Responses to submergence and recovery in seedlings of the rheophyte Dyckia brevifolia (Bromeliaceae)

Complete submergence refers to the situation when floodwaters rise to levels where plants’ shoots and roots are entirely underwater. It can be viewed as a sequence of distinct stressors comprising submergence and de-submergence periods. A plant’s tolerance to this abiotic stress is determined by its ability to acclimate to both phases. Here we aimed to characterize the response of Dyckia brevifolia seedlings, a bromeliad native to Brazil, to submergence and de-submergence periods in short- and long-term stress time frames in terms of morphology, biochemistry, and gene expression. We demonstrated that D. brevifolia seedlings are tolerant to complete submergence, at least over the course of the time frame evaluated. All seedlings survived 30 d completely submerged, despite reduced dry weight and rosette area (as compared with control plants). This species adopts the low oxygen quiescence syndrome (LOQS) strategy, which comprises decreased shoot elongation underwater, downregulation of energy consumption processes, and carbohydrate catabolism (mainly starch) during the period of stress. In addition, chlorophyll and carotenoid contents were preserved, even after 1 month underwater. Furthermore, in D. brevifolia rosettes, the relative expression of hypoxia marker genes, such as alanine aminotransferase (AlaAT), pyruvate decarboxylase (PDC), and alcohol dehydrogenase (ADH), remained unchanged over the entire course of the short-term submergence stress (10 d). Mainly due to both ascorbate peroxidase (APX) and catalase (CAT) activities, this species also demonstrated an efficient reactive oxygen species (ROS)-detoxifying system, primarily for hydrogen peroxide (H2O2), when completely submerged. During the recovery period, in addition to maintaining rosette turgidity, D. brevifolia seedlings demonstrated fast-growth resumption, total soluble sugar recovery, accumulation of chlorophyll and carotenoid, and ROS scavenging. The combination of these responses contributes to the robust adaptation of D. brevifolia to the challenging recurrent fluctuations within its unique environment.