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Detailed experimental research in the twentieth century could have ensured the full understanding of photosynthesis as a consequential source of life on Earth. Instead, epistemological misconceptions have hindered educators' and, of course, students' basic knowledge of this vital process. This paper appeals for an epistemological effort that would facilitate the refuting of a misconception regarding the flow of oxygen and carbon dioxide during photosynthesis. It provides a simple review of flow of matter and energy during photosynthesis, and suggests simple K-12 lesson plans. Finally, the paper emphasizes that collaborative work is needed between K-12 teachers and academics; also, between biologists and epistemologists., Recommended Citation Authors William A. Said, University of Georgia (Retired) Follow Said, William A. (2023) 'EPISTEMOLOGY OF A MISCONCEPTION REGARDING THE FLOW OF OXYGEN AND CARBON DIOXIDE DURING PHOTOSYNTHESIS,' Georgia [...]

Students often have difficulty visualizing complex processes such as cellular respiration and photosynthesis, and this can significantly impact the students' understanding of the relationship between the two processes. Therefore, the goal of this project was to develop a teaching tool for undergraduate educators and students that: (i) provides a published data set for students to compare their own photosynthesis and/or cellular respiration data to, (ii) develops an excel calculator that can convert oxygen (O2) and carbon dioxide (CO2) measured in part per million (ppm) to units that are easier to grasp, and (iii) shows that not all plants have the same rate of photosynthesis. Additionally, this project was developed as an effort to increase student motivation by promoting the application of scientific knowledge to the area they live in. Approximately ten grams of leaves were collected from twenty-six plant species across Georgia College's campus during October and November 2021. Leaves were placed in containers equipped with Vernier O2 and CO2 sensors, and gases were measured in light and dark conditions. A LabQuest2 data logger was used to collect data for 1800 seconds, and rates of cellular respiration and photosynthesis were determined in triplicate for each plant species. During photosynthesis, CO2 levels typically decrease while O2 levels increase. In our study, this was true for all plants except for Lopopetalum chinense, which has dark purple leaves, that produced CO2 during the light incubation (6.13 + 2.13 ppm min-1). The greatest rates of photosynthesis were observed in the Hydrangea macrophylla leaves (-23.62 + 1.85 CO2 ppm min-1). Total carbon dioxide retention was also calculated for all plant species; hydrangeas (337.67 + 30.44 ppm) and Hosta spp. (311.00 + 71.69 ppm) retained significantly more CO2 compared to the majority of the other plants surveyed. Conversely, Quercus robur, Lopopetalum chinense, and Salvia rosmarinus experienced a net loss in CO2 of -256.00 + 12.12 ppm, -291.00 + 241.02 ppm, and -371.33 + 45.21 ppm, respectively. Using our excel CO2 calculator, these values are equal to 0.92 + 0.04 mg, 1.04 + 0.86 mg, and 1.33 + 0.16 mg of CO2, respectively., Recommended Citation Authors Jinha Kim, Georgia College and State University, Milledgeville, GA, 31061 Follow Cooper Williams, Georgia College and State University, Milledgeville, GA, 31061 Follow C. Daniel Burt, Georgia College [...]

Bacteriochlorophylls (BChls) c, d, and e are the main light-harvesting pigments of green photosynthetic bacteria that self-assemble into nanostructures within the chlorosomes forming the most efficient antennas of photosynthetic organisms. All previous models of the chlorosomal antennae, which are quite controversially discussed because no single crystals could be grown so far from these organelles, involve a strong hydrogen-bonding interaction between the [3.sup.1] hydroxyl group and the [13.sup.1] carbonyl group. We have synthesized different self-assemblies of BChl c mimics having the same functional groups as the natural counterparts, that is, a hydroxyethyl substituent, a carbonyl group and a divalent metal atom ligated by a tetrapyrrole. These artificial BChl mimics have been shown by single crystal x-ray diffraction to form extended stacks that are packed by hydrophobic interactions and in the absence of hydrogen bonding. Time-resolved photoluminescence proves the ordered nature of the self-assembled stacks. FT-IR spectra show that on self-assembly the carbonyl frequency is shifted by [approximately equal to] 30 [cm.sup.-1] to lower wavenumbers. From the FT-IR data we can infer the proximal interactions between the BChls in the chlorosomes consistent with a single crystal x-ray structure that shows a weak electrostatic interaction between carbonyl groups and the central zinc atom. chlorosome model | crystal structure | FT-IR | light-harvesting | time-resolved fluorescence

Sedimentary 2-methyhopanes have been used as biomarker proxies for cyanobacteria, the only known bacterial clade capable of oxygenic photosynthesis and the only group of organisms found thus far to produce abundant 2-methylbacteriohopanepolyols (2-MeBHPs). Here, we report the identification of significant quantities of 2-MeBHP in two strains of the anoxygenic phototroph Rhodopseudomonaspalustris. Biosynthesis of 2-MeBHP can occur in the absence of [O.sub.2], deriving the C-2 methyl group from methionine. The relative abundance of 2-MeBHP varies considerably with culture conditions, ranging from 13.3% of total bacteriohopanepolyol (BHP) to trace levels of methylation. Analysis of intact BHPs reveals the presence of methylated bacteriohopane-32,33,34,35-tetrol but no detectable methylation of 35-aminobacteriohopane-32,33,34-triol. Our results demonstrate that an anoxygenic photoautotroph is capable of generating 2-MeBHPs and show that the potential origins of sedimentary 2-methylhopanoids are more diverse than previously thought. 2-methyhopanes | biomarkers | cyanobacteria | Rhodopseudomonas palustris

