钴对玉米幼苗生长发育及钴含量的影响

试验采用完全随机区组设计、盆栽与室内分析相结合的方法,研究了钴对玉米幼苗生长发育及其钴含量的影响,以期为玉米优质高产提供理论依据。研究结果表明:施用钴会降低玉米幼苗中叶绿素的含量,提高玉米幼苗氮的含量,但钴超过一定的浓度,玉米幼苗中的含氮量会下降;施用钴对玉米幼苗中磷和钾含量也有一定影响;施用钴会降低玉米幼苗根系活力,提高玉米幼苗地上、地下部分全钴含量。     

不同方法提取蒿属植物有效物质的抑菌活性研究

用生长速率法对大籽蒿、黄花蒿、猪毛蒿进行不同提取溶剂的抑菌活性筛选,结果表明,大籽蒿、黄花蒿最适提取溶剂为乙醇,猪毛蒿最适提取溶剂为丙酮。其中,黄花蒿乙醇提取物对杨树烂皮病和落叶松枯梢病菌丝生长抑制率分别为100%、91.74%;猪毛蒿丙酮提取物对杨树烂皮病和落叶松枯梢病菌丝生长抑制率为100%。用生长速率法,以筛选出的最适提取溶剂对大籽蒿、黄花蒿、猪毛蒿进行不同提取方法的抑菌活性筛选。黄花蒿、猪毛蒿最适提取方法为超声波法,大籽蒿最适提取方法为冷浸法。     

The impact of foliar fertilizers on growth and biochemical responses of Thymus vulgaris to salinity stress

Salinity reduces plant biomass and may lead to death when severe. To cope with the negative effects of this stress, plant species present specific physiological or biochemical responses. In this work, we hypothesized that spraying salt-stressed thyme leaves with K⁺ and Ca²⁺ could mitigate the negative effects of salinity on plant growth and metabolism. To test this hypothesis, we grew thyme plants under salinity stress for two and four weeks before applying foliar sprays. Also, to test the effect of stress relief, treated plants were allowed two weeks of recovery after four weeks of salt stress. In general, after two and four weeks of salinity stress, the leaf fresh weight of thyme plants was reduced by 31 and 43%, respectively. Salinity also decreased the relative water content, water, and osmotic potentials and led to ion imbalances and nutrient deficiencies. Salinity altered concentration of some essential oils, but leaf antioxidant contents remained fairly stable, except for a significant increase for plants under NaCl?+?KCl two weeks after treatment. Our results indicated that stressed plants accumulated significantly more soluble sugars and amino acids in comparison with the control. Foliar sprays with KCl and CaCl₂ reversed the negative effects of salinity on plant biomass and induced the accumulations of compatible solutes. Moreover, concentrations of some essential oils and gallic acid increased in sprayed plants, but these effects were dependent on the type and duration of the treatment. Overall, spraying leaves with K⁺ and Ca²⁺ was able to mitigate salinity stress in Thymus vulgaris even during the recovery period.     

Distribution of phosphatase activity and various bacterial phyla in the rhizosphere of Hordeum vulgare L. depending on P availability

Despite the importance of the rhizosphere for nutrient turnover, little is known about the spatial patterns of organic phosphorus mineralization by plants and by microorganisms in the rhizosphere. Therefore, the distribution of acid and alkaline phosphatase activity and the abundance of bacteria belonging to various bacterial phyla were investigated in the rhizosphere of barley (Hordeum vulgare L.) as dependent on the availability of inorganic P. For this purpose, we conducted a greenhouse experiment with barley growing in inclined boxes that can be opened to the bottom side (rhizoboxes), and applied soil zymography and fluorescence-in situ-hybridization (FISH). Acid phosphatase activity was strongly associated with the root and was highest at the root tips. Due to P fertilization, acid phosphatase activity decreased in the bulk soil, and less strongly in the rhizosphere. Alkaline phosphatase activity, i.e., microbial phosphatase activity was high throughout the soil in the control treatment and was reduced due to inorganic P fertilization especially in the rhizosphere and less strongly in the bulk soil. P-fertilization slightly increased the total number of bacteria in the rhizosphere. Moreover, P-fertilization decreased the abundance of Firmicutes and increased the abundances of Beta- and Gamma-Proteobacteria. The total number of bacterial cells was significantly higher at the root surface than at the root tip and at a distance of 30 μm from the root surface. Our results show that alkaline phosphatase activity decreased more strongly in the rhizosphere than in the bulk soil due to P fertilization, which might be because of greater C deficiency in the bulk soil compared to the rhizosphere. Furthermore, the results indicate a spatial separation between hotspots of acid phosphatase activity and hotspots of bacteria in the rhizosphere of H. vulgare. Taken together, our study shows that bacteria and phosphatase activity were very heterogeneously distributed in soil, and that the effects of P fertilization on phosphatase activity differed strongly between bulk soil and rhizosphere as well as between various zones of the rhizosphere.     

