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- Dirks-Mulder, Anita, et al.
(författare)
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Exploring the evolutionary origin of floral organs of Erycina pusilla, an emerging orchid model system
- 2017
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Ingår i: BMC Evolutionary Biology. - : BIOMED CENTRAL LTD. - 1471-2148. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Background: Thousands of flowering plant species attract pollinators without offering rewards, but the evolution of this deceit is poorly understood. Rewardless flowers of the orchid Erycina pusilla have an enlarged median sepal and incised median petal ('lip') to attract oil-collecting bees. These bees also forage on similar looking but rewarding Malpighiaceae flowers that have five unequally sized petals and gland-carrying sepals. The lip of E. pusilla has a 'callus' that, together with winged 'stelidia', mimics these glands. Different hypotheses exist about the evolutionary origin of the median sepal, callus and stelidia of orchid flowers. Results: The evolutionary origin of these organs was investigated using a combination of morphological, molecular and phylogenetic techniques to a developmental series of floral buds of E. pusilla. The vascular bundle of the median sepal indicates it is a first whorl organ but its convex epidermal cells reflect convergence of petaloid features. Expression of AGL6 EpMADS4 and APETALA3 EpMADS14 is low in the median sepal, possibly correlating with its petaloid appearance. A vascular bundle indicating second whorl derivation leads to the lip. AGL6 EpMADS5 and APETALA3 EpMADS13 are most highly expressed in lip and callus, consistent with current models for lip identity. Six vascular bundles, indicating a stamen-derived origin, lead to the callus, stelidia and stamen. AGAMOUS is not expressed in the callus, consistent with its sterilization. Out of three copies of AGAMOUS and four copies of SEPALLATA, EpMADS22 and EpMADS6 are most highly expressed in the stamen. Another copy of AGAMOUS, EpMADS20, and the single copy of SEEDSTICK, EpMADS23, are most highly expressed in the stelidia, suggesting EpMADS22 may be required for fertile stamens. Conclusions: The median sepal, callus and stelidia of E. pusilla appear to be derived from a sepal, a stamen that gained petal identity, and stamens, respectively. Duplications, diversifying selection and changes in spatial expression of different MADS-box genes shaped these organs, enabling the rewardless flowers of E. pusilla to mimic an unrelated rewarding flower for pollinator attraction. These genetic changes are not incorporated in current models and urge for a rethinking of the evolution of deceptive flowers.
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| 2. |
- Ardo, Shane, et al.
(författare)
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Pathways to electrochemical solar-hydrogen technologies
- 2018
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 11:10, s. 2768-2783
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Forskningsöversikt (refereegranskat)abstract
- Solar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process do not exist. In this perspective paper, we describe potential pathways for solar-hydrogen technologies into the marketplace in the form of photoelectrochemical or photovoltaic-driven electrolysis devices and systems. We detail technical approaches for device and system architectures, economic drivers, societal perceptions, political impacts, technological challenges, and research opportunities. Implementation scenarios are broken down into short-term and long-term markets, and a specific technology roadmap is defined. In the short term, the only plausible economical option will be photovoltaic-driven electrolysis systems for niche applications. In the long term, electrochemical solar-hydrogen technologies could be deployed more broadly in energy markets but will require advances in the technology, significant cost reductions, and/ or policy changes. Ultimately, a transition to a society that significantly relies on solar-hydrogen technologies will benefit from continued creativity and influence from the scientific community.
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| 3. |
- Li, Lin
(författare)
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Functional Photo-electrochemical Devices for Solar Cellsand Solar Fuels Based on Molecular Components
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the development and the study of molecular functional photo-electrochemical cells (PEC) for solar cells and solar fuels.The first chapter gives a general introduction about photosynthesis, dye-sensitized solar cell and photo-electrochemical device for water splitting.The second chapter describes a TiO2-Co-catalyst electrode manufactured by a direct photo-deposition method. The electrode showed activity for electrochemical water oxidation in an electrochemical device.In the third chapter, a photo-electrochemical cell (PEC) with two-electrodes for visible light driven water splitting has been successfully demonstrated. One electrode was a photo-anode, which assembled a ruthenium water oxidation catalyst (complex 1) into a dye-sensitized porous nanostructured TiO2 electrode by employing a cation-exchange membrane (Nafion). The other electrode was platinum which was used as a passive cathode for proton reduction.In the fourth chapter, an earth abundant metal complex with an anchoring group (cobalt complex 2) was synthesized and investigated as water oxidation catalyst. This complex was further applied into a photo-anode in a PEC. The photo-anode was assembled by co-sensitization of complex 2 to a dye-sensitized porous nanostructured TiO2 electrode. The PEC device gave ca. 250 υA/cm2 photo-current and 7.2 % IPCE without applying any bias voltage, which is much higher than the reported results in the sample type of PEC. Meanwhile, we have shown that the catalytic effect is not from free cobalt ions, CoOx film or nanoparticles formed in situ by using complex 2 in the device.The last two chapters describe an optimization of the NiO films prepared in two steps rather than one step film and applied in p-type DSSCs. This optimized film could adsorb more dye (P1), leading to a significant light harvesting efficiency (LHE) and IPCE in DSSCs. We further combined this P1 sensitized photo-cathode with a hydrogen evolution catalyst (complex 3) and applied this photo-cathode into a PEC for visible light hydrogen evolution.
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| 4. |
- Segev, Gideon, et al.
(författare)
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The 2022 solar fuels roadmap
- 2022
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 55:32
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Tidskriftsartikel (refereegranskat)abstract
- Renewable fuel generation is essential for a low carbon footprint economy. Thus, over the last five decades, a significant effort has been dedicated towards increasing the performance of solar fuels generating devices. Specifically, the solar to hydrogen efficiency of photoelectrochemical cells has progressed steadily towards its fundamental limit, and the faradaic efficiency towards valuable products in CO2 reduction systems has increased dramatically. However, there are still numerous scientific and engineering challenges that must be overcame in order to turn solar fuels into a viable technology. At the electrode and device level, the conversion efficiency, stability and products selectivity must be increased significantly. Meanwhile, these performance metrics must be maintained when scaling up devices and systems while maintaining an acceptable cost and carbon footprint. This roadmap surveys different aspects of this endeavor: system benchmarking, device scaling, various approaches for photoelectrodes design, materials discovery, and catalysis. Each of the sections in the roadmap focuses on a single topic, discussing the state of the art, the key challenges and advancements required to meet them. The roadmap can be used as a guide for researchers and funding agencies highlighting the most pressing needs of the field.
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