Displaying publications 61 - 80 of 130 in total

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  1. Changes in photosynthesis and leaf characteristics with tree height in five dipterocarp species in a tropical rain forest
    Kenzo T, Ichie T, Watanabe Y, Yoneda R, Ninomiya I, Koike T
    Tree Physiol, 2006 Jul;26(7):865-73.
    PMID: 16585032
    Variations in leaf photosynthetic, morphological and biochemical properties with increasing plant height from seedlings to emergent trees were investigated in five dipterocarp species in a Malaysian tropical rain forest. Canopy openness increased significantly with tree height. Photosynthetic properties, such as photosynthetic capacity at light saturation, light compensation point, maximum rate of carboxylation and maximum rate of photosynthetic electron transport, all increased significantly with tree height. Leaf morphological and biochemical traits, such as leaf mass per area, palisade layer thickness, nitrogen concentration per unit area, chlorophyll concentration per unit dry mass and chlorophyll to nitrogen ratio, also changed significantly with tree height. Leaf properties had simple and significant relationships with tree height, with few intra- and interspecies differences. Our results therefore suggest that the photosynthetic capacity of dipterocarp trees depends on tree height, and that the trees adapt to the light environment by adjusting their leaf morphological and biochemical properties. These results should aid in developing models that can accurately estimate carbon dioxide flux and biomass production in tropical rain forests.
    Matched MeSH terms: Photosynthesis*
  2. Midday depression of leaf CO2 exchange within the crown of Dipterocarpus sublamellatus in a lowland dipterocarp forest in Peninsular Malaysia
    Kosugi Y, Takanashi S, Matsuo N, Nik AR
    Tree Physiol, 2009 Apr;29(4):505-15.
    PMID: 19203974 DOI: 10.1093/treephys/tpn041
    We observed diurnal and seasonal patterns of leaf-scale gas exchange within the crown of a Dipterocarpus sublamellatus Foxw. tree growing in a lowland dipterocarp forest at Pasoh, Peninsular Malaysia. Observations were carried out nine times over 6 years, from September 2002 to December 2007. Observation periods included both wet and mild-dry periods, and natural and saturated photosynthetic photon flux density (PPFD) light conditions. In situ measurements of the diurnal change in net photosynthetic rate and in stomatal conductance were carried out on canopy leaves of a 40-m-tall D. sublamellatus tree, which was accessed from a canopy corridor. A diurnal change in electron transport rate was observed under saturated PPFD conditions. The maximum net assimilation rate was approximately 10 micromol m(-2) s(-1). There was a clear inhibition of the net assimilation rate coupled with stomatal closure after late morning and this inhibition occurred year-round. Although the electron transport rate decreased alongside this inhibition, it sometimes followed on. Numerical analysis showed that the main factor in the inhibition of the net assimilation rate was patchy bimodal stomatal closure, which occurred in both mild-dry and wet periods. The midday depression occurred year-round, though there are fluctuations in soil moisture during the mild-dry and wet periods. The magnitude of the inhibition was not related to soil water content but was related to vapor pressure deficit (VPD): that is, whether the days were sunny and hot or cloudy and cool. On cloudy, cool days in the wet period, the net photosynthesis was only moderately inhibited, but it still decreased in the afternoon and was coupled with patchy stomatal closure, even in quite moderate VPD, leaf temperature and PPFD conditions. Our results suggest that patchy stomatal closure signaled by the increase in VPD, in transpiration and by circadian rhythms, was the key factor in constraining midday leaf gas exchange of the D. sublamellatus canopy leaves.
    Matched MeSH terms: Photosynthesis/physiology
  3. Age- and size-related changes in physiological characteristics and chemical composition of Acer pseudoplatanus and Fraxinus excelsior trees
    Abdul-Hamid H, Mencuccini M
    Tree Physiol, 2009 Jan;29(1):27-38.
