Search results for "Chlorophyll"
showing 10 items of 453 documents
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…
FluorMODleaf: A new leaf fluorescence emission model based on the PROSPECT model
2010
International audience; A new model of chlorophyll a fluorescence emission by plant leaves, FluorMODleaf, is presented. It is an extension of PROSPECT, a widely used leaf optical properties model that regards the leaf as a pile of N absorbing and diffusing elementary plates. In FluorMODleaf, fluorescence emission of an infinitesimal layer of thickness dx is integrated over the entire elementary plate. The fluorescence source function is based on the excitation spectrum of diluted isolated thylakoids and on the emission spectra of isolated photosystems, PSI and PSII, which are the main pigment–protein complexes involved in the initial stages of photosynthesis. Scattering within the leaf is p…
Molecular structures of chlorophyll a aggregates: spectroscopic and molecular modeling study
1993
Molecular structures of chlorophyll a aggregates have been studied. Spectroscopic properties of these aggregates have been studied by absorption and fluorescence spectroscopy in hydrocarbon solution at various temperatures. Observed spectroscopic shifts were interpreted in terms of simple exciton theory. Exciton splittings were estimated from computer optimized models of previously suggested Chl a aggregate structures.
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…
Interactions between nitrogen fertilization and ozone in watermelon cultivar Reina de Corazones in open-top chambers. Effects on chlorophyll alpha fl…
2006
Watermelon (Citrillus lanants) plants were grown for two consecutive years in open-top chambers with three different ozone concentrations (O-3-free air, O-3 ambient, and air with additional O-3; CFA, NFA, and NFA+O-3) and three nitrogen fertilizer concentrations [0, 14.0, and 29.6 g N per pot; N0, N1, and N2). There was an interaction between ozone and N fertilizer for the major parameters studied. O-3 and N2 treatments led to a significant decrease in maximum efficiency of photosystem 2 (PS2) photochemistry (F-v/F-m), and induced a significant decrease in the actual quantum yield of PS2 (Phi(PS2)), due mainly to the increased closure of PS2 reaction centres (q(P)) and to an increase in the…
Chlorophyll a Fluorescence Emission, Xanthophyll Cycle Activity, and Net Photosynthetic Rate Responses to Ozone in Some Foliose and Fruticose Lichen …
2000
The lichens Parmelia quercina, Parmelia sulcata, Evernia prunastri, Hypogymnia physodes, and Anaptychia ciliaris were exposed to ozone (O3) in controlled environment cuvettes designed to maintain the lichens at optimal physiological activity during exposure. Measurements of gas exchange, modulated chlorophyll (Chl) fluorescence, and pigment analysis were conducted before and after exposure to 300 mm3 (O3) m−3, 4 h per d for 14 d. No changes in the efficiency of photosystem 2 (PS2) photochemistry, the reduction state of QA, or the electron flow through PS2, measured by Chl fluorescence, were detected in any of the five lichen species studied. Additionally, neither photosynthetic CO2 assimila…
Chlorophyll A Fluorescence and Chlorophyll Content in Parmelia Quercina Thalli from a Polluted Region of Northern Castellon (Spain)
1996
AbstractMeasurements of modulated chlorophyll a fluorescence emission and chlorophyll content were made in thalli of Parmelia quercina collected from northern Castellon(Spain). Althoug high air pollution concentrations have been measured in this area, the ratio of variable to maximal fluorescence is unaffected. Following dark-adaptation, the response to irradiance of chlorophyll fluorescence was examined. With respect to control samples, thalli collected in northern Castellon consistently showed differences in fluorescence quenching, the efficiency of excitation energy capture and quenching of basal fluorescence. However, the quantum ield of photochemistry and non-cyclic electron flow were …
Purification and identification of chlorophyll c1 from the green alga Mantoniella squamata
1987
Abstract The prasinophycean alga Mantoniella squamata contains besides chlorophyll a and b a third chlorophyll c -like pigment in its light-harvesting antenna. This third chlorophyll was purified by reverse phase and polyethylene chromatography in order to identify its chemical structure. The absorption and fluorescence spectra were measured not only from the doubly purified pigment, but also from its Mg-free derivates. The spectra were compared with those of authentic chlorophyll c and of Mg-2,4-desethyl-2,4-divinylpheoporphyrin a 5 monomethyl ester which was isolated from Rhodobacter capsulata . The results show that the pigment from Mantoniella agrees best with chlorophyll c 1 . In order…
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…