Unraveling the morphological patterns of a subantarctic eelpout: a geometric morphometric approach     

Fernanda S. ORREGO  Mathias HÜNE  Hugo A. BENÍTEZ  Mauricio F. LANDAETA 《Integrative zoology》2023,18(2):372-384

Phenotypic variation in organisms depends on the genotype and the environmental constraints of the habitat that they exploit. Therefore, for marine species inhabiting contrasting aquatic conditions, it is expected to find covariation between the shape and its spatial distribution. We studied the morphology of the head and cephalic sensory canals of the eelpout Austrolycus depressiceps (4.5–22.5 cm TL) across its latitudinal distribution in South Pacific (45°S–55°S). Geometric morphometric analyses show that the shape varied from individuals with larger snout and an extended suborbital canal to individuals with shorter snouts and frontally compressed suborbital canal. There was size variation across the sampled populations, but that size does not have a clear latitudinal gradient. Only 8% of the shape variation relates to this size variation (allometry), represented by a decrease in the relative size of the eye, and a depression of the posterior margin of the head. There were spatial differences in the shape of the head, but these differences were probably caused by allometric effects. Additionally, 2 of the canals of the cephalic lateralis pores and the head shape showed modularity in its development. This study shows that the morphology of marine fish with a shallow distribution varies across distances of hundreds of kilometers (i.e., phenotypic modulation).  相似文献   

Prevalence of virulent footrot in sheep flocks in southern New South Wales     

RH LOCKE  NE COOMBES 《Australian veterinary journal》1994,71(10):348-349

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Erfassung der Mineralstoffverteilung im wurzelnahen Boden durch Autoradiographie     

N. Claassen  L. Hendriks  A. Jungk 《植物养料与土壤学杂志》1981,144(3):306-316

Determination of the nutrient distribution in the soil-root interface by autoradiography A method is described to determine the nutrient concentration profile in soil in the vicinity of living plant roots. For this purpose plants are grown in flat boxes filled with radioactive labelled soil of 5 mm thickness and then autoradiographs of roots and surrounding soil are taken. The density of the x-ray film is scanned by use of a microdensitometer. The profile of the film density produced by ³³P, which is a β-emitter of relatively low energy, represents the P concentration profile rather accurately. In case of ³²P and ⁸⁶Rb, nuclides of higher β-energy, profiles of the film density deviate markedly from concentration profiles because of cross fire. To account for the cross fire a corrective calculation is applied. The result of the corrective calculation is shown with autoradiographs of maize roots grown in either sand or loess soil labelled with ⁸⁶Rb. Phosphate depletion zones around plant roots growing in soil usually do not exceed the distance of cross fire of ³²P. Therefore, this nuclide is not or at least less appropriate than ³³P.  相似文献   

Phosphatverarmung des wurzelnahen Bodens und Phosphataufnahme von Mais und Raps     

L. Hendriks  N. Claassen  A. Jungk 《植物养料与土壤学杂志》1981,144(5):486-499

Phosphate depletion at the soil — root interface and the phosphate uptake of maize and rape Maize and rape plants were grown in flat containers in a ³3P-labelled sandy soil and the distribution of soil phosphate near roots was determined by using densitometric scans of autoradiographs. The concentration of isotopically exchangeable phosphate at the root surface decreased within a few days by 42 per cent with rape and by 50–65 per cent with maize. Initially the width of the depletion zone is very small. Within six days the depletion zone extended to the final distance from the surface of the root cylinders of about 2 mm for maize and 2.6 mm for rape. The soil within the range of the mean length of root hairs (0.7 mm for maize and 1.3 mm for rape) is almost equally depleted. This indicates that root hairs are very important for P-uptake from soil. This is further supported by higher P-uptake rates per cm root length of rape than of maize. The P-concentration of the soil solution was estimated by means of the phosphate desorption curve. Within the root hair cylinder the P-concentration of the soil solution decreased from 0.8 to 0.03 mg P/l. Changes of the P-depletion profile with time were used to calculate P-uptake rates for roots of different age. The results indicate that for the first 3–5 days P-uptake rates remained near maximum, even though the P-concentration of the soil solution at the root surface had strongly decreased within two days. Phosphate uptake rates per cm root length did not decrease unless the whole root hair cylinder had been depleted.  相似文献   

A Method for Determining Phosphate Diffusion Coefficients by Bulk Diffusion in Soil     

Joachim Kaselowsky  Pratapbhanu B. S. Bhadoria  Norbert Claassen  Albrecht Jungk 《植物养料与土壤学杂志》1990,153(2):89-91