    PMID: 19203930 DOI: 10.1093/treephys/tpn001
    Forest growth is an important factor both economically and ecologically, and it follows a predictable trend with age. Generally, growth accelerates as canopies develop in young forests and declines substantially soon after maximum leaf area is attained. The causes of this decline are multiple and may be linked to age- or size-related processes, or both. Our objective was to determine the relative effects of tree age and tree size on the physiological attributes of two broadleaf species. As age and size are normally coupled during growth, an approach based on grafting techniques to separate the effects of size from those of age was adopted. Genetically identical grafted seedlings were produced from scions taken from trees of four age classes, ranging from 4 to 162 years. We found that leaf-level net photosynthetic rate per unit of leaf mass and some other leaf structural and biochemical characteristics had decreased substantially with increasing size of the donor trees in the field, whereas other gas exchange parameters expressed on a leaf area basis did not. In contrast, these parameters remained almost constant in grafted seedlings, i.e., scions taken from donor trees with different meristematic ages show no age-related trend after they were grafted onto young rootstocks. In general, the results suggested that size-related limitations triggered the declines in photosynthate production and tree growth, whereas less evidence was found to support a role of meristematic age.
    Matched MeSH terms: Photosynthesis/physiology*
  4. Fulltext Suboptimal Acclimation of Photosynthesis to Light in Wheat Canopies
    Townsend AJ, Retkute R, Chinnathambi K, Randall JWP, Foulkes J, Carmo-Silva E, et al.
    Plant Physiol, 2018 Feb;176(2):1233-1246.
    PMID: 29217593 DOI: 10.1104/pp.17.01213
    Photosynthetic acclimation (photoacclimation) is the process whereby leaves alter their morphology and/or biochemistry to optimize photosynthetic efficiency and productivity according to long-term changes in the light environment. The three-dimensional architecture of plant canopies imposes complex light dynamics, but the drivers for photoacclimation in such fluctuating environments are poorly understood. A technique for high-resolution three-dimensional reconstruction was combined with ray tracing to simulate a daily time course of radiation profiles for architecturally contrasting field-grown wheat (Triticum aestivum) canopies. An empirical model of photoacclimation was adapted to predict the optimal distribution of photosynthesis according to the fluctuating light patterns throughout the canopies. While the photoacclimation model output showed good correlation with field-measured gas-exchange data at the top of the canopy, it predicted a lower optimal light-saturated rate of photosynthesis at the base. Leaf Rubisco and protein contents were consistent with the measured optimal light-saturated rate of photosynthesis. We conclude that, although the photosynthetic capacity of leaves is high enough to exploit brief periods of high light within the canopy (particularly toward the base), the frequency and duration of such sunflecks are too small to make acclimation a viable strategy in terms of carbon gain. This suboptimal acclimation renders a large portion of residual photosynthetic capacity unused and reduces photosynthetic nitrogen use efficiency at the canopy level, with further implications for photosynthetic productivity. It is argued that (1) this represents an untapped source of photosynthetic potential and (2) canopy nitrogen could be lowered with no detriment to carbon gain or grain protein content.
    Matched MeSH terms: Photosynthesis/physiology*
  5. Fulltext Interactive effect of salicylic acid on some physiological features and antioxidant enzymes activity in ginger (Zingiber officinale Roscoe)
    Ghasemzadeh A, Jaafar HZ
    Molecules, 2013 May 21;18(5):5965-79.
    PMID: 23698049 DOI: 10.3390/molecules18055965
    The effect of foliar salicylic acid (SA) applications (10⁻³ and 10⁻⁵ M) on activities of nitrate reductase, guaiacol peroxidase (POD), superoxide dismutases (SOD), catalase (CAT) and proline enzymes and physiological parameters was evaluated in two ginger varieties (Halia Bentong and Halia Bara) under greenhouse conditions. In both varieties, tested treatments generally enhanced photosynthetic rate and total dry weight. Photosynthetic rate increases were generally accompanied by increased or unchanged stomatal conductance levels, although intercellular CO₂ concentrations of treated plants were typically lower than in controls. Lower SA concentrations were generally more effective in enhancing photosynthetic rate and plant growth. Exogenous application of SA increased antioxidant enzyme activities and proline content; the greatest responses were obtained in plants sprayed with 10⁻⁵ M SA, with significant increases observed in CAT (20.1%), POD (45.2%), SOD (44.1%) and proline (43.1%) activities. Increased CAT activity in leaves is naturally expected to increase photosynthetic efficiency and thus net photosynthesis by maintaining a constant CO₂ supply. Our results support the idea that low SA concentrations (10⁻⁵ M) may induce nitrite reductase synthesis by mobilizing intracellular NO³⁻ and can provide protection to nitrite reductase degradation in vivo in the absence of NO³⁻. Observed positive correlations among proline, SOD, CAT and POD activities in the studied varieties suggest that increased SOD activity was accompanied by increases in CAT and POD activities because of the high demands of H₂O₂ quenching.
