Stem Sections Research Articles

First Report of Damping-Off in Actinidia argute (Tara Vine) Caused by Fusarium proliferatum in China

Actinidia argute (tara vine) is a deciduous, fast-growing, twining woody vine typically grown for its attractive foliage and edible fruit and native to Japan, Korea, northern China, and the Russian Far East (Latocha et al. 2013). In March 2019, severe damping-off was observed in a base for seedling cultivation of A. argute located on Taihu farm of Jingzhou (N 111°15′, W 29°26′), Hubei province, China. Disease incidence in variety Longcheng No. 2 was approximately 30%, which resulted in severe seedling loss. At the early stage of the disease, seedlings showed symptoms of light to dark brown lesions on the lower stems near the soil and root necrosis. Finally, the seedlings became wilted and rotted. To isolate the pathogen, stem sections (3 × 2 mm) from 20 individual plants with symptoms were surface sterilized with 75% ethanol for 30 s and 2% NaOCl for 1 min. The sterilized tissue was rinsed four times with sterilized water and then put on potato dextrose agar (PDA) amended with 50 μg/ml of ampicillin and kanamycin to incubate at 25°C in the dark for 5 days. Isolated colonies were subcultured by the hyphal tip transferring method. Sixteen fungal isolates were obtained from 16 sterilized tissues, except for four tissues. Through the preliminary inoculation tests, we found that 13 isolates showed damping-off symptoms, except for three isolates. These 13 isolates with pathogenicity showed similar morphological characteristics with white to salmon pink colonies on PDA and abundant white aerial hyphae. Mung bean soup (MBS) medium was used to stimulate conidia production. Macroconidia were long, sickle shaped, three to four septa, 37.29 ± 6.03 × 3.56 ± 0.40 μm (n = 50), and microconidia were short oval, zero to one septa, 8.92 ± 1.74 × 2.88 ± 0.36 μm (n = 50). The isolation was identified as Fusarium sp. based on morphological characteristics (Leslie and Summerell 2006). Total genomic DNA of 13 isolates was extracted with the CTAB method (Stenglein and Balatti 2006). The ITS gene of all were sequenced using primers ITS4/ITS5 (White et al. 1990) and differed by only 1 or 2 bp of 466 nt total. A representative isolate, RZ1901, was used for further characterization using translation elongation factor 1α (EF-1α) (EF-728F/EF-986R) (Carbone and Kohn 1999) and β-tubulin genes (BT2-a/BT2-b) (Glass and Donaldson 1995), respectively. ITS (accession no. MN095191), EF-1α (MN227186), and β-tubulin (MN103540) sequences were deposited in GenBank. Three sequences were analyzed via FUSARIUM-ID (http://fusariumdb.org/index.php) and Fusarium MLST (http://www.wi.knaw.nl/fusarium/) and showed at least 99.57% identity to F. proliferatum (CBS130179, CBS 217.76, and NRRL 22109). For the pathogenicity test, isolate RZ1901 was cultured in MBS for 1 week to get spore suspension. Stems and main roots of 20 healthy 2.5-month-old A. argute seedlings were wounded by sterilized insect needle and soaked in RZ1901 conidial suspension (10⁶ spores/ml) for 60 min, and 10 seedlings with sterile distilled water were used as a control. All plants were transplanted to pots filled with autoclaved (121°C) peat moss and placed in a greenhouse (25 ± 2°C, 65% relative humidity). After 3 weeks, damping-off symptoms were observed on inoculated seedlings, similar to the diseased seedlings in the field. But there were no symptoms for the controls. The experiment was repeated twice. Reisolation was performed with surface-sterilized tissue from symptomatic seedlings in one experiment. Fungal isolates were confirmed as F. proliferatum based on morphological and molecular characters. F. proliferatum, a soilborne pathogen with a wide host range, has been reported to cause soybean damping-off in the United States (Diaz Arias et al. 2011). To our knowledge, this is the first report of damping-off by F. proliferatum on A. argute in China. The intensity and crop loss of this disease will be carefully monitored to determine if management strategies are justified for control.

