Surface disposition and stability of pest-interactive,trichome-exuded diterpenes and sucrose esters of tobacco

The precise physical location of trichome-exudate biochemicals on the plant surface is undoubtedly important in plant-pest interactions, perhaps particularly those involving fungal and bacterial pathogens that invade the plant through the epidermal layer. The chemical stability of exuded compounds is also important in this regard. Here we have studied these two aspects of trichome biology using the highly exuded tobacco line,Nicotiana tabacum, T.I. 1068. Particularly under high relative humidity growth conditions, sucrose esters (SE) were found to migrate from the exudate droplet around the gland down the trichome stalk to the epidermal cells below. Six days after labeling leaf midveins on plants grown in a high humidity environment, 29 and 71% of label found in SE were recovered with trichome glands and below gland regions, respectively. Corresponding disposition in the moderate humidity environment was 40 and 60%, respectively. Migration of less polar duvatrienediols (DVT) was less marked. Staining of SE with rhodamine B showed the occurrence of more extensive and physically different migration in the high humidity versus moderate humidity case. Both SE and DVT were stable between six and 18 days postlabeling, the period encompassing the time of maximum exudate formation through the beginning of tissue senescence. Our results suggest that even under conditions that avoid mechanical disturbance of tissue, SE and DVT are chemically stable, at least until senescence, and appear to migrate from the gland region to the epidermal surface, apparently according to their relative polarity.     

Repellency of oral exudate to eastern and western spruce budworm larvae (Lepidoptera: Tortricidae)

A two-choice feeding bioassay was used to investigate the intra-specific repellency of the larval oral exudate of eastern and western spruce budworms,Choristoneura fumiferana (Clem.) andC. occidentalis Free., respectively. Results of the bioassay indicated that feeding behavior on artificial diet-drop feeding stations was modified in the presence of exudate, with feeding stations treated with conspecific exudate being avoided when an untreated station was available 3 cm away. Feeding was suppressed when a single, exudate-treated station was provided, or when the treated and untreated stations were separated by only 1 cm. The repellent effect functioned both inter- and intraspecifically. When induced to produce exudate,C. occidentalis larvae were not immediately repelled by either their own or other individuals' exudate. However, 24 hr after induction, test larvae were repelled by exudate from either source. In both species, larval oral exudate probably functions to repel conspecific competitors.     

反复冻融牛肉肉品质和流失汁液分析

模拟牛肉在贮存不当,经历反复冻融的情况下,对牛肉肉品质和流失汁液的性质进行分析。牛通脊分割为8块,置于-20℃,冷冻8 h,分别对样品进行1~8次反复冻融,取出样品进行解冻后,测定牛通脊的pH值和微生物菌落总数,并对流失汁液的可溶性蛋白质含量和热变性进行分析。结果表明:随着冻融次数的增加,牛通脊的pH值呈现下降、微生物菌落总数增加、汁液流失率和溶解性蛋白损失增加,以及溶解性蛋白的变性温度也有变化。反复冻融会使得肉品性质发生变化,影响牛肉的食用品质和安全性。     

赤藓糖醇产生菌的筛选

叙述了从土壤中分离赤藓糖醇产生菌的过程和方法。得到的２００多株高渗透性酵母中，有２株产赤藓糖醇，Ｔ－１２４菌在葡萄糖培养基上，产率为１５ｇ／Ｌ。另得到儿株阿拉伯糖醇产生菌，其中一株阿拉伯糖醇产率为４５ｇ／Ｌ．     

Correlation Between Phytotoxicity on Annual Ryegrass (Lolium rigidum) and Production Dynamics of Allelochemicals Within Root Exudates of an Allelopathic Wheat

An improved allelopathic correlation between phytotoxicity measured in root growth bioassay upon annual ryegrass (Lolium rigidum Gaud.) and the concentrations of a selection of dynamically produced allelochemicals quantified in the root exudates of cv. Khapli wheat (Triticum turgidum ssp. durum (Desf.) Husn.) monitored during the first 15 days of wheat seedling growth in a sterile, agar–water medium, has been established. Changes over the 15-day growth period in the quantities of five exuded benzoxazinones and seven phenolic acids were measured simultaneously using GC/MS/MS. Substantiating pure compound dose–response measurements were conducted over a range of concentrations for the putative allelochemicals within the wheat exudates. One synergism-based proposal using the monitored compounds to explain the observed low-exudate-concentration phytotoxicity was explored, but was found to be experimentally inadequate.     

