白蜡虫研究进展情况

本文述及国内外白蜡虫研究进展概况,并提出一些尚需进一步探讨的问题。     

中山杉401无性系的染色体核型分析

观察分析了中山杉401无性系(Taxodium ascendens Brongn×Taxodium mueyonatum Tenore CL'401')的染色体核型,并与亲本的染色体核型进行了比较。结果表明,中山杉401无性系的染色体数目为2n=22,核型公式为K(2n)=20m+2sm。杂种后代有两条大小、形态不同的近中部着丝点染色体,一条为第11条,一条为第17条,仅第17条具大着丝点的特征。中山杉401无性系确系种间杂种,在该无性系中未发生染色体加倍、缺失的变异。     

杀菌剂烟剂防治侧柏叶枯病试验

本文在介绍烟剂使用方法的同时,着重指出了用杀菌剂烟剂防治侧柏叶枯病,宜在该病菌子囊孢子释放盛期的6月中旬,按每公顷15kg用量,于逆增气流强烈的傍晚放烟,可以获得良好的防治效果。杀菌剂Ⅰ号烟剂防治效果优于Ⅱ号烟剂。在丘陵山区郁闭度较大的侧柏林内应用是一种较好的防治方法。     

桐杉混交模式及栽培技术

根据在江苏丘陵山地和平原河堤进行泡桐杉木混交10年的研究结果,论述了桐杉混交的合理栽培模式和技术,可供杉木边缘产区丘陵立地平原大中型河堤立地借鉴与推广应用。     

甘薯AFLP分子标记体系建立

AFLP是目前最常用的几种标记之一。本文以甘薯为材料,通过DNA提取、酶切、PCR扩增、凝胶电泳等系列程序摸索和优化,建立了甘薯的AFLP分子标记体系。优化的甘薯AFLP分子标记体系的程序如下:将4μl100ng/μl的甘薯DNA用EcoRⅠ酶、MseⅠ酶各5U进行双酶切,在37℃下酶切3h后再在65℃下酶切3h;然后加入10μl连接混合液在22℃下连接3h后在16℃下连接10h;取连接产物5μl,10μmol/LEcoRⅠ预扩引物和10μmol/LMseⅠ预扩引物各1.5μl,PCR缓冲液25μl,ddH2O17μl进行预扩增;取5μl稀释20倍后的预扩增产物,50ng/μlEcoRⅠ选扩引物和50ng/μlMseⅠ选扩引物各1μl,PCR缓冲液10μl,ddH2O3μl,进行选择性扩增。本研究为甘薯黑斑病和其他真菌性病害的分子标记克隆及抗病育种的辅助选择提供了有力工具。     

外置气流式喷杆喷雾机的研制

气力辅助喷雾技术是目前世界上最为成熟的低漂移喷雾技术。本文表述了对采用此技术的3W－15F型外置气流式喷杆喷雾机的研制，室内性能及田间性能试验，并总结其优越性及应用范围。     

天灾与人祸：—对我国1998年长江,嫩江,松花江大洪水的反思

1998年长江、嫩江、松花江流域发生了百年不遇的特大洪涝灾害.本文就其水患原因进行了冷静的反思,并提出根治水患的对策建议.     

林业可持续发展问题探讨

林业持续发展,除考虑森林资源的持续利用、生态环境持续改善外,尚需实现林业部门的各种经济效益和保持其满足地方与国家需要的潜力.森林资源持续发展是林业持续发展的基础.森林永续利用强调资源数量与增长,即“采伐量不超过生长量”,不考虑生物多样性问题.     

Streamside trees: responses of male, female and hybrid cottonwoods to flooding

Cottonwoods, riparian poplars, are dioecious and prior studies have indicated that female poplars and willows can be more abundant than males in low-elevation zones, which are occasionally flooded. We investigated the response to flooding of clonal saplings of 12 male and 9 female narrowleaf cottonwoods (Populus angustifolia) grown for 15 weeks in a greenhouse, along with three females of a co-occurring native hybrid (Populus?×?jackii?=?Populus deltoides?×?Populus balsamifera). Three water-level treatments were provided, with substrate inundation as the flood treatment. In the non-flooded condition, the hybrids produced about four-fold more dry weight (DW) than the narrowleaf cottonwoods (P??P. angustifolia male?>?P.?×?jackii female. This indicates that narrowleaf cottonwoods are relatively flood tolerant and suggests that females are more flood tolerant than males. We propose the concept of 'strategic positioning', whereby the seed-producing females could be better adapted to naturally flooded, low-elevation streamside zones where seedling recruitment generally occurs.     

Ecophysiology of riparian cottonwoods: stream flow dependency, water relations and restoration

Cottonwoods (Populus spp.) are adapted to riparian or floodplain zones throughout the Northern Hemisphere; they are also used as parents for fast-growing hybrid poplars. We review recent ecophysiological studies of the native cottonwoods Populus angustifolia James, P. balsamifera L., P. deltoides Marsh., P. fremontii S. Watson and P. trichocarpa T. & G. in North America, and P. nigra L. in Europe. Variation exists within and across species and hybrids; however, all riparian cottonwoods are dependent on shallow alluvial groundwater that is linked to stream water, particularly in semi-arid regions. This conclusion is based on studies of their natural occurrence, decline following river damming and dewatering (water removal), water relations, isotopic composition of xylem water, and by the establishment of cottonwoods along formerly barren natural channels after flow augmentation in response to the conveyance of irrigation water. When alluvial groundwater is depleted as a result of river dewatering or groundwater pumping, riparian cottonwoods exhibit drought-stress responses including stomatal closure and reduced transpiration and photosynthesis, altered 13C composition, reduced predawn and midday water potentials, and xylem cavitation. These physiological responses are accompanied by morphological responses including reduced shoot growth, altered root growth, branch sacrifice and crown die-back. In severe cases, mortality occurs. For example, severe dewatering of channels of the braided Big Lost River in Idaho led to mortality of the narrowleaf cottonwood, P. angustifolia, and adjacent sandbar willows, Salix exigua Nutt., within 5 years, whereas riparian woodlands thrived along flowing channels nearby. The conservation and restoration of cottonwoods will rely on the provision of river flow regimes that satisfy these ecophysiological requirements for survival, growth and reproduction.