    Matched MeSH terms: Photosynthesis/drug effects
  6. Eustress responses of Musa acuminata cv. red banana using LED spectra
    Bege J, Pang WQ, Chew BL, Sivalingam E, Manickam S, Mad' Atari MF, et al.
    Photosynth Res, 2025 Jan 13;163(1):4.
    PMID: 39806013 DOI: 10.1007/s11120-024-01130-5
    This study examined the impacts of different LED spectra on the growth of in vitro cultures of Musa acuminata cv. red banana and their biochemical profile, including the antioxidant enzymes catalase and ascorbate peroxidase, photosynthetic pigment and accumulation of total carbohydrate content. The far-red LEDs significantly increase shoot elongation (10.04 cm). The greatest number of shoots (2.97) and the greatest multiplication rate (80%) were obtained under the treatment with blue + red LEDs. The formation of microshoots were also enhanced by blue and white LED exposure in a range of 2-2.57 shoots per explant. Root formation was also stimulated by dichromatic blue + red (6.00) LED using MS medium with 2 µM indole-3-butyric acid (IBA). The enzymes catalase and ascorbate peroxidase were significantly up-regulated by irradiation with far-red (0.11 ± 0.02 CAT, 0.18 ± 0.04 APX U/mg) and blue (0.08 ± 0.01CAT, 0.10 ± 0.01APX U/mg) LED light. Total chlorophyll (0.45 to 0.80 mg/g) was elevated significantly by blue, blue + red and mint-white LED. On the other hand, carotenoids (12.08-14.61 mg/g) were significantly boosted by blue + red, red and mint-white LED light. Meanwhile, porphyrin (294.10-350.57 mg/g) was highly synthesised after irradiation with mint-white light. Irradiation with LED light significantly increased the accumulation of carbohydrates with the highest carbohydrate content under blue + red LED light (102.22 ± 2.46 mg/g) and blue light (91.69 ± 2.10 mg/g). In conclusion, these results confirm that the vegetative properties and biochemical profile of red banana in vitro are eustress response to LED spectra.
    Matched MeSH terms: Photosynthesis/radiation effects
  7. The influence of hydrogen peroxide on the growth, development and quality of wax apple (Syzygium samarangense, [Blume] Merrill & L.M. Perry var. jambu madu) fruits
    Khandaker MM, Boyce AN, Osman N
    Plant Physiol Biochem, 2012 Apr;53:101-10.
    PMID: 22349652 DOI: 10.1016/j.plaphy.2012.01.016
    The present study represents the first report of the effect of hydrogen peroxide (H(2)O(2)) on the growth, development and quality of the wax apple fruit, a widely cultivated fruit tree in South East Asia. The wax apple trees were spray treated with 0, 5, 20 and 50 mM H(2)O(2) under field conditions. Photosynthetic rates, stomatal conductance, transpiration, chlorophyll and dry matter content of the leaves and total soluble solids and total sugar content of the fruits of wax apple (Syzygium samarangense, var. jambu madu) were significantly increased after treatment with 5 mM H(2)O(2). The application of 20 mM H(2)O(2) significantly reduced bud drop and enhanced fruit growth, resulting in larger fruit size, increased fruit set, fruit number, fruit biomass and yield compared to the control. In addition, the endogenous level of H(2)O(2) in wax apple leaves increased significantly with H(2)O(2) treatments. With regard to fruit quality, 20 mM H(2)O(2) treatment increased the K(+), anthocyanin and carotene contents of the fruits by 65%, 67%, and 41%, respectively. In addition, higher flavonoid, phenol and soluble protein content, sucrose phosphate synthase (SPS), phenylalanine ammonia lyase (PAL) and antioxidant activities were recorded in the treated fruits. There was a positive correlation between peel colour (hue) and TSS, between net photosynthesis and SPS activity and between phenol and flavonoid content with antioxidant activity in H(2)O(2)-treated fruits. It is concluded that spraying with 5 and 20 mM H(2)O(2) once a week produced better fruit growth, maximising the yield and quality of wax apple fruits under field conditions.
