WHEAT KERNEL DORMANCY AND PLUS-ABSCISIC-ACID LEVEL FOLLOWING EXPOSURETO FLURIDONE

Detached spikes from soft white winter wheat (Triticum aestivum L.) cu ltivars that produce caryopses with high dormancy levels (Brevor) or l ow dormancy levels (Greer) were cultured from anthesis in basal media and media amended with fluridone or fluridone plus ABA. Effects of flu ridone and exogenous ABA on kernel development and dormancy acquisitio n and maintenance were assessed by measuring fresh and dry mass of emb ryos and caryopses, ABA content in embryos and caryopses, and kernel p ost-desiccation dormancy levels. Caryopses and embryos exposed to flur idone accumulated very little ABA. Detached spike culture increased AB A concentration and reduced fresh and dry mass in both caryopses and e mbryos. Fluridone did not affect fresh and dry mass. Addition of ABA t o culture media slightly reduced media uptake by detached spikes. Duri ng desiccation, ABA and dry matter decreased in caryopses whereas embr yos continued to accumulate both. After 2 d, 95 % of Greer kernels exp osed to fluridone germinated while only 80 % of Brevor kernels were ge rminated after 4 d. Culture of detached spikes in media amended with f luridone and ABA induced higher dormancy levels in Brevor than in Gree r. Results from this study support the hypothesis that ABA may be invo lved in acquisition of dormancy as well as maintenance of dormancy in wheat kernels.