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Functional Analysis of the Photosynthetic Apparatus of Prochlorothrix hollandica (Prochlorales), a Chlorophyll b Containing Procaryote 总被引:1,自引:0,他引:1
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Light-shade adaptation of the chlorophyll a/b containing procaryote Prochlorothrix hollandica was studied in semicontinuous cultures adapted to 8, 80 and 200 μmole quanta per square meter per second. Chlorophyll a contents based on dry weight differed by a factor of 6 and chlorophyll b by a factor of 2.5 between the two extreme light conditions. Light utilization efficiencies determined from photosynthesis response curves were found to decrease in low light grown cultures due to lower light harvesting efficiencies; quantum requirements were constant at limiting and saturating irradiances for growth. At saturating growth irradiances, changes in light saturated oxygen evolution rate originated from changes in chlorophyll a antenna relative to the number of reaction centers II. At light-limiting conditions both the number of reaction centers II and the antenna size changed. The amount of chlorophyll b relative to reaction center II remained constant. As in cyanobacteria, the ratio of reaction center I to reaction center II was modulated during light-shade adaptation. On the other hand, time constants for photosynthetic electron transport (4 milliseconds) were low as observed in green algae and diatoms. The occurrence of state one to two and state two to one transitions is reported here. Another feature linking photosynthetic electron transport in P. hollandica to that in the eucaryotic photosynthetic apparatus was blockage of the state one to two transition by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Although chlorophyll b was reported in association with photosystem I, the 630 nanometer light effect does not exclude that chlorophyll b is the photoreceptor for the state one to two transition. 相似文献
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Calcium Transport in Protoplasts Isolated from ml-o Barley Isolines Resistant and Susceptible to Powdery Mildew 总被引:1,自引:1,他引:0
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Free cytoplasmic calcium has been postulated to play a role in preventing powdery mildew in a series of homozygous ml-o mutants of barley, Hordeum vulgare L. Protoplasts isolated from 7-day-old plants of the ml-o resistant-susceptible (R-S) barley isolines, Riso 5678/3* × Carlsberg II R and S, were used to test for differences in fluxes of Ca2+ across the plasmalemma. Greater influx or lesser efflux might account for a higher free cytosolic Ca2+ postulated to exist in ml-o R mutants. Uniform patterns of uptake were maintained for 3 hours from solutions of 0.2 and 2 millimolar Ca2+. Washout curves of 45Ca2+ from R and S protoplasts revealed three compartments—presumed to represent release from the vacuole, organelles, and the cytoplasm (which included bound as well as free Ca2+). Uptake and washout did not differ between isolines. On the basis of recent determinations of submicromolar levels of free cytoplasmic Ca2+ and our initial rates of 45Ca-labeled Ca2+ uptake, we show that measurement of the unidirectional influx of Ca2+ across the plasmalemma is not feasible because the specific activity of the pool of free cytoplasmic calcium increases almost instantaneously to a level that would result in a significant, but unknown, efflux of label. Similarly, measurement of the efflux of Ca2+ across the plasmalemma is not possible since the activity of the pool of free cytoplasmic calcium is a factor of 350 smaller than the most rapid component of the washout experiment. This pool of cytoplasmic free Ca2+ will wash out too rapidly and be too small to detect under the conditions of these experiments. 相似文献
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Potassium and sodium absorption kinetics in roots of two tomato species : lycopersicon esculentum and lycopersicon cheesmanii 总被引:1,自引:1,他引:0
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Excised roots of the tomato species, Lycopersicon esculentum Mill. cv Walter (the commercial species) and of Lycopersicon cheesmanii ssp. minor (Hook.) C.H. Mull. (a wild species from the Galapagos Islands), were used in comparative studies of their absorption of K+ and Na+. Uptake of 86Rb-labeled K+ and 22Na-labeled Na+ by excised roots of `Walter' and L. cheesmanii varied as a function of genotype and tissue pretreatment with or without K+. Excised roots of `Walter' consistently absorbed more 86Rb-labeled K+ than those of L. cheesmanii. Absorption of K+ from solutions ranging from 0.01 to 0.2 millimolar KCl showed saturation kinetics in both K+-pretreated and K+-depleted roots of `Walter,' and for K+-depleted roots of L. cheesmanii. K+-pretreated roots of L. cheesmanii had exceedingly low rates of K+ uptake with strikingly different, linear kinetics. Pretreatment with K+ caused a decrease in rates of K+ uptake in both genotypes. Potassium depleted roots of L. cheesmanii absorbed Na+ at a greater rate than those of `Walter,' whereas K+-pretreated roots of `Walter' absorbed Na+ at a greater rate than those of L. cheesmanii. The results confirm and extend previous conclusions to the effect that closely related genotypes may exhibit widely different responses to the two alkali cations, K+ and Na+. 相似文献
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Anovulatory domestic hens (pregnant mare serum-treated) and normally cyclic domestic hens were artificially inseminated with 0.034 ml of pooled semen. A subsequent microscopic assessment of the uterovaginal sperm storage glands on days 1, 3, 6, 9 and 12 post-insemination indicated that the sperm glands emptied over time in the normally cyclic hens, but not in the anovulatory hens. The data suggest that events associated with ovulation and/or oviposition are important to the sperm gland emptying process. 相似文献