Displaying publications 81 - 100 of 125 in total

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  1. Fulltext EFFECT OF PHOTO-SELECTIVE NETTING ON GROWTH DEVELOPMENT OF GREEN AMARANTH (Amaranthus viridis L.)
    SITI NABILAH MOHAMMAD SABRI, NURUL FAZIHA IBRAHIM, SITI NABILAH MOHAMMAD SABRI, SUHAIZAN LOB
    UMT Journal of Undergraduate Research, 2020;2(3):67-72.
    MyJurnal
    Green amaranth (Amaranthus viridis L.) is one of the most popular leafy vegetables cultivated in Malaysia. Photo-selective netting is a revolutionary agricultural-technical idea, allowing traditional nets to be improved to a sophisticated level, which can impact microclimate and solar radiation as well as protect crops from pests. This study aims to investigate the growth performance of green amaranth under different three different treatments of photo-selective nets including black, and yellow shade nets and control. The assessed physiological, pre-harvest and post-harvest parameters were air temperature and relative humidity, measurement of absorption of photosynthetically active radiation (PAR), plant height, number of leaves, and dry weight. This study found that the yellow shade net showed the best performance in plant growth with the average difference in plant height (4.11 cm), average leaves number (7 leaves) and average dry weight (18.58 mg) were the highest compared to black shade net and control (without shading). In conclusion, photo-selective yellow shade net was able to enhance the growth development of green amaranth and could be applied in the large scale production to boost the growth and yield of leafy vegetables.
    Matched MeSH terms: Photosynthesis
  2. Global Transcriptome Analysis of Gracilaria changii (Rhodophyta) in Response to Agarolytic Enzyme and Bacterium
    Lim EL, Siow RS, Abdul Rahim R, Ho CL
    Mar Biotechnol (NY), 2016 Apr;18(2):189-200.
    PMID: 26631182 DOI: 10.1007/s10126-015-9680-6
    Many bacterial epiphytes of agar-producing seaweeds secrete agarase that degrade algal cell wall matrix into oligoagars which elicit defense-related responses in the hosts. The molecular defense responses of red seaweeds are largely unknown. In this study, we surveyed the defense-related transcripts of an agarophyte, Gracilaria changii, treated with β-agarase through next generation sequencing (NGS). We also compared the defense responses of seaweed elicited by agarase with those elicited by an agarolytic bacterium isolated from seaweed, by profiling the expression of defense-related genes using quantitative reverse transcription real-time PCR (qRT-PCR). NGS detected a total of 391 differentially expressed genes (DEGs) with a higher abundance (>2-fold change with a p value <0.001) in the agarase-treated transcriptome compared to that of the non-treated G. changii. Among these DEGs were genes related to signaling, bromoperoxidation, heme peroxidation, production of aromatic amino acids, chorismate, and jasmonic acid. On the other hand, the genes encoding a superoxide-generating NADPH oxidase and related to photosynthesis were downregulated. The expression of these DEGs was further corroborated by qRT-PCR results which showed more than 90 % accuracy. A comprehensive analysis of their gene expression profiles between 1 and 24 h post treatments (hpt) revealed that most of the genes analyzed were consistently upregulated or downregulated by both agarase and agarolytic bacterial treatments, indicating that the defense responses induced by both treatments are highly similar except for genes encoding vanadium bromoperoxidase and animal heme peroxidase. Our study has provided the first glimpse of the molecular defense responses of G. changii to agarase and agarolytic bacterial treatments.
    Matched MeSH terms: Photosynthesis
  3. Reduction and biofixation of carbon dioxide in palm oil mill effluent using developed microbial granules containing photosynthetic pigments
    Najib MZM, Salmiati, Ujang Z, Salim MR, Ibrahim Z, Muda K
    Bioresour Technol, 2016 Dec;221:157-164.
    PMID: 27639234 DOI: 10.1016/j.biortech.2016.08.119
    The developed microbial granules containing photosynthetic pigments had successfully achieved approximately 18-21% of carbon dioxide (CO2) removal in POME for one complete SBR cycle. Also, the granules had reached CO2 removal at 15-29% within 24h and removal of 25% after 5 days. Both results were inconsistent possibly due to the slow mass transfer rate of CO2 from gas to liquid as well as the simultaneous effect of CO2 production and respiration among the microbes. Furthermore, results showed the removal of CO2 from air increases proportionally with the CO2 removed in liquid. The CO2 biofixation of granules attained was approximately 0.23g/L/day for a week. Using the regression model, the removal of CO2 between liquid and gas, CO2 biofixation rate were highly correlated with the treatment time. A statistically significant relationship was obtained between CO2 concentration in liquid, biomass productivity and treatment time for the CO2 biofixation rate of the granules.
