Evaluation of Light-Dependent Photosynthetic Reactions in Reynoutria japonica Houtt. Leaves Grown at Different Light Conditions

The Japanese knotweed (Reynoutria japonica Houtt.) is considered as one of the most aggressive and highly successful invasive plants with a negative impact on invaded habitats. Its uncontrolled expansion became a significant threat to the native species throughout Europe. Due to its extensive rhizome system, rapid growth, and allelopathic activity, it usually forms monocultures that negatively affect the nearby vegetation. The efficient regulation of partitioning and utilization of energy in photosynthesis enables invasive plants to adapt rapidly a variety of environmental conditions. Therefore, we aimed to determine the influence of light conditions on photosynthetic reactions in the Japanese knotweed. Plants were grown under two different light regimes, namely, constant low light (CLL, 40 μmol/m2/s) and fluctuating light (FL, 0–1,250 μmol/m2/s). To evaluate the photosynthetic performance, the direct and modulated chlorophyll a fluorescence was measured. Plants grown at a CLL served as control. The photosynthetic measurements revealed better photosystem II (PSII) stability and functional oxygen-evolving center of plants grown in FL. They also exhibited more efficient conversion of excitation energy to electron transport and an efficient electron transport beyond the primary electron acceptor QA, all the way to PSI. The enhanced photochemical activity of PSI suggested the formation of a successful adaptive mechanism by regulating the distribution of excitation energy between PSII and PSI to minimize photooxidative damage. A faster oxidation at the PSI side most probably resulted in the generation of the cyclic electron flow around PSI. Besides, the short-term exposure of FL-grown knotweeds to high light intensity increased the yield induced by downregulatory processes, suggesting that the generation of the cyclic electron flow protected PSI from photoinhibition.

Modeling indicates degradation of mRNA and protein as a potential regulation mechanisms during cold acclimation

Plants are constantly exposed to temperature fluctuations, which have direct effects on all cellular reactions because temperature influences reaction likelihood and speed. Chloroplasts are crucial to temperature acclimation responses of plants, due to their photosynthetic reactions whose products play a central role in plant metabolism. Consequently, chloroplasts serve as sensors of temperature changes and are simultaneously major targets of temperature acclimation. The core subunits of the complexes involved in the light reactions of photosynthesis are encoded in the chloroplast. As a result, it is assumed that temperature acclimation in plants requires regulatory responses in chloroplast gene expression and protein turnover. We conducted western blot experiments to assess changes in the accumulation of two photosynthetic complexes (PSII, and Cytb6f complex) and the ATP synthase in tobacco plants over two days of acclimation to low temperature. Surprisingly, the concentration of proteins within the chloroplast varied negligibly compared to controls. To explain this observation, we used a simplified Ordinary Differential Equation (ODE) model of transcription, translation, mRNA degradation and protein degradation to explain how the protein concentration can be kept constant. This model takes into account temperature effects on these processes. Through simulations of the ODE model, we show that mRNA and protein degradation are possible targets for control during temperature acclimation. Our model provides a basis for future directions in research and the analysis of future results.

Spatially separating redox centers on 2D carbon nitride with cobalt single atom for photocatalytic H2O2production

Redox cocatalysts play crucial roles in photosynthetic reactions, yet simultaneous loading of oxidative and reductive cocatalysts often leads to enhanced charge recombination that is detrimental to photosynthesis. This study introduces an approach to simultaneously load two redox cocatalysts, atomically dispersed cobalt for improving oxidation activity and anthraquinone for improving reduction selectivity, onto graphitic carbon nitride (C3N4) nanosheets for photocatalytic H2O2production. Spatial separation of oxidative and reductive cocatalysts was achieved on a two-dimensional (2D) photocatalyst, by coordinating cobalt single atom above the void center of C3N4and anchoring anthraquinone at the edges of C3N4nanosheets. Such spatial separation, experimentally confirmed and computationally simulated, was found to be critical for enhancing surface charge separation and achieving efficient H2O2production. This center/edge strategy for spatial separation of cocatalysts may be applied on other 2D photocatalysts that are increasingly studied in photosynthetic reactions.

Influence of Pollution on Photosynthesis Pigment Content in Needles of Picea abies and Picea pungens in Conditions of Development of Iron Ore Deposits

We studied photosynthetic pigments in needles of Pісеа аbies and P. pungens in plantings exposed to aerotechnogenic influence of various levels in the big industrial center of steppe zone of Ukraine (Kryvyi Rih). We analyzed the pigment content in needles of the second year of life sampled from 30 to 40-year-old trees of both species in 6 monitoring sites for 5 months. For the needles of P. аbies and P. pungens from all the sites, we noticed the decreasing content of chlorophyll a (to 27.2 and 25.0%, respectively) and chlorophyll b (to 17.9 and 20.0%, respectively) from May till September, in comparison with background territory. At the same time, the content of carotenoids performing the protective function in photosynthetic reactions increased up to 26.1 and 24.0%, respectively. For P. аbies and P. pungens growing in conditions of intensive technogenic pressure, we ascertained that, during investigations, the sum of chlorophylls (a + b) rate decreased to 24.4 and 23.6%, respectively; ratio (a/b) decreased to 11.4 and 12.3%, respectively; ratio (chlorophylls [a + b]/carotenoids) also decreased to 30.1 and 38.0%, respectively, in comparison with plants from the least polluted site. It is shown that the most intensive negative influence on plantings is caused by industrial pollution and exhaust gases: the minimum or, more rarely, the maximum rates of pigment content appeared in needles of the plants exactly from these sites. Our research results demonstrate the feasibility of using the pigment complexes of P. аbies and P. pungens, with the assimilative apparatus sensitive to air pollution damage, as indicators of air environmental conditions.

Фракционирование изотопов углерода -=SUP=-13-=/SUP=-С/-=SUP=-12-=/SUP=-С из углекислого газа атмосферы в продукты фотосинтеза в листьях растений в зависимости от спектральных характеристик световой среды

We have studied influence of the light with various spectral characteristics, coming to plants during its growth, on the distribution of carbon isotopes between atmospheric carbon dioxide and the primary products of photosynthesis in plant leaves, using the developed set of methods and laboratory setups. The difference between the carbon isotopic composition in the air near the plants and in their leaves varies from 7 to 19 ‰, increase in the red component of the spectrum resulting in leave enrichment with light carbon isotope 12C. This difference reflects the degree of isotope fractionation during the plant life, characterizes the rate of carbon assimilation due to photosynthetic reactions, and can be used as a phytomonitoring parameter.

Morphological and Stomatal Characteristics of Two Indonesian Local Orchids

Orchids are very famous for their beautiful and long-lasting flowers and variety among the most diverse family of flowering plants in the world, comprising thousand species and hybrids and very attractive. The research aimed to determine the morphological features of two local orchids Phalaenopsis amabilis L. and Dendrobium x Superbiens and the stomatal characteristics of both orchids. Plants were the only living organisms that are able to convert light energy/sunlight into chemical energy, and stomata is an important part of plants for CO­2 to enter the leaf and H­­2O to be released during the photosynthetic reactions. The results showed that Phalenopsis amabilis L. was monopodial orchid and Dendrobium x Superbiensis a sympodial orchid. A qualitative descriptive research method used to describe and interpreted the type of stomata of Phalaenopsis amabilis L and Dendrobium sp. stomatal density were counted on adaxial and abaxial part of the leaf, and the highest stomatal density was obtained on the abaxial part of Dendrobium x Superbiensleaf 290.81 mm­-2. The type of stomata was anomocytic for two local orchids.