浅析2007年北疆棉区棉花产量下降的原因及对策

<正>1北疆棉区棉花减产原因分析1.12007年北疆棉区棉花减产的主要原因。春季持续低温多雨,是植棉以来降水量最多的一年(见表1),4月中旬至5月末总降水量84.2mm,降水天数     

浅谈影响棉花保苗密度的关键栽培措施

<正>棉花是农场的主要经济作物,近几年来推行的是"密、矮、早"棉花栽培模式,棉花的收获株数是影响棉花产量的一个重要因素。总结近几年棉花生产中的经验,棉花密度不足严重影响了棉花产量的进一步提高,因此,实践中如何提高棉花保苗株数的关键技术措施总结如下:     

浅谈棉花异性纤维的溯源危害和预防对策

<正>我国加入世贸组织以来,对于棉纺行业来说,既是一种机遇,又是一种挑战,不仅改善了棉纺行业的深加工,而且也推动了棉纺行业的技术进步,扩大了棉纺行业的销售市场。但同时也应清醒地看到"世贸"对我国棉纺行业带来的冲击,在国际贸易中,我国的棉纱、棉布等棉织品由于异性纤维而招致外商索赔,损失额较大,这对本来就不景气的棉纺行业     

Assessment of different genetic distances in constructing cotton core subset by genotypic values

One hundred and sixty-eight genotypes of cotton from the same growing region were used as a germplasm group to study the validity of different genetic distances in constructing cotton core subset. Mixed linear model approach was employed to unbiasedly predict genotypic values of 20 traits for eliminating the environmental effect. Six commonly used genetic distances （Euclidean, standardized Euclidean, Mahalanobis, city block, cosine and correlation distances） combining four commonly used hierarchical cluster methods （single distance, complete distance, unweighted pair-group average and Ward＇s methods） were used in the least distance stepwise sampling （LDSS） method for constructing different core subsets. The analyses of variance （ANOVA） of different evaluating parameters showed that the validities of cosine and correlation distances were inferior to those of Euclidean, standardized Euclidean, Mahalanobis and city block distances. Standardized Euclidean distance was slightly more effective than Euclidean, Mahalanobis and city block distances. The principal analysis validated standardized Euclidean distance in the course of constructing practical core subsets. The covariance matrix of accessions might be ill-conditioned when Mahalanobis distance was used to calculate genetic distance at low sampling percentages, which led to bias in small-sized core subset construction. The standardized Euclidean distance is recommended in core subset construction with LDSS method.     

中美棉花期货价格波动特征的比较研究

利用GARCH（1,1）模型和EGARCH（1,1）模型分别对中国和美国棉花期货价格的波动特征进行对比分析。结果表明,从总体看郑州和纽约棉花期货市场都具有价格波动剧烈的特点,郑州棉花期货市场收益波动不具有杠杆效应,证明中国的棉花期货市场还不够成熟。     

诱变选育木醋杆菌以提高细菌纤维素产量

针对野生型木醋杆菌纤维素产量较低的问题,采用化学、物理以及物理一化学相结合的手段诱变筛选得到多株高产纤维素的木醋杆菌诱变株.其中,经亚硝酸诱变处理获得的3株高产菌株的纤维素产量是原始菌株的2.2～2.8倍,而经紫外照射结合氯化锂诱变处理得到的2株菌株的产量大约是原始菌株的1.4倍.该结果为今后工业化大规模生产奠定了坚实的基础.     

Molecular cloning and characterization of a cotton phosphoenolpyruvate carboxylase gene

Phosphoenolpyruvate carboxylase （PEPC） plays diverse physiological functions during plant development. In this study, a new phos- phoenolpyruvate carboxylase gene GhPEPC2 is isolated from cotton （Gossypium hirsutum cv, zhongrnian 35） by RACE-PCR, The cloned cDNA of GhPEPC2 is 3364 bp in length, and has an open reading frame of 2913 bp, encoding for 971 putative amino acids with a calculated molecular mass of 110,6 kD and pI of 5,56. The deduced amino acid sequence of GhPEPC2 shares high similarity with other reported plant PEPCs, Southern blot analysis indicates that the cotton PEPC exists as a small gene family and the GhPEPC2 might have two copies in the cotton genome, The semi-quantitative RT-PCR reveals that GhPEPC2 constitutively expresses in all the tissues of cot- ton and accumulated highly in roots, flowers and embryos but relatively low in stems and fibers, In addition, the recombinant GhPEPC2 has been purified by expressing it in Escherichia coli and the catalytic properties of it were also investigated. The results showed that GhPEPC2 is a typical C3 PEPC with a higher Km （83,6 p.M） and lower Vmax （8,0 p.mol min^-1 mg^-1） compared with the C3 PEPCs previously reported.