Detailed Pharmacognostical and Phytochemical Screening of Stem and Stem Bark of Ficus semicordata Buch.-Ham. Ex sm. - An Extra Pharmacopoeial Drug of Ayurveda

Introduction: Stem bark of Bhumi udumbara (Ficus semicordata Buch.-Ham. ex Sm.) is used traditionally in the treatment of leprosy, ulcer, dysentery, wound, pregnancy, complaints of gastric, liver, bladder and various disorders. In present study, stem and stem bark of F. semicordata are explored for their microscopic including powder microscopy, physiochemical and preliminary phytochemical aspects. Materials and Methods: Stem and stem bark of the plant, after proper authentication by BSI Kolkata, were evaluated following standard procedures. Results: Stem is hard, cylindrical, cut pieces measures about 10 - 25cm in length and 0.4 – 0.8 cm in diameter. Diagrammatic transverse section of stem shows outer cork followed by wide parenchymatous cortex with prismatic and rhomboidal crystals, starch grains and tannin content. Powder light brown in colour; odour woody; taste tasteless to astringent; texture fibrous. Stem bark is hard, single quilled after drying, outer dark reddish brown in colour with presence of lenticels, longitudinal cut fibres, rough in surface. Diagrammatic section, of the bark, shows outer several layered cork followed by cortical region along with medullary rays. Powder tortilla(brown) in colour; odour slightly aromatic; taste astringent; texture fibrous. Loss on drying at 110°C was found to be 7.41% and 8.60% of stem and stem bark respectively. HPTLC results shows 3 peaks and 0 peak at 254 and 366 nm of stem and 3 peaks at 254 and 366 nm of stem bark respectively. Discussion and Conclusion: Woody stem and presence of brown content, tannin, rhomboidal and prismatic crystals in stem and stem bark are the diagnostic characters.

A quantitative approach for assessing bark beetle infestations: A study of Pityokteines spinidens Reitt. egg gallery densities in windthrown Abies alba Mill.

Abstract The presented statistical method enables monitoring of bark beetles that colonise different parts of the windthrown tree stem at different densities. The bark beetle, Pityokteines spinidens Reitt. occurring in forests with the fir Abies alba Mill. was used as an example. We propose a three-step statistical procedure. In the first step, a hierarchical cluster analysis (HCA), the single gamma function, and the gamma mixture distributions are used to model the distribution of egg galleries of P. spinidens along an A. alba windthrown stem. In the second step, a generalised linear model (GLM) and a generalised additive model (GAM) are employed to analyse the relationships between the number of P. spinidens egg galleries in selected stem sections and the total P. spinidens egg gallery density on the entire A. alba windthrown stem. In the third step, the mean total P. spinidens egg gallery density in the investigated area is estimated using survey sampling with simple random sampling without replacement (SRSWOR). The first and second steps allow us to identify which sections of the A. alba windthrown stem should be evaluated to adequately estimate the total egg gallery density (to save time and money and to reduce the amount of debarking performed per tree). The third step enables the calculation of the estimated relative standard error (to analyse the precision of the proposed method). Data were collected between 1994 and 2003 (data set D1) and in 2014 (data set D2) in forests including A. alba in the Świetokrzyski National Park, Poland. D1 was used to build the GLM and GAM, while D2 was employed to validate the models and to illustrate the proposed method. Six main types of egg gallery distributions along the stem were distinguished. P. spinidens inhabited all parts of the stem of A. alba windthrowns. Validation of the models suggested that the GAM performed better than the GLM. The predicted and observed data were closely consistent. This statistical evaluation of P. spinidens egg gallery densities will aid in the assessment of the ecological roles played by this species in A. alba ecosystems. Similar statistical approaches can be developed for other bark beetles colonising tree stems.

Systemic Root-Shoot Signaling Drives Jasmonate-Based Root Defense against Nematodes.

