A comparative study of seed germination traits of 52 species from Gurbantunggut Desert and its peripheral zone

In order to determine seed germination traits and its ecological significance of species,seed germination characteristics(germination percentages,day when germination began,germination periods and time required for half the final germination to be reached(d)) of 52 species from the Gurbantunggut Desert and its peripheral zone were studied. Seeds of 52 species were collected at the time of seed dispersal from wild populations at Gurbantunggut Desert in northwest China during 2007.Seeds of each species were harvested from more than 20 individuals chosen at random.The seeds were allowed to dry naturally.The seed lot were stored dry in paper bags(about 23 ℃;RH: 20%-40%) until the experiment began.For each species,four replicates of 50 seeds were placed on two layers of moist filter paper in 9 cm diameter Petri dishes and then placed in temperature-and light-controlled incubators.Seeds of each species were incubated alternating temperature regime of at 25 ℃ in light for 12 h and 10 ℃ in dark for 12 h.This temperature regime corresponds to the mean high and mean low temperatures,respectively,at the study site during the spring germination period.Light was provided by cool-white fluorescent bulbs(photosynthetic photon flux density of 30 μmol m-2 s-1) in 12 h intervals coinciding with the higher temperature period.Seed germination was monitored every 24 h for 30 days,and a seed was considered as germinated if the radicle was visible;germinated seeds were counted and then removed.Un-germinated seed were tested for viability before initiation of experiments as follows: seed viability was checked by cutting the seeds and dipping into 0.5% triphenyltetrazolium chloride(TTC) for 1 h.Pink embryos were considered to be viable. Results showed that germination percentages of 52 species displayed a bimodal distribution,and the germination percentage of most species was exceeding 80% and less than 20%;Day when germination began displayed a skewed toward short periods,37 species began to germinate within 1-3 days after the test began,while 2 species failed to germinate in a period of more than 10 days;Germination period showed different,for 10 species,their germination period was less than 10 days,while 14 species had a germination period of more than 22 days;For 17 species,the days required for half the final germination rate to be reached were 1-7d.Principal component analysis(PCA) and clustering analysis were used,and divided 52 species into four main germination patters: rapid,transition,slow and low,and low.Germination percentage of woody plants was significantly higher than that of non-woody plants,suggested that the high germination percentage of woody plants ensured them rapidly occupying space and resources to increase competitive advantage;non-woody plants,especially annuals plants,had relatively low germination percent,which was risk contribution strategy for plant survival.