Role Of Chlorophyll Research Articles

My journey to photosynthesis.

I provide here both my personal and scientific autobiography. After giving a background and summary of most of my research, I present information on my parents, my childhood, schooling, university education, and postdoctoral research, all in Australia. This is followed by a presentation of my life and research in Cambridge, UK and then at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), in Australia, since 1955, where most of my research was done, especially on photosynthesis which included the following areas: Purification of a protochlorophyllide-protein complex; separation of the photochemical systems of photosynthesis; development of photochemical activity in photosynthesis; protein synthesis in plants; comparative photosynthesis of sun and shade plants; role of chlorophyll b in photosynthesis; photochemical properties of C4 plants; molecular interaction of thylakoid membranes; electron transport and ATP formation; and solar energy conversion in photosynthesis. In addition to research on the basics and applications of photosynthesis, I also mention at the end my service as a member of the executive of CSIRO.

Genome-Wide Identification of Kiwifruit SGR Family Members and Functional Characterization of SGR2 Protein for Chlorophyll Degradation.

The STAY-GREEN (SGR) proteins play an important role in chlorophyll (Chl) degradation and are closely related to plant photosynthesis. However, the availability of inadequate studies on SGR motivated us to conduct a comprehensive study on the identification and functional dissection of SGR superfamily members in kiwifruit. Here, we identified five SGR genes for each of the kiwifruit species [Actinidia chinensis (Ac) and Actinidia eriantha (Ae)]. The phylogenetic analysis showed that the kiwifruit SGR superfamily members were divided into two subfamilies the SGR subfamily and the SGRL subfamily. The results of transcriptome data and RT-qPCR showed that the expression of the kiwifruit SGRs was closely related to light and plant developmental stages (regulated by plant growth regulators), which were further supported by the presence of light and the plant hormone-responsive cis-regulatory element in the promoter region. The subcellular localization analysis of the AcSGR2 protein confirmed its localization in the chloroplast. The Fv/Fm, SPAD value, and Chl contents were decreased in overexpressed AcSGR2, but varied in different cultivars of A. chinensis. The sequence analysis showed significant differences within AcSGR2 proteins. Our findings provide valuable insights into the characteristics and evolutionary patterns of SGR genes in kiwifruit, and shall assist kiwifruit breeders to enhance cultivar development.

The role of chlorophyll in determining the resistance of soybean plants to prolonged soil flooding

Prolonged inundation of soybean plants leads to their death because of root hypoxia. Therefore, the search for markers of resistance to this factor will provide the opportunity to develop the varieties able to resist this stress. The research was aimed at the study of response of 3 varieties bred by Federal Research Center All-Russian Scientific Research Institute of Soybean to prolonged flooding according to the indicator of chlorophyll a and b content in soybean leaves. The study was carried out in 2019-2021 in laboratory experiments when growing plants on hydroponic installations with 24-day soil flooding (control - soil with optimal moisture content). In soybean varieties Evgeniya and Kukhanna, registered as resistant to overwatering soil, the response by content of chlorophyll forms in leaves under 24-day flooding of the soil surface with 1-2 cm layer of water differed. It was found that increase of chlorophyll a in leaves of Evgeniya variety under flooding was connected with providing the ability of this variety plants to resist the stressful flooding factor. The presence of chlorophyll b in the leaves of this variety before the ripeness phase indicates that it can serve as an indicator of plant resistance to root hypoxia to a greater extent, since the plants continued to grow and develop. In the Kukhanna variety, the content of both forms of chlorophyll at optimum soil moisture of the control variety was higher or at the same level as in the variant with flooding, that cannot serve as the criterion of resistance of this variety to root hypoxia. In the Kitrossa variety, the resistance of which to overwatering has not been noted by the breeders yet there were revealed wavy fluctuations in chlorophyll a/b ratio during the first 10 days of flooding. The fluctuations were caused by changes in the content of chlorophyll b, the concentration of which increased first and then decreased. This fluctuation is most clearly seen in the graph of the change in the ratio between chlorophyll a and b, that may serve as a marker for determination of resistance of soybean varieties to prolonged soil flooding.

