巨桉根系分解对菊苣生长及光合特性的影响

巨桉是我国退耕还林过程中采用的重要速生树种之一,被广泛用于人工造林。采用盆栽试验,研究了巨桉根系分解初期对菊苣幼苗生长和光合生理特性的影响。试验设置A1(50 g/盆)、A2(100 g/盆)和对照(CK)3个根系水平,将各处理的根系分别与10 kg土壤混合后装盆,播种菊苣。待A2处理植株的第3片真叶完全展开后测定菊苣光合生理指标及相关生长指标。结果表明:在巨桉根系分解初期,明显抑制了菊苣高生长、根生长、生物量积累、叶面积扩展及光合色素的合成,且随着根系添加量的增加抑制作用加大;菊苣叶片胞间CO2浓度(Ci)增加,而净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)均显著低于对照;随土壤中根系含量的增加,除CO2补偿点(CCP)呈增加趋势外,其他光响应和CO2响应的特征参数均呈明显的下降趋势,并与对照差异显著;各生长指标除与胞间CO2浓度呈现出负相关外,与其它光合特征参数、光合色素以及相应的响应曲线参数之间均呈现出显著或极显著的正相关关系;通过GC-MS检测表明,巨桉根系中含有2,6-二叔丁基对甲酚、N-甲基苯乙胺等多种具有化感潜力化学物质,在其分解过程中,这些化感物质逐步释放并作用于受体植物,抑制其光合色素合成和光合作用,降低其环境适应能力,从而抑制菊苣的生长。     

黄鳝体内寄生胃瘤线虫的染色体核型及G-带分析

采用常规空气干燥法制片,对寄生于黄鳝(Monopterus albus)体腔内的胃瘤线虫(Eustrongylidesignotus)染色体核型进行分析。结果表明:胃瘤线虫体细胞有12条染色体,为二倍体,核型公式为2n=12=10 m+2 sm。由5对常染色体和1对性染色体组成,性别决定模式为XX-XY,其中X、Y和1～4号染色体都为中着丝粒染色体,5号为亚中着丝粒染色体。每对染色体都有特定的G-带带型。     

尾叶桉无性系生长、干形和抗枝瘿姬小蜂综合选择

对尾叶桉60个无性系进行了生长量和桉树枝瘿姬小蜂的敏感性调查。结果表明, 生长性状在无性系单株间存在显著的相关性,而尾叶桉受姬小蜂的危害情况与生长性状间无显著相关性。对遗传参数的估算表明, 尾叶桉无性系抗桉树枝瘿姬小蜂水平有较高的重复力,可以通过无性系选择获得抗蜂、速生的尾叶桉无性系。最终通过独立淘汰法选择出6个优良的尾叶桉无性系。     

成熟马占相思林的蒸腾耗水及年际变化

利用Granier测定系统对华南丘陵植被恢复先锋群落马占相思林的树干液流进行了连续4a(2004-2007年)的监测研究,以了解已过生长高峰的马占相思林(20-22林龄)的水分利用特征。结果显示,液流密度(J_s)日变化为单峰型曲线,具有明显的季节差异,湿季J_s日变化幅度和峰值J_smax均大于干季。J_s与光合有效辐射(PAR)和水汽压亏缺(VPD)的偏相关分析显示,J_s与PAR或VPD正相关,干季的相关性较湿季显著;线性回归分析显示PAR和VPD对J_s日变化共同影响的程度达62.7%-82.7%。马占相思整树和林分的蒸腾强度和耗水量均表现出明显的干湿季差异,湿季明显高于干季。偏相关分析表明降雨量对蒸腾活动没有显著的直接影响,而PAR与蒸腾量显著相关,是影响林分蒸腾量的最重要环境因子。2004-2007年各年马占相思成熟林的蒸腾耗水量为238.64、136.39、217.45mm和273.85mm,分别占当年降雨量的24.7%、11.7%、9.8%和22.8%,年平均蒸腾耗水量为243.31±28.49 mm(n=3),降水对林分蒸腾的影响不仅仅取决于降雨量的大小,较多的降雨频次往往会削弱蒸腾的强度。研究的马占相思林处于生长后期,群落叶面积指数和蒸腾已有明显的下降,反映出该阶段林分已不能充分利用当地的辐射和水分资源,必要的林分改造可提高造林后期的生产效益。     

Physico-chemical and antifungal properties of protease inhibitors from Acacia plumosa

