Seed size variation and its relationship to germination for familiar species of Gramineae on the eastern Qinghai-Tibet Plateau

Gramineous plants distribute widely on Qinghai-Tibet Plateau.47 gramineous species in this area were chosen and the variation of the seed size was observed.After germination experiment in a plant growth chamber,the effect of seed size on the germination characteristics of gramineous plants under two different temperature regimes without light was studied.The result demonstrated that: the weight of alpine meadow gramineous plant seeds varied from 0.006 9 g to 1.436 3 g,their average weight was 0.1921g and the weight variation nearly reached 103.60% of the seeds within a weight range of 0.006 9～0.148 9 g.After cluster analysis on seed size,28 species were clustered into group 1(0.006 9～0.148 9 g),which illuminated that small seeds gramineous plants possessed the absolute superiority in alpine meadow.Under the temperature variation(12 h 10 ℃/12 h 20 ℃),the seed size showed positive correlation with germination ratio and index,whereas negatively correlated with beginning germination time.All these phenomena demonstrated that for alpine meadow gramineous plants the smaller the seed size was,the faster and earlier its seeds germinated,but also the lower the germination rate was(vice verse).The experiment results demonstrated that the seed size of gramineous plants had significant meaning to their germination characteristics to some extent.