Cyanobacterial laboratory cultures are widely assumed to be axenic, yet the diversity and associated microorganisms are rarely examined. In this study, 16S rRNA V4 amplicon sequencing was used to characterize microbial communities associated with multiple cyanobacterial strains maintained in laboratory cultures and large-scale photobioreactors. Analysis of 24 samples revealed persistent, culture-specific microbiomes dominated by heterotrophic bacteria. Distinct ecological patterns were observed, including consistent differences between thermophilic and mesophilic cyanobacterial cultures and repeated detection of taxa linked to geothermal or freshwater environments. Despite more than 14 years of cultivation and shared bioreactor infrastructure, no evidence of cross-contamination between cyanobacterial hosts was detected, suggesting that many associated organisms derive from original culture stocks or environmental recruitment. Although none of the detected taxa were oxygenic phototrophs, their presence may influence genomic, transcriptomic, metabolomic, and lipidomic analyses. These findings indicate that many laboratory cyanobacterial cultures represent stable microbial consortia rather than strictly axenic systems.
The effects of the light-emitting diode (LED) spectra on plant growth, flowering, and phytochemical accumulation of African marigold were assessed under controlled conditions. The combination of white, blue, and red LEDs prolonged the time to flower by up to 20 d compared to full white LEDs and other light treatments. The white LEDs are an insufficient lighting condition for marigold growth, indicated by the lower plant and flower biomass. The dichromatic blue-red light and the white-blue-red (WBR) light were most suitable for marigold growth, biomass production, as well as flower quantity and quality. In addition, the highest contents of flavonoids and phenolics were observed in leaves and petals of marigold plants under the WBR treatment. Importantly, the extended spectrum of LEDs, achieved by supplementing white LEDs with the blue-red LEDs, could provide a friendly visual environment for researchers and workers under closed environments and plant factories.
It is both a privilege and a pleasure to celebrate the upcoming 95th birthday of Pierre Joliot, one of the most influential figures in modern photosynthesis research. Across more than seven decades of scientific activity, Pierre has transformed our understanding of oxygenic photosynthesis through pioneering studies of oxygen evolution, excitation-energy transfer, photosynthetic electron transport, and membrane bioenergetics. His discoveries helped establish fundamental concepts that continue to guide contemporary research, including the now-classic period-four oscillation of oxygen evolution and the mechanistic framework underlying the Kok-Joliot model of water oxidation. Pierre Joliot is also part of one of the most remarkable scientific families in history. The Curie-Joliot family has been associated with three Nobel Prizes and generations of groundbreaking discoveries that have shaped both physics and chemistry. Yet Pierre's own scientific accomplishments stand firmly on their own merit and have earned him an enduring place among the pioneers of photosynthesis research. In this tribute, we briefly discuss the origins of the Joliot and Joliot-Curie names, summarize Pierre's education, scientific career, leadership roles, and honors, and highlight selected contributions that have profoundly influenced our understanding of photosynthesis. Above all, we celebrate a scientist whose curiosity, creativity, rigor, and humanity have inspired colleagues, students, and friends around the world.
Salicylic acid (SA) mitigates salt stress in plants, yet its combined effects with salinity on Osmanthus fragrans remain unstudied. O. fragrans is a key Chinese ornamental tree, whose growth and use are restricted by salinization. Therefore, we aimed to evaluate the effect of SA application on O. fragrans under salt stress. O. fragrans seedlings were subjected to NaCl, SA, and NaCl+SA treatments, and their physiological and growth responses to salt stress were examined. Under NaCl, plant height, leaf mass per area, photosynthetic rate, and pigments of O. fragrans decreased by 29.5, 20.6, 42.2, and 29.2%, respectively. Notably, the SA application alleviated these effects by enhancing photosynthesis and the activities of antioxidant enzymes, improving photosynthetic pigments, and the contents of compatible solutes. The findings provide important insights into physiological mechanisms underlying SA-mediated salt tolerance, and provide a practical basis for the application of SA in improving the growth of O. fragrans in saline soils.
The water-oxidation reaction (WOR) is a critical yet kinetically sluggish process, requiring a complex four-electron transformation. Manganese (Mn) is a premier candidate for WOR catalysts due to its low cost, low toxicity, and its fundamental role in natural photosynthesis. Consequently, extensive research has focused on designing Mn-based ligands and compounds. However, a significant challenge persists: harsh oxidizing conditions necessary for WOR often trigger unintended phase transformations. Spectroscopy reveals that many Mn complexes and salts - even biomimetic clusters - eventually degrade or rearrange into various Mn oxides. This typically occurs via a two-step mechanism where Mn ions leach into the electrolyte before redepositing as an oxide phase. Since the morphology and activity of the resulting oxide depend heavily on pH, ligands, and precursors, identifying the "true" catalyst remains difficult. These structural instabilities highlight the central hurdle in developing durable, well-defined Mn-based WOR systems.
