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Search Results: 1 - 10 of 1057 matches for " photosynthesis "
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The Effect of Photoacclimation on Photosynthetic Energy Storage Efficiency, Determined by Photoacoustics  [PDF]
Yulia Pinchasov-Grinblat, Razy Hoffman, Zvy Dubinsky
Open Journal of Marine Science (OJMS) , 2011, DOI: 10.4236/ojms.2011.12005
Abstract: Photosynthesis rates in phytoplankton depend on light intensity and its spectral composition, however their relation changes with photoacclimation. During the photoacclimation process algal cells optimize their har-vesting and utilization of available light through series of related physical, biophysical, biochemical and physiological changes. These changes result in the ability of phytoplankton to survive under dim light when transported to the depth of the water column and avoid photodynamic damage when exposed to the intense radiation at the surface. Any reduction in the efficiency of light utilization results in decreased rates of pho-tosynthesis rate and slow growth. We present here the study of changes in photosynthetic energy storage efficiency of three phytoplankton species upon photoacclimation to low and high light, as measured by photo-acoustics. Our results illustrate the power of photoacoustics as a tool in aquatic ecology and in the physiological research of phytoplankton.
Influence of Plasmon Excitations in Au Nanoparticles upon Fluorescence and Photostability of Photosynthetic Complexes  [PDF]
Bartosz Krajnik, Nikodem Czechowski, D. Piatkowski, Sebastian Mackowski, Eckhard Hofmann, Stefan Pichler, Wolfgang Heiss
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.31001

Fluorescence spectroscopy is applied to study the influence of plasmon excitations in spherical Au nanoparticles on the optical properties of chlorophyll-containing light-harvesting complexes. The separation between the two nanostructures is controlled via silica layer with varied thickness. We observe strong increase of the emission intensity for a 12- nm-thick spacer and the increase is accompanied with shortening of the fluorescence lifetime, which allows us to separate contributions of absorption and emission rate enhancement. At the same time we find an increase of photobleaching. These findings are interpreted as a result of spectral overlap between plasmon resonance and chlorophyll fluorescence.

Peculiarities of CO2 exchange in soybean genotypes contrasting in grain yield  [PDF]
Jalal A. Aliyev
Advances in Biological Chemistry (ABC) , 2012, DOI: 10.4236/abc.2012.23039
Abstract: The peculiarities of leaf carbon dioxide gas exchange in soybean genotypes grown in field over a large area and contrasting in duration of vegetation, photosynthetic traits and productivity were studied. Varietal differences in the daily and ontogenetic changes in photosynthesis and photorespiration were identified. It was established that the period of the high activity of photosynthetic apparatus in high productive soybean genotypes lasts for a longer time. The photosynthetic rate and the rate of CO2 release in light due to photorespiration are higher in high productive genotypes. A value of photorespiration in contrasting soybean genotypes constitutes about 28% - 35% of photosynthetic rate. The ratio of gross photosynthesis to photorespiration in genotypes with different productivity is constant enough during ontogenesis, indicating a direct positive correlation between gross photosynthesis and photorespiration. Therefore, contrary to conception arisen during many years on the waste-fulness of photorespiration, taking into account the versatile investigations on different aspects of photo-respiration, it was proved that photorespiration is one of the evolutionarily developed vital metabolic processes in plants and the attempts to reduce this process with the purpose of increasing the crop productivity are inconsistent.
Physiological Traits and Metabolites of Cacao Seedlings Influenced by Potassium in Growth Medium  [PDF]
Yan-Mei Li, Marshall Elson, Dapeng Zhang, Richard C. Sicher, Hang Liang, Lyndel W. Meinhardt, Virupax Baligar
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.45133

