New Wild Lactuca Genetic Resources with Resistance Against Bremia lactucae

A total of 1027 genotypes of wild Lactuca spp. (L. serriola, L. saligna, and L. aculeata), originating from Israel, Jordan, East Turkey, Armenia, Kazakhstan, China, and various other countries in Europe were screened for resistance to the lettuce downy mildew (Bremia lactucae Regel). The genotypes of L. serriola (N = 962); L. saligna (N = 43); and L. aculeata (N = 22) were tested at the seedling stage with two isolates of B. lactucae (race Bl-21 and Isr-74) isolated from cultivated lettuce in Italy and Israel, respectively. Altogether, the isolates possess virulence against 17 out of 20 Dm genes/R-factors composing the established differential set of lettuce lines/varieties. They could therefore be used for preliminary detection of the presence of new resistance factors. A total of 83 and three genotypes of L. serriola and L. saligna, respectively, were resistant to infection by each of the two isolates alone as well as to the infection by a mix of the two isolates. These genotypes probably carry previously unknown resistance, and therefore could be suitable for exploitation by breeders and further detailed research. The wild progenitor of lettuce, L. serriola, and related species harbor significant untapped genetic resources for lettuce improvement.     

In vitro determination of the indigestible fraction in foods: an alternative to dietary fiber analysis

Dietary fiber (DF) intakes in Western countries only accounts for about one-third of the substrates required for colonic bacterial cell turnover. There is a general trend among nutritionists to extend the DF concept to include all food constituents reaching the colon. In this line, a method to quantify the major nondigestible components in plant foods, namely, the indigestible fraction (IF), is presented. Analytical conditions for IF determination are close to physiological. Samples, analyzed as eaten, were successively incubated with pepsin and alpha-amylase; after centrifugation and dialysis, insoluble and soluble IFs were obtained. IF values include DF, resistant starch, resistant protein, and other associated compounds. IF contents determined in common foods (cereals, legumes, vegetables, and fruits) were higher than DF contents. Calculated IF intakes were close to the estimated amount of substrates reaching the colon. IF data could be more useful than DF data from a nutritional point of view; therefore, IF is proposed as an alternative to DF for food labeling and food composition tables.     

Empirical predictions of plant material C and N mineralization patterns from near infrared spectroscopy, stepwise chemical digestion and C/N ratios

Prediction of carbon (C) and nitrogen (N) mineralization patterns of plant litter is desirable for both agronomic and environmental reasons. Near infrared reflectance (NIR) spectroscopy has recently been introduced in decomposition studies to characterize biochemical composition. The purpose of the current study was to use empirical techniques to predict C and N mineralization patterns of a wide range of plant materials incubated under controlled temperature and moisture conditions. We hypothesized that the richness of information in the NIR spectra would considerably improve predictions compared to traditional stepwise chemical digestion (SCD) or C/N ratios. Initially, we fitted a number of empirical functions to the observed C and N mineralization patterns. The best functions fitted with R²=0.990 and 0.949 to C and N, respectively. The fractions of C and N mineralized at different points in time were then either predicted directly with regression functions or indirectly by prediction of the parameters of the empirical functions fitted to incubation data. In both cases, partial least squares (PLS) regressions were used and predictions were validated by cross-validations. We found that the NIR spectra (best R²=0.925) were able to predict C mineralization patterns marginally better than the SCD fractions (best R²=0.911), but considerably better than the C/N ratios (best R²=0.851). In contrast, N mineralization was better predicted by SCD fractions (best R²=0.533) than the C/N ratio (best R²=0.497), which was better than NIR predictions (best R²=0.446). Although the predictions with the NIR spectra were only slightly better for C and worse for N mineralization compared to SCD fractions, NIR spectroscopy still holds advantages, as it is a much less laborious and cheaper analytical method. Furthermore, exploration of the applications of NIR spectroscopy in decomposition studies has only just begun, and offers new ways to gain insights into the decomposition process.     