    Matched MeSH terms: Photosynthesis/drug effects*; Photosynthesis/physiology
  8. Carotenoid biosynthesis regulatory mechanisms in plants
    Othman R, Mohd Zaifuddin FA, Hassan NM
    J Oleo Sci, 2014;63(8):753-60.
    PMID: 25017864
    Carotenoids are bioactive compounds with remarkably special properties produced by plants in response to internal and external stresses. In this review paper, we focus on the subject of carotenoid biosynthesis and several factors that have been reported to significantly enhance or reduce carotenoid accumulation in studied plant species. These factors include varietal aspects, location, growing season, and type of stress experienced by a plant. In addition, we propose that there are three stress resistance mechanisms in plants: avoidance, tolerance, and acclimation. Better understanding of the environmental factors affecting carotenoid biosynthesis will help researchers to develop methods for enhancing the production of carotenoids and other pigments to desired concentrations in plant crops.
    Matched MeSH terms: Photosynthesis
  9. Biomass accumulation and energy conversion efficiency in aromatic rice genotypes
    Shahidullah SM, Hanafi MM, Ashrafuzzaman M, Razi Ismail M, Salam MA, Khair A
    C. R. Biol., 2010 Jan;333(1):61-7.
    PMID: 20176338 DOI: 10.1016/j.crvi.2009.10.002
    A field experiment was conducted to evaluate photosynthetic efficiency along with different growth parameters of aromatic rice genotypes. Forty genotypes including three non-aromatic checks exhibited enormous variations for leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), grain yield, total dry matter, harvest index and photosynthetic efficiency or energy use efficiency (Emu) at panicle initiation and heading stages. Minimum LAI-value was 0.52 in Khazar at PI stage and maximum was 4.91 in Sakkor khora at heading stage. The CGR-value was in the range of 4.80-24.11 g m(-2) per day. The best yielder BR39 produced grain of 4.21 t ha(-1) and the worst yielder Khazar gave 1.42 t ha(-1). Total dry matter (TDM) yield varied from 4.04 to 12.26 t ha(-1) where genotypes proved their energy use efficiency a range between 0.58 to 1.65%. Emu showed a significant positive relation with TDM (r=0.80(**)), CGR (r=0.72(**)) and grain yield (r=0.66(**)). A negative correlation was established between TDM and harvest index and LAI and RGR. Path analysis result showed that NAR at heading stage exerted highest positive direct effect (0.70) on Emu.
    Matched MeSH terms: Photosynthesis
  10. Diel changes in the CO2 exchange rates of reproductive organs of the tropical tree Durio zibethinus
    Ogawa K, Abdullah AM, Awang M, Furukawa A
    J Plant Res, 2005 Jun;118(3):187-92.
    PMID: 15937725
    The daily variations in the in situ CO(2) exchange of the reproductive organs of Durio zibethinus trees, growing in an experimental field at University Putra Malaysia (UPM), were examined at different growth stages. Reproductive organs emerged on the leafless portions of branches inside the crown. The photon flux densities (PFD) in the chambers used for the measurements were less than 100 mumol m(-2) s(-1) and were 40% of the PFD outside of the crown. The daytime net respiration rate and the nighttime dark respiration rate were higher at the time of flower initiation and during the mixed stages, when flower buds, flowers, and fruit coexist, than at the flower bud stage. The net respiration rate was lower than the daytime dark respiration rate at given temperatures, especially at the flower bud and fruit stages. Conversely, the net respiration rate was similar to the daytime dark respiration rate at the mixed stage. Photosynthetic CO(2) refixation reduced the daily respiratory loss by 17, 5, 0.3, and 24% at the flower bud, flower initiation, mixed, and fruit stages, respectively.
    Matched MeSH terms: Photosynthesis
  11. Comparative proteomic analysis of oil palm leaves infected with Ganoderma boninense revealed changes in proteins involved in photosynthesis, carbohydrate metabolism, and immunity and defense
    Jeffery Daim LD, Ooi TE, Ithnin N, Mohd Yusof H, Kulaveerasingam H, Abdul Majid N, et al.
    Electrophoresis, 2015 Aug;36(15):1699-710.
