Keeping the shoot above water – underwater stem elongation in watercress (Nasturtium officinale)

Flooding stress is a major environmental threat for many terrestrial plants. The detrimental effects of flooding stress, however, vary between different plant species. Whereas many crops are rather sensitive to flooding, some wild species from flood-prone areas are well adapted to excess water conditions. Morphological adaptations like adventitious roots and aerenchyma formation, or the ability to elongate rapidly the above-ground organs, allow these plants to thrive in water. The focus of this research is Nasturtium officinale, also known as watercress, which is an auto-tetraploid, dicotyledonous and stem-growing Brassicaceae species. Its natural habitat is near rivers and streams, but absent from stagnant water. Submergence induces underwater elongation of stems and growth suppression of petioles in Nasturtium officinale. By using the RNA sequencing technique, we aimed to uncover the underlying mechanisms for these contrasting responses. Combining submergence experiments with hormone manipulations revealed that ABA degradation is required for stem elongation. Overall design: One species (Nasturtium officinale) x two tissues (stem, petiole) x two treatments (air, submergence) x two timepoints (1 day, 2 days)