    Matched MeSH terms: Photosynthesis
  4. Fulltext Effects of temperature on the photosynthetic parameters of antarctic benthic microalgal community
    Salleh, S., McMinn, A., Mohammad, M., Yasin, Z., Tan, S.H.A.
    ASM Science Journal, 2010;4(1):81-88.
    MyJurnal
    Elevated temperature affects marine benthic algae by reducing growth and limits the transport of electron or carbon fixation which may reduce the ability of the cell to use light. This resulting excess light energy may cause photoinhibition. In this study, the photosystem II of the benthic microalgal communities from Casey, eastern Antarctic were relatively unaffected by significant changes in temperatures up to 8ºC, along with high PAR level (450 μmol photons m–2 s–1). Similarly, the community was able to photosynthesize as the temperature was reduced to –5ºC. Recovery from saturating and photoinhibiting irradiances was not significantly influenced by temperatures at both –5ºC and 8ºC. These responses were consistent with those recorded by past experiments on Antarctic benthic diatoms and temperate diatoms which showed that climate change did not have a significant impact on the ability of benthic microalgae to recover from photoinhibitory temperature stress.
    Matched MeSH terms: Photosynthesis
  5. Fulltext Autofluorescence study and selected cyanidin quantification in the Jewel orchids Anoectochilus sp. and Ludisia discolor
    Poobathy R, Zakaria R, Murugaiyah V, Subramaniam S
    PLoS One, 2018;13(4):e0195642.
    PMID: 29649288 DOI: 10.1371/journal.pone.0195642
    Anoectochilus sp. and Ludisia discolor are known as Jewel orchids. Both species are terrestrial wild orchids that grow in shaded areas of forests. The Jewel orchids are renowned for the beauty of their leaves, which are dark-green laced with silvery or golden veins. The orchids are used as a cure in various parts of Asia. Overharvesting and anthropogenic disturbances threaten the existence of the Jewel orchids in the wild, necessitating human intervention in their survival. An understanding of the structure and adaptations of a plant may assist in its survival when propagated outside of its habitat. In this study, ex vitro leaves of Anoectochilus sp. and L. discolor were subjected to freehand sectioning, and then inspected through brightfield and fluorescence microscopy. The study indicated that all parts of both plants presented typical monocotyledonous characteristics except the leaves. The leaves displayed dorsiventrality with distinct palisade and spongy mesophyll layers. The spongy mesophyll layer contained cells which fluoresced a bright red when exposed to ultraviolet, blue, and green light wavelengths, hinting at the presence of anthocyanins for photoprotection. Cyanidin was detected in the leaves of L. discolor, as enumerated through high performance liquid chromatography (HPLC). The observations indicated that Anoectochilus sp. and L. discolor are well-adapted to live under shaded conditions with minimal exposure to light.
    Matched MeSH terms: Photosynthesis
  6. Fulltext A Holistic Approach to Managing Microalgae for Biofuel Applications
    Show PL, Tang MS, Nagarajan D, Ling TC, Ooi CW, Chang JS
    Int J Mol Sci, 2017 Jan 22;18(1).
    PMID: 28117737 DOI: 10.3390/ijms18010215
    Microalgae contribute up to 60% of the oxygen content in the Earth's atmosphere by absorbing carbon dioxide and releasing oxygen during photosynthesis. Microalgae are abundantly available in the natural environment, thanks to their ability to survive and grow rapidly under harsh and inhospitable conditions. Microalgal cultivation is environmentally friendly because the microalgal biomass can be utilized for the productions of biofuels, food and feed supplements, pharmaceuticals, nutraceuticals, and cosmetics. The cultivation of microalgal also can complement approaches like carbon dioxide sequestration and bioremediation of wastewaters, thereby addressing the serious environmental concerns. This review focuses on the factors affecting microalgal cultures, techniques adapted to obtain high-density microalgal cultures in photobioreactors, and the conversion of microalgal biomass into biofuels. The applications of microalgae in carbon dioxide sequestration and phycoremediation of wastewater are also discussed.
