Effekte moderner Verfahren der Bodenbewirtschaftung auf die Aktivität epigäischer Raubarthropoden     

Christa Volkmar  Marita Lübke-Al Hussein  Thomas Kreuter 《Gesunde Pflanzen》2003,55(2):40-45

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The domestic animal in heraldry; Part 3, the horse     

Mache C 《Historia medicinae veterinariae》2003,28(3):84-88

The author presents in her paper the historical background of the heraldic. In the coming four papers she will discuss the use and position of different domestic animals in heraldic.  相似文献   

Mechanical perturbation affects conductivity, mechanical properties and aboveground biomass of hybrid poplars     

Kern KA  Ewers FW  Telewski FW  Koehler L 《Tree physiology》2005,25(10):1243-1251

Xylem development in trees is affected by dynamic mechanical stresses imposed on stems by wind. To assess clonal differences in response to mechanical perturbation (MP), we subjected seven greenhouse-grown F1 hybrids of Populus trichocarpa Torr. and A. Gray. x P. deltoides Bartr. ex Marsh. to a standard MP treatment consisting of 20 manually imposed stem flexures per day for 70-90 days. Effects of MP on aboveground biomass, hydraulic conductivity (k(h)), specific conductivity (k(s)), flexural stiffness (EI), modulus of elasticity (MOE) and modulus of rupture (MOR) were determined. Treatment increased stem radial growth and decreased height growth, leaf area and total aboveground biomass. It also significantly decreased k(s), MOE and MOR, but significantly increased EI and wood specific gravity in most clones. Mechanical perturbation caused greater stem rigidity, without having a significant effect on whole-stem k(h) or percent loss of conductivity due to embolism. Maximum k(h) was positively correlated with EI in both control (r(2) = 0.54, P < 0.0001) and MP-treated (r(2) = 0.61, P < 0.0001) plants, and k(s) and MOE were positively correlated with percent vessel lumen area (r(2) = 0.45, P < 0.0001 and r(2) = 0.28, P = 0.002, respectively). Thus, contrary to our expectation of a trade-off between conductivity and wood strength, there may be an opportunity to select clones for woody biomass production that are superior in both mechanical strength and hydraulic conductivity, as is the triploid Clone 19-61.  相似文献   

Hydraulic conductivity and embolism in the mangrove tree Laguncularia racemosa     

Ewers FW  Lopez-Portillo J  Angeles G  Fisher JB 《Tree physiology》2004,24(9):1057-1062

We measured xylem pressure potentials, soil osmotic potentials, hydraulic conductivity and percent loss of conductivity (PLC) due to embolism, and made microscopic observations of perfused dye in the white mangrove tree, Laguncularia racemosa (L.) Gaertn. f., (1) to determine its vulnerability to air embolism compared with published results for the highly salt-tolerant red mangrove tree, Rhizophora mangle L., and (2) to identify possible relationships between air embolism, permanent blockage of vessels and stem diameter. Laguncularia racemosa was more vulnerable to embolism than reported for R. mangle, with 50 PLC at -3.4 MPa. Narrow stems (5-mm diameter) had higher PLC than larger stems (8.4- or 14-mm diameter) of the same plants. Basic fuchsin dye indicated that up to 89% of the vessels, especially in the narrow stems, had permanent blockage that could not be reversed by high pressure perfusion. Air embolism could lead to permanent vessel blockage and eventual stem mortality. Such vulnerability to embolism may restrict the growth of L. racemosa and limit its distribution to less salty areas of mangrove communities.  相似文献   

Analyses of assumptions and errors in the calculation of stomatal conductance from sap flux measurements     