Shoot-root communication is crucial for plant adaptation to environmental changes. However, the extensive crosstalk between shoots and roots that controls the synthesis of jasmonates (JAs), in order to enhance defense responses against rhizosphere herbivores, remains poorly understood. Here, we report that the root-knot nematode (RKN) Meloidogyne incognita induces the systemic transmission of electrical and reactive oxygen species (ROS) signals from attacked tomato roots to the leaves, leading to an increased accumulation of JAs in the leaves. Grafting of 1.0-cm stem sections from mutants lacking GLUTAMATE RECEPTOR-LIKE 3.5 or the mutants deficient in RESPIRATORY BURST OXIDASE HOMOLOG 1 abolished the RKN-induced electrical signals and associated ROS and JA accumulation in the upper stems and leaves with attenuated resistance to RKN. Furthermore, the absence of systemic transmission of electrical and ROS signals compromised the activation of mitogen-activated protein kinases (MPKs) 1/2 in leaves. Silencing MPK1 or MPK2 abolished RKN-induced accumulation of JAs and associated resistance. These findings reveal a systemic signaling loop that integrates electrical, ROS, and JA signals to enhance the resistance in distal organs via root-shoot-root communication.

Anatomical structure associated with vegetative growth variation in macadamia

Low-vigour scion cultivars and dwarfing rootstocks are a significant contributing factor to the success of modern temperate orchard systems. Planting density and canopy efficiency are currently limited in macadamia by a lack of low-vigour cultivars and rootstocks. The relationships between xylem vessel diameter, hydraulic conductivity and vigour are implicated in dwarf cultivars and low-vigour rootstocks of peach and apple. This study aims to determine relationships between vessel anatomy and tree-scale vigour in subtropical macadamia, to stimulate the development of low vigour cultivars and dwarfing rootstocks. Stem sections from the most recent mature flush were collected from five replicates of three macadamia cultivars: ‘D4’ (high vigour), ‘B25’ (intermediate vigour) and ‘B63’ (low vigour). Sections were imaged under a fluorescence microscope in order to measure the number and size of all xylem vessels in the stem. The three cultivars showed distinct differences in height over 5 years of measurement (P < 0.001). Change in tree height related to the xylem vessel characteristics of mean vessel area of the ten largest vessels per section (R2 = 0.57, P < 0.001), pith size (R2 = 0.70, P < 0.001) and total additive vessel area (R2 = 0.41, P < 0.01). This study indicates that relationships between anatomical structure and vigour in macadamia are likely to be similar to those of well-studied temperate tree crops and that anatomical traits may be useful in the selection of low-vigour cultivars. Future work should investigate hydraulic relationships with vigour and rootstock-scion interactions in macadamia.

Turing-like mechanism in a stochastic reaction-diffusion model recreates three dimensional vascular patterning of plant stems.

Vascular tissue in plants provides a resource distribution network for water and nutrients that exhibits remarkable diversity in patterning among different species. In many succulent plants, the vascular network includes longitudinally-oriented supplemental vascular bundles (SVBs) in the central core of the succulent stems and roots in addition to the more typical zone of vascular tissue development (vascular cambium) in a cylinder at the periphery of the succulent organ. Plant SVBs evolved in over 38 plant families often in tandem with evolutionary increases in stem and root parenchyma storage tissue, so it is of interest to understand the evolutionary-developmental processes responsible for their recurrent evolution and patterning. Previous mathematical models have successfully recreated the two-dimensional vascular patterns in stem and root cross sections, but such models have yet to recreate three-dimensional vascular patterning. Here, a stochastic reaction-diffusion model of plant vascular bundle patterning is developed in an effort to highlight a potential mechanism of three dimensional patterning–Turing pattern formation coupled with longitudinal efflux of a regulatory molecule. A relatively simple model of four or five molecules recreated empirical SVB patterns and many other common vascular arrangements. SVBs failed to develop below a threshold width of parenchymatous tissues, suggesting a mechanism of evolutionary character loss due to changes in the spatial context in which development takes place. Altered diffusion rates of the modeled activator and substrate molecules affected the number and size of the simulated SVBs. This work provides a first mathematical model employing a stochastic Turing-type mechanism that recreates three dimensional vascular patterns seen in plant stems. The model offers predictions that can be tested using molecular-genetic approaches. Evolutionary-developmental ramifications concerning evolution of diffusion rates, organ size and geometry are discussed.

