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121.
Light-induced spectral absorbance changes in relation to photosynthesis and the epoxidation state of xanthophyll cycle components in cotton leaves 总被引:17,自引:10,他引:7
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When cotton (Gossypium hirsutum L., cv Acaia SJC-1) leaves kept in weak light were suddenly exposed to strong red actinic light a spectral absorbance change took place having the following prominent characteristics. (a) It was irreversible within the first four minute period after darkening. (b) The difference in leaf absorbance between illuminated and predarkened leaves had a major peak at 505 nanometers, a minor peak at 465 nanometers, a shoulder around 515 nanometers, and minor troughs at 455 and 480 nanometers. (c) On the basis of its spectral and kinetic characteristics this absorbance change can be readily distinguished from the much faster electrochromic shift which has a peak at 515 nanometers, from the slow, so-called light-scattering change which has a broad peak centered around 535 nanometers and is reversed upon darkening, and from absorbance changes associated with light-induced chloroplast rearrangements. (d) The extent and time course of this absorbance change closely matched that of the deepoxidation of violaxanthin to zeaxanthin in the same leaves. (e) Both the absorbance change and the ability to form zeaxanthin were completely blocked in leaves to which dithiothreitol (DTT) had been provided through the cut petlole. DTT treatment also caused strong inhibition of that component of the 535-nanometer absorbance change which is reversed in less than 4 minutes upon darkening and considered to be caused by increased light scattering. Moreover, DTT inhibited a large part of nonphotochemical quenching of chlorophyll fluorescence in the presence of excessive light. However, DTT had no detectable effect on the photon yield of photosynthesis measured under strictly rate-limiting photon flux densities or on the light-saturated photosynthetic capacity, at least in the short term. We conclude that it is possible to monitor light-induced violaxanthin de-epoxidation in green intact leaves by measurement of the absorbance change at 505 nanometers. Determination of absorbance changes in conjunction with measurements of photosynthesis in the presence and absence of DTT provide a system well suited for future studies of meachanisms of dissipation of excessive excitation energy in intact leaves. 相似文献
122.
Chr. Sjödin K. Glimelius 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,77(1):76-80
Summary The selective property of sirodesmin PL, a toxin produced by Phoma lingam, was studied on protoplasts, cell aggregates, leaves and roots. Directly after isolation, protoplasts from all the different Brassica accessions were sensitive when treated with toxin in a concentration higher than 1 M. When more differentiated plant tissue. i.e. cell aggregates, leaves or roots, were investigated, insensitivity to the toxin was found in the plant material resistant to P. lingam, while the plant material susceptible to P. lingam was sensitive. The results reveal that a clear correlation between resistance to P. lingam and insensitivity to sirodesmin PL is present, and that the toxin can be used to distinguish resistant plant material from susceptible both in vivo and in vitro. 相似文献
123.
M. D. Sacristán M. Gerdemann-Knörck O. Schieder 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,78(2):194-200
Summary With the idea to develop a selection system for asymmetric somatic hybrids between oilseed rape (Brassica napus) and black mustard (B. nigra), the marker gene hygromycin resistance was introduced in this last species by protoplast transformation with the disarmed Agrobacterium tumefaciens strain C58 pGV 3850 HPT. The B. nigra lines used for transformation had been previously selected for resistance to two important rape pathogens (Phoma lingam, Plasmodiophora brassicae). Asymmetric somatic hybrids were obtained through fusion of X-ray irradiated (mitotically inactivated) B. nigra protoplasts from transformed lines as donor with intact protoplasts of B. napus, using the hygromycin resistance as selection marker for fusion products. The somatic hybrids hitherto obtained expressed both hygromycin phosphotransferase and nopaline synthase genes. Previous experience with other plant species had demonstrated that besides the T-DNA, other genes of the donor genome can be co-transferred. In this way, the produced hybrids constitute a valuable material for studying the possibility to transfer agronomically relevant characters — in our case, diseases resistances — through asymmetric protoplast fusion. 相似文献
124.
Göran Bengtsson 《Microbial ecology》1989,18(3):235-248
Groundwater bacteria isolated from an oligotrophic-saturated soil showed a mixed strategy of economized metabolism and migration when grown in a continuous-flow column system simulating poor or nutrient-amended growth conditions. The cells were generally <0.5m in diameter in pure groundwater, but doubled in size when the concentration of dissolved organic carbon and phosphate in groundwater was increased 10-fold. The biomass, estimated from analysis of muramic acid (MuAc) in cell wall peptidoglucans, increased at the same time by a factor of 5 when the solid support in the columns was gravel and by a factor of 10 when it was glass beads. Bacteria in pure groundwater stored 10 times more of the energy-rich polysaccharide, poly--hydroxybutyric acid (PHB), than bacteria in enriched groundwater, and those cells that were attached to the gravel stored 10 times as much as cells in the interstitial pore water. Once phosphate was added to groundwater, stored PHB was metabolized. The proportion of free-living to attached bacteria was 2 to 10 times higher in enriched compared with pure groundwater indicating a mass transport of cells as the carrying capacity of their habitat rose. 相似文献
125.
