Dose-Dependent Effect of Salicylates in a Moss, Funaria hygrometrica

Plant growth regulators now include more than the classic examples auxin, cytokinin, ethylene, and gibberellin, but little is known about the activity of these additional classes of molecules in nonvascular plants. The formation of buds by protonema of the moss Funaria hygrometrica is perhaps the best known and most fully characterized developmental system in the nonvascular plants. Examination of the effects of exogenously supplied salicylic acid and acetylsalicylate on this bioassay system shows that salicylates can regulate growth and development in mosses, producing a dose-dependent inhibition of bud formation. Other experiments show that this action is distinct from any direct effect on the well-known cytokinin stimulation of bud formation, occurs late in the process of bud formation, occurs prior to the stable commitment of nascent buds, and is not an effect on the outgrowth of young shoots. Because mosses are the sister clade to the vascular plants, these results suggest that the ability to perceive and transduce salicylate signals is an ancient feature of land plant physiology.