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1.
T. N. Ul'janova 《Genetic Resources and Crop Evolution》1997,44(1):5-8
The paper presents a survey of the situation existing now in nature with wild relatives of crop species from the group of segetal and ruderal plants, found within the territories of Russia and of other CIS countries. The majority of non-specialized annual and perennial weeds have been shown still to occur in the territory of the former USSR. For the past 50 years they have not seriously vanished from agriculture. Some of them even have a tendency to expand their areas and to become more abundant. Hence they need not be conserved in gene banks. It is only for a relatively small group of species of specialized contaminants that care should be taken to preserve them and to store their seeds in gene banks. 相似文献
2.
当中蜂的巢脾中心距为32mm,脾间蜂路、框间蜂路、前后蜂路、底箱上蜂路、继箱上蜂路、继箱下蜂路、底箱下蜂路分别为9、7、8—10、5、8—10、5和25mm时,蜂路结构既合符中蜂生物学特性,又便于蜂群的饲养管理.通过本研究我们认为:在设计中蜂蜂箱时以此为蜂路结构的设计依据,并配合合理的巢框设计便可获得较理想的中蜂蜂箱. 相似文献
3.
J.G. Hawkes 《Genetic Resources and Crop Evolution》1999,46(2):163-168
Vavilov's ideas on New World centres of crop plant diversity are reviewed and the development of his ideas from 1926 to 1940 are described. More recent collecting work and taxonomic studies by the author confirm largely the delimitation of the American gene centres suggested by Vavilov, even in regard to details, e.g. within Bolivia. 相似文献
4.
对山西省境内已知蚜茧蜂种类,按植被划分的五个特定自然分布中心,如雁北干草草区、晋西北灌丛草原区等进行了分析。还归纳了蚜草蜂分布的生态地理特征。 相似文献
5.
The proportion of vitreous kernels in a sample is an internationally recognized specification for determining the value of durum wheat (Triticum durum Desf.). Vitreous kernels are mostly related to quality, which affects the pasta performance during cooking. Vitreousness and the amount of shrunken kernels are visually assessed during the grading process. This assessment is subjective and tedious.A machine vision system was developed to determine the percentage of vitreous, starchy, piebald and shrunken kernels in approximately 100 grain samples, using a trans-illuminated image of one layer of non-singulated kernels (in bulk) acquired by a digital camera. Classification models were developed with stepwise Linear Discriminant Analysis, as well as an on-line Bayesian classifier integrated with an image analysis system. The overall correct classification in Starchy classifier was high 98.58% in the Training set, made up of 6679 grains, following the Linear Discriminant Analysis classification, of 30 Italian cultivars harvested in 2005 in three localities. An independent Test set was constituted by samples collected in 30 Sicilian Storage Centres in the 2007 harvest season. The overall classification was 96.03%. For the Shrunken classifier 95.27% of the Training set and 99.58% of the Test set were correctly classified. The image analysis system was more reliable than the human inspectors who validated the system, both for the same samples measured many times and at different times. 相似文献
6.
Melano-macrophage centres and their role in fish pathology 总被引:14,自引:0,他引:14
Melano-macrophage centres, also known as macrophage aggregates, are distinctive groupings of pigment-containing cells within the tissues of heterothermic vertebrates. In fish they are normally located in the stroma of the haemopoietic tissue of the spleen and the kidney, although in amphibians and reptiles, and some fish, they are also found in the liver. They may also develop in association with chronic inflammatory lesions elsewhere in the body and during ovarian atresia. In higher teleosts, they often exist as complex discrete centres, containing lymphocytes and macrophages, and may be primitive analogues of the germinal centres of lymph nodes. Melano-macrophage centres usually contain a variety of pigments, including melanins, and these increase in range and volume in older fish or in the presence of cachectic disease. Melano-macrophage centres act as focal depositories for resistant intracellular bacteria, from which chronic infections may develop. Iron capture and storage in haemolytic diseases appears to be a primary function, but antigen trapping and presentation to lymphocytes, sequestration of products of cellular degradation and potentially toxic tissue materials, such as melanins, free radicals and catabolic breakdown products are among other functions that have been ascribed. Recent work suggests that they are a site of primary melanogenesis rather than mere storage. Melano-macrophage centres increase in size or frequency in conditions of environmental stress and have been suggested as reliable biomarkers for water quality in terms of both deoxygenation and iatragenic chemical pollution. 相似文献
7.
