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121.
Quantifying photosynthetic capacity and its relationship to leaf nitrogen content for global-scale terrestrial biosphere models 总被引:3,自引:0,他引:3
JENS KATTGE WOLFGANG KNORR† THOMAS RADDATZ‡ CHRISTIAN WIRTH 《Global Change Biology》2009,15(4):976-991
Photosynthetic capacity and its relationship to leaf nitrogen content are two of the most sensitive parameters of terrestrial biosphere models (TBM) whose representation in global‐scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Here, we use data of qualitative traits, climate and soil to subdivide the terrestrial vegetation into functional types (PFT), and then assimilate observations of carboxylation capacity, Vmax (723 data points), and maximum photosynthesis rates, Amax (776 data points), into the C3 photosynthesis model proposed by Farquhar et al. to constrain the relationship of (Vmax normalised to 25 °C) to leaf nitrogen content per unit leaf area for each PFT. In a second step, the resulting functions are used to predict per PFT from easily measurable values of leaf nitrogen content in natural vegetation (1966 data points). Mean values of thus obtained are implemented into a TBM (BETHY within the coupled climate–vegetation model ECHAM5/JSBACH) and modelled gross primary production (GPP) is compared with independent observations on stand scale. Apart from providing parameter ranges per PFT constrained from much more comprehensive data, the results of this analysis enable several major improvements on previous parameterisations. (1) The range of mean between PFTs is dominated by differences of photosynthetic nitrogen use efficiency (NUE, defined as divided by leaf nitrogen content), while within each PFT, the scatter of values is dominated by the high variability of leaf nitrogen content. (2) We find a systematic depression of NUE on certain tropical soils that are known to be deficient in phosphorous. (3) of tropical trees derived by this study is substantially lower than earlier estimates currently used in TBMs, with an obvious effect on modelled GPP and surface temperature. (4) The root‐mean‐squared difference between modelled and observed GPP is substantially reduced. 相似文献
122.
123.
Localization of Thermo-Osmotically Active Partitions in Young Leaves of Nuphar lutea 总被引:4,自引:0,他引:4
SCHRODER PETER; GROSSE WOLFGANG; WOERMANN DIETRICH 《Journal of experimental botany》1986,37(10):1450-1461
The submerged roots and rhizomes of the aquatic vascular macrophyteNuphar lutea (L.) Sm. are aerated, at least in part, by pressurizedventilation. Depending on temperature differences of up to 5K between the inside of young, just-emerged leaves and the surroundingair, pressure differences of 79 to 100 Pa higher than atmosphericare detectable inside the lacunuous spongy parenchyma of theleaf blades. The pressurization is a consequence of structuralfeatures of leaf tissues separating the air filled spaces ofthe spongy parenchyma from the atmosphere. These tissues areacting as thermo-osmotic partitions. Whereas the dimensionsof the stomatal openings (about 5·6 x 2·4 µm)and of the intercellular spaces of the palisade parenchyma (diametersabout 15 µm) are too large, those of the monolayers ofcells separating the palisade and the spongy parenchyma (diameters:0·71·2 µm) are small enough to impedefree gaseous diffusion. This inner non-homogeneous partitioninggives rise to the so-called Knudsen diffusion, a physical phenomenonleading to pressurization of the warmer air inside the spongyparenchyma. The rising pressure difference is strong enoughto establish an air flow through the aerenchyma of the wholeplant and out of the most porous older leaves in which a temperatureinduced pressurization is never detectable. These thermo-osmoticallyactive leaves enhance the influx of air to the rhizome and thediffusion path for oxygen to the roots is shortened to the distancebetween rhizome and root tips. Therefore, pressurized ventilationin Nuphar is seen to be of considerable ecological importancefor plant life in anaerobic environments. Key words: Aeration, leaf anatomy, thermo-osmosis of gases, Nuphar lutea 相似文献
124.
WOLFGANG EICHLER 《The Journal of eukaryotic microbiology》1989,36(6):577-582
Ornithine decarboxylase (ornithine carboxy lyase; EC 4.1.1.17) (ODC) from Tetrahymena thermophila was purified 6,300 fold employing fractionated ammonium sulfate precipitation, gel permeation chromatography on Sephadex G-150, ion exchange chromatography on DEAE-Sepharose CL-6B, and preparative isoelectric focussing. The product obtained in 24% yield was a preparation of the specific activity of 10,200 nmol CO2mdh-1mdmg-1. The purified enzyme was rather stable at 37°C (14% loss of activity within 1 h). The molecular and catalytic properties of this enzyme were investigated. The isoelectric point was 5.7 and the molecular weight (MW) was estimated to be 68,000 under nondenaturing conditions. The pH optimum was between 6.0 and 7.0, the Km for the substrate L-ornithine was 0.11 mM, and the Km for the cofactor pyridoxal 5-phosphate was 0.12 μM; the product of ODC catalysis, putrescine, was a poor inhibitor with an estimated Ki of about 10 mM. The enzyme was inhibited competitively by D-ornithine with a Ki of 1.6 mM and by α-difluoromethylornithine with a Ki of 0.15 mM. The latter one, an enzyme activated irreversible inhibitor of mammalian ODC, inactivated the enzyme from T. thermophila at high concentrations with a half life time of 14 min. Other basic amino acids, e.g. L-lysine, L-arginine, and L-histidine, were neither substrates nor inhibitors of the enzyme, as were the diamines 1,3-diaminopropanol and cadaverine, the polyamines spermidine and spermine and the cosubstrate analogues pyridoxal and pyridoxamine-5-phosphate. Polyanions were activators of the enzyme: The half maximal ODC stimulating concentrations were 2.2 μgmdml-1 for RNA, 6.1 μgmdml-1 for DNA, and 0.25 μgmdml-1 for heparin. These results indicate that ODC from T. thermophila shares several properties with ODC preparations from other organisms but in some respects, especially in activator and inhibitor specificity, there are some special qualities unique to this particular protozoan enzyme. 相似文献
125.
