.We investigated the seedling differences of germination traits seeds under the similar predation pressure in the seeds burial test.The results showed that the seedling rate of non-dormant Q.variabilis and Q.serrate seeds was significantly higher than that of dormant Q.acutissima and C.glauca seeds.5.Under artificial cotyledon removal,the seedling rate of non-dormant Q.variabilis and Q.serrate are higher than those of Q.acutissima and C.glauca,but there is no different in seed vigor.This indicated that seedlings of non-dormant have survival advantages without the nutritional support of cotyledons when the epicotyl was more than 1 cm in height.6.Therefore,non-dormant seeds transfer the nutrition into the taproot rapidly,and have a seedling advantage after seed dispersion,which is more conducive to population regeneration.