Morphological variation and the relationship with host leaves in the epiphyllous liverwort Cololejeunea chenii Tixier (Marchantiophyta: Lejeuneaceae)

Cololejeunea (Spruce 1884: 291) Stephani (1891: 208), with over 400 published binominals, is the largest genus of Lejeuneaceae Cavers (1910: 291) and the most species of the genus are distributed in the tropical and subtropical regions (Zhu &amp; So 2001, Yu et al. 2013). These usually small sized liverworts grow preferably in extreme habitats, such as on the surface of living leaves, on twigs, or in running water (Gradstein et al. 2003). The currently accepted generic concept of the genus is based on its incubous foliation, leaves consisting of a dorsal lobe and a ventral lobule, Lejeunea-type branching, lack of underleaves, and transverse section of stem comprising of 5(–8) cortical cells and 1 medullary cell (Yu et al. 2013, and references therein).

First Report of Neofusicoccum parvum Causing Stem Canker and Necrosis of Phoebe sheareri in Zhejiang Province, China

Phoebe sheareri is a popular species established in Zhejiang province of China for timber. During surveys in June 2016, severe canker problems were observed in one plantation of P. sheareri in Kaihua county, Zhejiang. The disease started with black fusiform necrosis (8 to 15 mm long, 3 to 5 mm wide) on the green bark of shoots, and the cankers could be found on branches and even the main stem (with diameter up to 10 cm). These cankers can girdle stems, resulting in the death of plant tissues above. Ten stem sections containing the junction between healthy and necrotic xylem from five symptomatic trees were collected. Sections of symptomatic xylem were surface sterilized in 5% sodium hypochlorite water solution and placed on potato dextrose agar (PDA) at 25°C in the dark. After 3 days, seven isolates were generated by subculturing single hyphal tips onto fresh PDA medium and grown for 7 days in the dark. All seven isolates initially developed white aerial mycelium that later turned dark gray. After 2 weeks, black globular pycnidia could be found. The fusiform hyaline conidia were aseptate, with thin walls, and measured 20.9 ± 2.2 × 5.1 ± 0.4 μm. Three isolates (KHZJZ1 to KHZJZ3, respectively) were selected randomly for molecular characterization. The rDNA internal transcribed spacer (ITS), partial β-tubulin (tub2), and translation elongation factor 1-α (tef1) gene regions were amplified by polymerase chain reaction using the primer pairs ITS1/ITS4, Bt2a/Bt2b, and EF1-728F/EF1-986R, respectively (Alves et al. 2008; Glass and Donaldson 1995; White et al. 1990). Gene sequences of all three fungal isolates were identical. The ITS, tub2, and tef1 sequences were deposited in GenBank (accession nos. MK131330, MK139576, and MK139575, respectively). A local BLASTn search revealed that the ITS, tub2, and tef1 sequences shared 99, 99, and 100% identity, respectively, to corresponding sequences of ex-type isolate Neofusicoccum parvum strain CMW9081 (accession nos. AY236943, AY236917, and AY236888, respectively). Pathogenicity tests were conducted by wounding stems of 2-year-old P. sheareri seedlings with a 5-mm-diameter cork borer. Wounds were inoculated with PDA plugs excised from 7-day-old cultures of the N. parvum isolate (KHZJZ1). Stems inoculated with sterile PDA plugs acted as controls. The inoculated stem wounds were wrapped with Parafilm, and the seedlings were kept under natural conditions grown in the field (18 to 30°C). There were five replicates of each treatment. After 21 days, the N. parvum-inoculated stems had developed black necrotic lesions (11 ± 5 mm long) on the bark, whereas the control plants remained asymptomatic. The fungus was reisolated from diseased plant tissue but not from the controls, thus fulfilling Koch’s postulates. N. parvum has previously been reported as the causal agent of canker and die-back of Eucalyptus (Iturritxa et al. 2011), stem blight of blueberry (Koike et al. 2014), and canker of other woody plants (Jayakumar et al. 2011). To our knowledge, this is the first report of N. parvum causing canker of P. sheareri, which is becoming increasingly important in timber plantations in south China.