Cacao (Theobroma cacao L.) is of significant economic importance in several tropical countries but its yield potentials are low mainly because of poor soil fertility especially low levels of potassium (K). Cacao has a high demand for K to maintain healthy growth and production. Knowledge of K use in cacao will help the development of suitable crop management practices and will aid breeding varieties adapted to environments with a limited soil K supply. Using a plant growth chamber, we investigated the growth and physiological traits among three cacao varieties at three levels of growth medium K (52, 156, and 469 mg·plant-1). Significant K effects were observed on growth traits including stem diameter, root length, chlorophyll b, and the ratio of chlorophyll a/b. Significant K effect was also found on carbohydrate metabolites, such as fructose, glucose, myo-inositol, raffinose and starch. However, no K effect was observed in other growth and physiological indicators, including biomass of seedling and net photosynthetic rate. There were significant genotype differences on seedling growth indicators, including stem diameter, stem height, total biomass, leaf biomass, leaf area, root length, chlorophyll a + b and carotenoids. Genotype difference was also found on all measured carbohydrate and starch metabolites, except maltose and raffinose. Results of this study indicate that although K plays a critical role in cacao tree growth and productivity, cacao may be less sensitive to K deficiency during the seedling stage. The present results improved our understanding about K and plants interaction in cacao seedlings, which is useful for crop management and germplasm utilization.

