Plants and flooding stress

Floods early this year in Queensland, Australia, received a great deal of attention in the media because they affected a land area the size of Germany and France combined. However, on a world scale this is not exceptional as in some years the land area exposed to flooding is > 17 million km, equal to twice the size of the USA. These dramatic floods occur in all continents of our planet and result in annual damage costs of > $80 billion (http://floodobservatory. colorado.edu/). Many wild plant species and nearly all crops are intolerant to these floods and thus excessive water will affect the natural patterns of plant distribution and biodiversity (Silvertown et al., 1999) and have a devastating impact on crop growth and survival and thus on food production (Normile, 2008). Flooding is a compound stress composed of interacting changes inside plant cells induced by the flood water surrounding the plant. The concentrations of oxygen (O2), CO2, reactive oxygen species (ROS) and ethylene change upon flooding and can occur in various combinations, as determined by the flooding regime.