Detection and identification of phytoplasma associated with witches’ broom and little leaf disease in Arundo donax: first report from India

During the survey of two successive years 2012–2013, in nearby places of Gorakhpur districts, Uttar Pradesh, India, Arundo donax plants were found to be exhibiting witches’ broom, excessive branching accompanied with little leaf symptoms with considerable disease incidence. Nested PCR carried out with universal primers pair R16F2n/R16R2 employing the PCR (P1/P7) product as a template DNA (1:20) resulted in expected size positive amplification ~1.2 kb in all symptom-bearing plants suggested the association of phytoplasma with witches’ broom disease of Narkat plants. BLASTn analysis of the 16S rRNA gene sequence showed the highest (99%) sequence identity with Candidatus phytoplasma asteris (16SrI group). In phylogenetic analysis, the sequence data showed close relationships with the members of 16SrI phytoplasma and clustered within a single clade of 16SrI group and closed to B subgroup representatives. This is a first report of 16Sr I-B group phytoplasma associated with witches’ broom accompanied with little leaf disease of Narkat in India.     

铜递进胁迫对芦竹生理指标、富集能力的影响

通过测定叶片中叶绿素含量、过氧化氢酶（CAT）、过氧化物酶（POD）和超氧化物歧化酶（SOD）活性、丙二醛（MDA）含量、脯氨酸含量及质膜透性,研究了不同浓度铜胁迫对芦竹幼苗植株的生理指标及富集能力的影响。结果表明：随铜处理浓度的增大,叶片中叶绿素含量、POD、SOD和CAT活性均呈先升高后降低的趋势,当铜处理浓度在100mg·kg^-1时,叶绿素含量、CAT活性达到最大值,而POD、SOD活性在200mg·kg^-1处理时达到最大值。MDA含量、脯氨酸含量及质膜透性均随铜浓度增大而升高,当铜处理浓度在800mg·kg^-1时,叶片中的MDA含量、脯氨酸含量及质膜透性达到最大值。检测芦竹中铜含量的分布规律为根（地下部分）〉茎、叶（地上部分）,当铜处理浓度未达800mg·kg^-1时,转运系数小于1,富集系数大于1。结果表明芦竹对铜污染土壤具有一定耐受力。     

赤泥掺拌马尾松叶对芦竹与翠芦莉生长的影响

赤泥是铝土矿提炼氧化铝后排放的强碱性废渣,数量巨大且环境风险大,如何改良及筛选适生植物是其生态修复的关键。该研究通过掺拌不同比例的马尾松叶2%,4%,6%(w/w),分析其对赤泥pH与有机质含量及芦竹与翠芦莉生长的影响。结果表明:掺拌马尾松叶35 d后,赤泥pH由11.08显著下降至9.70,但随后趋于平稳;随着掺拌比例的增加,赤泥pH呈下降趋势,有机质含量由6.13 g·kg~(-1)显著增至17.52 g·kg~(-1)。芦竹与翠芦莉在纯赤泥上生长2个多月后死亡,但在掺拌4%马尾松叶的赤泥上均能较好地生长。其中,芦竹的生物量及相对生长速率(RGR)与栽培土相比不受影响,但地下/地上生物量比(B/A)显著增加;相反,翠芦莉的生物量和相对生长速率与栽培土相比显著降低,但B/A不受影响。     

Reconstruction of lignin and hemicelluloses by aqueous ethanol anti‐solvents to improve the ionic liquid‐acid pretreatment performance of Arundo donax Linn

Ionic liquid (IL)‐acid pretreatment is known to not only enhance the enzymatic hydrolysis efficiency of lignocellulose but also to generate deposits on the surface of fiber by conventional water regeneration, which retard the increment. In this study, ethanol aqueous solution regeneration was developed as a new method to change the substrates characteristics for IL‐acid pretreatment and their effects on the enzymatic hydrolysis were evaluated. Following the IL‐acid reaction, the biomass slurry was subjected to ethanol aqueous solution at various concentration. Results indicated that anti‐solvent choice significantly influenced the reconstruction of both hemicelluloses and lignin as a result of the competition between water and ethanol. The partial removal of hemicelluloses and suitable lignin re‐localization contributed to a more porous structure. Consequently, the cellulose digestibility of aqueous ethanol regenerated samples was dramatically enhanced to ～100% and approximately 11‐ and 2‐fold higher than that of untreated and conventional water regenerated pretreated samples, respectively. A giant leap in the initial rate of enzymatic hydrolysis was also detected in 50% ethanol aqueous solution regenerated samples and only about 10 hr was needed to convert 80% of cellulose to glucose due to the appearance of cellulose II hydrate‐like and more porous structure.     