This study was aimed at investigating the purification, biological activity, and some structural properties of three serine protease inhibitors isoforms, denoted ApTIA, ApTIB, and ApTIC from Acacia plumosa Lowe seeds. They were purified from the saline extract of the seeds, using Superdex-75 gel filtration and Mono-S ion exchange chromatography. They were further investigated by mass spectrometry, spectroscopic measurements, surface plasmon resonance, and inhibition assays with proteases and phytopathogenic fungi. The molecular mass of each isoform was estimated at ca. 20 kDa. Each contained two polypeptide chains linked by a disulfide bridge, with different isoelectric points that are acidic in nature. The N-terminal sequences of both chains indicated that they were Kunitz-type inhibitors. Circular dichroism (CD) analyses suggested the predominance of both disordered and beta-strands on ApTI isoforms secondary structure, as expected for β-II proteins. In addition, it was observed that the proteins were very stable, even at either extreme pH values or at high temperature, with denaturation midpoints close to 75 °C. The isoinhibitors could delay, up to 10 times, the blood coagulation time in vitro and inhibited action of trypsin (Ki 1.8 nM), α-chymotrypsin (Ki 10.3 nM) and kallikrein (Ki 0.58 μM). The binding of ApTIA, ApTIB, and ApTIC to trypsin and α-chymotrypsin, was investigated by surface plasmon resonance (SPR), this giving dissociation constants of 0.39, 0.56 and 0.56 nM with trypsin and 7.5, 6.9 and 3.5 nM with α-chymotrypsin, respectively. The growth profiles of Aspergillus niger, Thielaviopsis paradoxa and Colletotrichum sp. P10 were also inhibited by each isoforms. These three potent inhibitors from A. plumosa may therefore be of great interest as specific inhibitors to regulate proteolytic processes.     

Validating the in vitro antimicrobial activity of Artemisia afra in polyherbal combinations to treat respiratory infections

Artemisia afra is one of the most widely used medicinal plants in African traditional medicine and is commonly administered in polyherbal combinations to treat respiratory infections. Focussing on plant volatiles, the aim of this study was to provide scientific evidence for the antimicrobial activity of A. afra (principle plant) in combination with essential oils from three medicinal aromatic plants; Agathosma betulina, Eucalyptus globulus and Osmitopsis asteriscoides. In vitro minimum inhibitory concentration (MIC) assays were undertaken on four pathogens (Enterococcus faecalis ATCC 29212, Moraxella catarrhalis ATCC 23246, Klebsiella pneumoniae NCTC 9633 and Cryptococcus neoformans ATCC 90112) to determine antimicrobial efficacy of the oils and their combinations. The fractional inhibitory concentration (FIC) and isobolograms were used to interpret pharmacodynamic interactions such as synergy, antagonism or additive profiles. The antimicrobial activity of the individual oils mostly displayed moderate activity. Predominantly, additive interactions were noted. The most prominent synergistic interaction (FIC value of 0.5) was observed when A. afra was combined with O. asteriscoides in the 8:2 ratio (eight parts A. afra with two parts O. asteriscoides) against C. neoformans. No antagonistic interactions were evident.     

An unusual Xanthophyllomyces strain from leaves of Eucalyptus globulus in Chile

Xanthophyllomyces sp. was isolated as an epiphytic red yeast from leaves of Eucalyptus glo-bulus in Concepción, Chile. Sexual reproduction was by basidiospores produced from one or rarely two metabasidia arising from a yeast cell without preceding paedogamy. The main carotenoid pigment was astaxanthin. This isolate did not cluster with the X. dendrorhous complex (including Phaffia rhodozyma) in ITS and 26S rDNA-based phylogenetic analyses. The phylloplane may be a further habitat for Xanthophyllomyces, in addition to the well-known spring sap-flows of deciduous trees and the recently-characterised ascostromata of Cyttaria hariotii.     

Volatiles associated with different flower stages and leaves of Acacia cyclops and their potential role as host attractants for Dasineura dielsi (Diptera: Cecidomyiidae)

