施肥对棉花养分吸收、分配、利用和产量的影响

通过田间膜下滴灌栽培,研究了施肥对棉花养分吸收分配规律、肥料利用率、棉花产量和经济效益的影响。结果表明,与农民习惯施肥(FP)相比,推荐施肥(OPT)处理的养分吸收、生殖器官中分配总量和肥料利用效率有不同程度的提高,其中氮肥和磷肥肥料利用效率分别提高29.5和10.8个百分点,氮肥和磷肥农学利用效率分别提高0.4和0.7 kg·kg~(-1)。且OPT处理增产4.5%,增加农民收入774元·hm~(-2),该地区棉花产量限制因子依次为氮、磷、钾。说明平衡施肥的氮、磷、钾养分投入基本合理。     

不同覆盖种植方式与平衡施肥对马铃薯产量及水分利用效率的影响

采用田间试验方法,研究了不同覆盖种植方式与平衡施肥对旱地马铃薯产量及水分利用效率的影响。结果表明,三种覆盖种植方式中,全膜覆盖垄播种植方式有利于马铃薯碳水化合物的合成,增加马铃薯干物质积累量,N、P、K平衡施肥干物质积累量增加效果显著;与裸地平作相比,全膜覆盖垄播和全膜覆盖平作马铃薯块茎产量分别增加43.4%~60.7%和18.8%~32.5%,水分利用效率分别提高59.4%~79.6%和38.3%~50.3%;N、P2O5和K2O的用量分别为210、105、90 kg·hm-2时,全膜覆盖垄播处理马铃薯产量和水分利用效率最高。研究表明,马铃薯在全膜覆盖垄播栽培条件下,平衡施肥可显著提高马铃薯块茎产量和水分利用效率。     

结球甘蓝1号和4号染色体双三体及其初级三体的分离与鉴定

 在结球甘蓝同源三倍体与二倍体杂交子代中, 获得了1个2n + 2的非整倍体植株, 经细胞学鉴定和核型分析, 确认该2n + 2植株为1号和4号双三体, 并由此进一步分离鉴定出了1号和4号两个初级三体。1号初级三体的主要特征是植株矮小, 株高仅为正常二倍体的1 /3左右; 4号初级三体的主要特征是花期提早, 较正常二倍体提早约14 d。1号和4号两个初级三体n + 1雌配子的传递率分别为8.89%和11.54%。     

雄蚕新品种“秋丰×平28”的育成

以家蚕平衡致死系平30为受体亲本,以茧丝质优、抗性强的现行家蚕品种白玉为优良基因的供体材料,通过杂交、自交和回交3个过程,育成了经济性状优良的家蚕性连锁平衡致死系平28,用该品种与皮斑限性品种秋丰组配成雄蚕杂交组合秋丰×平28。杂交种的雄蚕率达98%以上,茧层率、万蚕茧层量、鲜茧出丝率分别比对照品种秋丰×白玉高3.1%、0.166 kg、1.76%,而且解舒率较为稳定,是一对综合经济性状优良的雄蚕品种。2005年通过浙江省家蚕品种审定。     

我国当前就业态势的定量分析与对策

针对我国目前城镇失业率逐渐爬高的态势,先利用托达罗均衡失业率模型对我国历年的均衡失业率进行估算,进而得出我国目前的失业率在８％左右。然后又分别利用就业弹性理论分析我国三产业的就业状况,指出就业弹性的下降是我国失业问题的成因之一。最后提出了解决我国目前失业问题的若干政策建议。     

Identification of primary trisomics and other aneuploids in foxtail millet

A complete set of nine primary trisomics (2n+ 1) for cv.‘Yugu No. 1’of foxtail millet, Setaria italica (L.) Beauv. (2n= 2x= 18), was identified cytologically from progenies derived from crosses between autotriploids(2n= 2x= 27) and their diploid counterparts. Five autotriploid plants were identified from 2100 seedlings derived from 4x-2x crosses; the reciprocal crosses (2x-4x) failed to produce autotriploids. Autotriploids grew vigorously and were morphologically very similar to diploids. Theprimary trisomics (2n= 2x= 19) constituted ?32.5% of the total progeny from the 3x-2x crosses, whereas 59.8% of the descendants were aneuploids with chromosome numbers ranging from 20 (double trisomics and tetrasomics) to 37 (2n= 4x+ 1; or autotetraploid with one additional chromosome). The nine primary trisomics identified were self-fertile; seven had characteristic morphology, whereas trisomics VIII and IX resembled the disomics. The seed set for trisomic V was the lowest (20%), and trisomic VIII the highest (74%). Other aneuploids with 20 or more somatic chromosomes were either self-sterile or partially fertile with various, but low, levels of seed set. Each of the primary trisomics showed its unique transmission rate when self-pollinated; trisomic IX had the highest (45.8%), whereas trisomic V had the lowest (19.6%) transmission rate.     

Fishing for biodiversity by balanced harvesting

Fisheries are damaging and seemingly incompatible with the conservation of marine ecosystems. Yet fish are an important source of food and support the lives of many people in coastal communities. This paper considers an idea that a moderate intensity of fishing, appropriately scaled across species, could help in maintaining biodiversity, rather than reducing it. The scaling comes from an intuition that rates of fishing mortality of species should be kept in line with production rates of the species, a notion known as balanced harvesting. This places species conservation and exploitation on an equal footing in a single equation, showing quantitatively the relative levels of fishing mortality that species of different abundance can support. Using a dynamic model of a marine ecosystem, we give numerical evidence showing for the first time that fishing, if scaled in this way, can protect rarer species, while allowing some exploitation of species with greater production. This works because fishing mortality rates, when scaled by production, are density-dependent. Such fishing, operating adaptively to follow species' production rates over time, contains a feedback that would help to protect species from overfishing in the presence of uncertainty about how marine ecosystems work.     

空间平衡抽样及其在森林资源调查中的应用

我国现行的森林资源调查方法存在着空间关联性强、适应性差的缺陷.空间平衡抽样(SBS)强调样本点抽取的随机等概和空间上的均衡分布,通过包含概率栅格层的过滤运算,极大地减少了无反应样本单元现象的发生,在森林资源调查中具有较大的潜在应用价值.文章在简要回顾基于模型的抽样、基于设计的抽样两大类森林资源调查方法特点,分析4种传统概率抽样方法(简单随机抽样、系统抽样、分层抽样、整群抽样)弊端的基础上,介绍了基于通用随机方格分层算法(GRTS)的空间平衡抽样的原理和步骤,最后以紫金山国家森林公园为研究对象进行了风景林蓄积量调查空间平衡抽样案例研究.研究表明,空间平衡抽样在降低调查成本、减少空间关联性强方面明显优于简单随机抽样;但在提高抽样精度方面没有表现出明显的优势,只有当样本容量大于或等于理论计算容量时,空间平衡抽样才表现出一定的抽样精度优势.     

N、P、K配施条件下甜瓜Vc含量数学模型的研究

为分析氮磷钾肥料配施对甜瓜Vc的影响,通过采用3因素5水平二次正交旋转组合设计,研究N、P、K配施对甜瓜果实中Vc含量的影响,构建了肥料配施的数学模型,并对最佳施肥量、单因子效应及互作效应进行分析。结果表明：N与P、N与K、P与K之间存在明显的互作效应,且适宜的施肥配比可以提高果实中Vc的含量。分析认为,当N、P、K配比为,即氮(N)、磷(P₂O₅)、钾(K₂O)用量分别为157.5、77.4、260.38 kg/hm²时,甜瓜果实中Vc的含量可达25.32 mg/100 g。