Dehydration reduces photosynthetic performance in leaves and other photosynthetic organs in response to drought. This decline is linked to changes in chlorophyll fluorescence, which reflects reduced photosystem II activity and increased protective non-photochemical quenching (NPQ). This study examined NPQ dynamics during desiccation across diverse species, including lichens, mosses, conifers, crops, and C3 and C4 plants, using the method of NPQ induction and relaxation curves. Gradual dehydration from a full-hydration state (RWC 100%) to complete dryness (RWC 0%) was applied in order to compare poikilohydric and homoiohydric species. NPQmax (light period), NPQrelax (dark period end), and the initial slopes of NPQ rise (α) and decline (β) were evaluated. Relative electron transport rate curves were also assessed. Results showed the above NPQ parameters are highly sensitive to dehydration, suggesting their usefulness - along with standard maximum (FV/FM) and effective quantum yield (ΦPSII) - as early indicators of drought stress in PSII across plant groups.
This Special Issue of Photosynthetica is dedicated to celebrating the distinguished scientific life and 75th birthday of Professor Suleyman I. Allakhverdiev (born 1 August 1950), whose contributions have left an enduring mark on modern photosynthesis research, photobiology, and bioenergetics. His pioneering studies of Photosystem II advanced the field in fundamental ways, including establishing pheophytin as the primary electron acceptor, defining the functional Mn4 water-oxidizing cluster and its reconstitution, and clarifying the redox properties of key cofactors such as QA, QB, and P680. He also significantly deepened understanding of photoinhibition by distinguishing donor-and acceptor-side processes and illuminating broader roles for bicarbonate in proton management and repair. Building on these mechanistic insights, his work helped inspire artificial photosynthesis, catalytic systems for water oxidation and hydrogen evolution, and biohybrid energy platforms. As a scholar, editor, organizer, mentor, and scientific diplomat, Professor Allakhverdiev has built a truly global legacy that this Special Issue is proud to honor.
Studies of the physiological and morphological characteristics of invasive plants contribute to understanding their invasive capacity. However, it remains unclear whether the same invasive plant species relies equally on morphological and physiological traits to enhance its invasiveness potential across different light habitats. In this study, the invasive plant Sphagneticola trilobata (L.) Pruski was used to examine eight morphological traits and nine physiological traits of the leaf under contrasting light conditions. Results revealed that under full light, growth, biomass, and all physiological traits, as well as most morphological traits of S. trilobata were significantly higher than those under low-light conditions. This suggests that S. trilobata achieves invasion success by altering its morphological and physiological traits. Notably, under full light, the species exhibited higher physiological plasticity but lower morphological plasticity. The study confirms that S. trilobata possesses greater invasive potential under full light, further underscoring the importance of physiological plasticity during the invasion process.
Leaf spectral reflectance across 450-850 nm has been shown to predict maximum carboxylation rate (V cmax), which varies with leaf temperature (T leaf). However, the mechanism by which temperature-induced variation in V cmax is predicted from reflectance remains unclear. The objective of this study was to explore this mechanism using spectral reflectance across 450-850 nm. We measured V cmax across a range of T leaf (18-31°C) and reflectance in cucumber (Cucumis sativus L.) leaves. Partial least squares regression models moderately predicted V cmax (R² = 0.73), whereas T leaf was weakly predicted (R² = 0.32). When only visible reflectance (450-700 nm) was used, prediction accuracy for both V cmax and T leaf declined (R² = 0.59 and 0.17). Because predicting T leaf from reflectance suggests that temperature-related information may help predict temperature-induced variations in V cmax, our results indicate that reflectance in 700-850 nm possibly captures temperature-induced variation in V cmax.
Knowledge about plant species' growth dynamics is essential in restoring degraded environments. In this study, we evaluated the growth dynamics of Allagoptera arenaria (Gomes) Kuntze in a chronosequence of plantations in the Restinga. The sampling was taken from three populations with different planting ages (n = 12): group GI-8 months; GII-4 years; GIII-7 years. We analyzed biometric measurements, leaf traits, photosynthetic pigments, and chlorophyll a fluorescence. The GI group's maximum quantum yield of primary photochemistry was significantly higher. On the other hand, the energy dissipation by heat was significantly higher in GIII. Our findings demonstrate that A. arenaria has high ecophysiological plasticity as it can adjust its photosynthetic machinery to avoid permanent damage to the proteins and structures of the photosystems. GI plants group can invest in greater carbon allocation, which is essential for survival in the field, as observed in groups GII and GIII.