SlZHD17 is involved in the control of chlorophyll and carotenoid metabolism in tomato fruit

Chlorophylls and carotenoids are essential and beneficial substances for both plant and human health. Identifying the regulatory network of these pigments is necessary for improving fruit quality. In a previous study, we identified an R2R3-MYB transcription factor, SlMYB72, that plays an important role in chlorophyll and carotenoid metabolism in tomato fruit. Here, we demonstrated that the SlMYB72-interacting protein SlZHD17, which belongs to the zinc-finger homeodomain transcription factor family, also functions in chlorophyll and carotenoid metabolism. Silencing SlZHD17 in tomato improved multiple beneficial agronomic traits, including dwarfism, accelerated flowering, and earlier fruit harvest. More importantly, downregulating SlZHD17 in fruits resulted in larger chloroplasts and a higher chlorophyll content. Dual-luciferase, yeast one-hybrid and electrophoretic mobility shift assays clarified that SlZHD17 regulates the chlorophyll biosynthesis gene SlPOR-B and chloroplast developmental regulator SlTKN2 in a direct manner. Chlorophyll degradation and plastid transformation were also retarded after suppression of SlZHD17 in fruits, which was caused by the inhibition of SlSGR1, a crucial factor in chlorophyll degradation. On the other hand, the expression of the carotenoid biosynthesis genes SlPSY1 and SlZISO was also suppressed and directly regulated by SlZHD17, which induced uneven pigmentation and decreased the lycopene content in fruits with SlZHD17 suppression at the ripe stage. Furthermore, the protein–protein interactions between SlZHD17 and other pigment regulators, including SlARF4, SlBEL11, and SlTAGL1, were also presented. This study provides new insight into the complex pigment regulatory network and provides new options for breeding strategies aiming to improve fruit quality.

Effect of glutamic acid foliar applications on lettuce under water stress

The yield and quality of leafy vegetables can be compromised by reduced water availability. Glutamic acid is involved in different biological processes and among them it plays an important role in chlorophyll and proline biosynthesis. The aim of this work was to evaluate the possible efficacy of glutamic acid in counteracting water stress in romaine lettuce. Lettuce plants were grown in pots filled with substrate and subjected to water deprivation. A glutamic acid solution (1.9 mM) was applied as foliar treatment, both in stressed and non-stressed plants. The effect of the treatment was evaluated at different time points during the experiment in order to evaluate changes at a molecular, physiological, biochemical and agronomic level. Yield was reduced by 35% in stressed plants, while no significant changes in quality parameters were observed, except for nitrate content, which increased under water stress. At a molecular level, the expression of genes encoding for ROS scavenging enzymes was monitored but, apparently, glutamic acid did not significantly prevent the water stress response. Slightly positive effects deriving from glutamic acid application were found for nitrate and proline contents, suggesting that a possible mode of action of glutamic acid would involve a role for these molecules. Further studies are required, also on other crop species, for confirming these results. Different concentrations and application modes should be also tested.

Role of sulphur in pulse crops: A review

Sulphur is essential nutrient for every living cell; it is component of 21 amino acids which form protein. It is fourth key plant nutrient after nitrogen, phosphorus and potassium. Pulses are particularly sensitive to sulphur deficiency which gives low quality and less yields. sulphur plays a key role In chlorophyll and oil synthesis. Plants uptake sulphur only in sulphate form (so42-) and it reduces to form sulphur containing amino acids and other compounds. Application of sulphur increases the nitrogen use. Efficiency of N, P, K is seriously affected under sulphur deficiency. Field experiments in many agro climatic conditions shown that application of 30 and 40 kg S/ha-1 along with recommended dose given the highest yields and protein content in pulses. Moreover, this review highlights the availability of sulphur for profitable crop production, effects of different sources and levels of sulphur in pulse crops, effect of sulphur on various parameters and it also includes the sulphur absorption and translocation in plants. Moreover this review provides new sights to revisit the sulphur significance in pulse crops.

