不同温度条件下香水文心兰花香气的成分分析及感官评定

Flower aromatic components and their relative contents of Oncidium Sharry Baby ‘Sweet Fragrance ’ at full flowering stage under conditions of 10 ℃, 20 ℃ and 30 ℃ were analyzed by solid phase micro-extr...     

入侵杂草五爪金龙在切割处理下的再生能力

对五爪金龙(Ipomoea cairica (Linn.) Sweet)进行切割试验,对其在不同光环境及不同季节的萌芽率、成活率、主茎长度和生物量等进行研究。结果表明:五爪金龙切条越短其萌芽越迟,其成活率、主茎长度和生物量下降;五爪金龙在光下和林下的成活率无显著差异,但林下生物量较低;切条越短,林下条件越不利于主茎的伸长;冬季五爪金龙的主茎长度和生物量最低;夏季在光下和林下不能再生的最长切条长度均为4 cm;秋季均为1 cm;而冬季光下为1 cm,林下为3 cm;春季光下则为4 cm,林下为5 cm。春季时将五爪金龙切割为5 cm并置于林下是最经济的防除方法;如果不考虑季节性及光条件,应将其切割至1 cm以下的片段,可以有效防止五爪金龙再生。     

The Effect of the Sequence of Infection of the Causal Agents of Sweet Potato Virus Disease on Symptom Severity and Individual Virus Titres in Sweet Potato cv. Beauregard

Sweet potato virus disease (SPVD) is caused by dual infection of plants with Sweet Potato Feathery Mottle Virus (SPFMV) and Sweet Potato Chlorotic Stunt Virus (SPCSV). Because SPFMV and SPCSV are transmitted by aphids and whiteflies, respectively, infection in nature occurs independently rather than simultaneously. To investigate the effect of consecutive infection on symptom development and individual virus titres, plants infected with a single virus were later inoculated with the second virus. Symptoms were significantly more severe in plants infected with SPCSV followed by SPFMV compared to plants infected with SPFMV followed by SPCSV. Virus titres were not significantly different for SPCSV, but SPFMV titres, in plants infected with SPCSV followed by SPFMV, were significantly higher than all other treatments. The results indicate that the sequence of infection of sweetpotato plants with the causal agents of SPVD influence the severity of symptoms and SPFMV titres in SPVD affected plants.     

Unexpected mode of action of sweet potato β-amylase on maltooligomer substrates

β-Amylase (EC 3.2.1.2), one of the main protein of the sweet potato, is an exo-working enzyme catalyzing the hydrolysis of α(1,4) glycosidic linkages in polysaccharides and removes successively maltose units from the non-reducing ends. The enzyme belongs to glycoside hydrolase GH14 family and inverts the anomeric configuration of the hydrolysis product. Multiple attack or processivity is an important property of polymer active enzymes and there is still limited information about the processivity of carbohydrate active enzymes. Action pattern and kinetic measurements of sweet potato β-amylase were made on a series of aromatic chromophor group-containing substrates (degree of polymerization DP 3-13) using HPLC method. Measured catalytic efficiencies increased with increasing DP of the substrates. Processive cleavage was observed on all substrates except the shortest pentamer. The mean number of steps without dissociation of enzyme–product complex increases with DP of substrate and reached 3.3 in case of CNPG11 indicating that processivity on longer substrates was more significant. A unique transglycosylation was observed on those substrates, which suffer processive cleavage and the substrates were re-built by the enzyme. Our results are the first presentation of a transglycosylation during an inverting glycosidase catalyzed hydrolysis. The yield of transglycosylation was remarkable high as shown in the change of the CNPG11 quantity. The CNPG11 concentration was doubled (from 0.24 to 0.54 mM) in the early phase of the reaction.     

Purification and Properties of meso-α,∊-Diaminopimelate Decarboxylase from Bacillus sphaericus

Soybean 7S and 11S globulins were stored at relative humidities (RHs) of 11% and 96% at 50°C. The redispersibility of the proteins at RH 96% decreased in a short time. However, it did not decrease, when stored for 45 days at RH 11%. Gel filtration showed that the proteins polymerized during storage. The effects of urea, sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (2-ME) on the redispersibilities of the proteins at RH 96% showed that the hydrogen, hydrophobic and disulfide bonds participate in the polymerization of 7S globulin, and that the disulfide bond is strongly related to the polymerization of 11S globulin. Redispersibility was restored with 2-ME in both the 7S and 11S globulins and some of the proteins in the supernatant redispersed with 2-ME were observed to be similar to the native ones with respect to the gel filtration, electrophoretic behavior and circular dichroism spectrum.     

