Browsing by Author "Hofman, Jan Dirk"
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- Compared physiological performances of Caulerpa prolifera and native seagrasses of Ria FormosaPublication . Hofman, Jan Dirk; Barrote, Isabel; Silva, JoãoSeagrasses are among the most important and also mostly threatened ecosystems in the marine environment. Seagrass loss can occur in their competition with other macrophytes, like invasive macroalgae. These pose a serious threat and present numerous consequences to their new environment. Among those that can affect seagrasses, Caulerpa sp. are one of the most recognized genus. Different mechanisms can grant them a competitive advantage over seagrasses, resulting in partial or even complete replacement. Therefore, knowing how Caulerpa sp. functions and interacts with a new environment is crucial, especially in a system like Ria Formosa, where three of the four European seagrass species can be found. We aimed to study and compare different photo-physiological components of the subtidal seagrasses Cymodocea nodosa and Zostera marina and of the macroalgae Caulerpa prolifera along diel cycles, while at the same time identifying possible consequences of their interaction, using a mesocosm experiment. The first experiment was performed over the course of two days (48 hour cycle), collecting samples for biochemical analysis at pre-dawn and solar noon at the end. The mesocosm experiment involved planting Z. marina and C. prolifera separately and mixed. After 4 weeks, photosynthetic performance was tested using photosynthesis-irradiance curves and rapid light curves, and samples for biochemical analysis were collected. The seagrasses revealed higher effective quantum yield and non-photochemical quenching, mainly related to their xanthophyll pigments, while C. prolifera displayed a typical shade-adapted response. Furthermore, it displayed a different carbohydrate usage regime, which was related to its higher respiration rates. Although no different overall photosynthetic performance was detected in the interaction of the species, starch content in Z. marina rhizomes was significantly lower when C. prolifera was present. This work gives initial insight on the physiological performance of C. prolifera in Ria Formosa.
- Daily regulation of key metabolic pathways in two seagrasses under natural light conditionsPublication . Ruocco, Miriam; Barrote, Isabel; Hofman, Jan Dirk; Pes, Katia; Costa, Monya; Procaccini, Gabriele; Silva, João; Dattolo, EmanuelaThe circadian clock is an endogenous time-keeping mechanism that enables organisms to adapt to external environmental cycles. It produces rhythms of plant metabolism and physiology, and interacts with signaling pathways controlling daily and seasonal environmental responses through gene expression regulation. Downstream metabolic outputs, such as photosynthesis and sugar metabolism, besides being affected by the clock, can also contribute to the circadian timing itself. In marine plants, studies of circadian rhythms are still way behind in respect to terrestrial species, which strongly limits the understanding of how they coordinate their physiology and energetic metabolism with environmental signals at sea. Here, we provided a first description of daily timing of key core clock components and clock output pathways in two seagrass species, Cymodocea nodosa and Zostera marina (order Alismatales), cooccurring at the same geographic location, thus exposed to identical natural variations in photoperiod. Large differences were observed between species in the daily timing of accumulation of transcripts related to key metabolic pathways, such as photosynthesis and sucrose synthesis/transport, highlighting the importance of intrinsic biological, and likely ecological attributes of the species in determining the periodicity of functions. The two species exhibited a differential sensitivity to light-to-dark and dark-to-light transition times and could adopt different growth timing based on a differential strategy of resource allocation and mobilization throughout the day, possibly coordinated by the circadian clock. This behavior could potentially derive from divergent evolutionary adaptations of the species to their bio-geographical range of distributions.