An evaluation of three potential methods for preventing the spread of larval Lepeophtheirus salmonis (Krøyer, 1837)

Within the State of Maine, only a portion of the farm sites experience sea lice (Lepeophtheirus salmonis) infections on an annual basis. There has been concern about the further spread of lice by farming activities to unaffected areas despite routine disinfection of equipment with sodium hypochlorite or iodophors. We examined the effects of Povidone‐iodine, sodium hypochlorite and desiccation on egg strings of L. salmonis and the potential of these methods for preventing hatching of nauplii or development to the copepodid stage. L. salmonis egg strings were exposed to one of eight treatments: 200 ppm of sodium hypochlorite or Povidone‐iodine solutions for 1 min, 500 ppm of either disinfectant for one minute or 10 min, or desiccation for either 4 or 24 h. The egg strings were then incubated and the hatched copepods were kept for 6 days in filtered natural seawater at 32 ppt salinity at 12°C. Desiccation for 4 or 24 h were the only methods that prevented L. salmonis nauplii from hatching or developing to the infective copepodid stage. Common disinfection procedures against pathogenic bacteria and virus were not found to be effective against L. salmonis eggs.     

西北地区提高森林培育质量的研究与途径

在总结西北地区土壤水分生产力及林草适宜覆盖率、抗旱育苗及苗木快繁技术、抗旱造林技术和造林树种优化配置模式等有关提高森林培育质量研究进展的基础上,论述了目前与该地区森林培育密切相关的土壤干燥化、有害生物防治和森林培育质量三大热点问题,并对提高该地区森林培育质量的途径进行探讨.认为要在加强森林培育学科自身发展的同时,注重相关学科新理论和技术的应用,并且有必要在政策和法规等方面进行相应的研究.     

软叶刺葵种子萌发生理和脱水耐性研究

对软叶刺葵种子进行不同的化学催芽处理，结果表明：20％过氧化氢和浓硫酸浸泡5min、0．3％亚硝酸钠和0．2％的硝酸钾溶液浸种24h后，发芽率显著升高，发芽速度显著加快，尤以亚硝酸钠和浓硫酸处理效果为好；200～1000mg／L赤霉素和20～100mg／L激动素溶液浸泡24h也能显著促进种子萌发，但催芽效果与其溶液浓度有关。成熟种子轻度脱水，发芽率有所上升，但含水量下降至17％以下，发芽率急剧下降；当含水量下降10％以下，发芽力完全丧失，表明软叶刺葵种子很可能是中间型种子。     

枇杷种子脱水敏感性的初步研究

枇杷（EriobotryajaponicaL.）种子成熟采收时含水量高达58.7％，其中子叶含水量为55.3％，胚轴的含水量为73.2％。新鲜种子的发芽率和活力指数分别为90％和0.81。轻度脱水能较大幅度地提高发芽率和活力指数。但随着脱水程度的不断加深，子叶和胚轴的超氧物歧化酶（SOD）活性下降，丙二醛（MDA）含量和种子浸泡液的电导率增加，种子活力迅速降低。当子叶和胚轴的含水量分别降至35.5％和28.0％时，种子发芽力完全丧失。枇杷种子脱水敏感的一个重要原因就是在脱水劣变过程中，发生了膜脂过氧化作用，从而使膜脂含量下降，膜结构和功能受损，最终导至种子活力丧失。     

Effects of desiccation and a change in temperature on germination of immature grains of wheat (Triticum aestivum L.)

A study was made of the effects of desiccation and a change in temperature on the germination of wheat grains harvested 20 days after anthesis. When the germination test was performed immediately after harvesting, germination percentages ranged from 5.2% to 10.7%. Germination percentages increased to 48.2% to 90.3% after grain had been desiccated at 20 °C and then hydrated at 10 °C. This increase occurred even if grains had been desiccated in an atmosphere of high relative humidity. The germination percentage of non-desiccated grains depended on the germination temperature. When the pericarp and testa were removed from embryos, the germination percentage of grains incubated at 20 °C and then at 10 °C was higher than that of grains incubated at 10 °C. In general, a low germination temperature is believed to be effective in breaking dormancy of wheat grains. However, a change in temperature stimulated germination to a greater extent than a constant low temperature. The germination percentage of 5-day cycle alternating temperature was greater than that with 1-day, 2-day and 10-day cycles. Although the germination of immature wheat grains was stimulated by both high and low germination temperatures, it is likely that cycles shorter and, also, longer than a critical period induce limited germination. Loss of dormancy commonly occurs when development of wheat grains proceeds at a high temperature, with imbibition at a low temperature. However, germination ability of non-desiccated immature wheat grain was enhanced by a change in temperature during germination. This revised version was published online in August 2006 with corrections to the Cover Date.     

