Environmentally induced morphological variation in the Barnacle Goose,Branta leucopsis

The environmental conditions to which juvenile barnacle geese (Branta leucopsis) were exposed during growth were found to affect their body size at fledging as well as their final adult body size. Small juveniles showed compensatory growth from the time of fledging up to one year of age, but this did not fully compensate the differences in body size that were established before fledging. The variation in protein content in plants eaten during growth could probably explain the observed body size differences, sometimes of more than 10%, between different categories of adult geese. Our results imply that one cannot infer selection on morphological characters from differences between samples of adult birds from different localities or from different cohorts within a population, without first showing that environmental conditions during growth do not affect the development of the characters under study.     

Increased protoplast yield from oat leaves and bean internodes by non-injurious mechanical perturbation

Summary A simple new technique has been developed to greatly increase the yield of protoplasts from plant organs without injury to the plant. Mechanical perturbation (MP) by non-stressful rubbing of oat leaf segments and bean internodes yielded ten to twenty times more viable protoplasts than did controls. The increase in protoplast yield due to MP is best manifested, if the organs are excised and transferred to the cellulytic enzymes immediately after MP is given to the intact organ. The enzymes begin digesting from the lower end of the bean internodes and proceed acropetally. Vacuum infiltration of control oat leaf segments for 15 min with enzyme solution resulted in increased yield but less than due to MP. Increased levels of calcium (10 mM) in the medium decreased the yield of protoplasts from both control and MP-treated plant organs. EGTA significantly increased the yield of protoplasts from control oat leaf segments and marginally over that found in the control bean internodes. Cycloheximide increased the yield of protoplasts from oat leaf segments but not from bean internodes. It is suggested that MP may increase the susceptibility of cell wall polymers to cellulytic enzymes by reducing calcium cross linking. MP is thus a tool for increasing the yield of protoplasts from plant organs without causing injury.Abbreviations CHI cycloheximide - EGTA ethyleneglycol-bis-(ß-aminoethyl ether)-N,N-tetraacetic acid - FDA fluorescein diacetate - MP mechanical perturbation     

Host Status of Five Weed Species and Their Effects on Pratylenchus zeae Infestation of Maize

The host suitability of five of the most common weed species occurring in maize (Zea mays L.) fields in South Africa to Pratylenchus zeae was tested. Based on the number of nematodes per root unit, mealie crotalaria (Crotalaria sphaerocarpa) was a good host; goose grass (Eleusine indica), common pigweed (Amaranthus hybridus), and thorn apple (Datura stramonium) were moderate hosts; and khaki weed (Tagetes minuta) was a poor host. Only the root residues of khaki weed suppressed the P. zeae infestation of subsequently grown maize. When goose grass, khaki weed, and mealie crotalaria were grown in association with maize in soil infested with P. zeae, goose grass and khaki weed severely suppressed maize root development; this resulted in a low number of nematodes per maize root system and a high number of nematodes per maize root unit. Mealie crotalaria did not restrict maize root growth and did not affect nematode densities per maize root system or maize root unit. Special attention should be given to the control of mealie crotalaria, which is a good host for P. zeae, and goose grass, which, in addition to its ability to compete with maize, is also a suitable host for P. zeae.     

Effect of presowing seed treatment with molybdenum and cobalt on growth,nitrogen and yield in bean (Phaseolus vulgaris L.)

Summary Bean (Phaseolus vulgaris L. Cv. Burpees Stringless) seeds were subjected to two cycles of presowing soaking and drying treatments with sodium molybdate and cobalt nitrite at 1 and 5 ppm concentrations used separately and also in combination. Sodium molybdate 2 ppm and cobalt nitrite 1 ppm used singly proved better than the remaining treatments with respect to nodulation, dry matter, nitrogen and yield. Combined treatment with sodium molybdate and cobalt nitrite did not produce additive effect on any parameter studied compared to their usage alone.     

