北京地区无土栽培越冬茬番茄品种筛选

为了筛选出适宜北京地区无土栽培的越冬茬番茄品种,对从国外引进的"丰收560""迪安娜""玛丽娅""粉妮娜"4个番茄品种进行了品种比较试验,以综合比较各品种的生长指标、果实性状和果实营养品质。结果表明:"迪安娜"综合表现较好,更适于北京地区无土栽培越冬茬生产。     

民和县生态建设工程的现状问题及对策

通过对民和县生态建设工程现状的调查,针对存在的问题,分析了原因,并提出了今后的思路和对策。     

论我国旅游投诉解决机制及其完善——以非诉讼纠纷解决方式为视角

随着我国旅游业规模的不断扩大，旅游体系也日趋完善。在推进旅游产业快速发展的进程中，各种类型的旅游纠纷也随之迅速增加。在目前我国多元化纠纷解决机制日趋完善的背景下，旅游投诉解决机制对于确保旅游业和谐稳步推进有着特殊的功能优势。但鉴于旅游投诉解决机制的固有局限性，需要从明确旅游投诉处理结果的效力、增设旅游投诉解决机制为司法救济的前置程序等方面予以完善。     

我国微生物航天诱变育种的应用及研究进展

航天诱变是近些年发展迅速的一种新型的微生物诱变育种技术。根据国内微生物航天诱变的研究状况,综述了微生物航天诱变的机制以及产生代谢产物的研究进展,提出了其存在的问题,并对微生物航天诱变育种进行了展望。     

The source of autumn and spring downstream migrating juvenile Atlantic salmon in a small lowland river

Over 3 years, 32,444 age‐0 group Atlantic salmon (Salmo salar) parr tagged with passive integrated transponder tags throughout the River Frome catchment were assigned to one of three groups, nonmigrants, autumn migrants and spring smolts, depending on the detection and the timing of detection at downstream tag readers (situated 8.6 km above the tidal limit). We examined the effect of density at the time of tagging (n·m^?2), distance upstream from the tidal limit (km), fish length (mm), Fulton condition index, habitat type (divided into two types, main river and carrier), days after 1 September that each fish was tagged and year (replication) on the proportions of fish in each of the migration groups. Distance upstream from tidal limit was strongly negatively related to the proportion of autumn migrants and positively related to the proportion of spring smolts. Nonmigrants had a lower average body size than migrants, although there were no differences in the sizes of autumn migrants and spring smolts in September prior to migration. Fish density had no effect on migration strategy. A lower proportion of fish migrated as autumn migrants from the smaller carrier habitats than the main river channel. There is some evidence that those parr destined to become autumn migrants underwent a lower mortality rate during September before tagging than those destined to become spring migrants indicating possible physiological or behavioural differences between these two groups of fish at that time. More research into the factors responsible for initiating the autumn migration is required.     

Developmental temperature stress and parental identity shape offspring burst swimming performance in sockeye salmon (Oncorhynchus nerka)

Abstract – The persistent effects of embryonic temperature stress and individual parentage on fry swimming performance were examined in a cross‐fertilisation experiment using sockeye salmon (Oncorhynchus nerka). A fixed‐velocity test of burst swimming was used to assess the endurance capacity and behavioural performance of individual fry from 10 offspring families incubated at 12, 14 or 16 °C to hatch and then reared through yolk absorption and exogenous feeding stages in a common posthatch environment (average 6.9 °C). Fry burst swim time (BST) was influenced by an interaction between incubation temperature and family identity. Average BST was longer for fry from the 12 °C prehatch treatment compared to 14 and 16 °C, although differences were largely attributable to temperature effects on average fry size. Behavioural observations revealed that fish incubated at 16 °C performed more poorly, having a larger proportion of individuals that required stimulation to swim, fatigued more frequently or were classified as ‘nonswimmers’. Within all three incubation temperature treatments, mean BST varied significantly among offspring families, independent of fry mass and length. An interesting relationship was observed within the 16 °C treatment, whereby families with higher survivorship were characterised with lower mean BSTs. Collectively, these findings demonstrate that exposure to high temperatures in early sockeye salmon development can result in persistent, parentally mediated effects on fry performance. As such, these results provide important insight into how elevated temperature events during egg incubation may affect early life history selection processes and survival in stages beyond when the stressor is experienced.     

Mechanisms responsible for high levels of permethrin resistance in the house fly

The mechanisms responsible for > 6000-fold permethrin resistance in a pyrethroid-selected strain of house fly, Learn-PyR, were investigated. Through electrophysiological, in vitro metabolism, in vivo penetration and synergism studies it was demonstrated that the resistance mechanisms consisted of enhanced metabolic detoxification via the mixed-function oxidase (MFO) system, target-site insensitivity and decreased cuticular penetration. The major resistance mechanism was the MFO-mediated detoxification. The elevated MFO activity was correlated with higher levels of cytochrome P-450, cytochrome b₅ and NADPH-cytochrome c reductase activity. The kinetics of the latter showed similar K_m but greater V_max values in the Learn-PyR than in the susceptible strain, suggesting that the elevated activity was due to an altered amount, but not an altered form, of the enzyme. The Learn-PyR strain showed widely varying levels of resistance to the pyrethroids tested. Comparison of the pyrethroid structures with the resistance ratios revealed that resistance was highest in the presence of an unsubstituted phenoxybenzyl alcohol moiety. Substitution or certain modifications of the alcohol moiety reduced the level of resistance. Structure of the acid moiety or the presence or absence of an a-CN group did not affect the resistance level. These results are discussed with reference to the resistance mechanisms present.