Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.     

Expected selection efficiency for resistance to cacao pod rot (Phytophthora palmivora) comparing leaf disc inoculations with field observations

Summary A genetic analysis of resistance of cacao to Phytophthora palmivora was carried out in a 5 × 5 diallel and in a 4 × 2 NC II factorial design, involving cross-progenies and parental clones planted in the nursery and field, respectively. Resistance was scored in the laboratory by inoculation of leaf discs with P. palmivora spores with four replicates and, for the factorial design, results were compared with the percentage of rotten pods in the field assessed over a seven-year period. Significant differences between genotypes were observed for both laboratory and field evaluation methods. For the laboratory test, no reciprocal effect was observed and plant effects within seedling progenies were more significant than plant effects within clones. General combining ability was the main source of variation but specific combining ability was also significant for the leaf disc test applied to the diallel. Heritabilities increased with the number of replicates, reaching values of 0.34 and 0.67 for narrow sense heritability, and 0.60 and 0.67 for broad sense heritability, for the diallel and the factorial design, respectively. These values were higher than observed for the percentage of rotten pods in the field in the factorial design (0.42 and 0.47, respectively). For the leaf test, the expected genetic gains were around 30% with a selection intensity of 5%. The existence of significant genetic (0.71) and phenotypic (0.39) coefficients of correlation between resistance on leaves and percentage of rotten pods in the field in the factorial design confirms the feasibility of using the leaf disc test for early selection of resistance to Phytophthora pod rot of cacao.     

The Experimental and Commercial Release of Transgenic Crop Plants

With advances in recombinant DNA methods and transformation procedures, it is possible to transfer genes into crop plants from unrelated plants, microbes and animals. Many of the modifications being carried out, or envisaged, are for disease and pest resistance, product quality and tolerance to environmental stress, but there are additional opportunities to modify crops to give specialized products for industrial or pharmaceutical use. Some of the characteristics of transgenic plants are considered, including: transgene copy number, position, expression, stability, pleiotropy, selectable marker genes and somaclonal variation. There have been several hundreds of field trials with transgenic plants, and the first transgenic varieties are likely to be approved for commercial production in 1993. Before releasing transgenic plants, it is necessary to carry out a risk assessment to determine whether the transgenic variety will behave differently from a conventionally bred variety. Assessment procedures are being harmonized internationally by various organizations. There is a growing commitment to apply these genetic modification methods to crops in developing countries, as genes relevant to their crops and environments become available.     

The Location of Sources of Field Resistance to Bremia lactucae in Wild Lactuca Species

Thirty-one accessions of four Lactuca species (L. serriola, L. saligna, L. aculeata, L. squarrosa) and one L. serriola×L. sativa hybrid were screened for field resistance to Bremia lactucae. In the L. serriola group, significant differences in the level of field resistance were distinguished. The accessions PI 281876 and PI 253467 were free of infection. Moreover, all L. saligna accessions tested were totally free from disease during three-year-investigation.     

The identification and characteristics of field resistance to lettuce downy mildew (Bremia lactucae Regel)

Summary Eighty-one accessions of three Lactuca species which showed no recognisable race specific resistance to Bremia lactucae when tested in the laboratory as seedlings, exhibited different degrees of susceptibility when exposed to natural field infection. As a group, crisp genotypes had less mildew and a slower rate of disease development than other types of lettuce. Wild forms of Lactuca sativa and Lactuca serriola were particularly susceptible. In a further trial, the low field susceptibility of three lettuce cultivars (Iceberg, Batavia blonde de Paris and Grand Rapids) was confirmed. Disease development on cv. Iceberg was compared to that on the highly susceptible cv. Hilde in experiments where the two cultivars were grown either in close proximity or in isolation. The absolute level of attack on cv. Iceberg depended upon disease pressure and differences between the two types only became apparent approximately 8 wk after sowing.     

