洋葱先期抽薹的原因及防止对策

洋葱在鳞茎膨大前抽薹,这一现象在栽培学上称为洋葱的先期抽薹。先期抽薹不仅影响洋葱的产量而且严重影响其产品质量及耐贮性,是洋葱生产的大忌。洋葱属于绿体春化作物,通过春化阶段有3个条件:一是幼苗必须生长到一定大小以后才能有效地通过低温春化,一般认为幼苗叶鞘基部的径粗小于0.5ｃｍ时几乎不形成花芽;二是需要一定的低温,低温是诱导洋葱花芽分化的主导因子,多数品种在2～5℃的低温下即完成春化;三是一定数量的低温积累,一般需经60～70ｄ的时间,品种间差异大,有的南方品种只需40～50ｄ,而有的北方品种需100ｄ以上。此外幼苗绿体越大(…     

Cryptic occurrence of <Emphasis Type="Italic">Chattonella marina</Emphasis> var. <Emphasis Type="Italic">marina</Emphasis> in mangrove sediments in Probolinggo,East Java Province,Indonesia

Mangrove forests and adjacent creeks are known to be highly productive estuaries, which are partly supported by benthic microalgae that grow on the sediments. During surveys investigating the microalgal floras of mangrove swamps in the eastern part of Java Island, a mud sample unexpectedly included large numbers of a notorious fish killer, Chattonella-like motile cells, and its resting cysts. These motile cells were established as clonal cultures for further identification and physiological tests. The cysts were examined through palynological and molecular biological means. Identification based on light microscopy and ribosomal RNA gene sequences confirmed that these cells and cysts were Chattonella marina var. marina. While the strains were genetically identical to the temperate strains isolated from Japan and China, temperature experiments showed that the Indonesian strains possessed a high maximum quantum yield of photosystem II even after exposure to 34 °C, a temperature at which the Japanese strain could not survive. Salinity experiments showed adaptation of the strains to a salinity of 15. These findings, together with the discovery of populations of cysts in the mangrove sediment, highlight the tough and unique nature of the Indonesian strains, which are likely adapted to wide fluctuations of temperature and salinity in mangrove swamps, and pose a potential risk to fisheries in Indonesia.     

立式金属油罐容量检定中的几个问题

针对JJG168-87计量规程在实际使用中的缺陷，对罐壁圈板径向偏差测量位置的确定，油罐充满油品后直径增大值的修正等问题，提出了具体的解决方法。     

蓝花棘豆硬实种子特性的研究

每天从发芽皿中挑选吸胀的蓝花棘豆种子作为对照。第一天的称为CK1，依此类推分别为CK2，CK3……等。对照种子的硬实程度随着吸胀时间的延长而增强，即CK5＞CK4＞CK3＞CK2＞CK1。将第八天尚未吸胀的作为硬实种子。用浓硫酸处理25分钟。结果表明，硬实种子的发芽率、活力指数、脱氢酶活性及抗逆性均高于对照。后者CK1→CK5的上述指标呈逐渐上升趋势。硬实种子的电导率则低于对照。后者CK1→CK5电导率呈下降趋势。综上所述，作者认为蓝花棘豆中硬实种子的活力高于非硬实种子，其活力随着硬实程度的增加而递增。     

樟子松人工林生长与收获预估模型的研究

以可变密度全林分预估模型理论为指导,探讨建立了樟子松人工林地位级指数和林分密度指数经验方程,结合林分密度动态预估模型,建立了樟子松人工林断面积预估模型和蓄积量预估模型。经检验模型预测值与实测值误差为3.64%,模型精度96.37%。     

基于Landsat的高山松地上生物量动态变化估测模型构建

以香格里拉市高山松为研究对象,基于1987—2017年的国家森林资源清查固定样地和对应年的Landsat TM/OLI数据提取对应的遥感因子,计算30 a期间生物量和遥感因子的5、10 a定期变化量、年平均变化量、5、10 a变化率;采用多元线性回归（MLR）和随机森林（RF）方法构建地上生物量模型,提高高山松森林AGB动态变化遥感估测的精度。结果表明：基于5种变化量类型的RF模型效果均优于相应的MLR模型,RF模型中采用5 a变化率效果最好,其拟合R²为0.956,RMSE为0.664 t/(hm²·a),预测结果中RMSE为2.285 t/(hm²·a);纹理因子在高山松地上生物量变化量建模中贡献最大。采用遥感因子变化率构建的高山松地上生物量动态变化估测模型,提高了生物量变化的估测精度,可为森林地上生物量的动态估测研究提供参考。     

Factors affecting the adoption of agroforestry practices by farmers in Cameroon

This paper presents empirical evidence on the impact of socio-economic factors on the adoption of agroforestry practices in Cameroon. The analysis uses primary farm-level data collected from June to December 1996. Three major provinces of the country were covered, namely Centre, Southwest and Northwest Several agroforestry technologies have been promoted among farmers in the zone, including alley farming, improved fallow, live fencing, cut-and-carry fodder and apiculture. The status of adoption of each agroforestry practice is described and factors that affect adoption identified. These are gender of farmer, household family size, level of education, farmer’s experience, membership within farmers’ associations, contact with research and extension, security of land tenure, agroecological zone, distance of the village from nearest town, village accessibility and income from livestock. Research findings indicate that since factors affecting farmers’ adoption of agroforestry practices differ across techniques, generalisation is to be avoided.     

干法灰化—石墨炉原子吸收法测定面制食品中铝含量

建立了面制食品中铝残留量的石墨炉原子吸收测定方法。通过干法灰化样品,筛选最佳石墨炉原子吸收分析条件,并对面制食品中铝进行测定。结果显示,该法在质量浓度20～50μg/L内呈线性关系,相关系数R=0.9998,回收率96.4%～98.5%,RSD为1.46%～3.32%;定量限下限7.35μg/L,最低检出质量浓度3.50μg/L。该方法结果符合要求,操作简便、快速、准确、干扰小、检出限低,适用于面制食品中铝含量的测定。     

关于黑龙江省森林食品资源开发利用的思考

通过对黑龙江省森林食品资源及产业现状的优势分析,提出了森林食品产业发展的措施及建议,以期为促进森林食品资源的合理开发利用,调整森林食品产业结构,增加林区经济收入提供参考。