不同处理方法对美国截叶胡枝子种子发芽的影响

截叶胡枝子(Lespedezacunecta)是原产于亚洲东部的一种多年生的豆科植物,在我国南方地区野生分布很广。它具有耐瘠、耐旱、耐酸、耐热、固土能力强、适应性广等特性,在国外也颇受重视。我国于1983年从美国引种,通过对其生物学和生态学特性、经济性状和栽培技术研究证明,引进的美国截叶胡枝子在人工栽培条件下,表现出良好的经济性状,是南方草地改良的希望种子。但是在生产中,由于其硬实的存在,使得种子的发芽率很低,往往造成出苗困难和草地建植缓慢,甚至出现严重缺苗断垄的现象,直接影响田间产量,限制了它的进一步推广应用。试验采用不同处…     

Climate and vegetation history of the midcontinent from 75 to 25 ka: A speleothem record from crevice cave, missouri, USA

Four Missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago (ka). The thorium-230-dated records reveal that between 75 and 55 ka, the midcontinental climate oscillated on millennial time scales between cold and warm, and vegetation alternated among forest, savanna, and prairie. Temperatures were highest and prairie vegetation peaked between 59 and 55 ka. Climate cooled and forest replaced grassland at 55 ka, when global ice sheets began to build during the early part of Marine Oxygen Isotope Stage 3.     

Geographical cline of DNA variation within the F intersterility group of Heterobasidion annosum in Italy

Eighty-six Heterobasidion annosum isolates, mainly belonging to the F intersterility group and obtained from 32 different geographical localities in Italy, were subjected to genetic analysis by the Random Amplified Polymorphic DNA (RAPD) markers. The similarity between F and S groups was higher than that between F and P. In UPGMA Cluster Analysis, the F isolates originating from the same locality usually grouped in the same cluster. The isolates also showed a tendency to group at the level of larger geographical areas. Within the F group, isolates from the south of the Italian peninsula showed the highest genetic variation and northern isolates from the Alpine regions showed the lowest. This indicates a gradual cline along the peninsula. The genetic variability in the Italian F group is discussed in relation to the past and present distribution of the host species in Italy and Europe.     

RELATION OF SEVERAL PEDOLOGICAL CHARACTERISTICS TO ENGINEERING QUALITIES OF SOIL

An attempt to predict engineering qualities which are needed in soil evaluation and to enhance nonagricultural use of soil survey data was made. Data from a variety of soils were subjected to simple correlation and multiple regression analyses to relate three pedologic characteristics: clay content, cation-exchange capacity (CEC), and organic matter content to two engineering qualitites: plasticity index, and optimum moisture. Simple correlation coefficients showed that clay content and CEC correlated significantly with the engineering determinations. The relationship between organic matter content and these engineering determinations was weaker. Multiple regression analyses showed that the three pedologic characteristics accounted for most of the variation in each of the engineering qualities, and that prediction was feasible.     

17种报春苣苔属植物的组培苗移栽季节研究

探讨不同季节对报春苣苔属植物组培苗移栽成活的影响,为其今后组培苗工厂化、规模化生产提供技术支持.以17种报春苣台属植物的组培生根苗为材料,研究季节对移栽成活的影响,分析不同物种间在同一季节的移栽成活差异以及同一物种在4个不同季节的移栽成活差异.大部分种类在春季移栽具有较高的成活率;成活率最高与最低的种类为三苞报春苣苔和...     

绵羊LDHβ基因的生物信息学分析及其在不同剩余采食量绵羊肝脏和肌肉组织中的表达

【目的】为鉴定绵羊乳酸脱氢酶β(lactate dehydrogenase B,LDHβ)基因的分子特征,研究其在不同剩余采食量绵羊肝脏和肌肉组织中的表达差异.【方法】测定了137只‘湖羊’公羔的剩余采食量(residual feed intake,RFI),按RFI进行排序,分别筛选出RFI最高(high-residual feed intake,H-RFI)和RFI最低(low-residual feed intake,L-RFI)的羊各15只,屠宰后,采集肝脏和肌肉组织,利用Q-PCR技术检测绵羊LDHβ基因分别在H-RFI和L-RFI羊肝脏和肌肉中表达量,并利用生物信息学软件构建了该基因的系统进化树和预测其结构与功能.【结果】绵羊LDHβ基因开放阅读框(open reading frame,ORF)为1 005bp,编码334个氨基酸,其蛋白质分子质量为36 479.43U,理论等电点为6.40.绵羊LDHβ基因与山羊的亲缘关系较近,其次为牛,序列同源性高.功能结构域预测结果显示,该基因编码产物在内质网中参与辅酶因子生物合成的可能性最高.Q-PCR结果显示,绵羊LDHβ-mRNA基因在L-RFI羊肝脏和肌肉中表达量均显著低于H-RFI羊(P0.01).【结论】绵羊LDHβ基因作为能量代谢的关键酶参与绵羊饲料效率的调控.     

Serum prolactin and growth hormone responses to naloxone and intracerebral ventricle morphine administration in heifers

These studies examined responses of serum prolactin (PRL) and growth hormone (GH) to opioid agonist and antagonist administration in heifers. To minimize nonspecific and behavioral effects and to facilitate future studies with specific opioid receptor agonists, a cannula was placed within the third cerebral ventricle of the brain of 4- to 10-mo-old heifers to directly access hypothalamic regions involved in the regulation of PRL and GH secretion. Increasing doses of morphine (M) from 2 to 1,500 micrograms injected into the third cerebral ventricle increased (P less than .001) serum PRL concentrations in a dose-related manner. Growth hormone responses were variable, resulting in elevated (P less than .05) serum concentrations following morphine, but no dose-related effects were apparent. Both PRL and GH responses to 700 micrograms M were absent when an intracerebral ventricle injection of an equimolar dose of naloxone, an opioid receptor antagonist, was administered prior to M. In a replicated 4 x 4 latin square, the effects of intravenous naloxone on PRL and GH responses was tested in young (86 +/- 11 d) and older (234 +/- 6 d) heifers. Naloxone at doses of 1, 2 and 4 mg/kg reduced (P less than .05) serum concentrations of PRL for 45 to 60 min. Mean concentrations of GH tended to be higher (P less than .07) in older heifers All doses of naloxone decreased (P less than .05) serum GH concentrations in older heifers but proved ineffective in younger heifers. There were no differences between doses of naloxone on either PRL or GH. These data suggest that endogenous opioids are involved in the regulation of PRL and GH secretion in heifers.