The geographic origins of the invasive Phytophthora species, P. lateralis and P. ramorum are unknown. In 2008 soil samples were collected in an old growth yellow cedar (Chamaecyparis obtusa var. formosana) stand in the Ma‐kau Ecological Park in north eastern Taiwan and subjected to Phytophthora baiting procedures at 18°C. Cedar needle baits yielded isolates of a slow growing Phytophthora culture from one soil sample, together with P. cinnamomi. Phytophthora bisheria sp. nov. was obtained from another sample. The slow growing isolates conformed closely to P. lateralis in the morphology of their sporangia and chlamydospores, growth–temperature relationships, absence of gametangia and their ITS and cox II sequences. The isolates’ sporangia were partially caducous, with short pre‐formed pedicels of ca. 3–5 μm, a highly unusual feature in a non‐papillate Phytophthora. The isolates also produced multicellular stromata on cedar decoction agar. Small morphological and molecular differences were observed between the Taiwan‐isolates and Oregon‐control isolates. Taiwan may lie within the geographic centre of origin of P. lateralis. By analogy Japan may also lie within the natural range of P. lateralis; and Japan, along with Taiwan and Yunnan, could be an origin for the closely related P. ramorum. 相似文献
8.
9.
Catechol-O-methyltransferase, involved in the methylation of catechol substrates, was localized in the brain of the male African
catfish,Clarias gariepinus, by means of a radiometric assay using [Methyl-3H]S-adenosylmethionine as methyldonor and catecholestrone as substrate. Fore- and midbrain were divided into eighteen, 500
μm thick, transverse sections. With a hollow needle (diameter 1 mm), specific areas of the brain were punched out and assayed.
The catechol-O-methyltransferase activity was calculated from the amount of radioactive methoxyestrone formed from catecholestrone
and expressed in pmol.mg−1 tissue.h−1.
The enzyme could be demonstrated throughout the brain. Although the enzyme activity did not differ very much between the various
brain regions (max. 15.4; min. 7.5 pmol), there were some areas in the brain with a more than average activity,i.e., the lateral telencephalon (10.3 pmol), the nucleus preopticus (13.1 pmol), nucleus lateralis tuberis (11.0 pmol) and nucleus
recessus posterioris (12.0 pmol) of the diencephalon, the tectum opticum (15.4 pmol) and torus semicircularis (13.6 pmol)
of the mesencephalon, and the caudal cerebellum of the metencephalon (10.8 pmol). The lowest activity was detected in the
caudal metencephalon (7.5 pmol).
The presence of the enzyme catechol-O-methyltransferase in the brain of the African catfish and the observation that both
catecholestrogens and dopamine can be methylated by this enzyme suggest that catecholestrogens can influence the methylation
(inactivation) of dopamine. Incubations of forebrain homogenates with dopamine and catecholestrone or catecholestradiol confirmed
that both catecholestrogens can inhibit the methylation of dopamine. Lineweaver-burk plots with various concentrations of
the catecholestrogens indicated that the inhibition is competitive. Dixon plots from the inhibition studies gave inhibition
constants of 1.4 and 0.6 μM for catecholestrone and catecholestradiol, respectively, indicating that catecholestradiol is
a two times stronger inhibitor than catecholestrone.
The significance of the inhibition of the methylation of dopamine by the catecholestrogens in the brain is discussed in the
light of the negative feedback of gonadal steroids on the central regulation of reproductive processes. 相似文献
10.
Lobna Zribi Gharbi Fatma Rezgui Fatma Rejeb Salwa Nahdi Hassan Rejeb Mohamed Néjib 《Scientia Horticulturae》2009
To study the response of tomato (Solanum lycopersicum cv. Rio Grande) to salinity, the effect on plant growth, water relations, stomatal conductance and Chlorophyll fluorescence was investigated. Tomato plants were grown in peat culture under controlled conditions and submitted during 28 days to saline stress ranging from 0 to 25, 50, 100, 150 and 200 mM of NaCl. At the end of the experiment period, plant growth was significantly decreased with increasing salinity. 相似文献