    PMID: 25930948 DOI: 10.1002/elps.201400608
    The basidiomycete fungal pathogen Ganoderma boninense is the causative agent for the incurable basal stem rot (BSR) disease in oil palm. This disease causes significant annual crop losses in the oil palm industry. Currently, there is no effective method for disease control and elimination, nor is any molecular marker for early detection of the disease available. An understanding of how BSR affects protein expression in plants may help identify and/or assist in the development of an early detection protocol. Although the mode of infection of BSR disease is primarily via the root system, defense-related genes have been shown to be expressed in both the root and leafs. Thus, to provide an insight into the changes in the global protein expression profile in infected plants, comparative 2DE was performed on leaf tissues sampled from palms with and without artificial inoculation of the Ganoderma fungus. Comparative 2DE revealed that 54 protein spots changed in abundance. A total of 51 protein spots were successfully identified by LC-QTOF MS/MS. The majority of these proteins were those involved in photosynthesis, carbohydrate metabolism as well as immunity and defense.
    Matched MeSH terms: Photosynthesis
  12. Fulltext Coral mass spawning predicted by rapid seasonal rise in ocean temperature
    Keith SA, Maynard JA, Edwards AJ, Guest JR, Bauman AG, van Hooidonk R, et al.
    Proc Biol Sci, 2016 05 11;283(1830).
    PMID: 27170709 DOI: 10.1098/rspb.2016.0011
    Coral spawning times have been linked to multiple environmental factors; however, to what extent these factors act as generalized cues across multiple species and large spatial scales is unknown. We used a unique dataset of coral spawning from 34 reefs in the Indian and Pacific Oceans to test if month of spawning and peak spawning month in assemblages of Acropora spp. can be predicted by sea surface temperature (SST), photosynthetically available radiation, wind speed, current speed, rainfall or sunset time. Contrary to the classic view that high mean SST initiates coral spawning, we found rapid increases in SST to be the best predictor in both cases (month of spawning: R(2) = 0.73, peak: R(2) = 0.62). Our findings suggest that a rapid increase in SST provides the dominant proximate cue for coral mass spawning over large geographical scales. We hypothesize that coral spawning is ultimately timed to ensure optimal fertilization success.
    Matched MeSH terms: Photosynthesis
  13. Influence of treated palm oil mill effluent sludge on maize (zea mays) growth performance and gas exchange
    Mohd Nizar K, Abd Jamil Z, Isharudin M, Hazandy A
    Sains Malaysiana, 2018;47:961-969.
    The presence of abundant oil palm residues in Malaysia prompted the need to utilize this waste to avoid environmental
    pollution. This waste was abundant at the oil palm mill and accounted for almost 50% of production. The study was
    conducted to determine the morphological effect of Palm Oil Mill Effluent (POME) sludge on the maize growth performance
    and gas exchange. Physicochemical, growth morphology and gas exchange was measured after treated with POME sludge
    from different treatment pond systems: Mixing, anaerobic, facultative, algae and dumping. The results indicated the
    pH, C, and CEC of mixing the < anaerobic < facultative < algae < dumping ponds. There was a significant presence of
    macronutrient (N, Mg, Ca, Fe, S) in the treated POME sludge, contrary to the presence of heavy metal (Cd, Cu, Ni and
    Pb) elements which were not significantly different in all the treatments and lower than WHO/FAO standard. Root Shoot
    Ratio (RSR) and Specific Leaf Area (SLA) indicated significant difference in biomass accumulation and yield compared to
    the control. The gas exchange variable was a significant difference on stomata conductivity (Gs) and transpiration rate
    (E). However, the POME sludge from the facultative, algae and dumping ponds showed positive correlations between net
    photosynthesis, stomata conductivity and transpiration rate. Indeed, the increased transpiration rate (E) was correlated
    with stomata conductance (Gs) after treatment with anaerobic, facultative, algae and dumping ponds. In conclusion, the
    POME sludge amendment was able to increase the maize biomass and yield.
    Matched MeSH terms: Photosynthesis
  14. Dissection of synechococcus rubisco large subunit sections involved in holoenzyme formation in escherichia coli by combinatorial section swapping and sequence analyses
    Yee Hung Yeap, Teng Wei Koay, Boon Hoe Lim
    Sains Malaysiana, 2018;47:2269-2289.
