3种前体化合物对茅苍术组培苗中主要挥发油成分积累的影响(英文)

[目的]研究三种前体化合物对茅苍术组培苗中主要挥发油成分积累的影响,以期为人工栽培茅苍术的品质提高提供帮助。[方法]在茅苍术组培苗MS生根培养基中添加不同化合物,对组培苗进行一段时间培养后,超声提取植株所含的挥发油,利用气相色谱法测定挥发油中苍术酮、苍术醇、β-桉叶醇和苍术素的量。[结果]添加木糖、异戊二烯和四氢呋喃对茅苍术组培苗的生长指标、挥发油得率及四种组分相对百分含量均有影响。6g/L木糖组优化培养基中,检出挥发油中苍术酮、β-桉叶醇的相对百分含量分别达到4.23%和56.34%,分别比对照高出1.41和1.66个百分点;四氢呋喃组优化培养基中苍术酮、苍术醇和苍术素的相对百分含量均有提高,四氢呋喃浓度为0.07g/L时总挥发油含量较对照相比增加49.97%;添加异戊二烯到培养基中虽能提高苍术酮的相对百分含量,但对总挥发油含量的积累起到一定的抑制作用,较对照分别减少23.67%、31.06%和7.10%。[结论]添加木糖和四氢呋喃对茅苍术组培苗中主要挥发油的积累具有促进作用,而异戊二烯则具有抑制作用。     

中生菌素的抗生作用

 本文研究了中生菌素对革兰氏阳性菌、革兰氏阴性菌、丝状真菌的抗生作用。结果表明,中生菌素是一种抗菌谱比较广的农用抗生素。其对菌体细胞膜无明显的影响。100 ppm时引起部分菌体原生质凝聚。同位素标记前体物掺入实验表明,中生菌素15.6 ppm对白菜软腐病菌DNA、RNA的合成影响很小,但强烈抑制菌体蛋白质的合成。用化学测定法分析了中生菌素对枯草杆菌细胞内大分子物质含量的影响,得到了和前体物掺入法相似的结果。说明了中生菌素的作用机制是抑制菌体蛋白质的合成。     

不同前体对黄芪悬浮培养细胞中黄芪多糖积累的影响

[目的]研究苯丙氨酸、草酸和油酸等前体对黄芪细胞生长和黄芪多糖合成的影响.[方法]在细胞培养的第O天,向细胞悬浮培养液中加入3种前体,测定细胞干重增殖倍数和黄芪多糖的含量.[结果]添加2 mmol/L的草酸可以明显地促进黄芪细胞中黄芪多糖的积累,其含量为对照组的1.80倍;较低浓度苯丙氨酸能有效促进黄芪细胞中黄芪多糖的合成;当苯丙氨酸浓度为1.Ommol/L,黄芪多糖的含量达最大,为33.429 mg/g,为对照组的1.70倍;当油酸添加浓度由0.1mmol/L增加至2 mmol/L时,细胞中黄芪多糖的含量逐渐提高;2 mmol/L的油酸使黄芪多糖的含量达37.565 mg/g,为对照组的1.91倍.[结论]前体的添加可有效促进黄芪悬浮培养细胞中黄芪多糖的积累.     

湖南双季稻区5月低温特征及预警信号研究

利用湖南双季稻区66个气象站1961-2013年5月逐日气温资料,建立5月低温强度指数,对5月低温的时空分布和强度特征进行分析,并采用大气变量物理分解法探寻5月低温天气过程的前期信号。结果表明：5月低温在研究区具有南少北多的地域特点,根据影响范围主要可分为全省一致型、湘中以北型和湘北型3种空间分布形态。5月低温过程强度较大,80%达中度及以上程度,影响范围较广,50%的低温过程影响双季稻区70%以上的站点。研究期内15次5月低温过程中有14次分别在850hPa和300hPa图上出现温度扰动和位势高度扰动负值中心,因此,通过追踪850hPa层的温度扰动能提前5～10d预测5月低温的出现。温度扰动的移动路径主要有东路、西北路和西路3条,且以东路为主。移动路径为东路时,出现湘北型5月低温概率最大,为西北路时,一般出现湘中以北型5月低温。     