Acacia cyclops (Fabaceae) is an Australian species which was introduced into South Africa in the nineteenth century. Because of its invasive status in South Africa, a gall midge, Dasineura dielsi (Diptera: Cecidomyiidae), was released in 2001 in order to impact its reproduction by inducing galls on the flowers and thereby preventing seed set. Nothing is known about the cues used by D. dielsi for locating its host flowers. As part of an initial investigation into whether or not chemical cues might play a role in host finding, we analysed headspace samples of Acacia cyclops volatiles from leaves and reproductive parts at different stages (early bud, late bud, early flowering, and senescing flowering stages) using gas chromatography–mass spectrometry (GC–MS). In total, 72 different compounds were detected of which 62 were identified. The analyses showed that open flowers, the stage used by D. dielsi for oviposition, and yellow buds had similar odour compositions with (Z)-3-hexen-1-ol acetate, 4-oxoisophorone, (Z)-β-ocimene, an unknown aliphatic compound, heptadecane, and nonadecane dominating in open flowers. Leaf volatiles were distinct from those in the reproductive plant parts by their high relative amount of (Z)-β-ocimene. (Z)-3-Hexen-1-ol acetate had its maximum relative amount in the green bud samples and was much lower in the later floral stages. In contrast, 4-oxoisophorone peaked in yellow buds and open flowers with little or none of it found in younger or older stages. The volatile compounds of the different flower stages and leaves are discussed in relation to their potential role as attractants used by the biocontrol agent D. dielsi to locate its host plant.     

不同林龄尾巨桉人工林的生物量及其分配特征

根据1,2,3,5,8a共5个不同年龄的15块1000 m2尾巨桉样地(3次重复)调查资料,利用18株不同年龄和径阶的样木数据,建立以胸径(D)为单变量的生物量回归方程。采用样木回归分析法(乔木层)和样方收获法(灌木层、草本层、地上凋落物)获取不同林龄尾巨桉人工林的生物量,分析了其组成、分配及不同林龄生物量的变化趋势。结果表明:林分总生物量随林龄而增加,1,2,3,5年生和8年生尾巨桉人工林生物量分别为12.49,47.75,64.51,105.77和137.51 t/hm2,其中活体植物占85.60%—97.61%,地上凋落物占2.39%—14.40%;层次分配方面乔木层占绝对优势,占54.80%—91.56%,且随林龄的增加而增大,其次为凋落物,灌木层和草本层生物量较小,分别占1.02%—6.47%和0.28%—24.33%,均随林龄的增加呈递减趋势;乔木层以干所占比例最高,占51.07%—98.48%,且随林龄而增加,枝、叶、根分别占5.76%—11.80%,2.17%—21.01%和6.72%—14.87%,均随林龄而下降;灌木层以枝所占比例最高,为37.89%—56.79%,叶和根分别占16.35%—34.24%和19.52%—39.52%,随林龄的变化均不大;草本层分配1—5年生以地上所占比例较大,8年生地下所占比例高达63.87%;尾巨桉人工林乔木层各器官、地上凋落物及总生物量具有良好的优化增长模型,其总生物量的增长模型为Y=-1.693×104+3.337×104X-1.761X2;8年生尾巨桉人工林总生物量与30年生的木莲人工林持平,低于热带雨林,但其年均净生产量高达17.19 t/hm2,是一个光合效率高、固碳潜力大的速生丰产优良造林树种。     

Ultrastructure of the spermatozoon of the digenean Cricocephalus albus (Kuhl & van Hasselt, 1822) Looss, 1899 (Platyhelminthes, Pronocephaloidea, Pronocephalidae), parasite of “the hawksbill sea turtle” Eretmochelys imbricata (Linnaeus, 1766) in Senegal

The mature spermatozoon of Cricocephalus albus is filiform, tapered at both ends and shows the following features: 2 axonemes of different lengths presenting the 9 + “1” trepaxonematan pattern, 2 bundles of parallel cortical microtubules, a mitochondrion and a nucleus. Nevertheless, the particularity of the spermatozoon of C. albus is its anterior extremity with an apical electron-dense material associated with extramembranar ornamentation, a cytoplasmic dorsolateral expansion and spine-like bodies. To our knowledge, such an anterior extremity of the spermatozoon has not previously been described from a species of the superfamily Pronocephaloidea. Our study provides new data on the mature gamete of C. albus in order to improve our understanding of the pronocephaloidean phylogenetic relationships.     

Phenotypic and genotypic characterization of rhizobia associated with Acacia saligna (Labill.) Wendl. in nurseries from Algeria

Twenty seven rhizobial strains associated with Acacia saligna grown in northern and southern Algeria were characterized, including generation time, host-range, the 16S rRNA gene and 16S–23S rRNA intergenic spacer restriction patterns, 16S rRNA gene sequence analysis and tolerance to salinity and drought. Cross inoculation tests indicated that 11 slow-growing isolates from northern nurseries were able to nodulate introduced Australian acacias exclusively, whereas 16 fast-growing isolates, mainly from southern nurseries, were capable of also nodulating native acacias. Restriction patterns and sequence analysis of the 16S rRNA gene showed that strains of the first group belonged to Bradyrhizobium while strains of the second group were related to Sinorhizobium meliloti and Rhizobium gallicum. Interestingly, five strains of the first group formed a distinct cluster phylogenetically close to Bradyrhizobium betae, a non-nodulating species causing tumour-like deformations in sugar beet roots. Bradyrhizobium strains were in general more sensitive to NaCl and PEG than the S. meliloti and R. gallicum representatives. Among the latter, strains S. meliloti BEC1 and R. gallicum DJA2 were able to tolerate up to 1 M NaCl and 20% PEG. This, together with their wide host-range among Acacia species, make them good candidates for developing inoculants for A. saligna and other acacia trees growing in arid areas.     

