Most crops are sensitive to excess water, and consequently floods have detrimental effects on crop yields worldwide. In addition, global climate change is expected to regionally increase the number of floods within decades, urging for more flood-tolerant crop cultivars to be released. The aim of this thesis was to assess mechanisms conferring rice (Oryza sativa) and wheat (Triticum aestivum) flood tolerance, focusing on the role of leaf gas films during plant submergence.
Reviewing the literature showed that wheat germplasm holds genetic variation towards waterlogging (soil flooding), and highlighted traits such as improved internal aeration of the root system and short term anoxia tolerance of seminal roots as conferring tolerance. However, further work on especially anoxia tolerance and genotype × environment interactions is required in order to explore the available genetic resources. Experimental work assessed the physiologic, metabolomic and genetic response of wheat subjected to complete submergence, documenting contrasting submergence tolerance between two cultivars. While both cultivars displayed similar leaf gas film retention times and carbohydrate consumption rates, results indicated that the contrasting submergence tolerance could rather be governed by tolerance to radical oxygen species or contrasting metabolic responses (other than carbohydrate consumption) to ethylene accumulation. Manipulating leaf gas film presence affected wheat and rice submergence tolerance such as plant growth and survival. However, leaf gas film retention times did not differ between 14 winter wheat cultivars, and leaf gas films did not prevent significant leaf Na+ and Clintrusion, and K+ loss, during rice submergence in saline water. Due to the significant salt intrusion and low genetic variation in wheat gas film retention times, a future prominent role of leaf gas films in improving (i) wheat submergence and (ii) rice salinity tolerance was not generally supported.