肉风味前体物质与风味品质的关系研究进展

风味是重要的食用品质指标,良好的风味可引起人的食欲。肉的风味是烹调过程中风味前体物质、中间反应产物和降解产物经一系列复杂的化学反应形成的。肉风味前体物质是指鲜肉中对肉的香气形成起重要作用的非挥发性成分,主要包括水溶性风味前体物质和脂质。本文综述了主要的肉风味前体物质及其与风味品质的关系,为阐释风味品质形成差异的机理提供理论基础。     

Driving forces of landscape change - current and new directions

The concept of driving forces is gaining increasing attention in landscape-change research. We summarize the state of the art of this field and present new conceptual and methodological directions for the study of driving forces of landscape changes. These new directions address four major challenges faced by landscape-change studies, i.e., studying processes and not merely spatial patterns, extrapolating results in space and time, linking data of different qualities, and considering culture as a driver of landscape change. The proposed research directions include: studying landscape change across borders and transects, focusing on persistence as well as change, investigating rates of change, considering attractors of landscape change, targeting correlation and causality, and searching for precursors of landscape change. Based on established knowledge and the new approaches we outline a standard procedure to study driving forces of landscape change. We anticipate that our analytical and systematic approach increases the relevance of studies of landscape change for science as well as for the solution of real world problems.     

Driving forces of landscape change - current and new directions

The concept of driving forces is gaining increasing attention in landscape-change research. We summarize the state of the art of this field and present new conceptual and methodological directions for the study of driving forces of landscape changes. These new directions address four major challenges faced by landscape-change studies, i.e., studying processes and not merely spatial patterns, extrapolating results in space and time, linking data of different qualities, and considering culture as a driver of landscape change. The proposed research directions include: studying landscape change across borders and transects, focusing on persistence as well as change, investigating rates of change, considering attractors of landscape change, targeting correlation and causality, and searching for precursors of landscape change. Based on established knowledge and the new approaches we outline a standard procedure to study driving forces of landscape change. We anticipate that our analytical and systematic approach increases the relevance of studies of landscape change for science as well as for the solution of real world problems.     

利用大口黑鲈加工上海熏鱼的工艺及风味特点

上海熏鱼是以青鱼或草鱼为原料,经过浸渍和油爆过程制作出的传统中式菜肴。为解决青鱼养殖量下降和草鱼肌间刺多、土腥味重的问题,弥补加工上海熏鱼的不足,以大口黑鲈替代草鱼制作上海熏鱼,采用单因素试验设计和正交试验设计改良上海熏鱼的加工工艺,采用顶空固相微萃取-气相色谱-质谱法（SPME-GC-MS）分别测定油爆后的上海熏鱼、用不含香辛料的油爆后浸渍液处理的上海熏鱼及上海熏鱼成品中的挥发性风味活性物质,通过GC-MS的定性定量分析得出上海熏鱼的主要风味化合物,采用高效液相色谱法(HPLC)测定呈味核苷酸。结果表明,优化工艺参数为油爆时间6 min,油爆后浸渍液中酱油∶白砂糖=4∶3（鱼块质量的20%∶15%）。3个样品中的挥发性化合物分别有37、47和55种,其中醛酮类、醇类、烃类、芳香类和含氮含硫类物质是上海熏鱼的主要风味化合物。肌苷酸是主要鲜味核苷酸。研究表明,高温油爆过程中发生的美拉德反应、热降解、脂肪酸氧化有助于去除鱼腥味,形成上海熏鱼的特色风味。浸渍和油爆是提高鱼肉制品品质的优良加工工艺。