Search results for "Photosynthesis"
showing 10 items of 304 documents
Carbon autonomy of peach shoots determined by 13C-photoassimilate transport
2009
We used (13)CO(2) tracing and source-sink manipulation to determine if fruiting shoots of peach (Prunus persica (L.) Batsch) trees are autonomous or if they import carbon from neighboring shoots, and if the degree of shoot autonomy is influenced by the source-sink relationship of the shoot. In three experiments, leaf to fruit ratio (L:F) of selected fruiting shoots was moderately (2005 and 2006) or strongly (complete sink removal, 2006) altered to either enhance or inhibit movement of carbon from (13)C-labeled fruiting shoots (LFS) to adjacent non-labeled shoots (NLFS), both located within 10 cm on the same main scaffold of V-shaped peach trees. At Stages I and III of fruit growth, fruit an…
Red and far-red sun-induced chlorophyll fluorescence as a measure of plant photosynthesis
2015
Remote estimation of Sun-induced chlorophyll fluorescence emitted by terrestrial vegetation can provide an unparalleled opportunity to track spatiotemporal variations of photosynthetic efficiency. Here we provide the first direct experimental evidence that the two peaks of the chlorophyll fluorescence spectrum can be accurately mapped from high-resolution radiance spectra and that the signal is linked to variations in actual photosynthetic efficiency. Red and far red fluorescence measured using a novel airborne imaging spectrometer over a grass carpet treated with an herbicide known to inhibit photosynthesis was significantly higher than the corresponding signal from an equivalent untreated…
Growth and Photosynthesis of Nanochlorum eucaryotum, a New and Extremely Small Eucaryotic Green Alga
1982
Nanochlorum eucaryotum is a very small species of unicellular coccoid green algae (1.5 pm). The growth of Nanochlorum under different conditions of salinity, pH and light intensities was studied. Optimal growth rates were observed with normal sea water salinity and low light conditions at pH 7.0. The contents of chlorophylls, carotinoids, soluble proteins and the chlorophyll a to chlorophyll b ratio were measured. The light saturating curves of Nanochlorum cells grown under light intensities of 100 lx, 2000 lx and 10000 lx reveal a very narrow capacity of light adaptation. When cultured under higher light intensities, Nanochlorum was not able to reach high photosynthetic activities but unde…
Climate Over the Ages; Is the Environment Stable?
2010
As described in Chaps. 3 and 4, the advent of oxygenic photosynthesis triggered worldwide environmental changes. A world that had been reductive passed over into a state in which free dioxygen was available in the oceans and the atmosphere. We have already described the likely catastrophic effects on an anaerobic biota, but the changes were much broader than that. Dioxygen in the seas led to major changes in seawater chemistry. Iron, which had previously been soluble as ferrous salts, was precipitated in the ferric form. Copper, which had been insoluble in the anaerobic ocean as cuprous sulphide (Cu+-state), now became moderately soluble in the cupric form (Cu++-state).
Effects of SO2 fumigations on photosynthetic CO2 gas exchange, chlorophyll a fluorescence emission and antioxidant enzymes in the lichens Evernia pru…
1999
The effects of elevated gaseous SO2 concentrations in the lichens Evernia prunastri (L.) Ach. and Ramalina farinacea (L.) Ach. were investigated by means of gas exchange, modulated chlorophyll fluorescence analysis and antioxidant enzyme assays. The response to SO2 of the studied species differed markedly. Net photosynthetic rates were more adversely affected in E. prunastri than in R. farinacea. In addition, processes dependent on thylakoid membrane integrity such as PSII-mediated electron flow and nonphotochemical quenching were reduced to a greater extent by exposure to SO2 in E. prunastri. Moreover, the ability to reoxidize the quinone pool was lower in this species. Finally, the activi…
Folding in vitro of light-harvesting chlorophyll a/b protein is coupled with pigment binding.
2002
The major light-harvesting chlorophyll a/b protein (LHCIIb) of the plant photosynthetic apparatus is able to self-organise in vitro. When the recombinant apoprotein, Lhcb1, is solubilised in the denaturing detergent sodium (or lithium) dodecylsulfate (SDS or LDS) and then mixed with chlorophylls and carotenoids under renaturing conditions, structurally authentic LHCIIb forms. Assembly of functional LHCIIb, as indicated by the establishment of energy transfer between complex-bound chlorophyll molecules, occurs in two apparent kinetic steps with time constants of 10 to 30 seconds and 50 to 300 seconds, depending on the reaction conditions. Here, we use circular dichroism (CD) in the far-UV ra…
Changes of Photosynthesis-Related Parameters and Productivity of Spring Oilseed Rape under Different Nitrogen and Sulphur Fertilizers Supply
2015
Fertilization with essential mineral elements is important to get high quality yield results. The lack of necessary mineral elements in soil can affect oilseed rape plant physiological functions, photosynthesis and plant productivity. Oilseed rape plants have high requirements for nitrogen and as oil crop – for sulphur. The aim of the investigation was to explain changes of chlorophyll a fluorescence parameters in spring oilseed rape leaves and yield changes under nitrogen and sulphur supply. During laboratory experiments changes of chlorophyll a fluorescence parameters and during field experiments changes of yield parameters under different nitrogen and sulphur supply were observed. Labora…
Physiological Aspects of Nitrogen Fertilizer Impact on Latvian Origin Cannabis Sativa L .
2015
The aim of the present study was to evaluate nitrogen fertilizer impact on photosynthesis and yield of hemp, applying modern non-destructive methods. The main object of the investigation – hemp cultivar of Latvian origin ‘Pūriņi’. Laboratory and field experiments showed diverse effects of different nitrogen fertilizer doses on various parameters. Additional nitrogen fertilizer dose of 60 kg ha-1 is most effective as evaluated by chlorophyll content in hemp leaves and changes of chlorophyll a fluorescence parameters. Nitrogen fertilizer negatively affected fiber content in hemp stems, therefore while cultivating hemp only for fiber production use of nitrogen fertilizer should be reduced. Acc…
Impact of elevated ozone on chlorophyll a fluorescence in field-grown oat (Avena sativa).
2001
Oat (Avena sativa) plants were grown in the field near the urban area of Valencia, Eastern Spain. The data on air quality showed that ozone was the main phytotoxic pollutant present in ambient air reaching a 7-h mean of 46 nl l(-1) and a maximum hourly peak of 322 nl l(-1). The effect of ambient ozone on PSII activity was examined by measurements of chlorophyll (Chl) a fluorescence. In leaves with visible symptoms, the function of PSII was changed at high actinic irradiances. Nonphotochemical quenching (NPQ) was higher and quantum efficiency of PSII (Phi(PSII)), photochemical quenching (q(p)), quantum efficiency of excitation capture and PSII electron flow (F(v)'/F(m)') were lower. An enhan…
Effects of ozone on photosynthetic CO2 exchange, chlorophyll a fluorescence and antioxidant systems in lettuce leaves
2002
The effects of ozone exposure on lettuce leaves were investigated by means of gas exchange, modulated chlorophyll a fluorescence and antioxidants systems. High ozone concentration decreased the rate of photosynthesis at light saturation level and changes in stomatal conductance and transpiration rate. However, an increase in intercellular CO 2 concentration indicated a decrease in the carboxylation efficiency. These data agreed with a reduction of non-cyclic electron flow and lower capacity to reduce the quinone pool. Ozone affected the ascorbate pool and decreased ascorbate peroxidase activity, increased lipid peroxidation, altered membrane properties and reduced the development of non-pho…