Summary. Seeds of Polygonam persiaria were collected from seven localities during 1962. In 1963 plants of these seven populations were grown in the field and sampled at regular intervals over the period 21st June to 13th August. At all samplings there were differences between populations in total dry weight, in leaf area index and in total nitrogen content, and populations also differed in the date of flowering. The populations also differed significantly in relative growth rate, leaf area ratio, net assimilation rate and relative nitrogen absorption rate. The variations in net assimilation rate did not appear to be closely associated with variations in leaf area index. Certain growth attributes were correlated with the latitude of origin, and it is tentatively suggested that the populations may represent genetically distinct latitudinal ecotypes. Études sur des espèces de mauvaises herbes du genre Polygonum L. 相似文献
Although most of the magnetic flux observed on the sun originates in the low-latitude sunspot belts, this flux is gradually dispersed over a much wider range of latitudes by supergranular convective motions and meridional circulation. Numerical simulations show how these transport processes interact over the 11-year sunspot cycle to produce a strong "topknot" polar field, whose existence near sunspot minimum is suggested by the observed strength of the interplanetary magnetic field and by the observed areal extent of polar coronal holes. The required rates of diffusion and flow are consistent with the decay rates of active regions and with the rotational properties of the large-scale solar magnetic field. 相似文献
1. Two experiments were conducted to evaluate the effects of including ascorbic acid (AA), palm oil or a combination of both in the diets of laying hens during the hot months in a tropical environment.
2. The inclusion of AA improved egg production, food intake and efficiency of utilisation, and decreased the cost of food per kg egg. The addition of 400 mg AA/kg diet gave the most efficient performance.
3. Palm oil inclusion reduced the effect of heat stress and increased egg production, egg weight, food intake and efficiency of utilisation.
4. When 200 mg AA and 50 g palm oil/kg were used, additive responses were obtained with further improvements in egg production, food cost and efficiency.
5. Ascorbic acid and palm oil when fed alone or in combination reduced the incidence of cracked eggs.
6. Thus, 400 mg ascorbic acid/kg of diet, 50 g palm oil or 200 mg AA plus 50 g palm oil/kg diet ameliorated the effects of heat stress in laying hens. 相似文献
1. The growth of three distinct adipose tissue depots around the abdomen, neck and thigh was measured in a commercial strain of broiler, and related to the changes in activity of lipoprotein lipase within each depot.
2. At 10 d of age there was no significant difference between the weights of the depots. Thereafter the abdominal fat pad exhibited a much greater rate of growth than the other two depots so that by 55 d of age the abdominal fat pad was 4 times the size of the leg depot and 3.4 times the size of the neck depot.
3. Changes in total lipoprotein lipase activity for all three depots showed a similar pattern to the changes in their weight.
4. When [14C]‐VLDL was injected intravenously into birds at 15 and 57 d of age the percentage taken up into the abdominal fat pad was greater than that into the other two depots at both ages. At 57 d of age the abdominal fat pad had a 2.3‐fold greater uptake than at 15 d whereas the other two depots showed no significant differences at the two ages.
5. These results provide further evidence for a key role of lipoprotein lipase in regulating adipose tissue growth in broilers. They also demonstrate that although the abdominal fat pad has been used in a number of studies of adipose tissue metabolism it is not necessarily representative of other depots. 相似文献
Lungs from 48 feedlot cattle that had died from bacterial pneumonia were examined grossly and microscopically. Criteria based on microscopic lesions were adopted to age these pneumonias. In 38 cases, pneumonic lesions were of relatively uniform age throughout the affected tissue. In eight other cases, the presence of older lesions confined to one or two lobes suggested a previous episode of pneumonia. The aging criteria adopted were in agreement with the duration of the observed clinical signs in 26 cases. In 13 other cases, the pneumonia was estimated to be of longer duration than suggested by the history, whereas in the remaining nine cases, it was estimated to be more recent. Areas of tan discoloration of the parenchyma surrounded by white or yellow borders were considered the best areas to examine microscopically since they offered the best chances of revealing necrosis and fibrosis, the main lesions used to age the pneumonia. 相似文献
1. One hundred and twenty (60 male and 60 female) 21‐d‐old Ross 1 broiler chicks were reared in cages in rooms kept at 21°C or 31°C and were killed at body weights of 1.0, 1.5, 2.0, 2.5 or 3.0 kg.
2. Birds reared at either of the two temperatures ate similar quantities of food to reach their slaughter weight although at 31°C they took longer to reach it.
3. The meat yields of the birds at each slaughter weight were similar at both rearing temperatures, but at body weights greater than 2.0 kg, the broilers reared at 21 °C had more breast meat than those reared at 31°C.
4. Females ate more food than males to reach each of the slaughter weights. The females deposited more fat and had a greater skin weight than the males and, although they had a similar amount of total meat, they had more breast meat. 相似文献
Adult populations ofMaladera matrida Argaman (Coleoptera: Scarabaeidae), a beetle highly injurious to agricultural crops, were studied in the coastal plain of Israel from 1985 to 1988. There were two generations annually. Adults emerged in March, April or May and disappeared in October or November. The beetles are on the wing, mate, and feed at twilight and in the dark. Feeding and mating behavior, sex ratio, and preferred food plants were studied. 相似文献
The rate of multiplication of fire blight causing bacteriumErwinia amylovora (Burrill) Winslow et al. depends on the availability of water. Water availability can be quantified by means of the parameter water potential. The relationship between water potential and relative multiplication rate ofE. amylovora was derived from experiments of L. Shaw (1935). This relationship appears to be applicable toE. amylovora in plant tissues and in nectar of flowers.Multiplication and expansion ofE. amylovora in a restricted space, e.g. an intercellular hole, creates a pressure, which may cause schizogenic cavities in soft tissue. Strong tissue, however, may be able to resist this multiplication pressure of the bacteria, so that symptom progression can be prevented. A hypothesis is formulated on how the multiplication pressure may be quantified by means of the parameter water potential. Expansion of bacterial ooze may alo be due to absorbtion of water without increase of dry weight (e.g. a daily cycle of shrinkage and expansion). This expansion may give rise to a swelling pressure, which again may be quantified by means of the parameter water potential.Samenvatting De vermenigvuldigingssnelheid van de bacterie die bacterievuur veroorzaakt (Erwinia amylovora (Burrill) Winslow et al.,), hangt af van de beschikbaarheid van water. De beschikbaarheid van water kan worden gekwantificeerd met de parameter waterpotentiaal. De relatie tussen waterpotentiaal en relatieve vermenigvuldigingssnelheid vanE. amylovora werd afgeleid uit experimenten van L. Shaw (1935, Cornell University Agricultural Experiment Station, Ithaca. Memoir 181). Deze relatie kan zowel worden toegepast op de pathogenese in planteweefsel als op de epifytische ontwikkeling in nektar.Vermenigvuldiging vanE. amylovora in een beperkte ruimte, bijvoorbeeld in een intercellulaire holte, creëert een druk, die tot scheuren van zacht weefsel kan leiden. Sterk weefsel kan de vermenigvuldigingsdruk van de bacteriën vermoedelijk wel weerstaan, zodat uitbreiding wordt verhinderd. In een hypothese wordt beschreven hoe de vermenigvuldigingsdruk zou kunnen worden gekwantificeerd met behulp van de parameter waterpotentiaal. Wateropname door bacterieslijm zonder toename van het drooggewicht (bijvoorbeeld een dagelijkse gang van krimpen en zwellen) kan ook leiden tot een druk. Deze druk kan eveneens worden berekend met de parameter waterpotentiaal. 相似文献
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