Mass spectrometry imaging guided molecular networking to expedite discovery and structural analysis of agarwood natural products

Structural analysis of biomolecules is essential to natural product discovery, especially for precious biomaterials such as agarwood. However, one of the greatest challenges to the characterization of natural products is the profound cost in time and manpower to the structural elucidation of these highly diverse compounds. Here, we demonstrate a multi-modal mass spectrometric strategy, integrating matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) and mass spectral molecular networking, to uncover agarwood natural products of Aquilaria sinensis trees. A simple workflow for preparing wood sections for MALDI-MSI analysis was demonstrated. Notably, tens of natural products in the agarwood region in wood stem section of A. sinensis were spatially revealed by MALDI-MSI. For the first time, such a great number of plant specialized metabolites is obtained by a single wood section MSI. Guided by the spatially resolved features, mass spectral molecular networking was subsequently applied for structural analysis of the agarwood natural products, in which three major classes of 2-(2-phenylethyl)chromones and their analogues were putatively characterized. These results suggest an efficient strategy to the dereplication of plant natural products.

Endophytic ability of the insecticidal bacterium Brevibacillus laterosporus in Brassica.

Brevibacillus laterosporus (Bl), is an insecticidal bacterium recorded as toxic to a range of invertebrates after ingestion. Isolates of Bl, which were initially recovered from surface-sterilised cabbage (Brassica oleracea var. capitata) seeds, were able to colonise brassica plants in the laboratory and field. The bacterium was recovered from surface-sterilised leaf, stem and root sections of seedlings after inoculation with Bl vegetative cells under laboratory conditions, and from mature cabbage plants sprayed with Bl in a field trial. The identity of the recovered bacterial isolates was confirmed by PCR through amplification of 16S rDNA and two strain-specific regions. The effect on diamondback moth (DBM) insect herbivory was tested with cabbage seedlings treated with one isolate (Bl 1951) as the strains are toxic to DBM after direct ingestion. While no effect on DBM larval herbivory was observed, there was a significant reduction of DBM pupation on the Bl 1951 colonised plants. The presence of Bl 1951 wild type cells within cabbage root tissue was confirmed by confocal microscopy, establishing the endophytic nature of the bacterium. The bacterium was also endophytic in three other brassica species tested, Chinese kale (Brassica oleracea var. alboglabra), oilseed rape (Brassica napus var. oleifera) and radish (Raphanus sativus).

Axial diffusion of respired CO2 confounds stem respiration estimates during the dormant season

Efflux-based estimates of stem respiration in oak trees during the dormant season were biased by axial diffusion of locally respired CO 2 . Light-induced axial CO 2 diffusion along the stem due to woody tissue photosynthesis may lead to equivocal estimates of stem respiratory coefficients during the dormant season, which are generally used to estimate maintenance respiration throughout the year. Stem CO2 efflux (EA) does not reflect respiratory rates of underlying tissues. Recent research has focused on the significance of CO2 transport via the transpiration stream. However, no studies have yet addressed the potential role of light-induced axial CO2 diffusion on EA during the dormant season when there is no transpiration. This study investigated to which extent woody tissue photosynthesis and axial diffusion of respired CO2 affect EA during the dormant season. EA was measured in a stem cuvette on dormant oak trees in a growth chamber at constant temperature. Different rates of axial CO2 diffusion were induced by woody tissue photosynthesis by means of illuminating stem sections at varying distances from the stem cuvette, while light was excluded from the remainder of the tree. Axial diffusion of respired CO2 led to reductions in EA of up to 22% when the stem section closest to the cuvette was exposed to light. Dormant-season efflux-based estimates of stem respiration might be biased by axial diffusion of respired CO2, particularly in open forest stands with sufficient light penetration. Consequently, this may lead to ambiguous estimates of dormant season EA coefficients (Q10 and EA_0) generally used to estimate maintenance respiration throughout the year.

