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141.
无性系培养技术在水稻遗传改良中的应用前景 总被引:1,自引:0,他引:1
概述了体细胞无性系变异发生的特点与其在水稻遗传改良中的应用状况,分析了体细胞无性系变异在实际应用中所存在的问题,并提出了加速水稻育种进程的新途径。 相似文献
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从光干涉和载波的原理出发,利用载波、调制、解调这三步对变形物体的离面转角进行测量,在理论上对该法进行了探讨、推导,阐述了其光路简单、灵敏度高等特点 相似文献
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马淑贤 《大连水产学院学报》1987,(1):47-54
本文用矩阵位移法进行了柔性桩台横向排架内力分析的精确计算。并用编制的程序在AppLE Ⅱ微机上作了算例.证明本文方法比原来的方法较为经济合理.本文方法可用于实际工程设计. 相似文献
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真胃变位(abomasal displacement)是指真胃正常解剖学位置发生改变,引起消化功能障碍,导致营养失调的消化系统疾病。真胃变位是奶牛常见疾病,多发于高产奶牛分娩前后,一般情况下多发生左方变位,在断奶前一般发生右方变位。该病主要造成奶牛的淘汰率增加,生产能力下降,治疗费用增多,给奶牛养殖业造成严重损失。本文介绍在富宁兰养殖场实习期间遇到的奶牛真胃变位病例,并从发病原因、临床症状、诊断、治疗、预防等几个方面进行总结,以期为有效防治奶牛真胃变位提供参考。 相似文献
148.
《Journal of plant nutrition》2013,36(12):2689-2704
ABSTRACT Salinity is among the most widespread and prevalent problems in irrigated agriculture. Many members of the family Chenopodiaceae are classified as salt tolerant. One member of this family, which is of increasing interest, is quinoa (Chenopodium quinoa Willd.) which is able to grow on poorer soils. Salinity sensitivity studies of quinoa were conducted in the greenhouse on the cultivar, “Andean Hybrid” to determine if quinoa had useful mechanisms for salt tolerant studies. For salt treatment we used a salinity composition that would occur in a typical soil in the San Joaquin Valley of California using drainage waters for irrigation. Salinity treatments (ECi ) ranging from 3, 7, 11, to 19?dS?m?1 were achieved by adding MgSO4, Na2SO4, NaCl, and CaCl2 to the base nutrient solution. These salts were added incrementally over a four-day period to avoid osmotic shock to the seedlings. The base nutrient solution without added salt served as the non-saline control solution (3?dS?m?1). Solution pH was uncontrolled and ranged from 7.7 to 8.0. For comparative purposes, we also examined Yecora Rojo, a semi-dwarf wheat, Triticum aestivum L. With respect to salinity effects on growth in quinoa, we found no significant reduction in plant height or fresh weight until the electrical conductivity exceeded 11?dS?m?1. The growth was characteristic of a halophyte with a significant increase in leaf area at 11?dS?m?1 as compared with 3?dS?m?1 controls. As to wheat, plant fresh and dry weight, canopy height, and leaf area did not differ between controls (3?dS?m?1) and plants grown at 7?dS?m?1. Beyond this threshold, however, plant growth declined. While both quinoa and wheat exhibited increasing Na+ accumulation with increasing salinity levels, the percentage increase was greater in wheat. Examination of ion ratios indicated that K+:Na+ ratio decreased with increasing salinity in both species. The decrease was more dramatic in wheat. A similar observation was also made with respect to the Ca2+:Na+ ratios. However, a difference between the two species was found with respect to changes in the level of K+ in the plant. In quinoa, leaf K+ levels measured at 19?dS?m?1 had decreased by only 7% compared with controls. Stem K+ levels were not significantly affected. In wheat, shoot K+ levels had decreased by almost 40% at 19?dS?m?1. Correlated with these findings, we measured no change in the K+:Na+ selectivity with increasing salinity in quinoa leaves and only a small increase in stems. In wheat however, K+:Na+ selectivity at 3?dS?m?1 was much higher than in quinoa and decreased significantly across the four salinity levels tested. A similar situation was also noted with Ca2+:Na+ selectivity. We concluded that the greater salt tolerance found in quinoa relative to wheat may be due to a variety of mechanisms. 相似文献
149.
《Journal of plant nutrition》2013,36(3):683-690
Abstract A field experiment was conducted at Star City (legal location SW6‐45‐16‐W2); Saskatchewan, Canada from May 2000 to June 2000, to measure nitrogen (N) and phosphorus (P) supply rates from fertilizer bands to the seed‐row of canola crop. Ion exchange resin membrane probes (PRSTM) were used to measure N and P supply rates in four treatments [80 kg N ha?1 of urea as side‐row band, 80 kg N ha?1 of urea as mid‐row band, check/no N (side‐row)/P side‐row, check/no N (mid‐row)/seed placed P]. The treatments were arranged in a randomized complete block design with four replications. Two anion and cation exchange resin probes (PRSTM) were placed in each plot in the seed‐row immediately after seeding and fertilizing. The probes were allowed to remain in the field for 2 days and replaced with another set of probes every 4 days for a total of 14 days until canola emerged. Ammonium‐N, nitrate‐N and P supply rates were calculated based on the ion accumulated on the probes. Urea side‐row band treatments (fertilizer N 2.5 cm to side of every seed‐row) had significantly higher cumulative available N supply rates than mid‐row band placement in which fertilizer N was placed 10 cm from the seed‐row in between every second seed‐row. No significant differences were observed in P supply rates. The higher N rates (120 kg N ha?1) resulted in lower grain yield in side‐row banding than mid‐row banding possibly due to seedling damage. However, the earlier fluxes of N into the seed‐row observed with side‐row banding may be an advantage at lower N rates in N deficient soils. 相似文献
150.