    Engineering the CO2
    -fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) to improve photosynthesis
    has long been sought. Rubisco large subunits (RbcL) are highly-conserved but because of certain undefined sequence
    differences, plant Rubisco research cannot fully utilise the robust heterologous Escherichia coli expression system and its
    GroEL folding machinery. Previously, a series of chimeric cyanobacteria Synechococcus elongatus Rubisco, incorporated
    with sequences from the green alga Chlamydomonas reinhardtii, were expressed in E. coli; differences in RbcL sections
    essential for holoenzyme formation were pinpointed. In this study, the remaining sections, presumably not crucial for
    holoenzyme formation and also the small subunit (RbcS), are substituted to further ascertain the possible destabilising
    effects of multiple section mutations. To that end, combinations of Synechococcus RbcL Sections 1 (residues 1-47), 2
    (residues 48-97), 5 (residues 198-247) and 10 (residues 448-472), and RbcS, were swapped with collinear Chlamydomonas
    sections and expressed in E. coli. Interestingly, only the chimera with Sections 1 and 2 together produces holoenzyme and
    an interaction network of complementing amino acid changes is delineated by crystal structure analysis. Furthermore,
    sequence-based analysis also highlighted possible GroEL binding site differences between the two RbcLs.
    Matched MeSH terms: Photosynthesis
  15. Physiological and metabolic responses of Scenedesmus quadricauda (Chlorophyceae) to nickel toxicity and warming
    Yong WK, Sim KS, Poong SW, Wei D, Phang SM, Lim PE
    3 Biotech, 2019 Aug;9(8):315.
    PMID: 31406637 DOI: 10.1007/s13205-019-1848-8
    An ecologically important tropical freshwater microalga, Scenedesmus quadricauda, was exposed to Ni toxicity under two temperature regimes, 25 and 35 °C to investigate the interactive effects of warming and different Ni concentrations (0.1, 1.0 and 10.0 ppm). The stress responses were assessed from the growth, photosynthesis, reactive oxygen species (ROS) generation and metabolomics aspects to understand the effects at both the physiological and biochemical levels. The results showed that the cell densities of the cultures were higher at 35 °C compared to 25 °C, but decreased with increasing Ni concentrations at 35 °C. In terms of photosynthetic efficiency, the maximum quantum yield of photosystem II (Fv/Fm) of S. quadricauda remained consistent across different conditions. Nickel concentration at 10.0 ppm affected the maximum rate of relative electron transport (rETRm) and saturation irradiance for electron transport (Ek) in photosynthesis. At 25 °C, the increase of non-photochemical quenching (NPQ) values in cells exposed to 10.0 ppm Ni might indicate the onset of thermal dissipation process as a self-protection mechanism against Ni toxicity. The combination of warming and Ni toxicity induced a strong oxidative stress response in the cells. The ROS level increased significantly by 40% after exposure to 10.0 ppm of Ni at 35 °C. The amount of Ni accumulated in the biomass was higher at 25 °C compared to 35 °C. Based on the metabolic profile, temperature contributed the most significant differentiation among the samples compared to Ni treatment and the interaction between the two factors. Amino acids, sugars and organic acids were significantly regulated by the combined factors to restore homeostasis. The most affected pathways include sulphur, amino acids, and nitrogen metabolisms. Overall, the results suggest that the inhibitory effect of Ni was lower at 35 °C compared to 25 °C probably due to lower metal uptake and primary metabolism restructuring. The ability of S. quadricauda to accumulate substantial amount of Ni and thrive at 35 °C suggests the potential use of this strain for phycoremediation and outdoor wastewater treatment.
    Matched MeSH terms: Photosynthesis
  16. Fulltext Potential of Zeolite and Algae in Biomass Immobilization
    Emami Moghaddam SA, Harun R, Mokhtar MN, Zakaria R
    Biomed Res Int, 2018;2018:6563196.
