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111.
IRVING FINGER CAROL HELLER CAROLYN VON ALLMEN 《Differentiation; research in biological diversity》1978,11(1-3):51-57
Paramecia may induce in other paramecia specific changes in the expression of genes determining surface protein synthesis, probably via cell-to-cell contact. Transformation from one antigenic type to a newly induced one is stimulated by the pretreatment of a cell with 5-fluorouracil. These observations are considered in terms of the regulation of the activity of genes in stable cells and in unstable cells which tend to transform spontaneously. 相似文献
112.
VON BRAND T 《Biodynamica》1945,5(101-105):353-366
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S. VON CAEMMERER V. QUINN N. C. HANCOCK G. D. PRICE R. T. FURBANK & M. LUDWIG 《Plant, cell & environment》2004,27(6):697-703
Carbonic anhydrase (CA, EC 4.2.1.1) catalyses the first reaction in the C4 photosynthetic pathway, the conversion of atmospheric CO2 to bicarbonate in the mesophyll cytosol. To examine the importance of the enzyme to the functioning of the C4 photosynthetic pathway, Flaveria bidentis (L.) Kuntze, a C4 dicot, was genetically transformed with an antisense construct in which the cDNA encoding a putative cytosolic CA (CA3) was placed under the control of a constitutive promoter. Some of the primary transformants had impaired CO2 assimilation rates and required high CO2 for growth. The T1 progeny of four primary transformants were used to examine the quantitative relationship between leaf CA activity and CO2 assimilation rate. CA activity was determined in leaf extracts with a mass spectrometric technique that measured the rate of 18O exchange from doubly labelled 13C18O2. Steady‐state CO2 assimilation rates were unaffected by a decrease in CA activity until CA activity was less than 20% of wild type when they decreased steeply. Transformants with less than 10% of wild‐type CA activity had very low CO2 assimilation rates and grew poorly at ambient CO2 partial pressure. Reduction in CA activity also increased the CO2 partial pressure required to saturate CO2 assimilation rates. The present data show that CA activity is essential for the functioning of the C4 photosynthetic pathway. 相似文献
115.
Interannual variability of seasonal succession events in a temperate lake and its relation to temperature variability 总被引:1,自引:0,他引:1
The assessment of possible implications of anthropogenic climate change requires the evaluation of results obtained with complex climate models. Here we considered the problem of assessing the impact of climate variability on successional events in a lake (Plußsee) of the temperate region between January and May. We first established a statistical link between large-scale air temperature, at about 1500 m height, and the local temperature, in order to bridge the spatial gap of information obtained from global climate models and local climate which forces processes in the lake. Secondly, the local temperatures were statistically related to biologically induced dynamic features in the lake, derived from Secchi depths readings (as integrated measures). The observed relationships were compared with results from a phyto- and zooplankton population-dynamic model run under different temperature regimes. The local temperatures approximated closely the large-scale temperature. The timing of phyto- and zooplankton maxima (clearwater phase) were negatively related to the temperature. Thus, with a temperature increase both occurred earlier. The intensity of the spring algal maximum was negatively related to its timing, whereas no clear relation between the timing and intensity of the clearwater phase (zooplankton maximum) could be obtained. 相似文献
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IRMGARD VON TEICHMAN F.L.S. 《Botanical journal of the Linnean Society. Linnean Society of London》1991,107(1):35-47
VON TEICHMAN, I., 1991. Ontogeny of the seed-coat of Rhus lancea L. fil., and pachychalazy in the Anacardiaceae. The bitegmic, anatropous ovule develops into an exalbuminous, partially pachychalazal and endotegmic seed. In the mature seed-coat the extensive chalaza with associated tanniniferous hypostase sensu lato manifests externally as a characteristic brown patch. The walls of the cells of the hypostase are impregnated with callose and lipidic substances, which most probably represent cutin. Ultimately the outer integument and outer parts of the inner integument are more or less squashed. However, the cell walls of the inner epidermis of the inner integument show distinct secondary thickening and lignification. The pachychalazal seed with undifferentiated seed-coat characterizes not only a number of the genera of the tribe Anacardieae, but also occurs in Heeria of the tribe Rhoeae. A number of genera of the tribe Spondiadeae have a partially pachychalazal seed. The seed-coat of the latter shows varying degrees of traces of an exo-, meso- and/or endotestal lignification. The seed of certain genera of the Rhoeae, is partially pachychalazal and endotegmic, or probably only endotegmic. 相似文献
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119.
Six new species of Protodrilus (Annelida, Polychaeta) from Europe and New Zealand, with a concise presentation of the genus 总被引:2,自引:0,他引:2
Protodrilus haurakiensis sp.n., P. jouinae sp.n., P. jägersteni sp.n., P. submersus sp.n. and P. litoralis sp.n. from New Zealand and P. gracilis sp.n. from Europe are described. Protodrilus jägcrsteni, P. submersus and P. litoralis are sibling species. Sperm dimorphism in all species investigated by the author is recorded for the first time in polychaetes. Two of the three so-called 'ecological forms' of P. hypoleucus and P. adhaerens are classified as variations of the type species without a particular taxonomic rank. In a table the partly actualized data of all 30 known Protodrilus species are presented, 8 of which are very insufficiently described. Synonyms in Protodrilus and similarities between P. rubropharyngeus Jägersten and P. flavocapitatus Uljanin are mentioned. 相似文献
120.