A method is described for the determination of phosphate diffusion coefficients by bulk diffusion in soil using the concentration distance method. Two soil blocks only differing in phosphate concentration are brought into contact. After a diffusion period of two weeks the soil blocks are separated, frozen in liquid nitrogen and sliced into layers about 0.02 cm thick by means of a refrigerated microtome. The soil samples are extracted with 4 N HCl, a procedure which fully recovers the added amount of fertilizer P and thus includes the total amount of P that diffuses from one soil block to the other. A concentration distance profile for P and a calculation of the P diffusion coefficient is presented.  相似文献   

A method for determining Michaelis-Menten kinetic parameters of nutrient uptake for plants growing in soil     

Bjrn Seeling  Norbert Claassen 《植物养料与土壤学杂志》1990,153(5):301-303

The relationship between nutrient influx (I_n) and solution concentration at the root surface (C_lo) has not yet been determined for roots growing in soil because of difficulties in measuring C_lo. Corn was grown on two soils with 12 and 21% clay. Each soil had five K levels ranging from low to very high. Potassium influx (I_n) was determined from K uptake between two harvests and root length. C_lo was then calculated from the average soil solution concentration and I_n by assuming that diffusion is the main transport mechanism for K to the root. Potassium influx plotted against C_lo showed a saturation curve, typical of a Michaelis-Menten kinetic relationship. The Michaelis-Menten uptake parameters, maximum influx (I_max) and Michaelis constant (K_m), were obtained by the “Hanes” plot. There was close agreement, without lack of fit, between calculated and observed data. The proposed procedure therefore appears to be suitable for estimating the uptake kinetics of roots growing in soil. Requirements for applications of the method are discussed.  相似文献   

Growth and phosphorus uptake of maize cultivated alone,in mixed culture with other crops or after incorporation of their residues     

Hanadi El Dessougi  Alexander zu Dreele  Norbert Claassen 《植物养料与土壤学杂志》2003,166(2):254-261

Intercropping or rotating of P‐efficient crop species which mobilize sparingly soluble P by their root exudates can have beneficial effects on growth and P uptake of P‐inefficient species. We aimed at studying the effect of intercropping or incorporating of crop residues of P‐efficient crops on the components of maize P‐uptake, i.e. the root‐system size and P influx (P‐uptake rate per unit root length). This was studied in 3 pot experiments in a low‐P sandy soil. In the first experiment, maize was intercropped with white lupine, sugar beet or oilseed rape, and with groundnut in the second experiment. In the third experiment, maize was grown after incorporating the crop residues of white lupine, sugar beet or oilseed rape. Maize growth and yield was strongly inhibited when intercropped with white lupine, sugar beet or oilseed rape, probably because of competition for nutrients. But with groundnut as the accompanying species, maize yield was increased by a factor of 3, mainly because of an enhanced P influx. Crop residues of oilseed rape and sugar beet increased the yield of maize by factors 2 and 1.6, respectively, because of a 3 and 2 times higher P uptake as compared to maize grown after maize without incorporation of crop residue. The reason for the higher maize P‐uptake after oilseed rape was an 11 times higher P influx as compared to maize without crop residues, and after sugar beet residues because of an enhanced root growth and a 4 times higher P influx. Lupine residues did not improve maize growth, mainly because of a low P influx, which was even less than that of maize grown without crop residues. The soil solution P concentration and calcium acetate lactate‐extractable P (CAL P) measured in this study did not reflect the P availability as indicated by the plants (P uptake, P influx). This indicates that other mechanisms such as P mobilization in the rhizosphere by root exudates or cell‐wall components were responsible for the increased P availability. These mechanisms need further investigation.  相似文献   

Availability of phosphate and potassium as the result of interactions between root and soil in the rhizosphere     

