Flood tolerance of wetland and dryland crops

Vast area of arable land is each year flood resulting in loss of yield. Rice, being a wetland plan, tolerates flooding to some extend whereas wheat shows little tolerance to waterlogged soils. We have recently worked extensively with submergence tolerance of both rice and wheat and we have shown that both species possess superhydrophobic leaf cuticles that enhance gas exchange with the flood water when completely submerged.  See recent examples of research in flood tolerance of dryland crops or flood tolerance of rice, and also the list of publications

Flooding of winter wheat during in Denmark.  The seedlings are frozen into ice and frost crystals have formed on the leaves. Apparently, winter floods are less disastrous than summer floods due to the low metabolism at low temperature.

Oryza longistaminata is a giant rice species from Africa. As opposed to other species of rice, O. longistaminata forms rhizomes and can spread quickly by vegetative reproduction.

Like other species of rice, Oryza longistaminata also possesses superhydrophobic leaf cuticles, which retain a thin leaf gas film during submergence. On the photo, the leaf gas film is seen a silvery sheen underneath the big water droplet.

Rice and wheat both possess superhydrophobic leaf cuticles that retain a thin gas film when submerged. The leaf gas films greatly enhance exchange of CO2 and O2 with the floodwater during the day increasing underwater net photosynthesis. During darkness, the leaf gas films enhance O2 uptake from the floodwater and thereby sustain aerobic respiration.

We have recently identified a gene, 
Leaf Gas Film 1 (LGF1) that codes for a C30 alcohol, which is a wax precursor. Mutation in this gene can lead to total loss of hydrophobicity and hence the mutant is a perfect tool in the eco-physiological study of the role of leaf gas films as flood tolerance trait.

Leaf gas films are found in numerous plant species and the feature is not restricted to flood-exposed habitats. Superhydrophobic cuticles is an important trait resulting not only in gas film retention during flooding but also self cleansing in rain so that the leaf surface remains free from dust and pathogens resulting in longer leaf life spans.

Although we have published more than 15 peer-reviewed papers over the past 10 year, we do not yet fully understand the regulation of leaf gas films, the importance for flood tolerance and survival - and most all, why the leaf gas film disappear over time. In all plants test so far, the hydrophobicity is lost with time of submergence and so the trait is not considered important for tolerance to longer term submergence but rather to floods that come and go such as in the tidal zone.