Molecular functional group and optical analysis on chlorophyll of green choy sum and cassava leaves extracts

Recently, chlorophyll can improve the optical characteristics of thin films. The role of chlorophyll is a dopant in the thin film. Chlorophyll is very good in transferring electron which is strongly related to energy. If the energy gap of the film is low, the characteristics of the film are better because it requires less energy to jump one electron from the valence band to the conduction band. However, an important factor to consider in this case is the chlorophyll content. The more chlorophyll content will improve the light absorption rate. This study examined the characterization of chlorophyll of green choy sum and cassava leaves extracts. The analysis was carried out based on the Fourier Transform Infra-Red (FTIR) and UV-Vis Spectrophotometer. The results of the analysis were molecular functional groups, vibration frequencies, bond force constants between molecules, optical characteristics and chlorophyll content on both of chlorophyll extracts.

Far-red light allophycocyanin subunits play a role in chlorophyll d accumulation in far-red light.

Some terrestrial cyanobacteria acclimate to and utilize far-red light (FRL; λ = 700-800nm) for oxygenic photosynthesis, a process known as far-red light photoacclimation (FaRLiP). A conserved, 20-gene FaRLiP cluster encodes core subunits of Photosystem I (PSI) and Photosystem II (PSII), five phycobiliprotein subunits of FRL-bicylindrical cores, and enzymes for synthesis of chlorophyll (Chl) f and possibly Chl d. Deletion mutants for each of the five apc genes of the FaRLiP cluster were constructed in Synechococcus sp. PCC 7335, and all had similar phenotypes. When the mutants were grown in white (WL) or red (RL) light, the cells closely resembled the wild-type (WT) strain grown under the same conditions. However, the WT and mutant strains were very different when grown under FRL. Mutants grown in FRL were unable to assemble FRL-bicylindrical cores, were essentially devoid of FRL-specific phycobiliproteins, but retained RL-type phycobilisomes and WL-PSII. The transcript levels for genes of the FaRLiP cluster in the mutants were similar to those in WT. Surprisingly, the Chl d contents of the mutant strains were greatly reduced (~ 60-99%) compared to WT and so were the levels of FRL-PSII. We infer that Chl d may be essential for the assembly of FRL-PSII, which does not accumulate to normal levels in the mutants. We further infer that the cysteine-rich subunits of FRL allophycocyanin may either directly participate in the synthesis of Chl d or that FRL bicylindrical cores stabilize FRL-PSII to prevent loss of Chl d.

Carbon‐Dot/Natural‐Dye Sensitizer for TiO2 Solar Cells Prepared by a One‐Step Treatment of Celery Leaf Extract

AbstractAttempts have been made to create artificial photovoltaic (PV) devices that can harness sunlight in a clean and efficient way by mimicking natural photosynthesis processes. Inspired by the role of chlorophyll in photosynthesis, we introduced pheophytin‐ or pyropheophytin‐capped carbon dots (CDs) into the dye‐sensitized solar‐cell system. The CD hybrids were synthesized by means of a single‐step hydrothermal treatment of celery leaf extract. The effects of hydrothermal temperature on the physical properties of CDs and the survival rate of the natural dyes were studied. CDs heated at 120 °C (C‐120) display a relatively homogenous smaller particle size distribution and lower photoluminescence emission intensity relative to their counterparts obtained at higher temperatures. Heated at lower temperatures, the achieved CD hybrids contain a higher amount of surviving dye molecules which would be converted into pheophytins or pyropheophytins. The nanocrystalline TiO2 solar cells based on C‐120 gave the highest power conversion efficiency (PCE) of 0.48 % under AM 1.5G one full sun illumination, which can be compared favorably to the average value of 0.20 % normally reported for other biomass‐derived carbon‐dot‐sensitized devices. Besides functioning as a light sensitizer, C‐120 CDs with a lower amount of trap states can also work as an effective electron‐transfer intermediate to improve the interaction between the dye and TiO2 and suppress the photogenerated carrier recombination, thus improving solar‐cell performance.