Dr. Hansjörg Wunderer Serge Picaud Nicolas Franceschini 《Cell and tissue research》1989,257(3):565-576
Summary Single photoreceptor cells in the compound eye of the housefly Musca domestica were selectively illuminated and subsequently compared electron-microscopically with the unilluminated photoreceptors in the immediate surroundings. The rhabdomeres of the illuminated cells remain largely unaffected, but the cells show an increase in the number of coated pits, various types of vesicles, and degradative organelles; some of the latter organelles are described for the first time in fly photoreceptors. Coated pits are found not only at the bases of the microvilli, but also in other parts of the plasma membrane. Degradative organelles, endoplasmic reticulum (ER) and mitochondria aggregate in the perinuclear region. The rough ER and smooth ER are more elaborate, the number of Golgi stacks, free ribosomes and polysomes is increased, and the shape and distribution of heterochromatin within the nuclei are altered. Illuminated photoreceptors also interdigitate extensively with their neighbouring secondary pigment cells. These structural changes in illuminated fly photoreceptor cells indicate an increase in membrane turnover and cellular metabolism. When applied to the eye, Lucifer Yellow spreads into the extracellular space and is taken up only by the illuminated photoreceptor cells. These cells show the same structural modifications as above. Horseradish peroxidase applied in the same way is observed in pinocytotic vesicles and degradative organelles of the illuminated cells. Hence, the light-induced uptake of extracellular compounds takes place in vivo at least partially as a result of an increase in pinocytosis. 相似文献
126.
H+/sugar symport in the obligatory aerobic yeastRhodotorula glutinis was analyzed under conditions where the plasma membrane was selectively depolarized by the lipophilic cation tetraphenylphosphonium (TPP+). Control experiments showed that this treatment did not impair the transmembrane pH, the cell energy charge, and the function of plasma membrane H+-ATPase. The kinetic data were fitted to elementary functions derived from a model constructed on the basis of some simplifying premises for ordered (either C + H+ + S or C + S + H+) and random reaction mechanisms. In addition, the comparison of the kinetic parameters in fully energized and depolarized cells provided information about the free carrier charge. It was concluded that the binding sequence of formation of the ternary carrier/H+/substrate complex follows a random mechanism and that the carrier bears a negative charge. 相似文献
127.
128.
129.
Wolfgang Witt Peter Hampel Klaus Böcker Angelika Mertsching 《Archives of microbiology》1989,151(2):154-158
Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 M. The inhibition by nucleotides in low concentrations is enhanced by divalent cations. 相似文献
130.
Archaeoglobus fulgidus is an extremely thermophilic archaebacterium that can grow at the expense of lactate oxidation with sulfate to CO2 and H2S. The organism contains coenzyme F420, tetrahydromethanopterin, and methanofuran which are coenzymes previously thought to be unique for methanogenic bacteria. We report here that the bacterium contains methylenetetrahydromethanopterin: F420 oxidoreductase (20 U/mg), methenyltetrahydromethanopterin cyclohydrolase (0.9 U/mg), formyltetrahydromethanopterin: methanofuran formyltransferase (4.4 U/mg), and formylmethanofuran: benzyl viologen oxidoreductase (35 mU/mg). Besides these enzymes carbon monoxide: methyl viologen oxidoreductase (5 U/mg), pyruvate: methyl viologen oxidoreductase (0.7 U/mg), and membranebound lactate: dimethylnaphthoquinone oxidoreductase (0.1 U/mg) were found. 2-Oxoglutarate dehydrogenase, which is a key enzyme of the citric acid cycle, was not detectable. From the enzyme outfit it is concluded that in A. fulgidus lactate is oxidized to CO2 via a modified acetyl-CoA/carbon monoxide dehydrogenase pathway involving C1-intermediates otherwise only used by methanogenic bacteria.Non-standard abbreviations APS
adenosine 5-phosphosulfate
- BV
benzyl viologen
- DCPIP
2,6-dichlorophenolindophenol
- DMN
2,3-dimethyl-1,4-naphthoquinone
- DTT
DL-1,4-dithiothreitol
- H4F
tetrahydrofolate
- H4MPT
tetrahydromethanopterin
- CH2
H4MPT, methylene-H4MPT
- CH
H4MPT, methenyl-H4MPT
- Mes
morpholinoethane sulfonic acid
- MFR
methanofuran
- Mops
morpholinopropane sulfonic acid
- MV
methyl viologen
- Tricine
N-tris(hydroxymethyl)-methylglycine
- U
mol product formed per min 相似文献