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The proportion of phosphatase activity demonstrable in brain by histological techniques 总被引:1,自引:0,他引:1 下载免费PDF全文
PRATT OE 《The Biochemical journal》1953,55(1):140-145
54.
Changes in Adenosine Pyrophosphates in Cantaloupe Fruit Ripening Normally and after Treatment with Ethylene 总被引:1,自引:0,他引:1
During the climacteric rise in respiration of cantaloupe fruit(Cucumis melo L., var. reticulatus Naud.) the concentrationper gramme fresh weight of adenosine triphosphate (ATP) increasedand that of adenosine diphosphate (ADP) did not change; thusa net synthesis of adenosine pyrophosphate occurs during therespiratory climacteric. A net synthesis of protein which wasobserved was positively correlated with the concentration ofATP. Ethylene treatment stimulated a climacteric-like rise inthe respiration and in the rate of ripening in fruit harvestedat 9 to 32 days after anthesis. The ratio ATP/ADP increasedin fruit ripened with ethylene only when harvested 20 days ormore after anthesis. 相似文献
55.
Seasonal hysteresis of net ecosystem exchange in response to temperature change: patterns and causes 总被引:1,自引:0,他引:1
SHULI NIU YIQI LUO SHENFENG FEI LEONARDO MONTAGNANI GIL BOHRER IVAN A. JANSSENS BERT GIELEN SERGE RAMBAL EDDY MOORS GIORGIO MATTEUCCI 《Global Change Biology》2011,17(10):3102-3114
Understanding how net ecosystem exchange (NEE) changes with temperature is central to the debate on climate change‐carbon cycle feedbacks, but still remains unclear. Here, we used eddy covariance measurements of NEE from 20 FLUXNET sites (203 site‐years of data) in mid‐ and high‐latitude forests to investigate the temperature response of NEE. Years were divided into two half thermal years (increasing temperature in spring and decreasing temperature in autumn) using the maximum daily mean temperature. We observed a parabolic‐like pattern of NEE in response to temperature change in both the spring and autumn half thermal years. However, at similar temperatures, NEE was considerably depressed during the decreasing temperature season as compared with the increasing temperature season, inducing a counter‐clockwise hysteresis pattern in the NEE–temperature relation at most sites. The magnitude of this hysteresis was attributable mostly (68%) to gross primary production (GPP) differences but little (8%) to ecosystem respiration (ER) differences between the two half thermal years. The main environmental factors contributing to the hysteresis responses of NEE and GPP were daily accumulated radiation. Soil water content (SWC) also contributed to the hysteresis response of GPP but only at some sites. Shorter day length, lower light intensity, lower SWC and reduced photosynthetic capacity may all have contributed to the depressed GPP and net carbon uptake during the decreasing temperature seasons. The resultant hysteresis loop is an important indicator of the existence of limiting factors. As such, the role of radiation, LAI and SWC should be considered when modeling the dynamics of carbon cycling in response to temperature change. 相似文献
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Peroxidase activity and enzymic production of ethylene werestudied in tomato fruits (Lycopersicon esculentum MILL.) at3 ripeness stages. As the fruit ripens, one isoperoxidase disappears,and 3 new ones are formed. Activity of peroxidase and of ethylene-formingenzyme both increased 3 to 4 times as the fruit ripened. Histochemicalstaining showed that peroxidase is confined to the outermostand innermost layers of the pericarp, the placental tissue andvascular tissues; stained particles were neither mitochondrianor plastids. (Received October 27, 1969; ) 相似文献
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LESLIE E. TINGLE WILLIAM A. PAVLAT IVAN L. CAMERON 《The Journal of eukaryotic microbiology》1973,20(2):301-304
SYNOPSIS. The behavior and ultrastructure of Tetrahymena pyriformis was assessed after exposure to dosages of 8 and 16% of the lethal concentration of HgCl2 (TLm 96 hr). The lower dosage caused no abnormal changes in cell motility, activity of the water explusion vesicles, or cell shape; the higher dosage caused deleterious changes in these parameters. The higher sublethal HgCl2 concentration (0.50 mg/liter) elicited damage of several cell structures. This damage persisted and accumulated with time up to 24 hr. At the lower HgCl2 dosage (0.25 mg liter) there were extensive changes after 1-hr exposure involving primarily mitochondria; however, all major changes were repaired after 24 hr of constant exposure to the HgCl2, indicating adaptation to the toxicant. Based solely on cytotoxic evidence an attempt is made to apply the findings defining what constitutes a “safe'’concentration of HgCl2 in the cell's environment. 相似文献
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KELLY R. ZAMUDIO JEANNE M. ROBERTSON LAUREN M. CHAN IVAN SAZIMA 《Biological journal of the Linnean Society. Linnean Society of London》2009,97(2):259-274
Based on population genetic theory and empirical studies of small populations, we expect that species with very small ranges (narrow endemics) will exhibit reduced genetic diversity, increasing their susceptibility to the negative effects of genetic homogeneity. Although this pattern of reduced diversity applies to most narrow endemics, conservation biologists have yet to identify a general pattern for the degree of spatial population genetic structure expected in species with very small ranges. In part, this is because the degree of population structure within narrow endemics will be highly variable depending on the equilibrium between the homogenizing effects of dispersal and the diversifying effects of drift and local selection in small populations, thus precluding general predictions about the relative importance of small range, small population sizes, and habitat patchiness for maintaining genetic diversity in narrowly-distributed species. We document a striking example of high population structure in the tiny geographic range of a stream-dwelling catfish, Trichogenes longipinnis , endemic to the Atlantic Forest of Brazil. The maintenance of this diversity results from a combination of asymmetrical and limited dispersal, and drift in small populations. Our results highlight the need to understand population structure, and not only overall genetic diversity, of narrowly-distributed species for their conservation planning. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 259–274. 相似文献
60.
STEPHEN K. DONOVAN C. GILES MILLER IVAN J. SANSOM ALAN P. HEWARD JAN SCHREURS 《Palaeontology》2011,54(3):525-533
Abstract: Early and early Middle Ordovician crinoids are rare globally, and are best known from North America and the British Isles. The first Arenig crinoid from the Arabian Peninsula is Iocrinus sp. cf. I. subcrassus (Meek and Worthen), known from two near‐complete individuals, and numerous fragmentary specimens and ossicles. These are the stratigraphically oldest Iocrinus specimens, and provide an unexpected extension of the palaeogeographical range of a genus known otherwise from slightly younger deposits in Laurentia (North America) and Avalonia (Wales). The Oman specimens differ from Gondwanan Heviacrinus melendezi Gil Cid et al., currently classified as a maennilicrinid, but morphologically close to Iocrinus, in having arms that branch at least seven times instead of four and in having columnals typical of Iocrinus. Three species from Wales and the Welsh Borders, previously placed in Iocrinus, but differing in having smooth, conical dorsal cups, are reclassified as Margoiocrinus Donovan gen. nov., type species Iocrinus shelvensis Ramsbottom. 相似文献