High chlorophyll a concentration in a low nutrient context: discussions in a subtropical lake dominated by Cyanobacteria

<p>Temporal variability in some water quality parameters can play an important role in determining the presence and abundance of primary producers, and consequently in the trophic state and other characteristics and uses of lake ecosystems. In this sense, the present study aimed at understanding temporal dynamics of some trophic relevant water quality parameters in different time scales and their correlation and influence in phytoplankton biomass (chlorophyll <em>a</em>) in a shallow subtropical coastal lake. Peri Lake is located in Florianópolis island in Southern Brazil and samples were taken monthly between March 2007 and February 2013. The lake showed low dissolved nutrients concentration, especially phosphorus (P) (median dissolved P: 2.0 µg.l<sup>-1</sup>) and high chlorophyll <em>a</em> (median: 20.8 µg.l<sup>-1</sup>) concentration. Total nitrogen (TN) concentration varied broadly, with a median of 672.8 µg L<sup>-1</sup>, and total P (TP) concentration was low (median: 13.5 µg L<sup>-1</sup>). A seasonal pattern of variation concerning dissolved and total P and chlorophyll a concentration was observed, associated mainly with temperature and wind speeds, but no clear pattern was observed for nitrogen (N) fractions. Significant differences were observed in different years for some parameters, with higher chlorophyll a and lower N concentration in the last three years sampled. The lake was considered potentially P limited during the majority of the study period and a positive correlation was found between chlorophyll <em>a</em> and total and dissolved P concentration. Phytoplankton biomass (as chlorophyll <em>a</em>) was apparently controlled by water temperature and P availability (TN:TP ratio and dissolved P). Water transparency (as Secchi depth) was strongly and negatively influenced by chlorophyll <em>a</em> concentration. <em>Cylindrospermopsis raciborskii</em> abilities to compete for P and light seem to be important factors determining its success and dominance in this low P coastal ecosystem. The fluctuating P supply, probably associated to sediment resuspension by wind in this shallow waterbody, is an advantageous factor for cyanobacteria and has an important role in chlorophyll <em>a</em> dynamics. Thus, high chlorophyll <em>a</em> concentration in this subtropical lake seems to be related to the P-limited condition, shallowness and low water column transparency, which are probably favouring the dominance of <em>C. raciborskii</em>, especially in higher summer temperatures, and leading to high chlorophyll <em>a</em> concentration even in a low dissolved nutrient environment.</p>

Influence of anthocyanin co-pigment on electron transport and performance in black rice dye-sensitized solar cell

This work reports the novel contribution of chlorophyll b as natural anthocyanin co-pigment in unpurified black rice extract for improved electron transport and performance of natural dye-sensitized solar cell. The dyes are extracted as prominent photosensitizers by considering the concentration, the dye electronic structure, the extraction, and immersion time. The anthocyanin dye containing 1.92 mM cyanidin-3-O-glucoside structure has been extracted without purification. Interestingly, 0.33 mM chlorophyll b is found as a natural co-sensitizer in unpurified anthocyanin. The role of chlorophyll b supporting the electron transfer of anthocyanin dye will be investigated for improved cell performance. Both purified and unpurified dyes are compared in the same anthocyanin concentration. The combined Tauc plot and voltametric method will be conducted to show the interfacial electronic band edges of TiO2-dye-electrolyte. Electrochemical impedance spectroscopy method will investigate electron transfer dynamic in both cell systems. As a result, chlorophyll b has dominantly acted as two intermediate states in boosting electron injection and dye regeneration to improve cell efficiency from 1.31 to 2.17 % due to the narrower LUMO–TiO2 conduction band gap and the narrower HOMO-iodide (I −) potential gap, respectively. According to the electron transport, the co-sensitizer contributes to the smaller transport resistance (R t = 21.9 Ω), the higher chemical diffusion coefficient (Dn = 1.696 × 10−3 cm2/s), the higher chemical capacitance (Cμ = 14.32 μF), and the faster electron transport (τd = 39.88 μs).

The Teaching of Photosynthesis in Secondary School: A History of the Science Approach

In this article we present a synthesis of the research affecting pupils' conceptions of photosynthesis and plant nutrition. The main false conceptions of the pupils identified in this literature review are: that green plants find their food in the soil; that water and mineral salts are sufficient to the growth of a plant; the role of chlorophyll, where the transformation of luminous energy into chemical energy is never evoked; and air as a source of matter, which is never underlined. Secondly, we are going to see that several of these false conceptions have been developed during history. For example, the famous philosopher Aristotle (384–322 BC) thought that plants receive their food from the soil already elaborated. Several centuries later, the physician and chemist Van Helmont (1677–1644) added more precision to Aristotle’s conception while claiming that plants use only water for their growth. Finally, we will see that the analysis of the false theories developed during history will permit in a context of teaching to valorize the false conceptions of the pupils. Indeed, the history of sciences could incite a teacher to valorize his pupils’ false conceptions while considering them as an indication of difficulties that deserve particular pedagogical and didactic tools. The false conceptions constructed by the pupils don’t have to be ignored in a teaching context because they obey particular reasoning rules, sometimes similar to those that once guided some scientific steps. This view, drawing on false conceptions developed during history, gives a dynamic and human picture of the science very distant from the one sometimes carried on by dogmatic teaching.

