Behavior of phenolic substances in the decaying process of plants

The behavior of phenolic substances in the decaying process of rice straw, ladino clover, and fanen leaves of red oak under moist conditions, and also of rice straw under various conditions were compared in the laboratory. The amounts of phenolic substances, divided into either humic acid and fulvic acid fractions, or ether-extractable, butanol-extractable and organic solvent-unextractable fractions, and the amounts of individual phenolic acids were periodically determined during incubation for 150 days. The following results were obtained.

1) The amounts and behavior of phenolic substances in various fractions differed considerably among the plant materials. The total amount of phenolic substances was remarkably larger in red oak leaves than in the others during the whole period of incubation. The amounts of phenolics in the fulvic acid fraction changed to a larger extent than those in the humic acid fraction during the decaying process of plant materials. The changes in total amount of phenolics in decaying red oak leaves and ladino clover were mainly due to changes in the level of relatively hydrophilic phenolics in the fulvic acid fraction, but the changes in decaying rice straw were mainly due to changes in the level of relatively lipophilic phenolics.

2) Rice straw and ladino clover, especially the former, contained large amounts of p-coumaric and ferulic acids, but these decreased rapidly in the early stage of the decaying process. The amounts in red oak leaves were small, but did not decrease markedly during incubation.

3) The changes in amounts of phenolics in both humic acid and fulvic acid fractions in the decaying process of rice straw were largely influenced by temperature, moisture, and pH, but not to a large extent by C/N ratio and the presence of soil. At higher temperatures under moist conditions, phenolic substances disappeared rapidly. Also, acidification of the system inhibited the degradation process.     

Effects of inbreeding on nodal root system morphology and architecture of white clover (<Emphasis Type="Italic">Trifolium repens</Emphasis> L.)

Plants of white clover (Trifolium repens L.) cultivar Crau, a self-fertile Crau genotype, and nine generations of inbred progeny were raised in sand culture in a glasshouse experiment. Digital images of the root systems were made and root morphological characteristics were determined on all the plants. Root architectural parameters were measured on the Crau parent and the S₁, S₄, S₆, and S₉ inbred lines. The clover roots became shorter and thicker with inbreeding but the number of root tips per plant was unchanged. Root architecture (branching pattern) was largely unaffected by inbreeding. It is concluded that inbreeding white clover will lead to shorter, thicker roots, and reduced nutrient uptake efficiency compared with the parent clover. The degree to which these deleterious traits are overcome during the development of F₁ hybrids needs to be determined.     

不同钠浓度对白三叶草和多年生黑麦草生长的影响

白三叶草对Na 的反应比多年生黑麦草敏感.培养液中的Na 浓度从0.1mmol/L 增至0.5mmol/L 时,其干物质生产下降37%;增至2.5mmol/L 时,干重下降49%,而多年生黑麦草的干重仅降低6%.2种牧草的Na 含量均随培养液Na 浓度的增加而提高,K 含量未受影响.白三叶草的Na 含量低于多年生黑麦草,而K 含量高于多年生黑麦草.试验结果暗示,白三叶草对K 的选择吸收能力较多年生黑麦草强,但耐盐能力较差,生态适应性不如多年生黑麦草广.     

氮肥对红三叶和鸭茅草地生产性能影响的研究

本文对红三叶和鸭茅单、混播草地对施氮肥的反应情况进行了研究，发现氮肥对鸭茅的株高、分蘖及产草量具明显的促进作用，而红三叶对氮肥的反应则不十分明显。同时施肥后，单播处理牧草的产量增幅比混播处理大。试验结果还表明，鸭茅和红三叶产量与施氮肥量均呈指数关系。通过对单播鸭茅和混播草地总产对氮肥的反应规律进行分析，可以把混播草地对氮肥的利用情况及氮肥对该草地中红三叶固氮作用影响的变化规律分为３类：第１类为混播草地投入最低氮肥量，草地生产力较低，此时红三叶能提供较高氮素价值量；第２类，混播草地投入中等氮肥量，草地生产力中等，但红三叶提供氮素的价值量减小；第３类，投入较高氮肥量，但红三叶失去提供氮素价值。本试验显示，从经济效益角度考虑，对混播草地以少施氮肥为好，特别是在０～０．３ｔ／ｈａ范围内较为适宜。     

氮锌复合作用对白三叶叶片叶绿体超微结构的影响

在砂培条件下，研究了不同水平氮锌配施对白三叶生长、叶片叶绿素含量和叶绿体超微结构的影响。结果表明，在缺锌条件下，随供氮水平增加，植株干物重、叶片叶绿素含量显著下降，氮锌配施表现为拮抗效应。在足量供锌条件下，中量供氮，植株干物重、叶片叶绿素含量高于低量供氮，氮锌配施表现为协同效应；与低水平供氮相比，当高水平供氮时，白三叶各组分干物重、叶片叶绿素含量显著下降，氮锌配施表现为拮抗效应。白三叶叶片超显微结构表明，低锌条件下，随供氮水平增加，叶绿体结构变差，基粒及基粒片层、基质片层数量下降甚至解体，光合能力显著下降。足量供锌时，以中量供氮叶绿体基粒及基粒片层、基质片层数量最多，内部结构有序性最高，光合能力最强。叶绿体超显微结构变化与白三叶干物重、叶绿素含量变化趋势相一致。     