Three-component model of runoff generation,Lysina catchment,Czech Republic

The forested Lysina catchment is situated in an area very susceptible to acid deposition. The stream water is characterized by extremely high concentrations of total dissolved Al (volume weighted mean 66 Μmol L^?1) and H⁺ (average pH=3.87). In a simple two-component model, the surface runoff component contributes only 6% of runoff in winter and 4% of runoff in summer. During flood episodes, the direct runoff contributes up to 20% of streamflow. There is a strong positive correlation between stream acidity and stream discharge. The observed exponential increase in streamwater acidity with discharge during high flow periods cannot be explained by the simple two-component model. A three-component model used for hydrograph separation is based on chemical and¹⁸O analysis of precipitation, soil water and runoff. It incorporates a soil water component along with groundwater and rainfall components in streamwater generation. Dissociated organic acids leached during the flow of water through the uppermost soil horizon help to balance an apparent anion deficit. The apparent anion deficit was found to increase exponentially with flow rate. Low variability in streamwaterδ ¹⁸O corresponds to a high contribution of indirect components (i.e., soil and ground water) in the runoff. The soil water contribution to indirect runoff calculated from the apparent anion deficit of streamwater, varied from 0 at base flow up to 80% during floods. On average, 40% of the streamwater is derived from soil water (from 31 to 39% in winter and from 47 to 54% in summer).     

Precipitation chemistry and atmospheric processes in the forested part of Croatia

The influence of mesoscale weather patterns on the chemical composition of daily precipitation samples is analysed. The data of pH, sulphur from sulphates and total nitrogen are analysed for two rural sites: Plitvice station in forested part of Central Croatia (1981 to 1990) and Puntijarka suburban station on the mountain near Zagreb, the capital of Croatia (1982–1991). The two prevailing weather types in precipitation days are selected and the comparison of chemical composition of precipitation is made for each of them. The frequency distributions of pH, sulphur and nitrogen show that concentration of major ions in precipitation apparently depends on the regional scale weather type. It is shown that the seasonal variation of deposition is related to the seasonal variation in precipitation amount. In both weather types Plitvice receives more pollution than Puntijarka that is closer to urban and industrial pollution sources. Both locations are under the prevailing influence of regional pollution sources.     

利用SSH技术鉴定香蕉体细胞胚发生相关基因

本研究以野生蕉胚性悬浮系为材料,将胚性细胞增殖培养基上的香焦胚性悬浮系作为对照,体胚诱导培养基上的培养材料为处理,利用抑制性消减杂交(suppression subtractive hybridization,SSH)技术,构建野生蕉胚性悬浮系激素诱导的胚胎发育差异表达cDNA文库,随机挑选阳性克隆并进行生物信息学分析...     

柑橘属2n花粉自然发生与沙田柚2n花粉诱导研究

果树2n配子育种较其他植物起步晚,尤其是利用2n花粉进行育种的研究在柑橘上还无先例。试验中初步观察了柑橘属部分品种的2n花粉自然发生情况,证实了柑橘属内未减数花粉的存在。同时通过秋水仙碱不同浓度与作用时间处理促进了柑橘2n花粉的发生,将长寿沙田柚2n花粉发生比例由当年的自然发生率0.87%提高到9.76%。初步观察了2n花粉离体萌发状况,其萌发率与花粉管伸长速度较为正常,但萌发启动比单倍性花粉慢。     

湖南省茶叶产品出口创汇关联分析

本运用灰色关联分析方法，对在“七·五”期间湖南省出口茶的各项投资与各产品创汇之间的相互关系作了定量地分析，得出了计算结果，同时对结果作了定性分析，探讨了各项投资的现状和调整方向。     

Feynman's path-integral approach for intense-laser-atom interactions

Atoms interacting with intense laser fields can emit electrons and photons of very high energies. An intuitive and quantitative explanation of these highly nonlinear processes can be found in terms of a generalization of classical Newtonian particle trajectories, the so-called quantum orbits. Very few quantum orbits are necessary to reproduce the experimental results. These orbits are clearly identified, thus opening the way for an efficient control as well as previously unknown applications of these processes.