A comparison of callus induction in 4 Garcinia species

Abstract Background This research is intended to determine suitable types and concentrations of plant growth regulators (PGRs) to induce callus on stem and leaf sections of 4 species of the genus Garcinia, namely, Garcinia mangostana, Garcinia schomburgkiana, Garcinia cowa, and Garcinia celebica. The base medium was MS medium containing 30 g l-1 sucrose, 0.5 g l-1 polyvinylpyrrolidone (PVP), and 7 g l-1 agar, and for the different treatments, PGRs were added to the medium as follows: thidiazuron (TDZ) at concentrations of 0, 0.1, 0.5, 1, and 2 mg l-1; 6-(3-hydroxybenzylamino) purine (meta-topolin) at concentrations of 0, 0.5, 2.5, and 5 mg l-1; 4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid (picloram) at concentrations of 0, 0.5, 2.5, and 5 mg l-1; and 2,4-dichlorophenoxyacetic acid (2,4-D) at concentrations of 0, 0.5, 1, 2, and 4 mg l-1. The occurrence of callus was observed after 4 weeks. Results A maximum of 100% and 93% of G. mangostana leaf explants formed callus in the 0.5 mg l-1 and 1 mg l-1 TDZ treatments, respectively, while 100% of G. schomburgkiana stem explants formed callus in the 1 mg l-1 TDZ treatment and 89% of G. schomburgkiana leaf explants formed callus in the 0.5 mg l-1 picloram treatment. The highest callus induction rate for G. cowa was 62% in the 1 mg l-1 TDZ treatment and for G. celebica was 56% in the 0.5 mg l-1·mT-1 treatment. Conclusions For all 4 species, the greatest amount of large nodular callus was observed in the TDZ treatments. White, friable callus was observed on most of the 2,4-D and picloram treatment groups. Most meta-topolin treatments resulted in minimal callus formation. How to cite: Suwanseree V, Phansiri S, Yapwattanaphun C. A comparison of callus induction in 4 Garcinia species. Electron J Biotechnol 2019;40. https://doi.org/10.1016/j.ejbt.2019.04.006

Effect of irrigation on charcoal rot severity, yield loss and colonization of soybean and sunflower

Charcoal rot incidence in soybean and sunflower in South Africa is increasing. Irrigation as a means to manage charcoal rot is limited as water resources are decreasing and oil seed production is predominantly on dry land. The effect of reduced soil moisture on charcoal rot incidence, severity and colonization of host tissues, as well as subsequent yield loss, was investigated under optimal and sub-optimal conditions for disease development on hosts grown in rotation with Zea mays (maize). Pot experiments were carried out in a greenhouse using a locally planted Glycine max (L.) Merr. (soybean) and Helianthus annuus L. (sunflower) cultivar, which were inoculated with Macrophomina phaseolina (Tassi) Goid. Isolated from sunflower grown in a major oil seed-producing region in South Africa. The disease index, calculated as the product of incidence and severity divided by the total number of observations made per treatment, ((incidence × severity)/(total number of observations made per treatment)), was 20% higher in soybean than in sunflower, even though colonization of sunflower, calculated as the frequency of M. phaseolina isolated from the stem section between the roots and the cotyledon, was 10% more than that of soybean. M. phaseolina was not isolated past the first node of either crop. Yield loss due to charcoal rot amounted to 6.13% in soybean and 12% in sunflower, relative to the uninoculated, reduced soil moisture controls. Microsclerotia were more concentrated in soybean than in sunflower, which indicates that a soybean crop could increase soil inoculum more readily than sunflower. Consideration should therefore be given to the charcoal rot susceptibility of the crop following soybeans. Reduced soil moisture and infection were synergistic to disease incidence and yield loss, but independent of colonization and disease severity. Results showed that an increase in soil moisture cannot prevent initial infection of the host, but can significantly reduce colonization of the stem at maturity.

The importance of maximum allowable stem torque in valves

Maximum allowable stem torque/thrust (MAST) is defined as the maximum torque/thrust that can be applied to the valve train without risk of damage, as defined by the valve manufacturer/supplier. The valve train consists of all parts of the valve drive between the operator and closure member, including the closure member but excluding the valve operator such as the gearbox. The important point is that the actuator maximum output torque/thrust based on the maximum supply voltage or operating pressure generated by the actuator should not exceed the valve MAST at any point of travel. The actuator is a component or machine installed on the valve that is responsible for moving (e.g., opening or closing) the valve. This paper provides a formula for calculation of MAST in different sections of a valve stem installed on an oil export pipeline. The result of this calculation shows that the MAST in rectangular section of stem is less than the actuator torque. Two solutions are proposed in this paper; one is to increase the rectangular section diameter, and the second is to upgrade the material to a higher strength option such as Inconel 718. The second solution, which is more expensive, improves the MAST of the stem in all four sections of the circular section with stem keys, stem keys, the circular section, and the rectangular section.

Micromorphological studies of Cleome felina L. f.