Reduction of riparian arthropod abundance and diversity as a consequence of giant reed (Arundo donax) invasion

The non-indigenous perennial grass, Arundo donax, is an aggressive invader of riparian areas throughout California and many sub-tropical regions of the world, and is hypothesized to provide poorer quality habitat for native wildlife in riparian systems. We sampled aerial and ground-dwelling insects and other terrestrial arthropods associated with Arundo, native willow vegetation (Salix spp.), and mixtures of the two vegetation types during two seasons to determine how Arundo influences invertebrate composition in a low gradient stream in central California. The total number of organisms, total biomass and taxonomic richness of aerial invertebrates associated with native vegetation was approximately twice that associated with Arundo vegetation, while mixed vegetation supported intermediate arthropod levels. Shannon-Weaver (Weiner) diversity associated with native vegetation stands was also higher than that of Arundo vegetation. Ground-dwelling assemblages did not show differences as great as aerial assemblages which are more critical to foraging avian species. These results indicate that vegetation type is a significant factor reducing the abundance and diversity of invertebrates in this, and presumably in many other riparian ecosystems where this invasive species has become a dominant component. Arundo invasion changes the vegetation structure of riparian zones and in turn, may increasingly jeopardize its habitat value for birds and other wildlife whose diets are largely composed of insects found in native riparian vegetation.     

Mechanical Properties of the Rhizome of Arundo donax L.

Abstract: The mechanical properties of rhizome segments of Arundo donax L. were studied in three dimensions: longitudinal (X), transverse-vertical (Y), transverse-horizontal (Z). Tensile, cyclic loading and torsional tests demonstrate that the distinct anisotropy found in the hollow stems is less pronounced in the rhizome. Morphological and anatomical examinations suggest that the mechanical anisotropy of the stem is caused by the arrangement parallel to the stem of the vascular bundles and sclerenchymatous fibres, embedded in lignified parenchyma. Anatomical inhomogeneity is less pronounced in the rhizome due to the short internode lengths, and predominance of nodal regions, where sclerenchymatous fibres form a complex three-dimensional arrangement embedded in unlignified starch-storing parenchyma. Cyclic loading experiments indicate viscoelastic behaviour of the rhizomatous tissues under tensile stress. Additionally, viscoelastic behaviour under torsional stress was studied. Mechanical behaviour of the rhizome under tension up to fracture is discussed with regard to the fracture surfaces, analysed by SEM.     

Growth and nutrient removal of three macrophytes in response to concentrations and ratios of N and P

Wastewater from different sources shows great differences in concentrations and ratios of N and P. In order to choose suitable plant species to remove excess N and/or P from polluted waters, it is important to know the performances of these plants under different N and P concentrations. In this study, we investigated the growth and N and P removal rate of three macrophytes, Coix lacryma-jobi, Iris wilsonii, and Arundo donax under six N and P combination treatments. C. lacryma-jobi preferred higher N and P concentrations (16 mg N L^?1 and 3.2 mg P L^?1), and increasing N supply could increase its P removal rate. I. wilsonii exhibited a growth preference at a combination of moderate N and P concentrations (8 mg N L^?1 and 0.8 mg P L^?1). A. donax could grow well at all combinations of N and P and had significantly higher relative growth rate and N and P removal rates than the other two species. These results showed A. donax is a promising species to treat various polluted waters and the other two species can be used specifically to treat certain types of wastewater.     

Invasive riparian plant litter alters aquatic insect growth

In a laboratory study, we examined growth and survival of the caddisfly, Lepidostoma unicolor, feeding on two types of native leaf litter (Alnus rhombifolia [Alder] and a Salicaceae mix [Salix spp. and Populus fremontii]) and two invasive, non-native species (Tamarix ramosissima [saltcedar] and Arundo donax [giant reed]). Larval survival was high (>85%), and did not differ, among those fed Alnus, Salicaceae, or Tamarix litter, but was much lower (20%) for larvae fed Arundo litter. Mean dry biomass of larvae fed Tamarix was 45% greater than that of larvae fed Alnus, and both were significantly greater than the biomasses of insects fed Salicaceae or Arundo. Although both Alnus and Tamarix increased in percent nitrogen with conditioning, Alnus had a significantly higher nitrogen content (4.9 and 3.6%, respectively). Final C : N-values for Alnus and Tamarix were below 18, while C : N for Arundo and Salicaceae were 56 and 44, respectively. Greater growth of larvae fed Tamarix is likely due to the high nutritive value of the conditioned litter, whereas conditioning of Arundo litter did not result in improved nutritive values. Larvae in the Alnus and Salicaceae treatments fed on the entire surface of the leaves until only the skeletons remained. In contrast, larvae in the Arundo treatments focused feeding activity along the margins and the torn portions of the blades. The low nutritional quality of Arundo and the high quality, but ephemeral nature of Tamarix litter potentially have negative effects on stream invertebrate production owing to the quality and duration of availability of leaf litter, as compared with native riparian vegetation.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.