Phycobilisomes, the light-harvesting complexes of cyanobacteria and red algae, contain two to four types of chromophores that are attached covalently to seven or more members of a family of homologous proteins, each carrying one to four binding sites. Chromophore binding to apoproteins is catalyzed by lyases, of which only few have been characterized in detail. The situation is complicated by nonenzymatic background binding to some apoproteins. Using a modular multiplasmidic expression-reconstitution assay in Escherichia coli with low background binding, phycobilin:cystein-84 biliprotein lyase (CpeS1) from Anabaena PCC7120, has been characterized as a nearly universal lyase for the cysteine-84-binding site that is conserved in all biliproteins. It catalyzes covalent attachment of phycocyanobilin to all allophycocyanin subunits and to cysteine-84 in the [beta]-subunits of C-phycocyanin and phycoerythrocyanin. Together with the known lyases, it can thereby account for chromophore binding to all binding sites of the phycobiliproteins of Anabaena PCC7120. Moreover, it catalyzes the attachment of phycoerythrobilin to cysteine-84 of both subunits of C-phycoerythrin. The only exceptions not served by CpeS1 among the cysteine-84 sites are the [alpha]-subunits from phycocyanin and phycoerythrocyanin, which, by sequence analyses, have been defined as members of a subclass that is served by the more specialized E/F type lyases. biliprotein biosynthesis | light-harvesting | photosynthesis | phycobilisome

Bacteriophytochromes RpBphP2 and RpBphP3 from the photosynthetic bacterium Rhodopseudomonas palustris work in tandem to modulate synthesis of the light-harvesting complex LH4 in response to light. Although RpBphP2 and RpBphP3 share the same domain structure with 52% sequence identity, they demonstrate distinct photoconversion behaviors. RpBphP2 exhibits the 'classical' phytochrome behavior of reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states, whereas RpBphP3 exhibits novel photoconversion between Pr and a near-red (Pnr) light-absorbing states. We have determined the crystal structure at 2.2-[Angstrom] resolution of the chromophore binding domains of RpBphP3, covalently bound with chromophore biliverdin IX[alpha]. By combining structural and sequence analyses with site-directed mutagenesis, we identify key residues that directly modulate the photochemical properties of RpBphP3 and RpBphP2. Remarkably, we identify a region spanning residues 207-212 in RpBphP3, in which a single mutation, L207Y, causes this unusual bacteriophytochrome to revert to the classical phenotype that undergoes reversible photoconversion between the Pr and Pfr states. The reverse mutation, Y193L, in the corresponding region in RpBphP2 significantly diminishes the formation of the Pfr state. We propose that residues 207-212 and the spatially adjacent conserved residues, Asp-216 and Tyr-272, interact with the chromophore and form part of the interface between the chromophore binding domains and the PHY domain that modulates photoconversion. biliverdin | red-light photoreceptor

In many plant communities, there is a negative interspecific correlation between relative growth rates and survival of juveniles. This negative correlation is most likely caused by a trade-off between carbon allocation to growth vs. allocation to defense and storage. Nonstructural carbohydrates (NSC) stored in stems allow plants to overcome periods of stress and should enhance survival. In order to assess how species differ in carbohydrate storage in relation to juvenile light requirements, growth, and survival, we quantified NSC concentrations and pool sizes in sapling stems of 85 woody species in moist semi-evergreen and dry deciduous tropical forests in the rainy season in Bolivia. Moist forest species averaged higher NSC concentrations than dry forest species. Carbohydrate concentrations and pool sizes decreased with the light requirements of juveniles of the species in the moist forest but not in the dry forest. Combined, these results suggest that storage is especially important for species that regenerate in persistently shady habitats, as in the understory of moist evergreen forests. For moist forest species, sapling survival rates increased with NSC concentrations and pool sizes while growth rates declined with the NSC concentrations and pool sizes. No relationships were found for dry forest species. Carbon allocation to storage contributes to the growth-survival trade-off through its positive effect on survival. And, a continuum in carbon storage strategies contributes to a continuum in light requirements among species. The link between storage and light requirements is especially strong in moist evergreen forest where species sort out along a light gradient, but disappears in dry deciduous forest where light is a less limiting resource and species sort out along drought and fire gradients. Key words: Bolivia; growth--survival trade-off; shade tolerance; starch; sugar; total nonstructural arbohydrates (NSC); tropical forest.

The physiology of Skeletonema costatum synthesized under a simple sinusoidal and unstable light environment was studied. The fluctuating light regime was similar to the effect caused by Langmuir circulation-induced vertical mixing. The culture resembling vertical mixing reduced the photosynthetic unit (PSU) size but augmented the number of photosynthetic units, therefore maximizing the rate of maximal photosynthesis at high, saturating irradiances.

Byline: Yunfeng Xu, Yan Wang, Yalin Wang, Huihui Yuan, Jinping Jia As a result of electrolysis, biomass was controlled to some extent and the protein content per gram wet algae decreased. The viability of the algae was measured by the flow cytometry. Without taking into account the consumption of substrate, Microcystis aeruginosa growth kinetics was demonstrated that the electrolysis would inhibit the algal growth. At the same time, photosynthetic efficiency (Fv/Fm) of the treated sample was clearly lower than that of the control sample. TEM observations showed that the algal cellularity was destroyed by electrolysis, including thylakoid, gas vesicles, starch grain and the lipid globule.

An economic evaluation regarding the industrial photosynthesis of fine chemical rose oxide using solar light is given and compared to conventional lamps as light source. A plant reaching a capacity of 100 t/a was designed containing app. 1,900 [m.sup.2] of parabolic troughs, 1,500 [m.sup.2] of flatbed reactors or 32 high-pressure mercury lamps doped with Thallium iodide (TlI) as a photounit. The investment and production costs were compared and graded. We reached the conclusion that solar application is more profitable than the lamp driven one. [DOI: 10.1115/1.1354996]