福州酸雨区次生林中台湾相思与银合欢叶片的12种元素含量

在酸雨区,研究叶片元素浓度变化规律对于理解树种选择与重建亚热带森林具有重要意义。在中亚热带丘陵次生林的酸雨区内,测定两个优势树种——台湾相思树(Acacia confusa)、银合欢(Leucaena glauca)的叶片元素(N、P、S、K、Ca、Na、Mg、Fe、Mn、Cu、Zn和Al)含量,并探讨其可能遭受酸雨的影响。结果表明,两树种叶片营养元素含量均表现为N > K > Ca > S > P > Mg > Na,重金属元素表现为Fe > Al > Cu。两树种叶片的P、Ca、Mg、Na、Mn和Cu含量差异极显著,Zn含量差异显著。受频繁酸雨影响,台湾相思(3.42 g/kg)和银合欢(2.70 g/kg)的S含量明显高于中国陆生被子植物叶片的平均值((1.66±3.06) g/kg),Na含量低于S含量,也明显低于中国陆生被子植物叶片Na含量的平均值((2.48±5.45)g/kg),表明研究区域植物叶片的Na元素的特异性,酸雨加速土壤酸化导致土壤Na含量低可能是一个原因。由N/P、Ca/Al摩尔比值的大小可得出,台湾相思为P制约型树种,虽然其Al含量并未超出正常范围值,但其Ca/Al摩尔比值小于12.5,表明存在Al的危害风险;而银合欢属N制约型树种,并未受到Al的危害,更适应研究区生长环境。若仅从叶片元素含量分析,该区域的台湾相思和银合欢受到Fe危害风险,且存在更大的Cu和Zn危害风险,银合欢的Zn、Cu元素累积量大于台湾相思,所以可以认为银合欢的抗性强于台湾相思,可能更适应于酸雨区域生长。     

Inhibitory effects of leachate from Eupatorium adenophorum on germination and growth of Amaranthus retroflexus and Chenopodium glaucum

Amaranthus retroflexus L. and Chenopodium glaucum L. are two widely distributed destructive weeds. Their strong adaptability and massive seed production make them the hardest weeds to deal with. This present study intended to investigate the effect of leachate from Eupatorium adenophorum on the growth of these weeds and explore the potential to develop an environmental friendly strategy to use the leachate to control the weeds. Seeds of A. retroflexus L. and C. glaucum L. were soaked in solutions containing 0%, 0.6%, 1.25%, 2.5%, and 5% leachate from E. adenophorum leaves. A. retroflexus and C. glaucum seedlings grown in pots were sprayed with leachate solutions in the same concentration range. The effects of these leachate solutions on membrane permeability and germination of seeds, and growth and physiological characteristics of the seedlings were investigated. The highest concentration of leachate (5%) caused significant damage to the cell membrane of seeds of both weed species, whereas lower concentrations (0.6%) promoted repair of the membrane system, as reflected by higher and lower than control in relative conductivity (RC), respectively. Different concentrations of leachate showed distinct allelopathic inhibitory effects on the two weed species; lower concentrations showed weak inhibitory or even positive effects, whereas higher concentrations showed stronger inhibitory effects. Higher concentrations of leachate (2.5% and 5%) delayed germination and significantly decreased the emergence rate of the seeds, survival rate, and dry matter accumulation of the seedlings. When treated by 5% leachate, the emergence date of A. retroflexus was delayed by 3.6 d, emergence rate of the seeds and survival rate was 69.1% and 70.6% of the control, respectively, seedling dry matter was 48.6% less than the control; In the case of C. glaucum, the emergence date was delayed by 2.7 d, emergence rate of the seeds and survival rate was 45.1% and 58.6% of the control, respectively, seedling dry matter was 44.7% less than the control. There were significant interactions among the different concentrations of leachate and the length of treatment period with respect to activities of antioxidant enzymes, malondialdehyde (MDA) contents, and chlorophyll contents. Seedlings treated with 0.6%, 1.25%, or 2.5% leachate solution for 24–72 h showed increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. When seedlings were treated with leachate solutions for 96 h, antioxidant enzyme activities and chlorophyll content decreased in A. retroflexus, but only CAT activity decreased in C. glaucum. When seedlings of the two weed species were treated with 5% leachate solution, CAT activity and chlorophyll content decreased and MDA content gradually increased with longer treatment times (from 24 to 96 h). The two weed species showed different allelopathic responses to E. adenophorum; A. retroflexus was more sensitive than C. glaucum. Based on the investigation, it could be speculated that the delayed germination and low germination rate of the weeds after treatment by leachate could be due to the fact that leachate damaged the membrane system of the seeds. By delaying germination, lowering the germination rate of the weeds and inhibiting seedling growth, leachate from E. adenophorum could provide an effective way of controlling the weeds.     

