Perspectives on allelopathy in mexican traditional agroecosystems: A case study in tlaxcala

Agroecosystems in Tlaxcala, Mexico, are surrounded by trees and water channels and have a great variety of cultivated and noncultivated plants. The main results of a study carried out on a traditional agroecosystem in Santa Inés, Tlaxcala are presented. Some ecological aspects of polycultures, plant covers (dry leaves ofAlnus firmifolia, Berula erecta, andJuncus sp.), and the allelopathic potential of crops and noncultivated plants (fresh and dry material) were analyzed. The main plants (trees, shrubs, and herbs) present in the agroecosystem were identified. The total number of weeds in plots where plant covers were added was reduced. The number of nodules ofRhizobium phaseoli and the production of bean and squash increased with plant covers. Corn, beans, and squash showed a clear allelopathic effect, as well asChenopodium murale, Tradescantia crassifolia, Melilotus indicus, andAmaranthus hybridus, among other weeds. The contribution of allelopathy in studies of traditional agroecosystems is of great importance for the management of species in space and time. Allelopathy can be the basis of biological control of pests and weeds and of the discovery of new useful substances.     

激光微束显微切割植物染色体的研究

激光微束是六十年代激光技术问世后在生物学和医学领域中出现的一项新技术。该技术利用激光方向性好、光色单一和亮度高等独一无二的特点,把激光束通过光路系统引入显微镜并聚焦成很小的光点对细胞或细胞器进行精细的细胞或亚细胞水平的显微外科术。染色体是细胞核里一种极重要的结构。每一种真核生物都有一定数目的染色体;每条染色体上都有排列次序一定的基因。任何染色体数目的变化和染色体上基因排列次序的变化,都会引起生物遗传性的变异。激光微束遗传操作真核生物染色体是激光生物学中重要和活跃的研究课题。Berns等以两栖类和哺乳动物细胞为材料进行了激光显微照射染色体及其子细胞遗传分析的大量研究。梁宏等用氩离子激光显微切割长鼻(鼠菐)培养细胞有丝分裂染色体或使受照染色体区域DNA失活都取得了成功。Monajembashi和Cremer建立了用激光微束显微切割人淋巴细胞染色体的技术。本文报道用激光微束切割高等植物染色体的实验结果,其目的是建立起对农作物染色体进行激光遗传操作的有效技术方法。     

快速法酿造豆酱

选择出快速法酿造豆酱的加工工艺条件 ,把浸豆时间提高到 2 4h ,采用高温发酵、液化糖化技术 ,并在发酵后期加入乳酸菌与酵母发酵液 ,以增加其风味物质的形成。与传统工艺相比 ,不但缩短了加工周期 ,而且豆酱中氨基酸态氮含量、还原糖含量也均比传统发酵产品提高。与现行速酿工艺相比弥补了其风味不足的缺陷。     

Textural properties of legume protein isolate and polysaccharide gels

The influence of legume proteins from lupin, pea and fababean on the formation of gels prepared by heat treatment in the absence or presence of xanthan gum, locust bean gum and NaCl was investigated. The resulting fracture and texture properties of gels not only are associated with the heating process used to form the gel but also depend on the conformational aspects of xanthan–locust bean gum in admixture with legume proteins, which after 10 days of aging reinforce the system. The fracture and textural properties are explained in terms of the effect of the protein–polysaccharide molecular structure and physicochemical conditions applied in the gel system during the gel preparation and measurements. Copyright © 2006 Society of Chemical Industry     

Are Chemical Compounds Important for Soybean Resistance to <Emphasis Type="Italic">Anticarsia gemmatalis</Emphasis>?