The study was to determine the micromorphological characters of Cleome felina L. f. The results revealed the presence of anomocytic stomata, multicellular and glandular trichomes in the leaves. The transverse section of stem shows the myrosin cell and idioblast sac in the pith region. The vessels are solitary, increases in diameter from centre to periphery noted in transverse section of root. The powder microscopy reveals the epidermal trichome, sclereids and vessel elements. The pharmacognostical standards of C. felina could be useful for the completion of a suitable monograph for its proper identification, determination of its quality, purity and detection of nature of adulteration.

Perimeter-area ratio effects of urbanization intensity on forest characteristics, landscape patterns and their associations in Harbin City, Northeast China

To maximize the ecological services of urban forests, a better understanding of the effects of urbanization on urban forest characteristics, landscape metrics, and their associations is needed for landscape-related regulations in space-limited green infrastructure of metropolitan regions. In this study, Harbin, a typical fast-growing provincial-capital city in Northeast China, is used as a case study. Based on remote sensing images, field surveys, and correlation and variation partitioning analyses, we conclude that landscape characteristics and forest attributes have large variations among different urbanization intensity (UI) regions. Forest patch density (PD), landscape shape index, woody plants species richness, and the Shannon–Wiener index (H′) increased linearly, while stem section area and tree height decreased linearly with the increasing of UIs. UI had a greater influence on tree size and forest community attributes than the forest landscape pattern. Accordingly, any landscape regulation on forest attributes should be implemented according to UIs. In addition, Euclidean nearest neighbor distance(ENN-MN), mean perimeter-area ratio (PARA-MN), fractal dimension index(FRAC-MN), and PD could probably indicate forest attributes the most, e.g., the increase of PARA-MN may be accompanied with taller trees in low and heavy UI regions, but lower woody plants species evenness in low and medium UI regions. More diversified woody plants species, and afforested areas should be advocated in a low UI region, while in a heavy UI region, the conservation of large trees should be implemented. Our results highlight that the implementation of urban forest management should vary according to different urbanization regions to maximize ecological services.

Reprogrammed endophytic microbial community in maize stalk induced by Trichoderma asperellum biocontrol agent against Fusarium diseases and mycotoxin accumulation

Maize stalk rot and ear rot, caused by Fusarium graminearum and Fusarium verticillioides, respectively, are major diseases that threaten the sustainable production of maize. In this study, an artificial inoculation assay demonstrated that the control efficacy of maize stalk rot and ear rot by Trichoderma asperellum granules were 49.83 % and 39.63 %, respectively. By high-throughput sequencing of maize plants, a total of 76 196 ITS1 sequences and 887 226 V3V4 16S rRNA sequences were analyzed and were grouped into 2934 fungal and 24 248 bacterial operational taxonomic units (OTUs), respectively. It revealed a significantly higher endophytic microbial abundance in the stem tissue of plants grown in T. asperellum-treated soil than in those grown in the control, with the largest increase observed in the basal stem section. In addition, the endophytic microbial diversity and corresponding control effects all gradually decreased from the basal to apical parts of the stem in plants grown in Trichoderma-treated soil, indicating that Trichoderma stimulated a more significant effect on the defense system in the basal section of the stalk than in the apical parts of plants. Furthermore, the accumulation of deoxynivalenol (DON) and fumonisin B1 (FB1) decreased in the stem and ear of maize grown in T. asperellum-treated soil.

Improved photosynthesis and growth of poplar during nitrogen fertilization is accompanied by phosphorus depletion that indicates phosphorus remobilization from older stem tissues