Combinatorial effect of endophytic and plant growth promoting rhizobacteria against wilt disease of Capsicum annum L. caused by Fusarium solani

Combination of biocontrol agents that are compatible with each other is a strategic approach to control the plant disease and pest. The present study was designed to evaluate the protective effects of compatible endophytic bacterial strains (Bacillus subtilis; EPCO16 and EPC5) and rhizobacterial strain (Pseudomonas fluorescens; Pf1) against chilli wilt disease caused by Fusarium solani. Our results showed that B. subtilis (EPCO16 and EPC5) and P. fluorescens (Pf1) were compatible and effectively inhibited the growth of the F. solani. The application of endophytic and rhizobacterial strains, singly and in combination in green house and field conditions were found to be effective in controlling the chilli Fusarium wilt disease by inducing systemic resistance (ISR) as evidenced by enhanced activities of PO, PPO, PAL, β-1,3-glucanase, Chitinase and Phenolic involved in the synthesis of phytolaexins thereby promoting the growth of plants. However, combinations of EPCO16 + EPC5 + Pf1 bacterial strains were more effective than single agents. These findings suggest that synergistic interactions of biocontrol agents may be responsible for the management of chilli wilt disease caused by F. solani.     

Dietary nitrogen availability in macroalgae enhances growth of the sea hare Aplysia californica (Opisthobranchia: Anaspidea)

Evidence suggests that marine herbivores select for prey items with elevated nitrogen content. We tested this hypothesis with experimental growth studies of the herbivorous gastropod Aplysia californica offered diets of the rhodophyte Gracilaria ferox with varying nitrogen content. A. californica had a sevenfold feeding preference by weight for G. ferox with higher tissue % N and % protein, and lower % C, % carbohydrate and carbon-to-nitrogen ratio (C/N) as compared to treatments with lower nitrogen and protein content. A. californica provided treatment diets of varying nitrogen availability (high, medium and low) also had significantly different growth rates within 30 days. The high N diet supported a two-fold higher growth rate than that of the medium N diet and four-fold higher than the low N treatment, with mean weights over the experiment reaching 20.4, 9.8, and 5.6 g, respectively. The evolutionary value of this dietary preference may facilitate faster growth to reproductive size, outgrowth of predators and sequestration of organic compounds from nitrogen-enriched macroalgae to deter predators. Despite recent attention, the importance of diet-derived compounds as anti-predatory chemical defenses in Aplysiids remains equivocal. Nitrogen-enriched macroalgal diets, however, may provide “primary metabolites” that serve as alternative defenses for Aplysiids.     

AMPK supports growth in Drosophila by regulating muscle activity and nutrient uptake in the gut

The larval phase of the Drosophila life cycle is characterized by constant food intake, resulting in a two hundred-fold increase in mass over four days. Here we show that the conserved energy sensor AMPK is essential for nutrient intake in Drosophila. Mutants lacking dAMPKα are small, with low triglyceride levels, small fat body cells and early pupal lethality. Using mosaic analysis, we find that dAMPKα functions as a nonautonomous regulator of cell growth. Nutrient absorption is impaired in dAMPKα mutants, and this defect stems not from altered gut epithelial cell polarity but from impaired peristaltic activity. Expression of a wild-type dAMPKα transgene or an activated version of the AMPK target myosin regulatory light chain (MRLC) in the dAMPKα mutant visceral musculature restores gut function and growth. These data suggest strongly that AMPK regulates visceral smooth muscle function through phosphorylation of MRLC. Furthermore, our data show that in Drosophila, AMPK performs an essential cell-nonautonomous function, serving the needs of the organism by promoting activity of the visceral musculature and, consequently, nutrient intake.