人工神经网络用于异噻唑啉酮的定量结构-活性关系研究

采用误差反传前向人工神经网络(artificial neural network,ANN)建立了21种2-(4-取代-苯基)-3-异噻唑啉酮类化合物的结构与其抗菌活性之间的定量关系模型(ANN模型),以21种3-异噻唑啉酮类化合物的量子化学参数和拓扑指数作为输入、抗菌活性作为输出,所构建网络模型的交叉检验相关系数为0.991 6、标准偏差为0.080 1、残差绝对值≤0.221,应用于外部预测集,预测集相关系数为0.973 1;而多元线性回归(multiple linearregression,MLR)法模型的相关系数为0.841 8、标准偏差为0.303 9、残差绝对值≤0.636。结果表明,ANN模型获得了比MLR模型更好的拟合效果。     

一株高活性纤维素降解细菌的筛选鉴定及酶学特性

利用小麦/玉米秸秆还田土壤样品,通过富集培养和刚果红平板染色法筛选分离出纤维素降解细菌XWS-12;对分离的菌株进行16S rRNA基因序列系统发育分析,初步鉴定为伯克氏菌属(Burkholderia),定名为Burkholderia sp.XWS-12。以玉米秸秆和麸皮为碳源,研究了氮源、发酵时间、初始发酵温度、培养基初始pH等条件对该伯克氏菌产纤维素酶的影响。结果显示,该菌株产纤维素酶最适氮源为硝酸钠,培养时间为60 h,培养温度为37℃,培养基初始pH为4,该菌株的CMC酶活力最高,可达25 U/ml。其粗酶液的最适反应温度为50℃,最适反应pH为5,在pH 4~8的范围内酶活力较稳定。粗酶液的热稳定较差,当温度超过50℃时,该酶活力显著下降;当温度为50℃时,保温1 h,该酶活力损失53%。     

蒲公英抗氧化活性部位研究

为研究蒲公英抗氧化成分的分布,采用传统水提法提取蒲公英中的有效成分,并依次用石油醚、乙酸乙酯和正丁醇萃取,然后用FRAP法、超氧阴离子清除率法和DPPH法研究各层提取物的体外抗氧化活性。结果表明,各层提取物均具有体外抗氧化活性,三种不同测试方法显示其抗氧化能力大小均为:正丁醇层乙酸乙酯层水层石油醚层。说明蒲公英中抗氧化活性最强的是正丁醇层和乙酸乙酯层中。     

高产小麦品种济麦22旗叶叶绿素和活性氧清除系统酶活性的变化

为明确济麦22高产的生理基础,对其旗叶自然衰老过程中叶绿素含量和活性氧清除系统SOD、POD活性和MDA含量的变化进行了研究。结果表明,在自然衰老过程中,济麦22旗叶始终保持较高的叶绿素含量,其缓降期较长,使旗叶功能期延长,延缓了植株衰老,有效地提高粒重;旗叶细胞内SOD和POD保持较高的活性,且在花后24天后(蜡熟期)仍维持较高活性水平,可有效地清除活性氧自由基,防御其对叶片的伤害;MDA含量相对较低且上升幅度很小,叶片细胞的膜脂过氧化作用较弱。这些说明济麦22旗叶细胞酶促防御系统具有很强的活性氧清除能力,有效地抑制膜脂过氧化作用,从而延长旗叶的功能期,延缓植株衰老。小麦育种实践中选择持绿型品种是实现品种产量突破的重要措施。     

栉孔扇贝血淋巴中酯酶活性及其性质

采用紫外分光光度法测定栉孔扇贝（Chlamysfarreri）血淋巴中酯酶的活性，并研究底物、抑制剂、激活剂、温度、pH对酯酶活力的影响及酶的热稳定性。结果表明，栉孔扇贝血清与血细胞中均存在酯酶，且血细胞中的酶活力高于血清。血清与血细胞中酯酶的最适作用底物有所不同，血清中为α-醋酸萘酯，而血细胞中为α-丁酸萘酯。当以α-醋酸萘酯为底物时，血清中酯酶的最适温度为45℃，最适pH值为7．5；以α-丁酸萘酯为底物时，血清中酯酶的最适温度为40℃，最适pH值为8．0。以α-醋酸萘酯及α-丁酸萘酯为底物分别测定酶的热稳定时，酶活力变化相似，在20℃时活力最高，而后缓慢下降。栉孔扇贝血淋巴中酯酶属中温型中性酶类，低温下较稳定，底物专一性不强，血清中的酯酶可能来自血细胞，该酶在贝类的免疫防御中町发挥重要的作用。     

具有抗氧化活性的猪血浆蛋白酶解产物的制备及理化特性

为系统考察酶解时间、酶种类和酶加入的顺序对猪血浆蛋白酶解产物抗氧化性的影响,采用风味蛋白酶、碱性蛋白酶及双酶(风味蛋白酶,碱性蛋白酶不同的加入顺序)在各自最适条件下对猪血浆蛋白进行酶解,并研究酶解产物的功能特性。结果表明:0~120min内,随着酶解时间的延长,水解度升高,各酶解产物的抗氧化性均有所增强;60~180min内,双酶酶解产物的清除DPPH自由基的能力、亚铁离子螯合能力和还原力显著高于单酶酶解产物(P0.05);90~150min内,先加碱性蛋白酶后加入风味蛋白酶酶解的酶解产物的水解度、清除DPPH自由基能力和还原力显著高于先加风味蛋白酶酶解后加入碱性蛋白酶酶解的酶解产物(P0.05);具有较高抗氧化性的酶解产物在不同pH条件下均有较好的溶解性和热稳定性;溶解性均在90%以上。