Flood or drought: how do aerosols affect precipitation?

Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer. We propose a conceptual model that explains this apparent dichotomy.     

宜昌百合体细胞胚诱导及植株再生

为了对秦岭野生宜昌百合资源进行保存,并有效地解决其扩繁和再生问题,以秦岭野生宜昌百合为材料,研究不同质量浓度的激素组合、鳞片的不同部位及光暗培养对秦岭野生宜昌百合的体细胞胚诱导的影响。结果表明,鳞片诱导体细胞胚的适宜培养基为MS+0.5 mg/L TDZ(N-苯基-N-′1,2,3-噻二唑-5-脲)+1.0 mg/L NAA(a-萘乙酸)。鳞片基部诱导体胚率最高,为90.00%,鳞片分化体细胞胚的能力为基部>中部>上部。暗培养下诱导率为90.00%,高于光培养条件。     

泉州市农村科技信息网络构建与应用

应用现代信息技术构建了泉州市农村科技信息网及其网络信息服务系统,开发了专题数据库,为＂三农＂提供网上信息服务,促进科技信息进村入户到企,助推海西现代农业发展和新农村建设。     

东莞市农区鼠害的发生动态及综合治理

采用夹夜法和百米有效鼠洞口数法调查东莞市农区鼠害的发生动态,研究害鼠的群落结构、生物量结构和栖息空间分布特征。根据害鼠的发生规律,提出以生态防治为基础,化学防治为重点的综合防治措施。     

Competition Affects the Production of First Backcross Offspring on F1-hybrids, Brassica Napus × B. Rapa

Summary Interspecific F₁-hybrids may arise in fields with transplastomic oilseed rape where B. rapa occurs as a weed. Spilled seeds, including transplastomic F₁-hybrids with B. rapa, may germinate, which creates an opportunity for production of transplastomic BC₁ with B. rapa as father (BC_1r). Field trials were made with three different proportions of B. napus, B. rapa and F₁-hybrids and three different densities. Contrary to most studies on how plant competition affects introgression between oilseed rape and B. rapa, this study focused on offspring produced on F₁-hybrids, where the F₁-hybrids had oilseed rape as maternal parent. We estimated the BC_1r production in all combinations of proportion and density, and found that B. rapa sired from 0.6–7.8% of the offspring. At the proportion with the highest abundance of F₁-hybrids the entire paternity was assessed. There was a significant density effect on the production of BC_1r but the effect differed among proportions. Both the highest and lowest frequencies of BC_1r were obtained at high plant density. Neither the proportion nor density affected the number of BC_1r per square-meter significantly. Biomass components decreased significantly from low to intermediate density, whereas a further increase in density only affected the thousand-seed weight significantly. On the basis of the results from the present experiment we conclude that introgression of transgenes from transplastomic oilseed rape to B. rapa seems most likely at current field densities of B. napus, and when B. rapa is an abundant weed.     

Chromosomal regions associated with the in vitro culture response of wheat (Triticum aestivum L.) microspores

Generation of doubled haploid plants is a powerful tool in breeding, as homozygous individuals will be obtained directly from hybrids. However, genotype variability in regeneration efficiency of most European wheat (Triticum aestivum L.) varieties has limited its use in wheat. This study intended to identify quantitative trait loci (QTLs) for green plantlet regeneration from wheat microspore cultures. A QTL analysis using DArT markers was conducted based on a bi‐parental F₃ population, derived from a cross between the varieties Svilena and Jensen, which displayed markedly different capacity for plantlet regeneration. Two QTLs on chromosome 1B and 7B explained 53% of the variation in green plantlet regeneration. Furthermore, a collection of 94 European wheat varieties was genotyped and phenotyped. The microspore response level was low among western and northern European wheat varieties, and the positive QTLs found in the bi‐parental population were rare in the variety collection. Identification of the two QTLs enables introduction of high regeneration efficiency into wheat germplasm. Moreover, our results proved that the efficient regeneration observed for one variety could be crossed into modern winter wheat.     

Increased genetic differentiation in house sparrows after a strong population decline: From panmixia towards structure in a common bird

A drastic decline in abundance prompts conservation measures, even though a species may still be common, partly because such a decline may be associated with loss of genetic variability. Longitudinal evidence (i.e. repeated measures across time) for loss of genetic diversity is scarce and mostly concerns organisms that have experienced a severe bottleneck. Here, we study the house sparrow in Finland, where a strong (50–86%) reduction in abundance occurred in four decades, starting earlier and resulting steeper decline in the south than in the north. Based on thirteen polymorphic microsatellites, we compared 12 Finnish populations both prior (mid-1980s) and after (2009) the major population decline. There was no evidence of bottlenecks and only little loss of genetic variation, but we found a significant threefold increase in genetic differentiation (F_ST) across the populations. This may reflect a non-equilibrium situation between the rates of change in the genetic diversity and differentiation and indicate future loss of genetic diversity. Our findings indicate that a strong decline in population size in a relatively common species still leaves a noticeable population-genetic imprint and warrants conservation concern.     

小RNA测序揭示miRNAs在油棕合子胚发育中的作用

油棕是世界上产油效率最高的热带木本油料作物,其棕榈油产量与合子胚发育密切相关.油棕的合子胚发育是一个系统且复杂的生物过程,其中涉及许多基因的精确调控.MicroRNAs(miRNAs)是重要的信号分子,调节植物的各种发育过程.一些miRNAs已经被整合到基因调控网络中协调植物胚发育的可塑性,但对于其在油棕合子胚发育过程...     

Detection of the effective refractive index of thermally modified Scots pine by immersion liquid method

The purpose of this study was to determine the effective refractive index of thermally modified Scots pine (Pinus sylvestris L.) wood specimens as a quantitative measure regarding the change of wood density which is due to the thermal modification. The refractive index of thermally modified Scots pine wood was obtained by introducing pine wood powder into an immersion liquid and measuring light backscattering with a homebuilt multifunction spectrophotometer. The present method provides useful information that in principle can be applied, for example, in the optimization of the thermal modification process and inspection of the quality of thermally modified wood.     

Processes affecting genetic structure and conservation: a case study of wild and cultivated <Emphasis Type="Italic">Brassica rapa</Emphasis>

When planning optimal conservation strategies for wild and cultivated types of a plant species, a number of influencing biological and environmental factors should be considered from the outset. In the present study Brassica rapa was used to illustrate this: to develop Scandinavian conservation strategies for wild and cultivated B. rapa, DNA-marker analysis was performed on 15 cultivated and 17 wild accessions of B. rapa plus 8 accessions of the cross compatible B. napus. The B. rapa cultivars were bred in Sweden and Finland in 1944–1997 and the wild B. rapa material was collected from Denmark, Sweden and United Kingdom. The B. napus accessions were bred within the last 20 years in the Scandinavian countries. Results were based on scoring of 131 polymorphic ISSR markers in the total plant material. A Bayesian Markov chain Monte Carlo (MCMC) approach implemented in NewHybrids demonstrated a clear distinction of B. rapa and B. napus individuals except for three individuals that seemed to be backcrosses. The backcrossed hybrids descended from two Swedish populations, one wild and one escaped. The overall pattern of genetic variation and structure in B. rapa showed that cultivated and wild B. rapa accessions formed two almost separated clusters. Geographical origin and breeding history of cultivars were reflected in these genetic relationships. In addition, wild populations from Denmark and Sweden seemed to be closely related, except for a Swedish population, which seemingly was an escaped cultivar. The study point to that many processes, e.g. spontaneous introgression, naturalisation, breeding and agricultural practise affected the genetic structure of wild and cultivated B. rapa populations.