    Matched MeSH terms: Photosynthesis
  7. The relationship between heavy metals and trophic properties in Sembrong Lake, Johor
    Nor Bakhiah Baharim, Ismail Yusoff, Wan Zakaria Wan Muhd Tahir, Muhamad Askari, Zainudin Othman, Mohamed Roseli Zainal Abidin, et al.
    Sains Malaysiana, 2016;45:43-53.
    The relationship between heavy metal and trophic properties in polymictic lake at Sembrong Lake, Peninsular Malaysia was assessed. Sixteen parameters, including heavy metals and trophic parameters were monitored. pH, temperature, dissolved oxygen and heavy metals level changes significantly influenced by the dynamic of polymictic mixing pattern. The mean concentrations of heavy metals in the reservoir decreased in the following order: Fe > Mn > Zn > Cu > As > Pb. The result showed that this polymictic lake is being threatened by cultural eutrophication with TSI value range from 72.40 to 80.41 and classified as a hypereutrophic lake. The levels of heavy metal pollution in the reservoir range from slightly polluted to polluted. Factor analysis was performed to determine the relationship between heavy metals and trophic parameters. Five factors were responsible for data structure and explained the 83% of total variance. These factors differentiate each group of parameters according to their common characteristics. Photosynthesis, respiration and redox processes were main factors contributing to the variability of both properties.
    Matched MeSH terms: Photosynthesis
  8. 5-aminolevulinic acid induces regulation in growth, yield and physiobiochemical characteristics of wheat under water stress
    Nudrat Aisha Akram, Shamim Kausar, Naila Farid, Muhammad Ashraf, Muhammad Ashraf, Fahad Al-Qurainy
    Sains Malaysiana, 2018;47:661-670.
    The production of wheat crop is below average in many regions of the world which is ascribed to adverse environmental
    conditions including drought stress. The present study was conducted to appraise the beneficial role of exogenouslyapplied
    5-aminolevulinic acid (ALA) on growth, yield and some key physio-biochemical characteristics of two commercially
    important wheat cultivars (Shafaq-06 and Uqab-2000) under well watered [100% field capacity (FC)] and water-deficit
    (60 and 80% FC) conditions. Imposition of varying water regimes significantly decreased fresh and dry weights of shoots,
    photosynthetic pigments (a and b), non-photochemical quenching of chlorophyll fluorescence (NPQ), quenching coefficient
    for non-photochemical (N) of chlorophyll fluorescence (qN), K+ (potassium ion), Ca2+ (calcium ion) and P (phosphorus)
    accumulation in shoot and root and yield-related attributes. In contrast, water deficit regimes caused improvement in
    Fv/Fm (chlorophyll fluorescence measurement), coefficient of photochemical quenching (qP), proline, glycinebetaine
    (GB) and hydrogen peroxide (H2O2) contents. Foliar spray of ALA at the rate of 50, 100 and 150 mg/Lalong with control
    (no spray (NS) and/or water spray (WS)) significantly enhanced chlorophyll a and b pigments, qN, NPQ, qP, K+, Ca2+
    and P accumulation in both roots and shoots, proline, GB, total phenolics and malondialdehyde (MDA) contents and
    yield. The wheat Shafaq-06 was better in shoot dry weight, qN, NPQ and Fv/Fm, shoot and root K+, root Ca2+, proline,
    GB accumulation and yield attributes, while Uqab-2000 was better in chlorophyll a contents, root P and MDA contents.
    Overall, better growth and yield of Shafaq-06 than Uqab-2000 under water deficit regimes was found to be associated
    with ALA improved leaf fluorescence (qN, NPQ and Fv/Fm), shoot and root K+, root Ca2+, proline and GB accumulation.
    Matched MeSH terms: Photosynthesis
  9. Molecular and physiological responses during thermal acclimation of leaf photosynthesis and respiration in rice
    Rashid FAA, Crisp PA, Zhang Y, Berkowitz O, Pogson BJ, Day DA, et al.
    Plant Cell Environ, 2020 03;43(3):594-610.
