Search results for "Photosynthesis"
showing 10 items of 304 documents
The intracellular Arabidopsis COPT5 transport protein is required for photosynthetic electron transport under severe copper deficiency
2011
Copper is an essential micronutrient that functions as a redox cofactor in multiple plant processes, including photosynthesis. Arabidopsis thaliana possesses a conserved family of CTR-like high-affinity copper transport proteins denoted as COPT1-5. COPT1, the only family member that is functionally characterized, participates in plant copper acquisition. However, little is known about the function of the other Arabidopsis COPT proteins in the transport and distribution of copper. Here, we show that a functional fusion of COPT5 to the green fluorescent protein localizes in Arabidopsis cells to the prevacuolar compartment. Plants defective in COPT5 do not exhibit any significant phenotype und…
Die Wirkung unterschiedlicher Lichtintensitäten auf die Nitratreduktase-Aktivität, den Gehalt an löslichen Proteinen und löslichen reduzierenden Zuck…
1977
Summary Plants of Sinapis alba (white mustard) grown under strong light conditions have a higher content of soluble reducing sugars, of soluble proteins and a higher dry wight during growth from germination to flowering. Furthermore, in these plants the nitrate reductase activity is essentially higher during the vegetative development, but before the beginning of the flowering phase the activity is less than the level of plants grown under low light intensities. The results obtained indicate a direct correlation between nitrate reductase activity and the content of soluble proteins. In the high-light plants both components show distinct maxima 13—14 days after sowing the seeds. The enhancem…
Measurement of Photosynthesis and Transpiration in Spruce Trees with Various Degrees of Damage
1987
Summary In the context of a project on physiological and biochemical characterization of spruce with different degrees of damage, the C02 and H2O gas exchange of 22-year-old spruce from a location in the Hunsru.ck (West Germany) were measured in summer 1985. The measurements were carried out on shoots from 1984 and were set up as a pair comparison, i.e. the measurement data of a tree with symptoms of damage were always compared with a tree in the immediate vicinity which phenotypically showed less damage. Diurnal course measurements in the open air revealed a marked reduction of photosynthesis depending on the degree of damage of the trees. If one plots photosynthetic rate against light int…
Morpho-physiological variations in response to NaCl stress during vegetative and reproductive development of rice
2012
The complex nature of plant resistance to adverse environmental conditions, such as salinity and drought requires a better understanding of the stress-induced changes that may be involved in tolerance mechanisms. Here we investigate stress-related morpho-physiological effects during vegetative and reproductive growth in two Japonica rice cultivars (Bomba and Bahia) exposed to a range of NaCl concentrations from the seedling stage. The stress-related detrimental effects were observed either earlier or to a higher extent in cv. Bomba than in Bahia. Damages to the photosynthetic apparatus were related to loss of chlorophyll (Chl) and to a decrease of the maximum potential efficiency of PSII (F…
Influence of Light on the Bioelectric Potential of the Bean (Phaseolus vulgaris) Hypocotyl Hook
1975
By use of surface electrodes electropotenlial measurements were carried out on hypocotyl hooks of Phaseolus vulgaris seedlings. The hooks were illuminated with a small spot of white, blue, red or far red light. The potential changes in bean hypocotyl hooks do not show the red-far red reversible characteristics of phytochrome-mediated processes. By experimenting with inhibitors of photosynthesis we could demonstrate that the light-triggered potential changes in green bean hooks are correlated to photosynthetic electron transport phenomena. The red-light-induced transient is a depolarization, whereas blue light induces a hyperpolarization. Etiolated beans exhibit no bioelectric potential chan…
Effects of Kinetin and Different Light Qualities on the Content of Carbohydrates
1983
Summary The effects of kinetin on the content of soluble redueing sugars, starch, soluble proteins and various components of the photosynthetic apparatus were studied with primary leaves of Sinapis alba, which were grown under different light qualities (white, red, blue Jight conditions). It was especially the content of soluble reducing sugars that was most influenced by kinetin. The enhancement of the sugar content was dependent on the duration of application as well as on the concentration of kinetin. The doseresponse curve shows that the sugar content strongly increased at low kinetin eoneentrations (0.01 to 1 mg · 1-1), whereas from 1 mg · 1-1 onwards the inerease was slower and linear…
Wirkung der Insektizide Allethrin, Lindan und Jacutin-Fogetten-Sublimat auf den photosynthetischen Elektronentransport
1977
Summary During our studies of Hill-reactions of isolated chloroplasts we observed an inhibition of electron transport after an application of the smoke of «Jacutine-Fogetten» in the plant growth chamber. Therefore we tested the influence of the insecticides Lindane (Gammexan), the sublimate formed by the fumigation of «Jacutin Fogetten», and of Allethrin on the photosynthetic electron transport reactions of PS II and PS I. 39 μ M Lindane inhibits the basal, coupled and uncoupled electron transport to ferricyanide of broken chloroplasts isolated from leaves of Pisum sativum up to 35%. A higher inhibitory effect with higher concentrations is limited by the low water solubility of Lindane. On …
Oxygen Availability, Energy Metabolism, and Metabolic Rate in Invertebrates and Vertebrates
1988
It has often been emphasized that primitive life originated in an environment devoid of oxygen. The first eukaryotic cells, however, appeared some 1.4 billion years ago when the earth’s atmosphere had already turned from a mildly reducing to an oxidizing one by the photosynthetic action of prokaryotes that used H20 as reducing agent (see Harold 1986, for review). The presence of free oxygen obviously was a major force shaping the evolution of eukaryotic cells. As a consequence all animals are primarily aerobes, using respiratory chains with oxygen as electron acceptor (oxidant) and membrane-bound ATP synthases for the production of ATP.
Changes in net photosynthesis, chlorophyll fluorescence and xanthophyll cycle interconversions during freeze-thaw cycles in the Mediterranean moss Le…
1999
The tolerance to freezing and thawing of Leucodon sciuroides, a moss growing in mountainous areas of the Mediterranean (south-east Spain), was investigated by means of CO2 gas exchange, modulated chlorophyll (Chl) a fluorescence and pigment analysis by high-performance liquid chromatography. Evidence is presented for freezing-induced decreases in CO2 fixation that enhance non-radiative dissipation of absorbed light energy, a process which protects the photosynthetic apparatus. The photosynthetic apparatus of L. sciuroides remained fully recuperable after freezing, as indicated by the recovery of photosynthetic CO2 fixation and Chl fluorescence parameters to pre-freezing values during thawin…
Changes in chlorophyll a fluorescence, photosynthetic CO 2 assimilation and xanthophyll cycle interconversions during dehydration in desiccation-tole…
1998
The interactions among water content, chlorophyll a fluorescence emission, xanthophyll interconversions and net photosynthesis were analyzed during dehydration in desiccation-tolerant Frullania dilatata (L.) Dum. and desiccation-intolerant Pellia endiviifolia (Dicks) Dum. Water loss led to a progressive suppression of photosynthetic carbon assimilation in both species. Their chlorophyll fluorescence characteristics at low water content were: low photosynthetic quantum conversion efficiency, high excitation pressure on photosystem II and strong non-photochemical quenching. However, dissipation activity was lower in P. endiviifolia and was not accompanied by a rise in the concentration of de-…