    PMID: 30643814 DOI: 10.1155/2018/6563196
    The interest in utilizing algae for wastewater treatment has been increased due to many advantages. Algae-wastewater treatment system offers a cost-efficient and environmentally friendly alternative to conventional treatment processes such as electrocoagulation and flocculation. In this biosystem, algae can assimilate nutrients in the wastewater for their growth and simultaneously capture the carbon dioxide from the atmosphere during photosynthesis resulting in a decrease in the greenhouse gaseousness. Furthermore, the algal biomass obtained from the treatment process could be further converted to produce high value-added products. However, the recovery of free suspended algae from the treated effluent is one of the most important challenges during the treatment process as the current methods such as centrifugation and filtration are faced with the high cost. Immobilization of algae is a suitable approach to overcome the harvesting issue. However, there are some drawbacks with the common immobilization carriers such as alginate and polyacrylamide related to low stability and toxicity, respectively. Hence, it is necessary to apply a new carrier without the mentioned problems. One of the carriers that can be a suitable candidate for the immobilization is zeolite. To date, various types of zeolite have been used for the immobilization of cells of bacteria and yeast. If there is any possibility to apply them for the immobilization of algae, it needs to be considered in further studies. This article reviews cell immobilization technique, biomass immobilization onto zeolites, and algal immobilization with their applications. Furthermore, the potential application of zeolite as an ideal carrier for algal immobilization has been discussed.
    Matched MeSH terms: Photosynthesis
  17. Fulltext Elevated CO2 improves both lipid accumulation and growth rate in the glucose-6-phosphate dehydrogenase engineered Phaeodactylum tricornutum
    Wu S, Gu W, Huang A, Li Y, Kumar M, Lim PE, et al.
    Microb Cell Fact, 2019 Sep 23;18(1):161.
    PMID: 31547820 DOI: 10.1186/s12934-019-1214-x
    BACKGROUND: Numerous studies have shown that stress induction and genetic engineering can effectively increase lipid accumulation, but lead to a decrease of growth in the majority of microalgae. We previously found that elevated CO2 concentration increased lipid productivity as well as growth in Phaeodactylum tricornutum, along with an enhancement of the oxidative pentose phosphate pathway (OPPP) activity. The purpose of this work directed toward the verification of the critical role of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the OPPP, in lipid accumulation in P. tricornutum and its simultaneous rapid growth rate under high-CO2 (0.15%) cultivation.

    RESULTS: In this study, G6PDH was identified as a target for algal strain improvement, wherein G6PDH gene was successfully overexpressed and antisense knockdown in P. tricornutum, and systematic comparisons of the photosynthesis performance, algal growth, lipid content, fatty acid profiles, NADPH production, G6PDH activity and transcriptional abundance were performed. The results showed that, due to the enhanced G6PDH activity, transcriptional abundance and NAPDH production, overexpression of G6PDH accompanied by high-CO2 cultivation resulted in a much higher of both lipid content and growth in P. tricornutum, while knockdown of G6PDH greatly decreased algal growth as well as lipid accumulation. In addition, the total proportions of saturated and unsaturated fatty acid, especially the polyunsaturated fatty acid eicosapentaenoic acid (EPA; C20:5, n-3), were highly increased in high-CO2 cultivated G6PDH overexpressed strains.

    CONCLUSIONS: The successful of overexpression and antisense knockdown of G6PDH well demonstrated the positive influence of G6PDH on algal growth and lipid accumulation in P. tricornutum. The improvement of algal growth, lipid content as well as polyunsaturated fatty acids in high-CO2 cultivated G6PDH overexpressed P. tricornutum suggested this G6PDH overexpression-high CO2 cultivation pattern provides an efficient and economical route for algal strain improvement to develop algal-based biodiesel production.

    Matched MeSH terms: Photosynthesis
  18. In-situ growth of TiO2 imbedded Ti3C2TA nanosheets to construct PCN/Ti3C2TA MXenes 2D/3D heterojunction for efficient solar driven photocatalytic CO2 reduction towards CO and CH4 production
    Tahir M, Tahir B
    J Colloid Interface Sci, 2021 Jun;591:20-37.
    PMID: 33588310 DOI: 10.1016/j.jcis.2021.01.099
    Constructing efficient structured materials for artificial photosynthesis of CO2 is a promising strategy to produce renewable fuels in addition of mitigating greenhouse effect. In this work, 2D porous g-C3N4 (PCN) coupled exfoliated 3D Ti3C2TA MXene (TiC) nanosheets with TiO2 NPs in-situ growth was constructed in a single step through HF treatment approach. The different exfoliated TiC structures were successfully synthesized for adjusting HF etching time (24 h, 48 h and 96 h). With growing etchant time from 24 to 96 h, the amount of TiO2 produced was increased, but it has adverse effects on CO and CH4 production rate. The maximum production rates for CO and CH4 of 317.4 and 78.55 µmol g-1 h-1 were attained when the 10TiC-48/PCN was employed than using TiC-24/PCN, TiC-96/PCN and PCN composite samples, respectively. The performance of 10TiC-48/PCN composite for CO and CH4 evolution were 9.9 and 6.7 folds higher than using pristine PCN sample, respectively. The possible mechanism is assigned to porous structure with intimate contact enabling efficient charge carrier separation with the role of TiO2 NPs to work as a bridge to transport electrons towards MXene surface. Among the reducing agents, water was favorable for CO evolution, whereas, methanol-water system promoted CH4 production. All these findings confirm that heterojunction formation facilitates charges separation and can be further used in solar energy relating application.