    PMID: 31860752 DOI: 10.1111/pce.13706
    To further our understanding of how sustained changes in temperature affect the carbon economy of rice (Oryza sativa), hydroponically grown plants of the IR64 cultivar were developed at 30°C/25°C (day/night) before being shifted to 25/20°C or 40/35°C. Leaf messenger RNA and protein abundance, sugar and starch concentrations, and gas-exchange and elongation rates were measured on preexisting leaves (PE) already developed at 30/25°C or leaves newly developed (ND) subsequent to temperature transfer. Following a shift in growth temperature, there was a transient adjustment in metabolic gene transcript abundance of PE leaves before homoeostasis was reached within 24 hr, aligning with Rdark (leaf dark respiratory CO2 release) and An (net CO2 assimilation) changes. With longer exposure, the central respiratory protein cytochrome c oxidase (COX) declined in abundance at 40/35°C. In contrast to Rdark , An was maintained across the three growth temperatures in ND leaves. Soluble sugars did not differ significantly with growth temperature, and growth was fastest with extended exposure at 40/35°C. The results highlight that acclimation of photosynthesis and respiration is asynchronous in rice, with heat-acclimated plants exhibiting a striking ability to maintain net carbon gain and growth when exposed to heat-wave temperatures, even while reducing investment in energy-conserving respiratory pathways.
    Matched MeSH terms: Photosynthesis
  10. Oil palm (Elaeis guineensis) plantation on tropical peatland in South East Asia: Photosynthetic response to soil drainage level for mitigation of soil carbon emissions
    McCalmont J, Kho LK, Teh YA, Chocholek M, Rumpang E, Rowland L, et al.
    Sci Total Environ, 2023 Feb 01;858(Pt 1):159356.
    PMID: 36270353 DOI: 10.1016/j.scitotenv.2022.159356
    While existing moratoria in Indonesia and Malaysia should preclude continued large-scale expansion of palm oil production into new areas of South-East Asian tropical peatland, existing plantations in the region remain a globally significant source of atmospheric carbon due to drainage driven decomposition of peatland soils. Previous studies have made clear the direct link between drainage depth and peat carbon decomposition and significant reductions in the emission rate of CO2 can be made by raising water tables nearer to the soil surface. However, the impact of such changes on palm fruit yield is not well understood and will be a critical consideration for plantation managers. Here we take advantage of very high frequency, long-term monitoring of canopy-scale carbon exchange at a mature oil palm plantation in Malaysian Borneo to investigate the relationship between drainage level and photosynthetic uptake and consider the confounding effects of light quality and atmospheric vapour pressure deficit. Canopy modelling from our dataset demonstrated that palms were exerting significantly greater stomatal control at deeper water table depths (WTD) and the optimum WTD for photosynthesis was found to be between 0.3 and 0.4 m below the soil surface. Raising WTD to this level, from the industry typical drainage level of 0.6 m, could increase photosynthetic uptake by 3.6 % and reduce soil surface emission of CO2 by 11 %. Our study site further showed that despite being poorly drained compared to other planting blocks at the same plantation, monthly fruit bunch yield was, on average, 14 % greater. While these results are encouraging, and at least suggest that raising WTD closer to the soil surface to reduce emissions is unlikely to produce significant yield penalties, our results are limited to a single study site and more work is urgently needed to confirm these results at other plantations.
    Matched MeSH terms: Photosynthesis
  11. Enhancing photosynthesis and root development for better fruit quality, aroma, and lessening of radioactive materials in key lime (Citrus aurantifolia) using Trichoderma harzianum and Bacillus thuringiensis
    Salem A, Khandaker MM, Mahmud K, Alsufyani SJ, Majrashi AA, Rashid ZM, et al.
    Plant Physiol Biochem, 2024 Jan;206:108295.
    PMID: 38154296 DOI: 10.1016/j.plaphy.2023.108295
    The present study was conducted to investigate the effects of Trichoderma harzianum and Bacillus thuringiensis alone or with gradual levels of NPK on photosynthesis, growth, fruit quality, aroma improvement and reduced radionuclides of key lime fruits. The lemon seedlings were treated with (T0) without fertilizers as control, (T1) 100g of NPK at 100%, (T2) 5 g of Trichoderma. harzianum at 50% + 50 g of NPK at 50%, (T3) 5 g of Bacillus thuringiensis at 50% + 50 g of NPK at 50 %, (T4) 7.5 g of Trichoderma harzianum at 75% + 25 g of NPK at 25 %, (T5) 7.5 g of Bacillus thuringiensis at 75% + 25 g of NPK at 25 %, (T6) 10 g of Trichoderma harzianum at 100 % and (T7)10 g of Bacillus thuringiensis at 100 %. The results showed that T2 increased net photosynthetic rate, stomatal conductance, transpiration rate, internal CO2 concentration, fresh and dry root biomass by 209%, 74%, 56%, 376%, 69.4% and 71.6%, while, T5 increased root volume, root length, and root tip number by 27.1%, 167%, and 67%, respectively over the control trees. The microbial treatments developed cortex, vascular cylinder and tracheal elements of the root. Fruit number, length, diameter, weight, pulp thickness, pulp/peel ratio, juice, total soluble solids (TSS), pigment contents and antioxidant activity increased significantly in the T2 treatment. Vitamin C, total phenols, total flavonoids, and total sugar content increased by 1.59-, 1.66-, 1.44- and 2.07- fold in T5 treated fruits compared to the control. The two microbes increased volatile compounds and decreased radionucleotides in the fruit, moreover, 27 identified and 2 (two) unmatched volatile compounds were identified by GCMS analysis. It is concluded that T. harzianum and B. thuringiensis with 25-50 g NPK treatments improved photosynthesis, root structure, fruit growth, fruit quality, aroma and lessened radionuclides in key lime fruits.
