The Ecological Significance of Adventitious Rooting as a Response to Flooding in Woody Species, with Special Reference to Alnus glutinosa (L.) Gaertn.

Abstract

The formation of adventitious roots on stems as a flooding response tends to be characteristic of woody species native to periodically flooded habitats and is therefore often seen as an adaptation conferring flooding tolerance, although experimental evidence for this is lacking. Physiol gical processes mediating between stimulus and response are summarised and some pathways suggested whereby these roots could have such a mitigating effect. A series of experiments on Alnus glutinosa seedlings showed that flooding adversely affected leaf number, leaf water potential, shoot growth and lateral shoot number. However excision of adventitious roots during flooding affected only leaf number and then only marginally. More root primordia were stimulated as a result of excision. The main conclusion drawn is that a flooding tolerant species such as Alnus glutinosa seemingly has many adaptations of which adventitious rooting is but one. Under the conditions and time scale of these experiments, the roots seemed to confer only a slight advantage.