The identification and quantification of flavonoids (rutin and genistin) present in extracts of soybean genotypes, and their effects on the biology and physiology of Anticarsia gemmatalis Hübner (Lep.: Noctuidae) were studied. Analysis of covariance and bicoordinate utilization plots were used to remove the effect of feeding time from pupal weight and consumption as well as to separate pre- and postingestive effects of treatment on A. gemmatalis growth. Genotypes PI 274454, PI 227687, and “IAC-100” extracts in general, caused higher mortality, negatively influenced initial larval and pupal weight, and elongated larval cycle. Larvae fed on the “IAC-100” extract diet ingested larger amounts of food per unit of time, but were less efficient in its conversion to biomass. Leaf extracts of PI 227687 had the largest concentration of rutin (quercitin 3-O-rhamnosylglucoside), followed by PI 274454, and “IAC-100”; PI 74454 also had the highest genistin (genistein 7-O-glucoside) content. The susceptible cultivar “BR-16” showed only a kaempferol-based flavonoid in its chemical profile, indicating that after successive crosses, secondary compounds responsible for plant defenses were eliminated. Genotypes PI 274454, PI 227687, and “IAC-100” showed accentuated resistance characteristics and were considered inadequate sources for the development of A. gemmatalis. Considering rutin and genistin concentration in these genotypes, it is suggested that flavonoids are important factors conferring resistance to A. gemmatalis.     

Cr：LISAF_6晶体的光谱和灯泵可调谐激光特性

本文阐述了新型可调谐激光晶体Ｃｒ：ＬｉＳＡＦ６的光谱特性及灯泵可调谐激光实验的结果。调谐光谱范围７７０．０—１０３６．０ｎｍ，最大激光输出能量１．１７Ｊ，斜率效率１．２７％，阈值１７．６Ｊ．     

豆豉与淡豆豉的成分测试及微生物菌群分析

目的 测试食品豆豉和中药淡豆豉样本中的药典成分,分离培养其留存的微生物菌株,分析微生物类别、发酵过程与功能成分的关系。方法 平板筛选培养、菌苔外观和显微镜鉴别微生物菌株,液相色谱法测定大豆异黄酮及苷元成分的含量,纤维平板法测试纤溶酶活性。结果 中药淡豆豉和食品豆豉的微生物以枯草芽孢杆菌最多,其次是霉菌和酵母;样本大豆异黄酮和苷元成分差异较大,有些中药材淡豆豉低于药典标准;个别食品豆豉样本具有纤溶酶活性,中药材淡豆豉少有纤溶酶活性。结论 留存于淡豆豉或豆豉中的微生物丰度顺序如下：枯草芽孢杆菌、霉菌和酵母;大豆异黄酮和苷元成分的含量与发酵过程有关,样本的差异较大;溶栓不是中药材淡豆豉的主要功效。     

气调储藏对绿豆球蛋白消化特性及其与蛋白二级结构的相关性研究

为明确气调储藏对绿豆蛋白质消化特性及蛋白二级结构和消化特性的相关性,以新鲜绿豆和在室温及4℃气调储藏18个月的绿豆为原料,利用傅里叶红外光谱技术分析经储藏后的绿豆蛋白其二级结构中α-螺旋结构增加,β-折叠结构减少;通过体外模拟消化实验发现不同气调储藏条件下绿豆球蛋白的胃肠消化率降低,消化产物中游离氨基酸含量降低。室温储藏后的绿豆球蛋白二级结构和胃肠消化率与新鲜绿豆球蛋白差异显著(P>0.05);而4℃气调储藏后的绿豆球蛋白二级结构和胃肠消化率与新鲜绿豆差异不显著(P<0.05)。说明4℃气调储藏可以减少绿豆球蛋白二级结构变化,从而影响胃肠消化率的变化。     

Evaluation of high pressure pretreatment for enhancing the drying rates of carrot,apple, and green bean

Preservation of fresh produce by drying dates back to ancient times and is still an indispensible technique. Conventional drying of fruits and vegetables is often accompanied by changes in color, texture, and taste. Suitable pretreatments can improve the drying process by reducing the drying time, yielding higher-quality products, and energy savings. In this study, two varieties of apples, Amasya and red delicious, green beans and carrots were pretreated with high hydrostatic pressure (HHP) at different pressure–time–temperature combinations (100–300 MPa for 5–45 min at 20 and 35 °C) prior to drying. The drying experiments were carried out by using a hot-air tunnel dryer at different temperatures (27–85 °C) and air velocities of 0.4 and 0.8 m/s with constant external conditions. Improving the drying conditions by increasing the drying temperature generally masked the effect of HHP pretreatment on drying rate. Generally, pressures of more than 100 MPa caused cell permeabilization resulting in higher drying rates. Among 14 models, the modified Page model was found to best explain the drying behaviors and model constants were evaluated accordingly. The Tukey multiple comparison test was applied on characteristic drying times to evaluate the relative effects of different pretreatments and drying conditions.