Plant carbonic anhydrases (CAs) are essential metalloenzymes catalyzing reversible hydration of CO2 to HCO3⁻, thereby optimizing photosynthetic efficiency and carbon fixation in plants. They facilitate CO2 delivery to Rubisco, enhance carbon assimilation, and play a role in plant responses to stresses (such as drought, high salinity) by modulating stomatal conductance and internal CO2 concentrations. Despite the well-established physiological importance of plant CAs, the influence of metal ions, particularly copper (Cu2+), on their structure and activity remains inadequately understood. Here, bCA II is used as a well-characterized model enzyme to investigate enzyme-metal interactions. We employed intrinsic tryptophan and tyrosine fluorescence quenching to elucidate the binding mechanism of Cu2+ with bCA II. Our results demonstrate static quenching, indicative of ground-state complex formation, with binding parameters assessed at 288 K and 298 K [Kb = (2.64 ± 0.15 and 1.68 ± 0.54) × 103, M-1, n ≈ 1] and negative ΔG°, ΔH°, ΔS°.
Tetraploidization was induced in the drought-tolerant tomato landrace 'de Ramellet' to evaluate its physiological and anatomical response under well-watered (WW) and water-deficient (WD) conditions. Under WW, tetraploid plants exhibited approximately 40% lower stomatal density and approximately 80% larger stomata than diploids. Net photosynthetic rate (PN), intrinsic water-use efficiency, and intercellular CO2 concentration remained unchanged between diploids and tetraploids. Under WD, both genotypes reduced PN and stomatal conductance by similar proportions; however, only diploids decreased leaf area and adjusted stomatal density and size, whereas the tetraploid maintained stomatal traits similarly to those in WW conditions. However, both genotypes maintained similar photosynthetic capacity under WD despite different stomatal display and total pore area, which suggests the involvement of morphophysiological mechanisms beyond stomatal traits, such as root traits and hydraulic regulation.
To clarify the stages of leaf growth and development, the young leaf stage was identified at 0-20 d after emergence (DAE). The functional stage was at 20-100 DAE, with the highest functional point at 80 DAE. The leaf aging stage occurred at 100-220 DAE. During the functional stage of leaf development, optimal photosynthetic parameters and anatomical structures were achieved; the leaf area (LA) was at its largest, and the thickening rate of the palisade parenchyma was the fastest. The palisade parenchyma and LA were closely related to photosynthetic characteristics. Stomatal opening and closing, and stomatal density were greater in the functional stage than in the early stage. Both decreased during the aging stage, and the net photosynthetic rate decreased.
Few studies have simultaneously assessed the growth characteristics and invasion potential of invasive plants in different habitats by integrating photosynthetic physiology with photoprotective strategies. In this study, we compared the growth, photosynthetic physiology, and photoprotective strategies of the widespread invasive plant Sphagneticola trilobata in three representative habitats: farmland, woodland, and riverside. Our results showed that S. trilobata exhibited the highest growth performance in farmland, which correlated with the highest net photosynthetic rate, electron transfer rate, and antioxidant substances. Plants from the riverside habitat showed intermediate growth, with the highest quantum yield of unregulated energy dissipation at PSII. Plants in the woodland had the worst growth status. These findings suggest that S. trilobata possesses the strongest invasion potential in farmland, intermediate potential at the riverside, and the weakest in woodland. This study provides novel insights for habitat-specific invasion risk assessment of alien plant species.
The main assumptions of the well-known Kitajima and Butler (1975) model, describing the relationship between the ratio of the maximum variable chlorophyll a fluorescence to the maximum fluorescence (FV/FM) and the photochemical quantum yield of PSII (ΦPo), have been analyzed. Using the experimental data from the literature, potential "weak points" of this model are discussed, as well as the reasons for the differences between the FV/FM values and the actual ΦPo values. Special attention is focused on the fluorescence measurement procedures using the saturating single turnover light flashes and the saturating multiple turnover light pulses. It is concluded that if the FV/FM measurements are made properly, the value of ΦPo can indeed be estimated.
The International Conference on "Photosynthesis and Hydrogen Energy Research" was inaugurated in 2004 in Trois Rivières, Canada, as "Photosynthesis and Post-Genomics Era". It was conceived by its founders, Suleyman I. Allakhverdiev (Russia), Vyacheslav (Slava) Klimov (Russia), Robert Carpentier (Canada), and Prasanna Mohanty (India) to be an alternating conference to the bigger International Congress on Photosynthesis, which was then held every three years. The name was changed to the International Conference on Photosynthesis (ICP) in 2011. In 2013, "Hydrogen Production" was added, and then finally the current name, "International Conference on Photosynthesis and Hydrogen Energy Research for Sustainability", was used in 2015. The conferences over the last twenty years have been held in three continents - North America, Europe, and Asia - and have been very successful in attracting participants with the latest ideas in photosynthesis, hydrogen production, and energy sustainability. Here we describe all 12 conferences, with details of the major events of each conference. Major points of the conference were: (1) Recent advances in the understanding of the basic mechanisms of water splitting (photosystem II) and the reactions around photosystem I in photosynthetic organisms. (2) The role of hydrogen production in photosynthesis. (3) The role of innovations in photosynthesis and hydrogen production in the development of global sustainability.
