The synaptonemal complex (SC) is the linear, tripartite structure that is believed to play a critical role in the orientation of homologous chromosomes during synapsis in prophase I. Over the past 25 years, a whole-mount spreading procedure has been used that allows for detailed examination of intact SCs. A follow-up to a study performed by Hansenkampf and colleagues (1984a,b, 1985) on Tradescantia ohiensis was recently performed using a modified SC spreading technique. The modified technique, which calls for desalted sulfatase enzyme in the bursting medium to break down the pollen mother cell walls, produced several nearly completely synapsed, whole pachytene spreads. The earlier studies had little success in obtaining pachytene SC spreads and mainly focused on spreads in zygotene in which synapsis was never complete. This current study demonstrates that synapsis in Tradescantia does progress nearly to completion. It agrees with the previous reports in that synapsis appears to initiate at the telomeres. Also, the average total SC length from the present study (109289.97 Ám) was comparable to the average obtained in the 1985 study (1246160.3 Ám). The current study also revealed for the first time, the "bouquet" arrangement of the pachytene SCs, which is often observed in cases where synapsis initiates at the telomeres, and has been reported for Rhoeo, another commelinaceous species.

Key words: chromosomes, cytogenetics, meiosis, synapsis, synaptonemal complex, Tradescantia