    Matched MeSH terms: Photosynthesis
  12. Fulltext Potential Health Benefits of Deep Sea Water: A Review
    Mohd Nani SZ, Majid FA, Jaafar AB, Mahdzir A, Musa MN
    Evid Based Complement Alternat Med, 2016;2016:6520475.
    PMID: 28105060 DOI: 10.1155/2016/6520475
    Deep sea water (DSW) commonly refers to a body of seawater that is pumped up from a depth of over 200 m. It is usually associated with the following characteristics: low temperature, high purity, and being rich with nutrients, namely, beneficial elements, which include magnesium, calcium, potassium, chromium, selenium, zinc, and vanadium. Less photosynthesis of plant planktons, consumption of nutrients, and organic decomposition have caused lots of nutrients to remain there. Due to this, DSW has potential to become a good source for health. Research has proven that DSW can help overcome health problems especially related to lifestyle-associated diseases such as cardiovascular disease, diabetes, obesity, cancer, and skin problems. This paper reviews the potential health benefits of DSW by referring to the findings from previous researches.
    Matched MeSH terms: Photosynthesis
  13. Fulltext Effects of acute gamma irradiation on physiological traits and flavonoid accumulation of Centella asiatica
    Moghaddam SS, Jaafar H, Ibrahim R, Rahmat A, Aziz MA, Philip E
    Molecules, 2011 Jun 17;16(6):4994-5007.
    PMID: 21694666 DOI: 10.3390/molecules16064994
    In the present study, two accessions of Centella asiatica (CA03 and CA23) were subjected to gamma radiation to examine the response of these accessions in terms of survival rate, flavonoid contents, leaf gas exchange and leaf mass. Radiation Sensitivity Tests revealed that based on the survival rate, the LD(50) (gamma doses that killed 50% of the plantlets) of the plantlets were achieved at 60 Gy for CA03 and 40 Gy for CA23. The nodal segments were irradiated with gamma rays at does of 30 and 40 Gy for Centella asiatica accession 'CA03' and 20 and 30 Gy for accession 'CA23. The nodal segment response to the radiation was evaluated by recording the flavonoid content, leaf gas exchange and leaf biomass. The experiment was designed as RCBD with five replications. Results demonstrated that the irradiated plantlets exhibited greater total flavonoid contents (in eight weeks) significantly than the control where the control also exhibited the highest total flavonoid contents in the sixth week of growth; 2.64 ± 0.02 mg/g DW in CA03 and 8.94 ± 0.04 mg/g DW in CA23. The total flavonoid content was found to be highest after eight weeks of growth, and this, accordingly, stands as the best time for leaf harvest. Biochemical differentiation based on total flavonoid content revealed that irradiated plantlets in CA23 at 20 and 30 Gy after eight weeks contained the highest total flavonoid concentrations (16.827 ± 0.02; 16.837 ± 0.008 mg/g DW, respectively) whereas in CA03 exposed to 30 and 40 Gy was found to have the lowest total flavonid content (5.83 ± 0.11; 5.75 ± 0.03 mg/g DW). Based on the results gathered in this study, significant differences were found between irradiated accessions and control ones in relation to the leaf gas. The highest PN and gs were detected in CA23 as control followed by CA23 irradiated to 20Gy (CA23G20) and CA23G30 and the lowest PN and gs were observed in CA03 irradiated to 40Gy (CA03G40). Moreover, there were no significant differences in terms of PN and gs among the irradiated plants in each accession. The WUE of both irradiated accessions of Centella asiatica were reduced as compared with the control plants (p < 0.01) while Ci and E were enhanced. There were no significant differences in the gas exchange parameters among radiated plants in each accession. Moreover, malondialdehyde (MDA) of accessions after gamma treatments were significantly higher than the control, however, flavonoids which were higher concentration in irradiated plants can scavenge surplus free radicals. Therefore, the findings of this study have proven an efficient method of in vitro mutagenesis through gamma radiation based on the pharmaceutical demand to create economically superior mutants of C. asiatica. In other words, the results of this study suggest that gamma irradiation on C. asiatica can produce mutants of agricultural and economical importance.
