Studies on the reproductive characteristics of annual bluegrass (Poa annua L.) —Regeneration from an immature panicle and a flag leaf node in annual bluegrass—

Abstract

In order to explain the various reproductive modes of annual bluegrass (Poa annua L.), regeneration from the panicles and the flag leaf nodes at the booting stage (BS), emerging stage (ES), flowering stage (FS) and ripening stage (RS) were evaluated for the putting green and the orchard populations. The results obtained from the present study were summarized as follows: In putting green populations, regeneration rate (the number of panicles in which at least one plant is generated/100 panicles×100 (%)) at FS and RS were high as much as more than 90%, but were very low at BS (2%) and ES (3%). In orchard populations, the regeneration rate was high at FS (78%) and RS (77%) as well as putting green populations, however, no plants were regenerated at BS and ES. On the other hand, regeneration from the flag leaf nodes were observed at only BS (1 plant with shoot and root) and ES (3 plants with root). These results suggest that 1) the seeds of both putting green and orchard populations exhibit early maturating characteristics and are not in dormancy as long as seeds attach to a panicle, 2) root and/or shoot were emerged from the flag leaf node at BS and/or ES with very low frequency, and 3) annual bluegrass is a gamethophytic apomixsis although it is unclear whether this characteristic is peculia to the putting green populations.