Effect of Chilling Stress on Synthesis of Antioxidant Enzymes,Osmotic Adjustment Substances and Membrane Lipid Peroxide Levels in Two White Clover Cultivars

Although white clover has been widely studied and applied, less is known about its physiological responses to chilling stress in northern China. The effects of acclimation time of chilling stress in the two white clover cultivars, Rivendel and Haifa, after exposure to 4℃ for 0, 4, 8, 12, 24 and 48 h were investigated. Seven physiological indexes were measured in shoots of the two cultivars. It was found that Rivendel had a strong ability to maintain the stability of cells, cope with oxidative damage and accumulate osmotic adjustment substances compared with Haifa. In addition, a comprehensive evaluation on the chilling tolerance of the two cultivars based on subordinate function value analysis showed a stronger chilling tolerance of Rivendel than Haifa.     

不同生育时期白三叶与黑麦草的化感作用研究

试验用分枝期,开花期和成熟期的白三叶品种海法以及分蘖期,孕穗期和成熟期的2个黑麦草品种顶峰、英斯派的根水浸提液处理,按照培养皿砂培的生物检测方法对白三叶和黑麦草的化感作用进行研究。结果表明:分枝期白三叶根浸体液对顶峰的发芽率具有显著的抑制作用,对顶峰苗长具有极显著抑制作用,抑制率分别为90.72%、48.61%;开花期白三叶根浸提液对顶峰及英斯派的发芽率、英斯派根长及顶峰根干重均具有极显著的抑制作用,抑制率分别为35.14%、36.17%、69.18%、68.34%,对英斯派的根干重具有显著的抑制作用,抑制率为49.52%;成熟期白三叶的根浸提液对3个受体的发芽率及根长均具有极显著的促进作用,分别比对照提高67.09%、54.21%、69.21%及93.08%、93.14%、93.04%,对顶峰的根干重具有极显著的促进作用,与对照相比提高了85.42%;顶峰及英斯派是他感作用大于自毒作用的黑麦草品种,且在分蘖期及孕穗期,黑麦草不同品种的根浸提液都显著的抑制了白三叶的干物重。     

Effects on animal performance and sward composition of mixed and sequential grazing of permanent pasture by cattle and sheep

Previous experiments have shown that mixed or conjoint grazing, when two or more animal species are grazed together, can lead to improved performance of one or more of the species and a higher total output per unit area. Sequential grazing systems, when different animal species graze an area in succession, also have the potential to improve productivity. This experiment directly compared these two approaches for integrating the grazing of cattle and sheep when pastured on improved permanent pasture. Four treatments were compared: 1) sheep only from May to October (S/S); 2) cattle only from May to July followed by sheep only from August to October (C/S); 3) cattle and sheep from May to July, sheep only for the rest of the growing season (C + S/S); and 4) cattle and sheep from May to October (C + S/C + S). Each treatment was replicated three times. From May until weaning at the end of July the plots were grazed by steers and ewes and lambs, and from weaning until October by steers and lambs. Sward heights were maintained at 6 cm using a “put and take” stocking system. Animal performance and sward composition data were collected during three growing seasons, 2001–2003. During the pre-weaning period lambs grazing plots which were grazed only by sheep had significantly poorer growth rates than those grazing plots where there was mixed grazing. Lambs grazing the sheep only plots also had lower liveweight gain during the post-weaning period, with the highest growth rates being recorded on the C + S/C + S treatment. Carrying capacity and total liveweight gain per unit area post-weaning were also consistently higher for the C + S/C + S treatment, while carrying capacity pre-weaning was highest for the C/S treatment. Measurements of clover content in the grazed horizon and botanical separation of material from quadrat cuts indicated that even under relatively controlled conditions choice of grazing system can influence sward composition. However, there was no clear link between any single sward change and the growth of the animals, indicating that the improved performance of cattle and sheep under mixed grazing is the result of a combination of factors, rather than a response to a particular sward parameter.     

Red clover mottle virus from Ukraine is an isolate of RCMV strain S

The relationship between red clover mottle virus (RCMV) isolated in the Ukraine (designated RCMV-Uk) and well-characterised strains from Sweden has been investigated. Nucleic acid hybridisation indicate that both RNAs from RCMV-Uk are highly homologous to their counterparts from RCMV strain S, a conclusion supported by protein sequence analysis of the two viral capsid proteins. Nucleic acid sequence analysis of a portion of RCMV-Uk RNA2 confirmed the high degree of similarity between RCMV-Uk and RCMV strain S. This information suggests that RCMV-Uk should be considered an isolate of RCMV strain S.