Effect of Water Deficit Imposed during the Early Developmental Phase on Photosynthesis of Cocoa (Theobroma cacao L.)  [PDF]
Kayode Olufemi Ayegboyin, Ezekiel Akinkunmi Akinrinde
Agricultural Sciences (AS) , 2016, DOI: 10.4236/as.2016.71002
Abstract: A greenhouse study was carried out at Cocoa Research Institute of Nigeria, Ibadan to study the effect of water stress on the four popular cocoa genotypes at the institute. F3 Amazon, T1, T7 and Amelonado were raised under different water regimes (daily, 3-day interval, 5-day interval and 7-day interval) at 100%, 50% and 25% field capacities. Data were collected on the height, leaf area, root length, stomata conductance, photosynthetic rate and water use efficiency of the plants. Results showed that plant performances showed genotypic variation in their response to water stress. Generally, there were linear and positive relationships between water level and values in both physiological and morphological responses of cocoa genotypes.
The effect of detergent as polluting agent on the photosynthetic activity and chlorophyll content in bean leaves  [PDF]
Branislav R. Jovanic, Srdjan Bojovic, Bratimir Panic, Bozidar Radenkovic, Marijana Despotovic
Health (Health) , 2010, DOI: 10.4236/health.2010.25059
Abstract: The paper investigates effects of detergent for domestic use on the photosynthetic activity and chlorophyll content in intact bean leaves. The plants were watered for 21 days with a solution of domestic washing powder of 0.60 g r/l. It was established that the activity of photosynthetic apparatus in the plant leaf PhACNorm [%] decreases exponentially with the length of plant treatment/watering. At the end of the treatment (21st day) the activity of photosynthetic apparatus in the dosed plant leaf was no more than 45% of that in control plant (those which were not watered with detergent solution). With increased plant treatment duration the changed chlorophyll concentration ΔChlNorm [%] rose non-linearly in plant leaves. The highest change ΔChlNorm [%] was observed on the 21st day and amounted to 12%.
The Pharmacologic Intensification of the Water Dissociation Process, or Human Photosynthesis, and Its Effect over the Recovery Mechanisms in Tissues Affected by Bloodshed of Diverse Etiology  [PDF]
Arturo Solís Herrera, María del Carmen Arias Esparza, J. Jesús Alvarado Esquivel, Graciela Landín Miranda, Ruth Isabel Solís Arias, Paola Eugenia Solís Arias, Martha Patricia Solís Arias
International Journal of Clinical Medicine (IJCM) , 2011, DOI: 10.4236/ijcm.2011.23058
Abstract: The photoreceptor layer of the human retina has several characteristics that are unique. Their energy requirements are the highest in the organism; in proportion, rods and cones require 10-fold the energy consumed by the cerebral cortex, 6-fold more than the cardiac muscle, and 3-fold more than the renal cortex. Astonishingly, the photoreceptor layer has no blood vessels at all. So, where is the energy to this tissue coming from? In this article we’ll describe the hitherto unknown explanation.
Temperature Dependency of Photosynthesis of Sphagnum spp. Distributed in the Warm-Temperate and the Cool-Temperate Mires of Japan  [PDF]
Akira Haraguchi, Nanae Yamada
American Journal of Plant Sciences (AJPS) , 2011, DOI: 10.4236/ajps.2011.25086
Abstract: We investigated the temperature dependency of photosynthetic rates for five Sphagnum species: Sphagnum palustre, S. fimbriatum in the Tadewara mire (south-western Japan in a warm-temperate zone) and S. papillosum, S. fuscum, S. fallax in the East Ochiishi mire (north-eastern Japan in a cool-temperate zone) measuring photosynthetic light response within a temperature range between 5 and 40C. The maximum photosynthetic rate was obtained at T = 35C for S. palustre, S. fuscum and S. papillosum, and at T = 30C for S. fimbriatum and S. fallax. Photosynthetic rates of all these species showed a maximum at 300 - 500 μmol·m-2·s-1 of PPFD and it decreased at higher PPFD (>500 μmol·m-2·s-1) under low temperature (5C - 10C). These results imply that Sphagnum species are not fully physiologically adapted to low temperature environments, although Sphagnum species distribute mostly in the circumpolar region.
Effects of flooding on grafted annona plants of different scion/rootstock combinations  [PDF]
Xin-Yu Fu, Song-Xing Peng, Shuai Yang, Yong-Hui Chen, Jing-Yi Zhang, Wei-Ping Mo, Jian-Yun Zhu, Yao-Xiong Ye, Xu-Ming Huang
Agricultural Sciences (AS) , 2012, DOI: 10.4236/as.2012.32029
Abstract: Annona atemoya Hort cv. African Pride (AP) is highly valued due to its high quality and unique flavor, but highly susceptible to water-logging. Prevalence of root diseases in saturated soils is one of the main problems in production, which restricts the development of AP in south China, where flooding frequently occurs in rainy seasons. However, some annona species, e.g. A. montana, A. glabra and A. muricata, are relatively tolerant to continuous flooding and periodic water-logging conditions, but of limited commercial value. Yet, the potential may exist to increase flood tolerance of commercial annona varieties by the use of flood tolerant rootstocks. An experiment was conducted with the aim to study the effects of continuous or periodical soil flooding on tree performances of four different annona scion/rootstock combinations: AP/AR/G (scion/interstock/rootstock), AR/G (scion/rootstock), AP/AR/M and AR/M, where AP stands for Annona atemoya Hort cv. African Pride, AR for the hybrid of “AP” atemoya × A. reticulata, used as an interstock, G for pond apple (A. glabra), and M for mountain soursop (A. montana). Plant growth, leaf net photosynthetic rates and chlorophyll fluorescence parameters were measured regularly after flooding treatments were applied. Flooding treatments reduced shoot extension, leaf production, net photosynthetic rates and maximum quantum efficiency of photosystem II (Fv/Fm) in plants of AP/AR/M and AR/M, which displayed wilting within 2 weeks of flooding, with a higher wilting percentage in AP/AR/M than in AR/M. The wilted plants shed all leaves but remained alive and sprouted new but weak shoots after 16 weeks of flooding. Long term flooding did not suppress but enhanced photosynthesis as well as tree growth in AP/AR/G and AR/G, with vigorous growth of adventitious roots. Thus, we suggest the use A. glabra instead of A. montana as a rootstock and AR as an interstock to increase flood tolerance of commercial annona varieties.
Advances in Utilizing Cyanobacteria for Hydrogen Production  [PDF]
Galyna Kufryk
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.36A008
Abstract: Cyanobacteria are photoautotrophic prokaryotes with a remarkable metabolic flexibility. Many species of cyanobacteria produce hydrogen, and the efficiency of this process can be improved by genetic engineering. Isolated photosynthetic complexes of cyanobacteria that are capable of light absorption and charge separation can be utilized in hydrogen-producing devices that are driven by solar energy. As photosynthetic microorganisms, cyanobacteria present a unique opportunity for creating low cost systems for hydrogen production in vivo and in vitro. This review is focused on recent advances in cyanobacterial hydrogen research.


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