    Matched MeSH terms: Photosynthesis
  19. Metal-Organic Framework Decorated Cuprous Oxide Nanowires for Long-lived Charges Applied in Selective Photocatalytic CO2 Reduction to CH4
    Wu H, Kong XY, Wen X, Chai SP, Lovell EC, Tang J, et al.
    Angew Chem Int Ed Engl, 2021 Apr 06;60(15):8455-8459.
    PMID: 33368920 DOI: 10.1002/anie.202015735
    Improving the stability of cuprous oxide (Cu2 O) is imperative to its practical applications in artificial photosynthesis. In this work, Cu2 O nanowires are encapsulated by metal-organic frameworks (MOFs) of Cu3 (BTC)2 (BTC=1,3,5-benzene tricarboxylate) using a surfactant-free method. Such MOFs not only suppress the water vapor-induced corrosion of Cu2 O but also facilitate charge separation and CO2 uptake, thus resulting in a nanocomposite representing 1.9 times improved activity and stability for selective photocatalytic CO2 reduction into CH4 under mild reaction conditions. Furthermore, direct transfer of photogenerated electrons from the conduction band of Cu2 O to the LUMO level of non-excited Cu3 (BTC)2 has been evidenced by time-resolved photoluminescence. This work proposes an effective strategy for CO2 conversion by a synergy of charge separation and CO2 adsorption, leading to the enhanced photocatalytic reaction when MOFs are integrated with metal oxide photocatalyst.
    Matched MeSH terms: Photosynthesis
  20. Fulltext Shading Effects on Leaf Gas Exchange, Leaf Pigments and Secondary Metabolites of Polygonum minus Huds., an Aromatic Medicinal Herb
    Mohd Yusof FF, Yaacob JS, Osman N, Ibrahim MH, Wan-Mohtar WAAQI, Berahim Z, et al.
    Plants (Basel), 2021 Mar 23;10(3).
    PMID: 33806923 DOI: 10.3390/plants10030608
    The growing demand for high value aromatic herb Polygonum minus-based products have increased in recent years, for its antioxidant, anticancer, antimicrobial, and anti-inflammatory potentials. Although few reports have indicated the chemical profiles and antioxidative effects of Polygonum minus, no study has been conducted to assess the benefits of micro-environmental manipulation (different shading levels) on the growth, leaf gas exchange and secondary metabolites in Polygonum minus. Therefore, two shading levels (50%:T2 and 70%:T3) and one absolute control (0%:T1) were studied under eight weeks and 16 weeks of exposures on Polygonum minus after two weeks. It was found that P. minus under T2 obtained the highest photosynthesis rate (14.892 µmol CO2 m-2 s-1), followed by T3 = T1. The increase in photosynthesis rate was contributed by the enhancement of the leaf pigments content (chlorophyll a and chlorophyll b). This was shown by the positive significant correlations observed between photosynthesis rate with chlorophyll a (r2 = 0.536; p ≤ 0.05) and chlorophyll b (r2 = 0.540; p ≤ 0.05). As the shading levels and time interval increased, the production of total anthocyanin content (TAC) and antioxidant properties of Ferric Reducing Antioxidant Power (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) also increased. The total phenolic content (TPC) and total flavonoid content (TFC) were also significantly enhanced under T2 and T3. The current study suggested that P.minus induce the production of more leaf pigments and secondary metabolites as their special adaptation mechanism under low light condition. Although the biomass was affected under low light, the purpose of conducting the study to boost the bioactive properties in Polygonum minus has been fulfilled by 50% shading under 16 weeks' exposure.
    Matched MeSH terms: Photosynthesis
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