南方菜豆花叶病毒外壳蛋白基因序列的分析

用重组DNA技术及序列分析法测定了南方菜豆花叶病毒RNA基因组3′端1,000个碱基的序列,以及由此序列推导出的整个外壳蛋白的氨基酸顺序,它与巳报导的基本上一致。介绍了用DNA的寡核苷酸水解混合物作为起始引物,以3′端不含PolyA尾巴且不能加上PolyA的病毒RNA作为模板合成互补DNA,及进一步无性繁殖此cDNA的方法。     

新疆石河子地区印度麻花叶病植株病毒分离物的鉴定

1984年,从新疆石河子农学院实验站印度麻花叶病植株上,分离到一株病毒分离物Sc-1,经汁液摩擦接种试验表明,它可以侵染10种豆科植物和2种藜科植物。在印度麻、蚕豆、豌豆、箭舌豌豆、扁豆、山藜豆、田菁和红三叶草上引起系统花叶,在豇豆上产生局部枯斑和系统花叶,在苋色藜、昆诺藜上表现为系统黄斑。失毒温度为55～60℃,稀释限点10~(-3)～10~(-4),体外保毒期3～4天。可经汁液和蚜虫传播,不通过种子传毒。病毒粒体为线条状,大小为13～15×750nm。光学显微镜检查可见,病叶表皮细胞内形成不定形的内含体。电镜下可见风轮状、环状内含体。分离物Sc-1与菜豆黄色花叶病毒(BYMV)抗血清呈阳性反应。我们将Sc-1归为菜豆黄色花叶病毒(BYMV),且为豇豆株系。     

Examination of the influences of density pressure on the pattern of adult emergence with reference to the azuki bean weevil,Callosobruchus chinensis

Summary The effect of competition pressure on the sequential pattern of adult emergence was studied by using the experimental population of the azuki bean weevil. The density and pattern of emergence curves of the parental adult induced the changes in the shape of emergence curve of the progeny as well as the number of progeny individuals. In order to explain these changes, a simple mathematical model which has two independent variables, the population density and the capacity of environment, was introduced. The model generated basically similar patterns of emergene curves as observed in the present experiments. This means that the model displayed well the competition pressure which differentially acted upon early-born and late-born individuals in the populations being at different densities and which were differentially received by individual progeny according to the sequential distributions of parents. This different severity of competition pressure resulted in the difference of time when the pressure compelled influences on the sequential distribution of adult emergence. Therefore, early developed individuals may have good chance to survive, but the competition pressure works as a factor modifying their fundamental superiority, especially in the scramble type of competition. Intense crowding of the azuki bean weevil gave rise to the scramble type of competition in the relation between the numbers of adults emerged in two successive generations. When parental emergence concentrated in a short term and at high density, the competition becomes intense, resulting in the inferiority of early developed individuals, in the decrease in number at the next generation and in the increase of duration for emergence.     

Studies on interspecies competition between the azuki bean weevil and the southern cowpea weevil

Experimental studies was made on the interspecies competition between the azuki bean weevil, Callosobruchus chinensis and the southern cowpea weevil, C. macultatus. And the following results were obtained.

1. The reverse result of competition between the two species observed under the air-tight condition and the air-free one. That is, the population of the azuki bean weevils destroyedby that of the southern cowpea weevils under the former condition and vice versa under the latter. It is thought that such a reversal is due to the difference of sensibility of each species to the air-tight condition.
2. Under the air-free condition, change of the time interval of food-supplying had no effect on the result of competition within the limits of this experiment. The population of the southern cowpea weevils was always destroyed by that of the azuki bean weevils. But there was a certain degree of correlation between the duration of co-existence and the interval of food-supplying.
3. From the results, it is possible to say that by changing the degree of air-tightness, or the time interval of food-supplying, the co-existence period and the final result of competition can be changed.
4. The different mechanism of competition between two species in the present experiment from the experiments ofUtida (1952) andYoshida (1957) were discussed.
5. A difference in the mechanism of interspecies competition and intraspecies competition was expected from the level of total population numbers of two species and the individual weight of C. chinensis.

     

二氧化硫对墨西哥豆瓢虫的影响

空气污染对害虫的影响,国内尚无研究报道。本文报道了作者在美国农业研究中心植物胁迫实验室进行的部分工作。实验结果表明,在0.30ppmSO_2的作用下,墨西哥豆瓢虫(Epilachna varivestis)的取食量和蛹重增加;与未受污染的寄主植物相比,豆瓢虫偏食受污染的植物;而且有嗜食含较高糖分寄主植物的倾向;在污染空气中长成的成虫可消耗更多的植物物质。