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冬春季节气侯多变,忽冷忽热,加上环境污染等影响,很容易导致呼吸道功能失调,防御能力减弱,从而给病原微生物的侵入以“可乘之机”,诱发呼吸道疾病的发生或加重。冬春季节,该防哪几种呼吸道疾病呢? 相似文献
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Since the first terpenoid synthase cDNA was obtained by the reverse genetic approach from grand fir, great pro-gress in the molecular genetics of terpenoid formation has been made with angiosperms and genes encoding a monoterpene synthase, a sesquiterpene synthase, and a diterpene synthase. Tree killing bark beetles and their vectored fungal pathogens are the most destructive agents of conifer forests worldwide. Conifers defend against attack by the constitutive and inducible production of oleoresin that accumulates at the wound site to kill invaders and both flush and seal the injury. Although toxic to the bark beetle and fungal pathogen, oleoresin also plays a central role in the chemical ecology of these boring insects. Re-cent advances in the molecular genetics of terpenoid biosynthesis provide evidence for the evolutionary origins of oleoresin and permit consideration of genetic engineering strategies to improve conifer defenses as a component of modern forest bio-technology. This review described enzymes of resin biosynthesis, structural feathers of genes genomic intron and exon or-ganization, pathway organization and evolution, resin production and accumulation, interactions between conifer and bark beetle, and engineering strategies to improve conifer defenses. 相似文献
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夏、秋季节是苍蝇、牛虻、飞蠓、蛾、蚊虫滋生的季节。多种昆虫附着于牲畜体表,其携带的病菌极易通过接触致使牲畜诱发疾病。特别是防御能力较差的结膜,是病菌较易进入的起始点。笔者在近些年来接触过多例由于苍蝇、蠓 相似文献
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<正>由于种植推迟及潮湿的土壤条件,专家预测玉米大豆叶用杀菌剂需求将增加。在水分胁迫下,植株不具备对病害及生物逆境的防御能力,将影响生长及发育,另外,过量的水分能带走重要的营养物质氮肥,并且饱和土壤中氧气稀缺, 相似文献
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研究了由追著驱赶引起的胁迫对斑尾鲈先天性防御能力的影响。斑尾鲈具有好斗相残性,实验中观察到,将不同个体大小的斑尾鲈放入同一水体中几小时后,个体稍大的追逐驱赶个体稍小的,处于生态主导地位,而小鱼则处于从属地位。对小鱼血浆内的皮质醇含量进行测定,其值显著高于大鱼血浆内皮质醇的含量。处于胁迫当中。注射灭活细菌到鱼鳔内,游向鱼鳔的嗜中性粒细胞,受胁迫鱼明显少于非受胁迫鱼。且其吞噬活力和呼吸爆发活力也相应下降。同时,体外研究也表明,胁迫抑制了斑尾鲈嗜酸性粒细胞的脱粒。另外,用爱德华氏茵进行感染,注射皮质醇的鱼表现出明显的易感性。从以上的研究我们可以看出,胁迫环境下,皮质醇含量分泌的增加,损害了斑尾鲈的先天性防御能力,对外来病原微生物的入侵也缺乏相应的抵抗力。 相似文献