    Matched MeSH terms: Photosynthesis/radiation effects
  14. Wheat mitochondrial respiration shifts from the tricarboxylic acid cycle to the GABA shunt under salt stress
    Che-Othman MH, Jacoby RP, Millar AH, Taylor NL
    New Phytol, 2020 02;225(3):1166-1180.
    PMID: 30688365 DOI: 10.1111/nph.15713
    Mitochondrial respiration and tricarboxylic acid (TCA) cycle activity are required during salt stress in plants to provide ATP and reductants for adaptive processes such as ion exclusion, compatible solute synthesis and reactive oxygen species (ROS) detoxification. However, there is a poor mechanistic understanding of how salinity affects mitochondrial metabolism, particularly respiratory substrate source. To determine the mechanism of respiratory changes under salt stress in wheat leaves, we conducted an integrated analysis of metabolite content, respiratory rate and targeted protein abundance measurements. Also, we investigated the direct effect of salt on mitochondrial enzyme activities. Salt-treated wheat leaves exhibit higher respiration rate and extensive metabolite changes. The activity of the TCA cycle enzymes pyruvate dehydrogenase complex and the 2-oxoglutarate dehydrogenase complex were shown to be directly salt-sensitive. Multiple lines of evidence showed that the γ-aminobutyric acid (GABA) shunt was activated under salt treatment. During salt exposure, key metabolic enzymes required for the cyclic operation of the TCA cycle are physiochemically inhibited by salt. This inhibition is overcome by increased GABA shunt activity, which provides an alternative carbon source for mitochondria that bypasses salt-sensitive enzymes, to facilitate the increased respiration of wheat leaves.
    Matched MeSH terms: Photosynthesis/drug effects
  15. Beyond the PAR spectra: impact of light quality on the germination, flowering, and metabolite content of Stevia rebaudiana (Bertoni)
    Rengasamy N, Othman RY, Che HS, Harikrishna JA
    J Sci Food Agric, 2022 Jan 15;102(1):299-311.
    PMID: 34091912 DOI: 10.1002/jsfa.11359
    BACKGROUND: Stevia rebaudiana is a high value crop due to the strong commercial demand for its metabolites (steviol glycosides) but has limited geographical cultivation range. In non-native environments with different daylength and light quality, Stevia has low germination rates and early flowering resulting in lower biomass and poor yield of the desired metabolites. In this study, artificial lighting with light-emitting diodes (LEDs) was used to determine if different light quality within and outside of the photosynthetically active radiation (PAR) range can be used to improve germination rates and yields for production of steviol glycosides for the herbal supplement and food industry.

    RESULTS: Plants treated with red and blue light at an intensity of 130 μmol m-2  s-1 supplemented with 5% of UV-A light under a 16-h photoperiod produced the most desirable overall results with a high rate of germination, low percentage of early flowering, and high yields of dry leaf, stevioside and rebaudioside A, 175 days after planting.

    CONCLUSION: While red and blue light combinations are effective for plant growth, the use of supplemental non-PAR irradiation of UV-A wavelength significantly and desirably delayed flowering, enhanced germination, biomass, rebaudioside A and stevioside yields, while supplemental green light improved yield of biomass and rebaudioside A, but not stevioside. Overall, the combination of red, blue and UV-A light resulted in the best overall productivity for Stevia rebaudiana. © 2021 Society of Chemical Industry.

    Matched MeSH terms: Photosynthesis/radiation effects*
  16. Characterization of Chlamydomonas Ribulose-1,5-bisphosphate carboxylase/oxygenase variants mutated at residues that are post-translationally modified
    Rasineni GK, Loh PC, Lim BH
    Biochim Biophys Acta Gen Subj, 2017 Feb;1861(2):79-85.