126.
AMOS FRISCH WOLFGANG BESSLER HANS JOACHIM LIPPS DIETER AMMERMANN 《The Journal of eukaryotic microbiology》1976,23(3):427-430
SYNOPSIS. Interaction of several plant lectins with the ciliates Stylonychia mytilus, Euplotes aediculatus, and Tetrahymena pyriformis GL, was investigated. The motility of Stylonychia is specifically inhibited by treatment with concanavalin A, with which the 2 other ciliates react only weakly. Stylonychia can regain its motility by shedding the lectin-loaded surface components and rebuilding a new pellicle. Other lectins used in this study did not interact with these ciliates. 相似文献
127.
The Capacity of Testicular Cells of the Postnatal Rat to Reorganize into Histotypic Structures 总被引:2,自引:0,他引:2
MARIA TERESA ZENZES WOLFGANG ENGEL 《Differentiation; research in biological diversity》1981,20(1-3):157-161
Cell reorganization experiments in vitro were performed with dissociated rat testes at different ages of postnatal development namely, newborn, 8–10, 18–25, 35–40, and 90 days. Only newborn and juvenile rat testicular cells reassociated into testicular-like organization in rotation culture. Puberal and adult rat testicular cells show morphogenetic organization when they were deprived of germ cells by busulphan pretreatment. A factor present in testicular tissue of puberal and adult rats inhibits reorganization. The inhibitor is confined to the spermatic cell fraction in the testis. 相似文献
128.
M. F. PERUTZ P. DEL PULSINELLI L. TEN EYCK J. V. KILMARTIN S. SHIBATA I. ÍUCHI T. MIYAJI H. B. HAMILTON 《Nature: New biology》1971,232(31):147-149
HAEMOGLOBIN Hiroshima is a variant with interesting physiological properties1,2 discovered in a Japanese family. Its Bohr effect is halved, its oxygen affinity at physiological pH increased about three-fold and haem-haem interaction is somewhat reduced compared with normal haemoglobin. In 0.1 M NaCl solutions initially stripped of phosphate, 2,3-diphospho-glycerate (2,3-DPG) diminishes the oxygen affinity as in haemoglobin A (H. F. Bunn, unpublished results). The amino-acid substitution originally deduced for this abnormal haemoglobin was histidine 143 (H21)β ? aspartic acid1. It was possible to conceive of a mechanism which accounted for its diminished Bohr effect3, but the normal response of its oxygen affinity to 2,3-DPG was inconsistent with the proposed role of histidine 143 in 2,3-DPG binding by haemoglobin A4,5. An X-ray crystallographic study of deoxyhaemoglobin Hiroshima has now revealed that the replacement occurs not in position 143 but 146β. This was confirmed by chemical methods and the physiological properties of this haemoglobin are now satisfactorily accounted for. The results support the role of histidine 146β in the alkaline Bohr effect6. 相似文献
129.
WOLFGANG ENGELMANN ERS JOHNSSON H. G. KARLSSON R. KOBLER M.-L. SCHIMMEL 《Physiologia plantarum》1978,43(1):68-76
The circadian petal movement rhythm of Kalanchoë flowers has been studied. The amplitude of the rhythm can be drastically reduced by an appropriate stimulus of a light pulse. It has also been shown that it is possible to stop the rhythm permanently by administering a single light pulse to the flowers. This is interpreted to indicate that the light pulse has sent the circadian rhythm into a stable state of singularity. The conditions which attenuate the rhythm have been investigated both theoretically (on the basis of a previously published model for circadian rhythms) and experimentally. 120 min red light of 230 μW · cm?2, starting briefly before the second petal closure about 30 h after transfer to constant safe light conditions is optimal in inducing rhythm-damping. Damping requires the same duration when the light is given at the corresponding phase during the third or fourth cycle of the rhythm. However, in the first cycle 240 min red light of 230 μW · cm?2 is required to get optimal damping of the rhythm. Conditions to achieve damping for other irradiances are investigated. Individual recordings are presented which show the behaviour of the rhythm when perturbed by light stimuli close to its singularity. 相似文献
130.
1. Many insects host secondary bacterial symbionts that are known to have wide‐ranging effects on their hosts, from host‐plant use to resistance against natural enemies. This has been most widely studied in aphids, which have become a model system to study insect–bacteria interactions. 2. While there is an increasing understanding of the role of symbionts in aphids from controlled laboratory studies, we are only beginning to explore the impact of hosting these symbionts on eco‐evolutionary dynamics in natural systems. To date, many research groups have identified bacterial symbionts from various aphid species, providing us with a bank of literature on aphid–symbiont associations in natural populations. 3. The role of secondary symbionts in aphids is discussed, and the taxonomic and geographical distribution of symbionts among aphids are summarised, and the potential reasons for the patterns observed. The need to test for multiple symbiont species (and co‐infections) across many individuals and the whole distribution range of an aphid is highlighted, including sampling on all known host‐plant species. 4. It is further important also to consider variation within the symbiont, the aphid‐host and the surrounding community, e.g. host‐plants or the natural enemies, to understand how these have the potential to mediate aphid–symbiont interactions. 5. Finally, the knowledge gained from experimental work should now be used to understand the role of aphid secondary symbionts in field systems, to fully understand the potentially far‐reaching consequences of aphid endosymbionts on community and ecosystem processes. 相似文献