荔枝和龙眼种子发育过程发芽率与脱水忍耐力变化

荔枝和龙眼种子发育成熟时不经历脱水干燥过程，成熟采收时种子含水量（fwb）分别达44．6％，42．5％。荔枝和龙眼新鲜种子不经脱水干燥处理即可萌发，并且在所有发育时期均不能忍耐较大程度的脱水。但对部分脱水的忍耐力在发育中有所升高，种子生理成熟时最大，然后略有下降。初步探讨了荔枝和龙眼种子发育过程脱水忍耐力与顽拗性种子采后生理行为的关系．     

黄土区土壤干化研究进展

全面回顾了国内对土壤干化研究所取得的成果，包括土壤干化的分布及在不同尺度上的分异特征、土壤干层类型、土壤干化的形成原因及其危害、量化指标、防治对策等。同时对这些研究成果作了简单的对比分析，指出了目前研究所面临的问题和不足。并指明今后该领域的研究应结合当前退耕还林还草的总体目标。探索土壤干化的形成机理，提出统一的量化指标，为黄土区退耕还林还草的生态恢复与重建工程提供参考。     

气候变化与人类活动对共和盆地生态环境的影响

利用共和盆地共和、贵南2个气象站1961～2006年46年逐月平均气温和降水量资料,分析了年和四季的气候特征及气候变化趋势,并对气候突变进行了检验.结果表明:近46年来共和盆地表现出气温升高、降水量呈微弱增加、地表蒸发量增大的变化趋势,并且在20世纪90年代后期变化趋势更加明显.这种气候变化趋势加速了共和盆地草地退化和沙化,同时人类活动又加剧了共和盆地草地的退化和沙化趋势.     

黄土丘陵沟壑区山地苹果林土壤干化及养分变异特征

揭示不同树龄苹果林土壤剖面水分特征及土壤养分演变规律,探明土壤干化引起的养分失衡原因,对黄土高原丘陵沟壑区苹果林地土壤水分、养分科学管理以及果园合理施肥具有重要现实意义。以陕北米脂县为研究区,选取不同树龄山地苹果林为研究对象,分别测定了7 a、10 a、18a、25 a、30 a和41 a苹果林地0~1 000 cm土层土壤湿度和0~300 cm土层土壤有机质、全氮、全磷、碱解氮、速效磷、速效钾含量,分析测定了深度范围内土壤干化情况、各养分指标丰缺状况及其随种植年限和土层深度的变异特征及不同树龄苹果林地60~300 cm土层土壤水分与养分的相互关系。结果表明:黄土丘陵沟壑区不同树龄山地苹果林深层土壤均出现严重或强烈干化,0~1 000 cm土层平均土壤含水量随树龄增加呈先增加后降低再略有增加趋势。该地区不同树龄苹果林0~300 cm土层土壤有机质、全氮和碱解氮含量均处于极缺状态,全磷、速效磷含量较缺,速效钾含量中等。幼龄期果树土壤水分与有机质、全氮、碱解氮相关性显著,而盛果期及衰退期果树土壤水分与各养分含量相关性不显著。建议不同树龄果园除应采取蓄水保墒措施外,尤其应注重有机肥和氮肥投入,适当增施磷肥,可少施或不施钾肥。相较于由干化引起的养分失衡,该地区土壤干化问题更应引起关注。     

蜂花粉干燥温度和时间对其活性和水份影响的初步研究

本实验以新鲜蜂花粉为材料，通过不同的干燥温度和时间的处理，测定其活性。以初步探求干燥温度、时间对蜂花粉活性的影响。实验结果表明：蜂花粉活性与干燥温度、时问有密切的关系，在适宜的范围内，呈现出负相关的现象。