A. Jungk  N. Claassen 《植物养料与土壤学杂志》1986,149(4):411-427

A number of findings are summarized in order to show the significance of individual plant properties and soil factors on the availability of phosphate and potassium to plants growing in soil. The flux of a nutrient into a given plant root depends directly on the concentration of the nutrient in the adjacent solution. In nutrient solution, P and K influx follows Michaelis-Menten kinetics. Almost maximum rates of influx have been observed in the range of soil solution concentrations usually found in German arable soils. Roots exhaust P and K from solutions to about 0.2 μmol P and 1 μmol K 1^?1 if not replenished. At the root surface P and K concentrations in soil decrease rapidly within one day; small changes occur after this period. Initially, the extent of the depletion zone is very small but it extends radially with time. After the initial phase therefore, P and K supply to the plant depends on transport from more remote parts of the soil and also on release from undissolved sources. The degree of depletion and the extent of the depletion zone are related to the diffusion coefficient; they decrease with increasing clay content of soil. Root hairs penetrate the soil and extend the volume of soil supplying nutrients to a unit of root. P and K influx therefore increase with the length of root hairs. Proton release of roots mobilize P and K in soil. This is clearly detected by the HCl-soluble P and K fractions within 2 mm of the root surface. The activity of acid and alkaline phosphatases strongly increase in the soil in the vicinity of the root surface of several plant species. It is supposed that organic P compounds can therefore be utilized by plants. P and K influx per unit of root length and root length per unit of shoot weight differed widely between species. The product of these two parameters however was closely related to the P and K concentration of the shoots. Calculations from a mathematical model were in good agreement with measured K depletion profiles and K uptake by plants. It is therefore concluded that the main factors influencing the P and K availability of plants growing in soil have been accounted for in the mathematical model and that the parameters have been accurately measured.  相似文献   

Differences in manganese efficiency of wheat (Triticum aestivum L.) and raya (Brassica juncea L.) as related to root‐shoot relations and manganese influx     

Upkar Singh Sadana  Debasmita Samal  Norbert Claassen 《植物养料与土壤学杂志》2003,166(3):385-389

Manganese efficiency is a term used to describe the ability of plants to obtain higher relative yields at low Mn supply compared to other species. To evaluate Mn efficiency of wheat (Triticum aestivum L.) and raya (Brassica juncea L.), a greenhouse pot experiment was conducted using Mn deficient Typic Ustochrept loamy sand soil, treated with 0, 50, and 100 mg Mn (kg soil)^–1. In the no‐Mn treatment, wheat had produced only 30 % of its maximum dry matter yield (DMY) with a shoot concentration of 10.8 mg Mn (kg DM)^–1 after 51 days of growth, while raya had produced 65 % of its maximum DMY with 13.0 mg Mn (kg DM)^–1. Taking relative shoot yield as a measure of Mn efficiency, raya was more efficient than wheat. Both crops produced the maximum DMY with 50 mg Mn (kg soil)^–1. Even though raya had a lower root length : DMY ratio and a higher shoot growth rate, it acquired higher Mn concentrations in the shoot than wheat under similar soil conditions, because of a 2.5 times higher Mn influx. Model calculations were used to calculate the difference of Mn solution concentration (ΔC_L) between the bulk soil (C_Li) and the root surface (C_L0) that is needed to drive the flux by diffusion equal to the measured influx. The results showed that ΔC_L was smaller than C_Li, which indicates that chemical mobilization of Mn was not needed to explain the observed Mn uptake even for raya. According to these calculations, the higher Mn influx of raya was caused by more efficient uptake kinetics, allowing for a 4.5 times higher Mn influx at the same Mn concentration at the root surface.  相似文献   

Variants of the recently discovered avian gyrovirus 2 are detected in Southern Brazil and The Netherlands     

dos Santos HF  Knak MB  de Castro FL  Slongo J  Ritterbusch GA  Klein TA  Esteves PA  Silva AD  Trevisol IM  Claassen EA  Cornelissen LA  Lovato M  Franco AC  Roehe PM  Rijsewijk FA 《Veterinary microbiology》2012,155(2-4):230-236

A genome of a virus preliminarily named avian gyrovirus 2 (AGV2), a close relative to chicken anemia virus, was recently discovered in a chicken in the state of Rio Grande do Sul, Southern Brazil. To study the occurrence of AGV2 in Rio Grande do Sul and the neighboring state Santa Catarina, a number of adult chickens (n=108 and n=48, respectively) were tested for the presence of AGV2 DNA. An AGV2-specific PCR was developed, optimized and used to analyze DNA extracted from clinical samples. AGV2 DNA was detected in 98/108 (90.7%) of samples collected in the state of Rio Grande do Sul and 29/48 (60.4%) of the samples collected in the state of Santa Catarina. In order to check whether AGV2 DNA would be detected in samples from a geographically distant region, DNA from brain samples of 21 diseased chickens from the Netherlands were tested independently, by the same method. In such specimens, 9/21 (42.9%) brain tissue samples were found to contain AVG2 DNA. Sequence analysis of some of the PCR products demonstrated that the amplified AGV2 sequences could vary up to 15.8% and could preliminarily be divided in three groups. This indicated the occurrence of variants of AGV2, which may reflect differences in geographical origin and/or in biological properties. The data presented here provides evidence that AGV2 seems fairly distributed in chickens in Southern Brazil and that AGV2 also circulates in the Netherlands. Besides, circulating viruses display genetic variants whose significance should be further examined, particularly to determine whether AGV2 would play any role in chicken diseases.  相似文献