Novel components from secretory hairs of azalea lace bugStephanitis pyrioides (Hemiptera: Tingidae)

The azalea lace bug secretes a clear fluid from secretory setae on the antennae and globulated spines on the dorsal and lateral aspects of the abdomen. The secretion contains 2-alkyl-5-hydroxychromones, the corresponding chromanones and diketones, and straight-chain aldehydes and ketones.     

Mycosynthesis of Zinc Oxide Nanoparticles Exhibits Fungal Species Dependent Morphological Preference (Small 15/2023)

Filamentous fungi can synthesize a variety of nanoparticles (NPs), a process referred to as mycosynthesis that requires little energy input, do not require the use of harsh chemicals, occurs at near neutral pH, and do not produce toxic byproducts. While NP synthesis involves reactions between metal ions and exudates produced by the fungi, the chemical and biochemical parameters underlying this process remain poorly understood. Here, the role of fungal species and precursor salt on the mycosynthesis of zinc oxide (ZnO) NPs is investigated. This data demonstrates that all five fungal species tested are able to produce ZnO structures that can be morphologically classified into i) well-defined NPs, ii) coalesced/dissolving NPs, and iii) micron-sized square plates. Further, species-dependent preferences for these morphologies are observed, suggesting potential differences in the profile or concentration of the biochemical constituents in their individual exudates. This data also demonstrates that mycosynthesis of ZnO NPs is independent of the anion species, with nitrate, sulfate, and chloride showing no effect on NP production. These results enhance the understanding of factors controlling the mycosynthesis of ceramic NPs, supporting future studies that can enable control over the physical and chemical properties of NPs formed through this “green” synthesis method.     

Allelopathy of yellow fieldcress (Rorippa sylvestris): Identification and characterization of phytotoxic constituents

Both the neutral and acidic fractions of the acetone extract of yellow fieldcress (Kireha-inugarashi,Rorippa sylvestris Besser) inhibited lettuce seed germination. Salicylic,p-hydroxybenzoic, vanillic, and syringic acid were identified in the acidic fraction. In the neutral fraction, hirsutin (8-methylsulfinyloctyl isothiocyanate), 4-methoxyindole-3-acetonitrile, and pyrocatechol were identified. Bioassay using a root exudate recirculating system showedR. sylvestris during flowering inhibited the lettuce seedling growth. Hirsutin (13g/plant/day) and pyrocatechol (9.3g/plant/day) were the major compounds released into the rhizosphere. Several combinations of pyrocatechol,p-hydroxybenzoic acid, vanillic acid, and hirsutin reduced lettuce seedling growth. These compounds seemed to be allelochemicals.     

Binding of Cu(II) to algae in a metal buffer

The interactions of Cu(II) with algal surfaces and exudates were studied in metal-NTA buffers by a combination of several analytical techniques. Suspensions of living algae in the presence of NTA were titrated at constant pH with Cu(II). The various Cu species were determined as follows: a copper ion selective electrode was used reliably in the pCu range 9–12; differential pulse polarography was used to measure separately Cu(II)-NTA complexes and labile Cu(II) species and to evaluate the complexation of copper by ligands in solution; copper bound to the algal surfaces was extracted by acid treatment and measured by AAS. Thus, we determined both the binding of Cu to the algal surfaces and to exudates excreted by the algae. The results were interpreted in terms of conditional equilibrium constants valid at a given pH; the conditional constants, both for the binding to the surfaces and with the exudates increase in the pH range 5.0–6.5. Simple equilibrium models using the experimentally determined binding capacities and equilibrium constants were able to simulate the results and to evaluate the speciation of copper. Under the experimental conditions used, the binding of Cu(II) to algal exudates has a more significant effect on copper speciation than the binding to the algal surfaces. These extracellular ligands may play an important role in decreasing the concentration of free copper ion and thus mitigating the potential toxic effects in organisms.     

贵州不同生态区域烤后烟叶表面提取物差异及其对烟叶风格的影响

为了探讨烟叶表面提取物与烟叶风格的关系,研究了贵州5个不同生态条件下烟叶表面提取物差异及其对烟叶风格的影响。结果表明,贵州不同生态烟叶表面提取物无论烷烃类,还是萜烯类均存在明显差异。烤后烟叶表面提取物对烟叶芳香类型有一定的影响,对香气量影响较大;缺少烟叶表面提取物,部分芳香类型会缺失,香气丰富感下降。