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An apparatus in which shoot and root CO2 exchange and acetylene reduction can be simultaneously measured in specific white cloverrhizobium associations is described. In mature stolonating clover there was a fairly constant ratio between net photosynthesis, root respiration and acetylene reduction. Of the net carbon fixed daily (12 h light of 80 W m-2, 400–700 nm; day/night temperature 15°C) 12% was lost during the dark period by the shoot and 17% by the nodulated root. Changes in the rate of acetylene reduction by nodulated root systems occurred more slowly than those in rates of root respiration in response to reduced irradiance. In 21·5 h continuous darkness the rate of acetylene reduction remained constant. Responses to increased irradiance were more immediate in both root respiration and acetylene reduction. In plants maintained at 15°C in a 12-h, 80-W m-2 photoperiod there was no significant diurnal variation in acetylene reduction or root respiration. Acetylene depressed root respiration by 20%. Assuming the energy requirement of the nitrogenase system to be the same when reducing acetylene and N the depression can be used as an indication of the energy requirement of fixed N assimilation, metabolism and export in the nodulated root. Of the net carbon fixed daily 3·4% was utilized in this way in plants growing in a 12-h photoperiod (80 W m-2, 400–700 nm) at 15°C. 相似文献
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研究了日粮核苷酸对早期断奶小鼠肝脏基因表达的影响:选取16~17日龄健康BALB/C雄性小鼠60只,分成对照组和实验组,分别饲喂添加0、0.25%核苷酸的无核苷酸基础日粮,在实验的第2、4、10天采用差异显示技术分离小鼠肝脏中差异表达的基因。结果表明:采用6对引物分离到4条差异表达的基因片断。采用差异显示技术初步分离到4个受核苷酸影响差异表达的基因,这些片段需要做进一步的验证。 相似文献
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AIMS: To determine some of the risk factors for cows not observed in oestrus within 35–42 days of an unsuccessful artificial insemination (AI; phantom cows), and the reproductive outcomes and effect of treatment of phantom cows.MATERIALS AND METHODS: Over 2 years, in dairy herds from the Waikato (n=10) and Canterbury (n=4) regions of New Zealand, pregnancy diagnosis was carried out 35–42 days after AI on cows that had been inseminated in the first 3 weeks after the start of mating (PSM) but had not been seen returning to oestrus. Risk factors for phantom cows were analysed using a generalised linear mixed effect model.In Year 1, all phantom cows were left untreated. In Year 2, phantom cows were categorised as having a corpus luteum (CL) (CL+ n=120), or having ovarian follicles ≥10 (n=101) or <10 (n=40)?mm in diameter. Cows with a CL were treated with cloprostenol or untreated and placed with bulls. Cows with no CL received intravaginal progesterone (P4) for 7 days, with injection of gonadotrophin-releasing hormone (GnRH) on Days 0 and 9, and cloprostenol on Day 7 followed by AI. Pregnancy diagnosis of all cows took place 100–120 days after PSM and interval to conception and final pregnancy rate determined.RESULTS: Overall, of cows inseminated in the first 3 weeks after PSM that did not return to oestrus, 610/6,734 (9.1%) were phantom cows. From the final multivariable analysis, treatment for anoestrus, BCS ≤4.0 at mating, being 2 or >6 years of age, and pure-bred, and decreasing interval between calving and mating, until 98 days post calving, were associated with increased odds of being a phantom cow. Compared to all other groups of cows, phantom cows had a longer interval to conception (p<0.001) and a lower final pregnancy rate (p<0.001).Treatment of CL+ cows or cows with follicles ≥10?mm did not affect reproductive outcomes (p>0.3). For cows with follicles <10?mm treatment decreased the final percentage not pregnant (3/27; 11%; p=0.01) and interval to conception (21 days; p=0.02) compared with controls (7/13; 54% and 37 days, respectively).CONCLUSIONS AND CLINICAL RELEVANCE: Risk factors for phantom cows were identified that could be manipulated to reduce the number of phantom cows in a herd, in particular increasing BCS. Treatment of the majority of phantom cows did not improve reproductive performance. 相似文献
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Daniel Mannix Flynn AJ Turner Jo Tess Flynn WA Snowdon 《Australian veterinary journal》2004,82(3):174-174
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PM Bartlewski BD Alexander NC Rawlings DMW Barrett WA King 《Reproduction in domestic animals》2008,43(3):299-307
In ruminants, superovulatory treatments started at the time of follicular wave emergence result in greater and less variable ovulatory responses and embryo yields compared with the treatments begun in the presence of a large growing antral follicle(s) from the previous waves. The progesterone–oestradiol treatment is routinely used for follicular wave synchronization in cattle. The main objective of this study was to characterize the ovarian responses, hormonal profiles and in vivo embryo production in anoestrous Rideau Arcott ewes (May‐June), which were superovulated after pretreatment with medroxyprogesterone acetate (MAP)‐releasing intravaginal sponges and a single dose of oestradiol‐17β (E2‐17β). Six days after insertion of MAP sponges, eight ewes were given an i.m. injection of 350 μg of E2‐17β (E2‐17β‐treated ewes); 10 ewes were given an i.m. injection of vehicle (control ewes). Multiple‐dose Folltropin®‐V treatment, followed by the bolus injection of GnRH (50 μg i.m.), began 6 days after E2‐17β/vehicle injection. Transrectal ovarian ultrasonography revealed that: (i) the interval between E2‐17β/vehicle injection and regression of all follicles ≥5 to 3 mm in diameter was shorter (p < 0.01; 2.6 ± 0.4 vs 4.8 ± 0.6 days respectively); and (ii) the interval between injection and emergence of the next follicular wave was longer (p < 0.05; 5.4 ± 0.3 vs 1.2 ± 0.4 days, respectively) in E2‐17β‐treated than in control ewes. During the 6 days after injection, the mean FSH peak concentration and basal FSH concentration were lower (p < 0.01) in E2‐17β‐treated ewes. The mean ovulation rate and the number of recovered embryos did not differ (p > 0.05) between the two groups of ewes. However, the number of luteinized unovulated follicles per ewe, and the variability in the number of luteal structures and overall embryo yield were less (p < 0.05) in E2‐17β‐treated compared with control ewes. In conclusion, the MAP–E2‐17β pretreatment significantly reduced the variability in ovarian responses and embryo yields, without affecting the embryo production in superovulated anoestrous ewes. 相似文献
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贵州足球场草坪建植及优化管理模型研究 总被引:1,自引:0,他引:1
在一定的生境和管理条件下,以修剪高度、修剪次数和施N、P、K量为因素,利用二次正交回归设计,用模糊综合评分法评定草坪质量,最佳3因子水平为:修剪高度5-7.4cm,修剪次数4-6次/月,施N量为2.5-3.7g(m^2.年),施P、K量各为1.25-1.85g/(m^2.年),建立了草坪质量与养护3因子间的显相关回归模型。 相似文献