The Pattern And Mechanism Of Within-inflorescence Resource Allocation In Sagittaria Trifolia

In anthesis,flowering plants often show a downward trend of resource allocation within inflorescence to floral organs,fruits,and seeds.Many studies suggest that this downward trend is caused by architectural effects due to the inherent structure,which results in differential resource acquisition by flowers of different position.Specifically,the flowers that are closer to plants' storage organs have more opportunities to acquire even truncate resource and therefore guarantee fully development of fruits and seeds.In contrary,other studies suggest that the uneven resource allocation within an inflorescence may be caused by changes in the mating environment.Plants are selected to put more resource to the fruit that have more outcross matings,in order to produce higher quality seeds,thereby forming a disproportionate investment in achieving optimal resource allocation.I refer this hypothesis to intra-inflorescence resource competition here after.In this thesis,I chose Sagittaria trifolia as the research material,mainly discussed the seed quantity and quality of sequential(base to top)fruit in the inflorescence of Sagittaria trifola.I subsequently use micro-satellite makers to estimate the outcrossing rate of the sequential(base to top)fruits in the inflorescences of Sagittaria trifolia,in order to explore the mechanism of resource competition.The results showed that the sequential fruits within-inflorescences of Sagittaria trifolia have a decreasing trend in both seed quantity and quality.Seed quality was evaluated by germination rate,which of main branches was 6.79%,and the lateral branch 3.50%,suggesting an intra-inflorescence decrease of resource allocation in Sagittaria trifolia.In order to estimate outcrossing rate,I screened out 3 microsatellite loci with high polymorphism,and the number of alleles at each locus were 5,6,and 6 combining multiple populations.I have also compared two alternative methodologies in analyzing PCR products,namely polyacrylamide gel electrophoresis imaging and quantitative fluorescence.After consider the accuracy,cost,manpower and time collectively,I recommended that when the sample size is large,quantitative fluorescence should be used.With the application of recommended methodology,I estimated the outcrossing rate of sequential fruits within-inflorescences of Sagittaria trifolia,Combining two years of data,the outcrossing rate of main branches was 80.48%and the lateral branches 85.95%,resulting in no significant difference.My study revealed that the intra-inflorescence downward trend of seed quantity and quality observed in Sagittaria trifolia was not supported by differential outcrossing rate.Therefore,the pattern of intra-inflorescence resource allocation in this system may be explained by architectural effects rather than resource competition.