Recommended isolation distances for the field multiplication of diploid tuber-bearing Solanum species

The sexual propagation of genebank accessions by hand pollination in the greenhouse is a very expensive and time-consuming routine task. The self-incompatibility of most diploid potato species allows their multiplication in isolated field plots, which is coupled with the advantage of the presence of natural pollinators and maintaining a high level of heterozygosity. The aim of this study was to determine the isolation distance required for minimizing pollen flow between neighbouring multiplication plots. The Solanum phureja clone IVP48 was used as the pollen donor since it possesses a dominant seed marker (‘embryo spot’). The centrally located pollen donor was surrounded by S. phureja recipient plots at distances of 10,20,40, and 80 m, respectively. The average pollen contamination ranged from 0.2% in the plots 80 m from the pollen donor to 5.1% in those 10 m away. In this study, procedures are suggested which will help to reduce cross-pollination between accessions.     

磁场抑制洋葱鳞茎萌发的生理机制的研究

分别用4个强度的恒定磁场对紫皮洋葱鳞茎进行不同时间的处理。结果表明：一定强度的恒定磁场和处理时间可以降低洋葱鳞茎可溶性蛋白质含量、可溶性糖含量、总淀粉酶活性，提高IAA氧化酶的活性，从而抑制洋葱鳞茎的发芽；可溶性蛋白质含量、可溶性糖含量、总淀粉酶活性与洋葱鳞茎发芽率的高低呈正相关关系，而IAA氧化酶活性与洋葱鳞茎发芽率的高低呈负相关关系。     

Screening techniques and sources of resistance to abiotic stresses in cool-season food legumes

Summary The adaptability and productivity of cool-season food legumes (chickpea, faba bean, lentil, pea) are limited by major abiotic stresses including drought, heat, frost, chilling, waterlogging, salinity and mineral toxicities. The severity of these stresses is unpredictable in field experiments, so field trials are increasingly supplemented with controlled-environment testing and physiological screening. For drought testing, irrigation is used in dry fields and rain-out shelters in damp ones. Carbon isotope discrimination (Δ¹³C) is a well-established screen for drought tolerance in C3 cereal crops which is now being validated for use in grain legumes, but it is relatively expensive per sample and more economical methods include stomatal conductance and canopy temperature. Chickpea lines ICC4958 and FLIP87-59C and faba bean line ILB938 have demonstrated good drought tolerance parameters in different experiments. For frost tolerance, an efficient controlled-environment procedure involves exposing hardened pot-grown plants to sub-zero temperatures. Faba beans Cote d’Or and BPL4628 as well as lentil ILL5865 have demonstrated good freezing tolerance in such tests. Chilling-tolerance tests are more commonly conducted in the field and lentil line ILL1878 as well as derivatives of interspecific crosses between chickpea and its wild relatives have repeatedly shown good results. The timing of chilling is particularly important as temperatures which are not lethal to the plant can greatly disrupt fertilization of flowers. Salinity response can be determined using hydroponic methods with a sand or gravel substrate and rapid, efficient scoring is based on leaf symptoms. Many lines of chickpea, faba bean and lentil have shown good salinity tolerance in a single article but none has become a benchmark. Waterlogging tolerance can be evaluated using paired hydroponic systems, one oxygenated and the other de-oxygenated. The development of lysigenous cavities or aerenchyma in roots, common in warm-season legumes, is reported in pea and lentil but is not well established in chickpea or faba bean. Many stresses are associated with oxidative damage leading to changes in chlorophyll fluorescence, membrane stability and peroxidase levels. An additional factor relevant to the legumes is the response of the symbiotic nitrogen-fixing bacteria to the stress.     

水旱交叉选育抗旱高产小麦新品种的研究

在抗旱高产小麦新品种选育中，采用渐近杂交法使目标性状得到有效的组合，采用水、旱地交叉选育法，为杂种后代基因型的潜在遗传特性的充分表达和选择提供了条件，使自然选择、人工选择和定向培育三者紧密地结合在一起，加大了选择压力和频率，提高了选种质量和效率，提高了选种质量和效率，为选育抗旱、高产、稳产小麦品种提供了一种新方法。     

Analysis of Essence of Urban Public Space from Viewpoint of Energy Aggregation

This paper aims at analysis on essence of urban public space from viewpoint of energy aggregation and puts forward the conception of potential energy field through the study on universal significance of energy exchange, reflection of important characteristics of energy exchange in urban public space form, static state and development about typical urban pubic space-street and square. Corresponding methods of urban design and conception of planning under the contemporary era are studied.