    PMID: 27816753 DOI: 10.1016/j.bbagen.2016.10.027
    BACKGROUND: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the chloroplast enzyme that fixes CO2 in photosynthesis, but the enzyme also fixes O2, which leads to the wasteful photorespiratory pathway. If we better understand the structure-function relationship of the enzyme, we might be able to engineer improvements. When the crystal structure of Chlamydomonas Rubisco was solved, four new posttranslational modifications were observed which are not present in other species. The modifications were 4-hydroxylation of the conserved Pro-104 and 151 residues, and S-methylation of the variable Cys-256 and 369 residues, which are Phe-256 and Val-369 in land plants. Because the modifications were only observed in Chlamydomonas Rubisco, they might account for the differences in kinetic properties between the algal and plant enzymes.

    METHODS: Site-directed mutagenesis and chloroplast transformation have been used to test the essentiality of these modifications by replacing each of the residues with alanine (Ala). Biochemical analyses were done to determine the specificity factors and kinetic constants.

    RESULTS: Replacing the modified-residues in Chlamydomonas Rubisco affected the enzyme's catalytic activity. Substituting hydroxy-Pro-104 and methyl-Cys-256 with alanine influenced Rubisco catalysis.

    CONCLUSION: This is the first study on these posttranslationally-modified residues in Rubisco by genetic engineering. As these forms of modifications/regulation are not available in plants, the modified residues could be a means to modulate Rubisco activity.

    GENERAL SIGNIFICANCE: With a better understanding of Rubisco structure-function, we can define targets for improving the enzyme.

    Matched MeSH terms: Photosynthesis/genetics
  17. Fulltext Impact of soil field water capacity on secondary metabolites, phenylalanine ammonia-lyase (PAL), maliondialdehyde (MDA) and photosynthetic responses of Malaysian kacip fatimah (Labisia pumila Benth)
    Jaafar HZ, Ibrahim MH, Mohamad Fakri NF
    Molecules, 2012 Jun 13;17(6):7305-22.
    PMID: 22695235 DOI: 10.3390/molecules17067305
    A randomized complete block design 2 × 4 experiment was designed and conducted for 15 weeks to characterize the relationships between production of total phenolics, flavonoid, anthocyanin, leaf gas exchange, total chlorophyll, phenylalanine ammonia-lyase (PAL) and malondialdehyde (MDA) activity in two varieties of Labisia pumila Benth, namely the var. alata and pumila, under four levels of evapotranspiration replacement (ER) (100%; well watered), (75%, moderate water stress), (50%; high water stress) and (25%; severe water stress). The production of total phenolics, flavonoids, anthocyanin, soluble sugar and relative leaf water content was affected by the interaction between varieties and SWC. As the ER levels decreased from 100% to 25%, the production of PAL and MDA activity increased steadily. At the highest (100%) ER L. pumila exhibited significantly higher net photosynthesis, apparent quantum yield, maximum efficiency of photosystem II (f(v)/f(m)) and lower dark respiration rates compared to the other treatment. The production of total phenolics, flavonoids and anthocyanin was also found to be higher under high water stress (50% ER replacement) compared to severe water stress (25% ER). From this study, it was observed that as net photosynthesis, apparent quantum yield and chlorophyll content were downregulated under high water stress the production of total phenolics, flavonoids and anthocyanin were upregulated implying that the imposition of high water stress can enhance the medicinal properties of L. pumila Benth.
    Matched MeSH terms: Photosynthesis*
  18. Flashing light as growth stimulant in cultivation of green microalgae, Chlorella sp. utilizing airlift photobioreactor
    Fathurrahman L, Hajar AH, Sakinah DW, Nurhazwani Z, Ahmad J
    Pak J Biol Sci, 2013 Nov 15;16(22):1517-23.
    PMID: 24511694
    One of the main limitations of productivity in photobioreactor is the inefficient conversion of the available light into biomass. Photoautotrophic cells such as microalgae only absorb a small fraction of supplied illumination due to limitation of its photosystem's (PS) absorbing rate. However, phenomenon of Flashing Light Effect (FLE) allows microalgae to utilize strong light exceptionally through intermittent exposure. Exposure of strong light at correct frequency of light and dark photoperiod would allow two pigment-protein complexes, PSI and PSII to be at the equilibrium mid-point potential to allow efficient light conversion. Narrow range of optimum frequency is crucial since overexposure to strong light would injured photosynthetic apparatus whereas longer dark period would contributed to loss of biomass due to triacylglycerol metabolism. The behaviour of microalgae towards various illumination conditions of FLE was determined at batch Photobioreactor (PBR) by varying the aeration flow rate: 16.94, 33.14 and 49.28 mL sec(-1) which yield, respectively the light exposure time of 3.99, 1.71 and 1.1 seconds per cycle. Maximum cell density in FLE-PBR was significantly higher at the exponential phase as compared to the continuously illuminated culture (p = 5.62 x 10(-5), a = 0.05) under the flow rate of 25.07 mL sec(-1). Maximum cell density yield of FLE-PBR and continuously illuminated PBR was, respectively 3.1125 x 10(7) and 2.947 x 10(7) cells mL(-1). Utilization of FLE as an innovative solution to increase the efficiency of microalgae to convert light into chemical energy would revolutionize the microalgae culture, reduce the time for cultivation and produce higher maximum biomass density.