Ewers BE  Oren R 《Tree physiology》2000,20(9):579-589

We analyzed assumptions and measurement errors in estimating canopy transpiration (E(L)) from sap flux (J(S)) measured with Granier-type sensors, and in calculating canopy stomatal conductance (G(S)) from E(L) and vapor pressure deficit (D). The study was performed in 12-year-old Pinus taeda L. stands with a wide range in leaf area index (L) and growth rate. No systematic differences in J(S) were found between the north and south sides of trees. However, J(S) in xylem between 20 and 40 mm from the cambium was 50 and 39% of J(S) in the outer 20-mm band of xylem in slow- and fast-growing trees, respectively. Sap flux measured in stems did not lag J(S) measured in branches, and time and frequency domain analyses of time series indicated that variability in J(S) in stems and branches is mostly explained by variation in D. Therefore, J(S) was used to estimate transpiration, after accounting for radial patterns. There was no difference between D and leaf-to-air vapor pressure gradient, and D did not have a vertical profile in stands of either low or high L suggesting a strong canopy-atmosphere coupling. Therefore, D estimated at one point in the canopy can be used to calculate G(S) in such stands. Given the uncertainties in J(S), relative humidity, and temperature measurements, to keep errors in G(S) estimates to less than 10%, estimates of G(S) should be limited to conditions in which D >/= 0.6 kPa.  相似文献   

Ticks and tick borne pathogens in domestic animals in the Netherlands     

Bodaan C  Nihof AM  Postigo M  Nieuwenhuijs H  Opsteegh M  Franssen L  Jebbink F  Jansen S  Jongejan F 《Tijdschrift voor diergeneeskunde》2007,132(13):517-523

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Influence of soil temperature and soil compaction on growth and P uptake of sugar beet     

Christa Hoffmann  Albrecht Jungk 《植物养料与土壤学杂志》1996,159(3):263-270

Sugar beet growth is often impaired by cold and compacted soil. The aim of this study was to determine the effect of soil temperature and soil compaction on the growth and function of sugar beet roots. For this purpose a pot experiment with sugar beet (Beta vulgaris) was conducted in a growth chamber in which the soil temperature was kept constant either at 10°C or 20°C and air temperature at 20°C. The soil was uncompacted (1.30 g cm^?3) or compacted to a bulk density of 1.65 g cm^?3. In order to find out whether growth restriction was caused by insufficient P supply of the plant the experiment was run without and with P application (300 mg per kg soil). Root growth was much smaller at 10°C compared to 20°C, whereas root/shoot ratio was not affected by soil temperature. Hence, root and shoot growth was inhibited to the same extent. P content of the plants was not reduced, neither by cold nor by compacted soil, although parameters of acquisition such as root length and morphological root properties were altered. Soil temperature strongly affected P influx, whereas compaction did not. The calculation with a simulation model showed that at 10°C soil temperature the predicted P uptake of the plants agreed with the measured P uptake irrespective of compaction and P application. However, at 20°C the model underestimated the P influx at low soil P availability even if allowance was made for root hairs. It is concluded that under conditions of high shoot P demand and low P availability in soil P has been mobilized by mechanisms not taken into account by the model.  相似文献   

A predator unmasked: life cycle of Bdellovibrio bacteriovorus from a genomic perspective     

Rendulic S  Jagtap P  Rosinus A  Eppinger M  Baar C  Lanz C  Keller H  Lambert C  Evans KJ  Goesmann A  Meyer F  Sockett RE  Schuster SC 《Science (New York, N.Y.)》2004,303(5658):689-692

Predatory bacteria remain molecularly enigmatic, despite their presence in many microbial communities. Here we report the complete genome of Bdellovibrio bacteriovorus HD100, a predatory Gram-negative bacterium that invades and consumes other Gram-negative bacteria. Its surprisingly large genome shows no evidence of recent gene transfer from its prey. A plethora of paralogous gene families coding for enzymes, such as hydrolases and transporters, are used throughout the life cycle of B. bacteriovorus for prey entry, prey killing, and the uptake of complex molecules.  相似文献   

Comment on "Avian extinction and mammalian introductions on oceanic islands"     

Didham RK  Ewers RM  Gemmell NJ 《Science (New York, N.Y.)》2005,307(5714):1412; author reply 1412

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Illusory statistics     

Ewers RM 《Science (New York, N.Y.)》2005,310(5750):973-974

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