两种一年生植物在替代试验中的相互竞争关系

（1）用替代试验研究了燕麦（Aneva sativa）和箭舌豌豆（Vicia sativa）在混播中的竞争相互作用。为了攻混播比例对两种植物在混播条件下的行为影响，田间试验设为5个混播总密度和5种混播比例，共了5次。（2）方差分析表明，相对总生物量（RYT）和竞争平衡指数（CBI）对总密度，混播比例和生长时间的反应敏感。总密度对RYT和CBI的影响高度显著，在大多数情况下，混播比例对RYT和CBI的影响不显著。（3）本文研究的结果表明，持续时间对RYT和CBI很强的影响，在第1次测定时，RYT值接近1而BI值接近0，这一事实表明，种间无竞争或互惠作用。而在生长旺盛期，种间竞争较为剧烈。（4）本研究结果表明，箭舌豌豆的生长严惩受到燕麦的抑制作用，这说明箭舌豌豆在与燕麦混播时表现为竞争上的弱者。     

桑悬浮细胞原生质体培养的研究

采用继代培养三个月后的桑子叶悬浮细胞为材料,进行了原生质体的分离和培养。桑悬浮细胞在纤维素酶、果胶酶、半纤维素酶的混合溶液中,酶解获得产量高、活力强的原生质体。原生质体在K8p(附加6—BA、NAA、2,4—D、LH)液体培养基中,再生细胞经多次分裂,得到肉眼可见的小愈伤组织。再通过增殖继代培养,获得浅黄色、具有明显颗粒结构的愈伤组织,转至各种激素含量的MSB固体培养基中,尚未获得绿苗分化。     

佐剂对鸡补体水平影响的研究

６０只未免疫的伊莎褐雄鸡雏分成４组，于２４日龄开始用试管法以５０％溶血度为标准样检测补体。３１日时Ａ，Ｂ，Ｃ三组分别皮下注射司盘－８０＋白油，氢氧化铝胶和ＢＣＧ，Ｄ组对照；４６日龄时再次注射。从３１日龄至５６日龄每隔５天检测一次。结果表明，佐剂使鸡的补体水平普遍升高。于每次注射后第５天达到高峰，第１０天左右接近正常。其中ＢＣＧ影响现大，并于５１日龄时天对照组异显著（０．０１＜Ｐ＜０．０５）．     

茶树种植密度与排列方式对个体与群体结构的通径分析

本文用通径分析方法对茶树不同种植密度与茶树骨架形成、分枝结构、蓬面结构三大要素进行对应分析,结果表明:1)随密度上升主干粗度、一、二级分枝粗度下降;2)分枝角度随密度上升而变小;3)随密度上升,小桩数随之增加,其它因子与之呈负相关。由于密度上升后,群体结构的光合面积增大,碳水化合物积累增多,而产量上升。选用合理密度与排列组合时,可用回归方程计算。     

影响奶牛初乳产量的因素探讨

奶牛初乳是指母牛分娩后7天内所分泌的乳汁。初乳中不仅含丰富的营养物质，而且含有大量的免疫因子，因此具有促进生长发育、改善胃肠道功能、增进免疫调节、延缓衰老、抵御疾病等作用，是人类功能性保健食品的重要基料。初乳及其制品被誉为天然、完美、完全、廉价的“21世纪保健食品”。我国有奶牛和改良牛426.5万头(1998)，初乳资源十分丰富，但迄今对初乳产量及其影响因素尚未见有报道，于是对此问题我们在新疆乌鲁木齐五一奶牛场进行了初步探讨。1材料收集整理原始产奶记录和产犊记录取自该场1965年至1997年资料，全都为舍饲中国荷斯坦…     

Effect of dietary vitamin C and ammonia concentration on the cellular defense response of Macrobrachium nipponense

This study examined the effects of dietary vitamin C and ammonia concentration on the cellular defense response of Macrobrachium nipponese . The response of the cellular defense was determined by monitoring changes in reactive oxygen intermediates in hemocytes, superoxide dismutase activity, catalase activity, glutathione peroxidase activity, glutathione reductase and glutathione transferase activity in muscle. The results showed that prawns fed the basal diet had a significant increase in reactive oxygen intermediates in response to exposure to ammonia-N. When dietary vitamin C was added to the feed, there was a significant decrease in reactive oxygen intermediates in response to exposure to ammonia-N. Total superoxide dismutase and glutathione peroxidase activity of prawns fed the basal diet decreased as ammonia-N increased. This decrease in activity was significantly less pronounced in prawns that were fed the dietary vitamin C supplement. In prawns that were fed the dietary vitamin C supplement there was no significant variation in catalase reductase or gluxathione reductase activity in response to variations in ammonia-N concentration. The glutathione transference activity increased at a low concentration of ammonia-N in prawns that were fed the dietary vitamin C supplement, but there was no significant variation in the prawns fed the basal diet. Overall the results indicate that dietary vitamin C supplements enhance the capacity of M. nipponese to respond to elevations in ammonia-N. This response involved several biochemical reactions known to be involved in cellular defense.     

Molecular structure of troponin C from chicken skeletal muscle at 3-angstrom resolution

The x-ray structure of chicken skeletal muscle troponin C (TnC), the Ca2+-binding subunit of the troponin complex, shows that the protein is about 70 angstroms long with an unusual dumbbell shape. The carboxyl and amino domains are separated by a single long alpha helix of about nine turns. Only the two high-affinity Ca2+-Mg2+ sites of the COOH-domain are occupied by metal ions resulting in conformational differences between the COOH- and NH2-domains. These differences are probably important in the triggering of muscle contraction by TnC. Also the structure of TnC is relevant in understanding the function of other calcium-regulated proteins, in particular that of calmodulin because of its strong similarity in amino acid sequence.     

规模猪场提高初生仔猪成活率的技术措施

初生仔猪是否健康是规模养猪生产中的首要环节,如何提高初生仔猪成活率,减少初生仔猪死亡率、弱仔率是增加猪场经济效益的关键。为帮助规模猪场尽可能减少初生仔猪死亡率所造成的损失,笔者根据多年实践将初生仔猪死亡的原因和防治对策简介如下,供参考。1初生仔猪死亡原因分析1.     

河北坝上农田垄向对土壤风蚀的影响

在河北省坝上选择试验区 ,利用移动式风洞研究了农田起垄方向对土壤风蚀的影响。结果表明 ,农田起垄方向对土壤风蚀具有影响作用 :垄向与风向成 0°时风蚀量最大 ,90°时风蚀量最小 ;在 15m·s-1风速和 3cm表土含水率为 4 5 %的条件下 ,垄向与风向成 0°时的风蚀量为 90°时的 4 8倍。为减轻土壤风蚀危害 ,在河北坝上地区农田起垄的方向宜采用与自然风向NW (西北风向 ,315°)成 90°,即东北方向 4 5°。     

中澳航空护林现状分析与对策

介绍了我国和澳大利亚航空护林的现状以及澳大利亚航空护林的成熟经验,分析了我国航空护林的特点和存在的不足,提出了适当借鉴澳大利亚航空护林的成熟经验,进一步完善我国航空护林管理体制,以推动我国森林防火事业的全面发展。