Natural ecosystems are exposed to increasing atmospheric nitrogen (N) deposition since many decades but the input of other nutrients including phosphorus (P) is negligible. Consequences could be nutritional imbalances that may impair growth of the individual tree. High N input into forests, however, has been observed to stimulate tree growth, but was also accompanied by increasing foliar N/P ratios that imply the beginning of P deficiency. At the long-term perspective, N induced P deficiency will affect the P nutrition of the whole tree, especially P reserves of the bark and wood with the consequence of reduced tree growth. To test this assumption, young poplar plants, which were established in pots with approximately 1 L sand at low N and medium P supply, were subjected to high N load via fertilization. Improved N supply resulted in depleted P pools of older stem sections where mature and senescent leaves were present. Simultaneously, mature leaves showed enhanced rate of CO2 fixation that enables enhanced growth. Obviously, poplars grown at low N were N but not P limited despite N:P ratios indicating P deficiency for mature leaves. To show limitation of P remobilization, poplars which were established at high N and medium P supply were subsequently withhold from continuous phosphate (Pi) fertilization. These poplars showed decreased growth increment and diminished photosynthesis of mature leaves. At the whole plant level, this was accompanied by restricted P remobilization from older stem sections. Nevertheless, P contents of fine roots remained mostly unaffected. In conclusion, if P reserves are present, P compounds can be mobilized from stem bark and wood and can compensate for an enhanced P demand at high N load. However, this compensation is limited upon prolonged excess N load and might lead to P limitation that restricts growth in the long run.

Identification and Field Assay of Two Aggregation Pheromone Components Emitted by Males of the Bark Beetle Polygraphus punctifrons (Coleoptera: Curculionidae)

The bark beetle Polygraphus punctifrons (Coleoptera: Curculionidae) is a species that feeds on Norway spruce (Picea abies) and is found in the Northern parts of Europe and Russia. The release of volatile organic compounds (VOCs) produced by males and females of P. punctifrons when the beetles bore into spruce stem sections in a laboratory environment was studied using solid phase microextraction (SPME). The sampled VOCs emitted by boring beetles were analysed by gas chromatography and mass spectrometry (GCMS). (+)-2-[(1R,2S)-1-Methyl-2-(prop-1-en-2-yl)cyclobutyl]ethanol [(+)-(1R,2S)-grandisol] and (−)-(R)-1-isopropyl-4-methyl-3-cyclohexen-1-ol [(−)-(R)-terpinen-4-ol] were identified to be male specific volatiles. The identity of the compounds was confirmed by comparison with synthetic samples. Field trials with synthetic compounds in Sweden showed that racemic grandisol per se was strongly attractive for both males and females, while (−)-(R)-terpinen-4-ol was not. Further, when adding (−)-(R)-terpinen-4-ol to rac-grandisol, a synergistic effect was observed as the trap catch of P. punctifrons was fourfold. (−)-(R)-Terpinen-4-ol by its own did not attract P. punctifrons but Polygraphus poligraphus, and the latter was also attracted to traps baited with a 10:90 mixture of the two compounds. Thus, we have identified (+)-(1R,2S)-grandisol as a main component and (−)-(R)-terpinen-4-ol as a minor component of the aggregation pheromone of P. punctifrons. This opens future possibilities to monitor and, if necessary, manage populations of P. punctifrons.

Changes in streamflow and sediment for a planned large reservoir in the middle Yellow River

AbstractChanges in streamflow and sediment runoffs would affect the reservoir's functional operation and the construction of soil and water conservation measures in China's Loess Plateau. In this study, the long‐term changes in streamflow and sediment were analyzed for a main stem section of the middle Yellow River where the to‐be‐built large Guxian Reservoir is to be located. Results showed that both streamflow and sediment had significant downward trends with the rates of −9.4 m3 s−1 yr−1 and −16.8 million t yr−1, respectively, during the period of 1961–2017. Using the range of variability approach, the change of streamflow regime in its postimpact period (1986–2017) was subjected to the moderate alteration, whereas the alteration of sediment regime was moderate and severe for the first (1980–1996) and second (1997–2017) postimpact periods. As an example, the attribution analyses of annual streamflow and sediment changes were conducted in a typical tributary catchment (Qingjian River) on the right bank of Guxian Reservoir. For the periods of 1980–2002 and 2003–2016, climate variability occupied the primary and secondary proportions to both streamflow and sediment reductions, respectively. Overall, human activities demonstrated the underlying contribution to the sharp declines of streamflow and sediment, accounting for 68% and 74%, respectively, during the period of 1980–2016. We suggest that, based on the operational life of warping dams (built on gully for mitigating gully erosion by raising the gully‐bed step‐by‐step), there are risks of flash flood and high sediment concentration events in the future because the streamflow/sediment‐reducing infrastructures may be damaged by extreme rainstorms and in turn become the flood and sediment amplifiers.