Effect of Glucose on the Uricase Formation by Streptomyces sp

The effect of glucose on the formation of uricase by a strain of Streptomyces sp. incubated under conditions of nitrogen limitation was investigated. Glucose stimulated uricase formation in the presence of potassium ion and inhibited it in the absence of the ion. Glucose metabolism by the organism was altered in the absence of the ion, and this appeared to cause the inhibition of the enzyme formation. The stimulatory effect of glucose in the presence of potassium ion was to shorten the lag period. Comparisons of the enzyme formation with and without urate in the presence and absence of glucose revealed that glucose promoted the utilization of exogenous urate as the inducer. The effect of glucose appeared to require protein synthesis, since it was prevented by chloramphenicol. Cyclic adenosine 3′,5′-mono-phosphate showed apparently no effect on uricase formation of this organism.     

Optimization of the immobilization of sweet potato amylase using glutaraldehyde-agarose support. Characterization of the immobilized enzyme

A simplified procedure for the preparation of immobilized beta-amylase using non-purified extract from fresh sweet potato tubers is established in this paper, using differently activated agarose supports. Beta-amylase glutaraldehyde derivative was the preparation with best features, presenting improved temperature and pH stability and activity. The possibility of reusing the amylase was also shown, when this immobilized enzyme was fully active for five cycles of use. However, immobilization decreased enzyme activity to around 15%. This seems to be mainly due to diffusion limitations of the starch inside the pores of the biocatalyst particles. A fifteen-fold increase in the Km was noticed, while the decrease of Vmax was only 30% (10.1 U mg^?1 protein and 7.03 U mg^?1 protein for free and immobilized preparations, respectively).     

Oviposition avoidance of parasitized aphid colonies by the syrphid predator Episyrphus balteatus mediated by different cues

Oviposition decisions made by members of a guild of natural enemies can have evolved to avoid intraguild predation, potentially avoiding the disruption of the extraguild prey control. We have studied the oviposition preference of the aphidophagous predator Episyrphus balteatus De Geer (Diptera: Syrphidae) within colonies of Myzus persicae Sulzer (Hemiptera: Aphididae) in the presence of two developmental stages of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae). Results from a greenhouse choice experiment showed that E. balteatus females lay significantly fewer eggs in colonies with mummified aphids than in unparasitized colonies. Colonies of parasitized, but not yet mummified did not contain significantly fewer eggs than colonies with unparasitized aphids. In three no-choice experiments, we assessed stimuli coming from aphid honeydew, from the aphids themselves and also from extracts of the aphid bodies, and all of these stimuli mediate the discrimination of mummified aphids from healthy aphids. To a lesser extent these stimuli also contribute to the discrimination against aphids that are parasitized but not yet mummified. These results suggest that the effects of these two species could be complementary for the control of M. persicae, since the species that acts as an intraguild predator, E. balteatus, avoids ovipositing on aphid colonies parasitized by the intraguild prey, A. colemani.     

福建甘薯病毒病病原鉴定及主要病毒多样性

【背景】病毒病是甘薯的一种重要病害,给甘薯生产带来了严重的经济损失,而生产中甘薯病毒病病原种类复杂多样。【目的】明确福建甘薯病毒病种类、分布及流行,对主要病毒进行多样性分析。【方法】从福建主要甘薯种植区采集病毒病样品,利用PCR/RT-PCR的方法对采集的样品进行病原检测,获得病毒序列,利用MEGA 6.0构建系统进化树进行遗传分析。【结果】从福建7个甘薯产区鉴定12种甘薯病毒,包括9种RNA病毒:甘薯羽状斑驳病毒(Sweet potato feathery mottle virus,SPFMV)、甘薯褪绿矮化病毒(Sweet potato chlorotic stunt virus,SPCSV)、甘薯G病毒(Sweet potato virus G,SPVG)、甘薯C病毒(Sweet potato virus C,SPVC)、甘薯2号病毒(Sweet potato virus 2)、甘薯褪绿斑病毒(Sweet potato chlorotic fleck virus,SPCFV)、甘薯潜隐病毒(Sweet potato latent virus,SPLV)、甘薯轻型斑点病毒(Sweetpotatomildspeakingvirus,SPMSV)、黄瓜花叶病毒(Cucumber mosaic virus,CMV),3种DNA病毒:甘薯卷叶病毒(Sweet potato leaf curl virus,SPLCV),甘薯无症状1号病毒(Sweet potato symptomless virus 1,SPSMV-1),甘薯杆状DNA病毒B (SPBV-B)。SPFMV、SPCSV、SPVG和SPLCV检出率最高,分别为50.28%、41.90%、35.75%和24.58%,CMV检出率最低,为2.79%,未检测到甘薯C-6病毒(SweetpotatoC-6)和甘薯轻型斑驳病毒(Sweetpotatomild mottle virus,SPMMV)。福建甘薯主要以2-6种病毒复合侵染为主,单一侵染率占14.39%,2种以上复合侵染占85.61%。福建SPFMV分离物存在EA、O和RC3种株系,SPCSV分离物存在WA1种株系,未发现EA株系,甘薯卷叶病毒分属于2个不同的株系群。【结论】福建甘薯病毒种类多样,以复合侵染为主,且存在多种株系,遗传结构复杂。