Chlorophyll catalyse the photo-transformation of carcinogenic benzo[a]pyrene in water.

Algal blooms cause great damage to water quality and aquaculture. However, this study showed that dead algal cells and chlorophyll could accelerate the photo-transformation of benzo[a]pyrene (BaP), a ubiquitous and persistent pollutant with potently mutagenic and carcinogenic toxicities, under visible light irradiation. Chlorophyll was found to be the major active substance in dead algal cells, and generated a high level of singlet oxygen to catalyse the photo-transformation of BaP. According to various BaP metabolites formed, the degradation mechanism was proposed as that chlorophyll in dead algal cells photo-oxidized BaP to quinones via photocatalytic generation of singlet oxygen. The results provided a good insight into the role of chlorophyll in the photo-transformation of organic contaminants and could be a possible remediation strategy of organic pollutants in natural environment.

Role of chlorophyll in Spirulina on photocatalytic activity of CO2 reduction under visible light over modified N-doped TiO2 photocatalysts

The combination of TiO2 nanoparticles and chlorophyll molecules is promising to provide potential new composite materials for improving photocatalytic CO2 reduction by merging the ability and features of both material types. In this research, the visible light reactive N-doped TiO2 (N–TiO2) catalysts were synthesized using a simple sol–gel method, and chlorophyll in Spirulina was consequently loaded onto the N-doped TiO2 catalysts (Sp/N–TiO2) in an attempt to enhance the photocatalytic efficiency. The effects of nitrogen and chlorophyll in Spirulina, and their loading amount on CO2 photoreduction with water under visible light of Sp/N–TiO2 catalysts were investigated. The activities of catalysts were in the order undoped TiO2<N–TiO2<Sp/N–TiO2. The addition of Spirulina was found to significantly improve the photocatalytic stability and C2+ (C2H4 and C2H6) product selectivity. The 0.5Sp/10N–TiO2 catalyst exhibited approximately 21.3 times and 1.9 times higher total production yield compared with undoped TiO2 and 10N–TiO2, respectively. This outstanding photocatalytic activity could be attributed to the enhancement in visible light harvesting, the surface oxygen vacancies (VO) facilitating reactants adsorption and dissociation, and the synergistic effect between N–TiO2 and chlorophyll in Spirulina.

On the role of chlorophyll b in ontogenetic adaptations of plants

Plants of the barley mutant chlorina3613, which completely lacks chlorophyll b, were investigated over their full life cycle growing in the field under natural light conditions. At various stages of the life cycle, plants were shaded for one week, and the effects of the shading on the further growth were monitored after restoration of the natural light regime. The resuts showed that chlorina3613 plants were characterized by a very low vegetative biomass as well as reproductive yield as compared to the wild type (cv. Donaria). However, when changes in the organization of the photosynthetic apparatus were induced by shading at the stage of booting, chlorina3613 could reach high levels of biomass production and yield in spite of the lack of chlorophyll b.

Chlorophyll d and Acaryochloris marina: current status

The discovery of the chlorophyll d-containing cyanobacterium Acaryochloris marina in 1996 precipitated a shift in our understanding of oxygenic photosynthesis. The presence of the red-shifted chlorophyll d in the reaction centre of the photosystems of Acaryochloris has opened up new avenues of research on photosystem energetics and challenged the unique status of chlorophyll a in oxygenic photosynthesis. In this review, we detail the chemistry and role of chlorophyll d in photosynthesis and summarise the unique adaptations that have allowed the proliferation of Acaryochloris in diverse ecological niches around the world.

