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根据雪灾发生的离均系数 (S)≥ 2 .0时 ,就会发生雪灾的这一规律 ,应用 GM(1 .1 )模型对青南地区雪灾可能发生的趋势进行了预测 ,并且提出了防御雪灾的对策。 相似文献
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不同株高夏玉米品种的氮素吸收与利用特性 总被引:6,自引:0,他引:6
选用鲁单981 (LD981)、郑单958 (ZD958)和登海661 (DH661) 3个不同株高玉米品种, 在大田和栽培池条件下分别设67 500株 hm-2和82 500株 hm-2 2个种植密度, 0和180 kg hm-2 2个施氮量。大田试验的氮肥以开沟方式施入, 栽培池试验氮肥分别以5、20和40 cm深度分层施入, 利用15N同位素示踪技术研究不同株高夏玉米对氮素的吸收与利用特性。结果表明, 与67 500株 hm-2种植密度比较, 82 500株 hm-2种植密度夏玉米籽粒产量及氮素偏生产力显著提高。夏玉米吸收的氮素69.3%~77.3%来自土壤, 22.7%~30.7%来自肥料, 土壤氮和肥料氮收获指数分别为54.6%和57.5%。与67 500株 hm-2种植密度比较, 82 500株 hm-2种植密度矮秆品种DH661氮素积累来自肥料的比例显著降低, 中品种ZD958和高秆品种LD981没有显著变化; 中、高秆品种肥料氮收获指数显著降低, 矮秆品种增加。5 cm土层施氮对植株肥料氮积累量贡献率最大, 40 cm土层施氮对植株肥料氮的贡献率最小, 随着株高增加, 深层(40 cm)氮对植株肥料氮积累量的贡献率逐渐增加, 浅层(5 cm)氮对植株肥料氮积累量的贡献率逐渐降低。中、高秆品种对土壤深层40 cm施氮的氮肥回收率较高, 而矮秆品种对土壤浅层20 cm施氮的氮肥回收率较高; 20 cm和40 cm 15N在20~40 cm和40~60 cm土层残留量分别达到60%, 说明矮秆品种对20~40 cm土层氮素回收率较高, 中、高秆品种对40~60 cm土层氮素回收率较高。 相似文献
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SA Bukhari N Ahmad N Akhtar A Ijaz MS Yousaf IU Haq 《Reproduction in domestic animals》2008,43(6):664-671
In the present study, ovarian follicular fluid and serum biochemical, hormonal, electrolytes and amino acids profiles in female dromedary camel (Camelus dromedarius), were investigated. Fluid from small (2–6 mm) and large follicles (7–20 mm) and blood samples were collected from 25 clinically healthy adult female camels. The concentrations of glucose, cholesterol, triglycerides, high‐density lipoproteins, urea, total proteins, albumin, globulin, fibrinogen, alanine aminotransferase, aspartate aminotransferase and tri‐iodothyronine were lower (p ≤ 0.05) in large follicles when compared with the small follicles. However, the concentrations of low‐density lipoproteins, uric acid, creatinine, alkaline phosphatase and acid phosphatase in small and large follicles did not differ. The concentrations of oestradiol 17‐β and progesterone were higher (p ≤ 0.05) in large follicles. The serum concentrations of these hormones were many folds lower (p ≤ 0.05) than those of follicular fluid. Among electrolytes, the concentration of phosphorus was higher (p ≤ 0.05) in the large follicles, while that of potassium and chloride were lower (p ≤ 0.05) in the small follicles. Serum concentrations of sodium, chloride, calcium and phosphorous were higher (p ≤ 0.05), while that of potassium lower (p ≤ 0.05) than corresponding concentrations in the follicular fluid. The concentrations of leucine and arginine were higher (p ≤ 0.05) in follicular fluid when compared with serum concentrations, while the reverse was true for other amino acids. In conclusion, this study is indicative of either low or high concentrations of certain biochemical metabolites, hormones, electrolytes and amino acids in small and large follicles for the individual roles that they play in the growth and development of follicles in the one‐humped she‐camel. 相似文献
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水稻抗白背飞虱基因Wbph2的初步定位 总被引:1,自引:2,他引:1
鉴定了ARC10239/明恢63 F2群体对白背飞虱的抗性,混合F2感虫稻株的DNA,构建感虫池。应用129个RFLP探针,结合4种限制性内切酶,检测抗虫亲本ARC10239、感虫亲本明恢63和感虫DNA池的多态性。检测到6个阳性探针,分布在5个染色体上(染色体3、6、8、11和12)。应用阳性探针分析了F2群体的142个个体,发现抗虫基因Wbph2与第6染色体上的标记RZ667、RG64和RG264连锁,其中, Wbph2与RZ667的遗传距离为25.6 cM (LOD=4.50)。 相似文献