Climate change leads to more extreme weather events, for example to more frequent and more intense periods of drought and heavy rainfall. The latter causes soil flooding that affects all ecosystems as well as agricultural land. Due to lower gas diffusion, plants have limited access to oxygen and carbon dioxide under water. Consequently, energy production by aerobic respiration and photosynthesis is lowered, leading to an energy crisis in plants. Several wild species have adapted to this stress by morphological and biochemical modifications, that will be summarized in this talk. One strategy of plants (“escape”) is to avoid oxygen deficiency within submerged plant parts by aerenchyma formation or shoot elongation. Another strategy (“quiescence”) is to slow down metabolism and growth until the flood is over.
Material and Methods
In one project, different grassland species were evaluated for aerenchyma formation and fermentation activity after waterlogging, i.e. with their root system in water. In a second project, different Brassicaceae were analyzed in respect to their responses to full submergence. Besides aerenchyma formation and fermentation activity, this second study also covered gene expression under stress conditions.
Results and conclusions
Waterlogging enhanced internal gas spaces within plant tissues of several, but not of all wetland species. Most species in our studies reduced their growth under complete submergence, and only a few species were able to show elongation growth of leaves or stems to reach the water surface for easier gas exchange. On the biochemical site, many plants also induced ethanolic fermentation under limited oxygen conditions. The type and intensity of the response was not necessarily predictable from the plant`s habitat. Rather, phylogenetic parameters might, at least in part, determine the ability to respond to flooding.