Abstract: The relationship between characteristics of genome size (ploidy, chromosome number, C-value and GS) and seed (1000-seed weight, oil content and protein content), which were searched from Plant C-value Database and Seed Mass Information Database, was analyzed by ANOVA and regression model for 282 species in Poaceae. The results showed that the C-value and 1000-seed weight changed from 0.35 to 19.7 pg and from 0.05 to 252 g, and the means were 4.14 pg and 7.1 g, respectively. With the ploidy increasing, the C-values increased significantly from diploid to octoploid, but the GS and mean DNA content of each chromosome decreased significantly from diploid to hexaploid (p<0.05). The C-value of Bromus and Festuca showed similar change as Poaceae, but GS did not decrease significantly. Linear correlation analysis showed that there were significantly positive correlations between C-value and ploidy, number of chromosome, GS and mean DNA content of each chromosome, but there were significantly negative correlations between GS and number of chromosome and ploidy (p<0.01). Regression analysis showed that there was significantly positive correlation between GS and 1000-seed weight (p<0.01), but there was almost no correlation between C-value and 1000-seed weight. There was significantly negative correlation between C-value and oil content of seeds, but no correlation between C-value and protein content. There was higher species in Poaceae increased their C-values primarily by ploidy doubling in the phylogeny and evolution history, but at the same time, the C-value was stopped to increase infinitely through reducing GS and mean DNA content. This study will give some reference to study the relationship between genome size evolution and plant phylogeny.

Key words: Poaceae, C-value, genome size, seed characteristic, evolution