    Matched MeSH terms: Photosynthesis/radiation effects
  19. Occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees distributed in a South-east Asian tropical rainforest in Peninsular Malaysia
    Kamakura M, Kosugi Y, Takanashi S, Uemura A, Utsugi H, Kassim AR
    Tree Physiol, 2015 Jan;35(1):61-70.
    PMID: 25595752 DOI: 10.1093/treephys/tpu109
    In this study, we demonstrated the occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees grown in a lowland dipterocarp forest in Peninsular Malaysia. To evaluate the patterns of stomatal behavior, we used three techniques simultaneously to analyze heterobaric or homobaric leaves from five tree species ranging from 0.6 to 31 m in height: (i) diurnal changes in chlorophyll fluorescence imaging, (ii) observation and simulation of leaf gas-exchange rates and (iii) a pressure-infiltration method. Measurements were performed in situ with 1000 or 500 μmol m(-2) s(-1) photosynthetic photon flux density. Diurnal patterns in the spatial distribution of photosynthetic electron transport rate (J) mapped from chlorophyll fluorescence images, a comparison of observed and simulated leaf gas-exchange rates, and the spatial distribution of stomatal apertures obtained from the acid-fuchsin-infiltrated area showed that patchy stomatal closure coupled with severe midday depression of photosynthesis occurred in Neobalanocarpus heimii (King) Ashton, a higher canopy tree with heterobaric leaves due to the higher leaf temperature and vapor pressure deficit. However, subcanopy or understory trees showed uniform stomatal behavior throughout the day, although they also have heterobaric leaves. These results suggest that the occurrence of stomatal patchiness is determined by tree size and/or environmental conditions. The analysis of spatial scale by chlorophyll fluorescence imaging showed that several adjacent anatomical patches (lamina areas bounded by bundle-sheath extensions within the lamina) may co-operate for the distributed patterns of J and stomatal apertures.
    Matched MeSH terms: Photosynthesis*
  20. Fulltext Effect of Root Restriction on the Growth, Photosynthesis Rate, and Source and Sink Relationship of Chilli (Capsicum annuum L.) Grown in Soilless Culture
    Zakaria NI, Ismail MR, Awang Y, Megat Wahab PE, Berahim Z
    Biomed Res Int, 2020;2020:2706937.
    PMID: 32090071 DOI: 10.1155/2020/2706937
    Chilli (Capsicum annum L.) plant is a high economic value vegetable in Malaysia, cultivated in soilless culture containers. In soilless culture, the adoption of small container sizes to optimize the volume of the growing substrate could potentially reduce the production cost, but will lead to a reduction of plant growth and yield. By understanding the physiological mechanism of the growth reduction, several potential measures could be adopted to improve yield under restricted root conditions. The mechanism of growth reduction of plants subjected to root restriction remains unclear. This study was conducted to determine the physiological mechanism of growth reduction of root-restricted chilli plants grown in polyvinyl-chloride (PVC) column of two different volumes, 2392 cm3(root-restricted) and 9570 cm3(control) in soilless culture. Root restriction affected plant growth, physiological process, and yield of chilli plants. Root restriction reduced the photosynthesis rate and photochemical activity of PSII, and increased relative chlorophyll content. Limited root growth in root restriction caused an accumulation of high levels of sucrose in the stem and suggested a transition of the stem as a major sink organ for photoassimilate. Growth reduction in root restriction was not related to limited carbohydrate production, but due to the low sink demand from the roots. Reduction of the total yield per plant about, 23% in root restriction was concomitant, with a slightly increased harvest index which reflected an increased photoassimilate partitioning to the fruit production and suggested more efficient fruits production in the given small plant size of root restriction.
    Matched MeSH terms: Photosynthesis*
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