Submergence is a severe stress for most plants. Striker et al. assess tolerances of partial and full submergence for fifteen accessions of Melilotus siculus (Fabaceae). Traits differing among accessions and associated with tolerance were leaflet gas film thickness upon submergence, gas-filled spaces in petioles and aerenchymatous phellem near the base of the main root.
All accessions re-orientated petioles towards the vertical in both submergence treatments. Petiole extension rates were maintained during partial submergence, but decreased during full submergence. Leaflet sugars accumulated during partial submergence, but were depleted during full submergence. The ability to retain green leaves was essential for recovery following de-submergence.