Spectrophotometric analysis of chlorophyll pigments in canola and rapeseed oils

AbstractOf all the vegetable oils commonly in production, rapeseed and canola oil have the highest level of undesirable chlorophyll pigments. Chlorophyll is desirable as a flavour and colour agent in olive oil, the other species with significant levels. In canola and rapeseed oils, chlorophyll is not desired because it imparts an undesirable colour, especially in North America where consumers are accustomed to colourless oils. It also makes the processed oils more susceptible to oxidation, even after the chlorophyll components have been removed. The content and role of chlorophyll in canola seed and oil have been well reviewed recently [1].

Differential degradation of photosystem I subunits under iron deficiency in rice

Rice (Oryza sativa) is one of the staple foods of the world. Iron (Fe) deficiency is a major abiotic stress factor that contributes world-wide to losses in crop yield and decline in nutritional quality. As cofactor for many enzymes and proteins, iron is an essential element. It plays a pivotal role in chlorophyll (Chl) biosynthesis, and iron deficiency may result in decreased Chl production and, thus, reduced photosynthetic capacity. Photosystem I (PSI) is a prime target of iron deficiency because of its high iron content (12 Fe per PS). To understand the protein level changes in the light-harvesting complex (LHC) of PSI (LHCI) under iron deficiency, rice seedlings were grown in Hoagland's nutrient medium with and without Fe. Chlorophyll content and photosynthetic efficiency decreased under iron deficiency. Protein gel blots probed with antibodies against the PSI core and Lhca 1–4 proteins revealed that the core subunits PsaA and PsaB remained stable under iron deficiency, whereas PsaC and PsaD decreased by about 50%, and PsaE was completely degraded. Among the LHCI subunits, Lhca1 and Lhca2 decreased by 40 and 50%, respectively, whereas Lhca3 and Lhca4 were completely degraded. We propose that the dissociation of LHCI subunits may be due to increased levels of reactive oxygen species, which is suggested by the increased activity of superoxide dismutase.

Role of chlorophylls and carotenoids in seed tolerance to abiotic stressors

It is found that chlorophylls are not fully destructed during seed ripening and can be detected in appreciable quantities in physiologically mature seeds. The elevated content of residual chlorophylls reduces seed tolerance to abiotic stresses. The seed carotenoids were represented mainly by lutein and, in much smaller quantities, by β-carotene. Carotenoids were found to accumulate in seeds during accelerated aging and during seed germination at high temperatures. The ratio of carotenoid to chlorophyll content (Car/Chl) is proposed to be a measure of seed tolerance to stress factors. The seeds with elevated Car/Chl ratio were characterized by higher tolerance to stress treatments. It is supposed that the presence of chlorophylls in seeds enhances oxidative stress induced by abiotic stress factors. Carotenoids are considered as antioxidants protecting the seeds against oxidative stress.

LIL3, a light-harvesting-like protein, plays an essential role in chlorophyll and tocopherol biosynthesis

The light-harvesting chlorophyll-binding (LHC) proteins are major constituents of eukaryotic photosynthetic machinery. In plants, six different groups of proteins, LHC-like proteins, share a conserved motif with LHC. Although the evolution of LHC and LHC-like proteins is proposed to be a key for the diversification of modern photosynthetic eukaryotes, our knowledge of the evolution and functions of LHC-like proteins is still limited. In this study, we aimed to understand specifically the function of one type of LHC-like proteins, LIL3 proteins, by analyzing Arabidopsis mutants lacking them. The Arabidopsis genome contains two gene copies for LIL3, LIL3:1 and LIL3:2. In the lil3:1/lil3:2 double mutant, the majority of chlorophyll molecules are conjugated with an unsaturated geranylgeraniol side chain. This mutant is also deficient in α-tocopherol. These results indicate that reduction of both the geranylgeraniol side chain of chlorophyll and geranylgeranyl pyrophosphate, which is also an essential intermediate of tocopherol biosynthesis, is compromised in the lil3 mutants. We found that the content of geranylgeranyl reductase responsible for these reactions was severely reduced in the lil3 double mutant, whereas the mRNA level for this enzyme was not significantly changed. We demonstrated an interaction of geranylgeranyl reductase with both LIL3 isoforms by using a split ubiquitin assay, bimolecular fluorescence complementation, and combined blue-native and SDS polyacrylamide gel electrophoresis. We propose that LIL3 is functionally involved in chlorophyll and tocopherol biosynthesis by stabilizing geranylgeranyl reductase.