Dispersal Ability And Strategy Of Wind Dispersal Seeds

Seed dispersal not only has the significance of developing new habitat for species,but also has the advantage of being far away from the parent plant and reducing the intraspecific competition.The dispersal of seeds affect most of the ecological process and the process of evolution,so people hope to quantify seed propagation distance and grasp the rules of seed dispersal,to provide a theoretical basis for in-depth understanding of the seed propagation mechanism and weed invasion control.Nine species of weeds were selected to study seed morphological structure(pappus length or pilose length,achene length or caryopsis length,seeds' weight,the ratio of pappus or pilose and fruits' weight,the number of pappus or pilose,the number of thorns on pappus)and the dispersal potential ability(settlement velocity,secondary dispersal distance).We also research the correlation between seed morphological structure and dispersal potential ability.Based on the local characterization of seeds and their habitats,their dispersal strategy was summarized.The main conclusions are as follows:(1)The pappus of Compositae seed have bigger diameters and bend angles.There are thorns on the pappus and achenes.The pilose of Gramineae seed spread divergently and have better flexibility.(2)The falling speed was significantly negatively correlated the horizontal dispersal distance within the nine species of weed seeds.(3)The falling speed of the seeds in Compositae family was significantly positively affected by both achene length and pappus length,while the falling speed of the seeds in Gramineae family was significantly negatively affected by caryopsis length and pilose length.The horizontal dispersal distance of the seeds in Compositae family was significantly negatively affected by both achene length and pappus length,while the horizontal dispersal distance of the seeds in Gramineae family was significantly positively affected by caryopsis length and pilose length.This result suggests that the morphological structure of the seeds affect dispersal potential ability both the Compositae seeds and the Gramineae seeds.The opposite ways of two family seeds indicate that seeds of Compositae adjusts to a dry habitat.The seeds fall rapidly to land with their achenes,and may geminate near their mother plants.The seeds of Gramineae have slow falling speed with their spherical pilose.These seeds can roll on the dry ground or fly again by wind to another place..Our research is helpful to understand the mechanism of seed dispersal mechanism and weed control and management.(4)There is no correlation between the dispersal ability and the proportion of pappus or pilose biomass.The dispersal ability is associated with the load of the pappus or pilose.(5)The settlement velocities and the sixth roots of seeds' weight of the nine species of weed seeds or four species of Compositae seeds have the linear positive correlation,which partially suit the model of Greene&Johnson V ? m1/6.There was no linear correlation between the settlement velocities and the sixth roots of seeds'weight of five species of Gramineae seeds,which is totally unsuited to the relation.It is possible that the interspecific structures of the Gramineae seeds are very different,and the model is too simple to describe the relationship between the settlement velocity and the structure.