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91.
Sunflower plants were grown under controlled environmental conditionswith either 0 or 10 mol m3 phosphate (Pi). From steady-statemeasurements of gas exchange and chlorophyll fluorescence madeon intact leaves, the in vivo CO2/O2 specificity factor (invivo Ksp) of ribulose 1,5-Aisphosphate carboxylase-oxygenase(Rubisco) was determined following two methods based on modelsof C3 photosynthesis by Brooks and Farquhar (1985) and Peterson(1989). The two methods gave in vivo Ksp values for controlsunflower leaves which were similar to published values forhigher plants. Extreme Pi deficiency decreased in vivo Ksp,in sunflower leaves compared to adequate Pi. This suggests thatPi deficiency affected photorespiration less than photosynthesis.The decrease in in vivo Ksp may be due to a real change in theenzyme kinetics favouring oxygenation more than carboxylationor due to an increase in the number of CO2 molecules releasedper oxygenation; in which case the observed decrease in thein vivo Ksp determined on intact leaves will not agree numericallywith the true Ksp of Rubisco determined in vitro using purifiedenzyme from the same leaf. We discuss the implications of therelatively large photorespiration in Pi-deficient sunflowerleaves with respect to the increased dissipation of photosyntheticelectrons and photorespiratory recycling of Pi in thechloroplaststroma. Although our results on in vivo Ksp suggested a relativelylarger photorespiratory potential in Pi-deficient than controlsunflower leaves, photosynthesis was insensitive to O2 in Pi-deficientleaves; the possible reasons for this phenomenon are discussed.Under extreme Pi deficiency, O2 sensitivity of photosynthesisis not a reflection of the in vivo photorespiratory rates. Determinationof in vivo Ksp of Rubisco is a useful approach to study thephotorespiratory potential of intact leaves. Key words: Chlorophyll fluorescence, phosphate deficiency, photorespiration, photosynthesis, PSII quantum yield, Rubisco specificity factor 相似文献
92.
Proliferation of Pneumocystis Trophozoites in Human Lymph Nodes and in Nude Mice Lungs 总被引:2,自引:0,他引:2
YOSHITSUGU MATSUMOTO JACOB K. FRENKEL MASAMICHI AIKAVVA YUKIO YOSHIDA 《The Journal of eukaryotic microbiology》1989,36(1):33S-34S
Pneumocystis infection in athymic nude mice lungs showed a particularly high trophozoite to cyst ratio. A similar observation was obtained from a study of a patient with lymph node infection with Pneumocystis . Eosinophilic foamy masses in these sites were observed by light microscopy. With the electron microscope, the masses were seen to be composed of large aggregates of trophozoites. Cystic forms (precysl, cyst and empty cyst) were extremely scarce in comparison with the huge numbers of trophozoites. These cystic forms were mostly undergoing degeneration. These observations indicate that the mode of proliferation in both situations was predominantly asexual, that is, proliferation by trophozoites, suggesting that certain conditions may enhance asexual reproduction or depress the fonnation of cysts. 相似文献
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Uncoupling of oxidative phosphorylation by cadmium ion 总被引:24,自引:0,他引:24
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Amplification success of multilocus genotypes from feathers found in the field compared with feathers obtained from shot birds 总被引:1,自引:0,他引:1
Effective DNA extraction methods from bird feathers have facilitated non‐invasive sampling, leading to the suggestion that feathers are a great source for genetic studies. However, few studies have assessed whether all feathers can be used or provide equal numbers of useful templates. In this study, feathers collected in various ways from Red Grouse Lagopus lagopus were examined to establish the quality of DNA extracted. Individual samples were classified into two categories according to whether they were collected from shot birds or found in the field. DNA was extracted from all samples and genotyped at 19 microsatellite loci. PCR products were analysed on a MegaBACE 1000. A total of 93% of the ‘shot’ category produced a genotype that was considered successful (i.e. 15 of 18 loci) and 23% of the ‘collected’ category produced successful genotypes under the same criteria. There was a significant difference between shot and collected samples in genotyping success and the observed number of missing loci. Recommendations and best practices are discussed along with the utility of bird feathers as a source of DNA for population and conservation biology. 相似文献