Allelochemical autotoxicity in the emergent wetland macrophyte Juncus effusus (Juncaceae)

Bioassays for allelochemical toxicity of aboveground Juncus effusus tissues were conducted with seeds and seedlings of Eleocharis obtusa and Scirpus cyperinus, two emergent sedge species (Cyperaceae) found sympatric with J. effusus, and with seeds and seedlings of J. effusus itself to evaluate potential autotoxicity. Bioassays were performed under controlled, axenic conditions with aqueous shoot extract treatments simulating in situ dissolved organic carbon concentrations. With respect to the two sedge species, neither shoot development nor seedling biomass accrual was significantly suppressed by lyophilized whole extracts from J. effusus. Although the extracts induced no significant reduction in growth of E. obtusa or S. cyperinus, biomass-specific chlorophyll a concentration was significantly reduced in E. obtusa seedlings. In contrast, seedlings of J. effusus exhibited significant reductions of biomass and chlorophyll a concentrations, and seedling shoot development was retarded in response to leachate exposure. Results of the present study suggest that J. effusus seedlings possess autotoxic sensitivity to extracts of dead, aboveground tissues of adult plants.     

The native subspecies of Juncus effusus (Juncaceae) in western North America

Juncus effusus s. str. has two native representatives on the coast of western North America. A new combination is provided forJuncus effusus subsp.pacificus, ranging from California to British Columbia.Juncus effusus subsp.austrocalifornicus is newly described from southernmost California, Arizona, and Baja California, México. It differs from subsp.pacificus by its pale sheaths, with less thickened and less overlapping margins, and its disjunct distribution. A key is provided for the subspecies ofJ. effusus in North America.     

Physiological responses of Juncus effusus (Rush) to chromium and relevance for wastewater treatment in constructed wetlands

Constructed wetlands are increasingly applied for industrial wastewater treatment. However, current knowledge of the stress responses of helophytes to selected toxicants such as dichromate is limited. The goal of the experiments presented here was to characterize the physiological response of Juncus effusus to different concentrations of dichromate dependent upon the growth and constitution of the plants. The growth parameters, shoot length, and dry weight already were strongly affected at low dichromate concentrations of approximately 34 microM. Concentrations of 340 microM impaired chlorophyll fluorescence and a decrease in chlorophyll a started at concentrations higher than 170 microM dichromate. The concentrations of chlorophyll b and carotenoids also were influenced negatively. Thus, the reduction of the pigment content started before any obvious influence on the chlorophyll fluorescence. The highest concentration of dichromate, which caused no permanent inhibition of growth and photosynthesis, was found to be 17 microM K2Cr2O7. In principle, J. effusus is suitable for constructed wetlands to treat chromium-containing wastewater. Because the stress resistance of J. effusus is limited, the maximum concentration of dichromate in the treated wastewater should not exceed 34 microM. The growth parameters, shoot length, and dry weight were sensitive to much lower dichromate concentrations and did react more quickly than the biochemistry-related parameters chlorophyll fluorescence and pigment concentration. Therefore, the example of Juncus effusus shows that the use of only biochemical parameters to define concentration limits for the treatment of dichromate-containing wastewater can lead to incorrect conclusions and result in disturbed long-term operation of the system.     

Decomposition of standing litter of the freshwater emergent macrophyte Juncus effusus

1. Standing dead plant litter of emergent macrophytes frequently constitutes a significant fraction of the detrital mass in many freshwater wetland and littoral habitats. Rates of leaf senescence and decomposition of the emergent macrophyte Juncus effusus were examined in a small freshwater wetland in central Alabama, U.S.A. Juncus effusus leaves in the initial stages of senescence were tagged in random plant tussocks and monitored periodically to determine in situ rates of leaf senescence and death. Fully senescent leaves were collected, placed in litter bags, and suspended above the sediments to simulate standing dead decay conditions. Litter bags were periodically retrieved over 2 years and analysed for weight loss, litter nutrient contents (N, P), associated fungal biomass and fungal taxa. 2. Senescence and death of J. effusus leaves proceeds from the leaf tip to the base at an exponential rate. The rate of senescence and death of leaf tissue increased with increasing temperatures. Plant litter decomposition was slow (k = 0.40 yr^–1), with 49% weight loss observed in 2 years. Both the nitrogen (N) and phosphorus (P) concentration (%) of litter increased during decomposition. However, the total amount of nitrogen (mg) in litter bags remained stable and phosphorus increased slightly during the study period. 3. Fungal biomass associated with plant litter, as measured by ergosterol concentrations, varied between 3 and 8% of the total detrital weight. Values were not significantly different among sampling dates (P > 0.05, ANOVA, Tukey). Fungi frequently identified on decaying litter were Drechslera sp., Conioscypha lignicola (Hyphomycetes), Phoma spp. (Coelomycetes), Panellus copelandii and Marasmiellus sp. (Basidiomycota). 4. These results support previous findings that plant litter of emergent macrophytes does not require submergence or collapse to the sediment surface to initiate microbial colonization and litter decomposition.     

Aerenchyma formation in the wetland plant Juncus effusus is independent of ethylene

Flooded plant roots commonly form aerenchyma, which allows gas diffusion between shoots and roots. The programmed cell death involved in this induced aerenchyma formation is controlled by the plant hormone ethylene, as has been shown for maize (Zea mays). However, the role of ethylene is uncertain in wetland species that form constitutive aerenchyma (also under nonflooded conditions). The aim of this study is to shed light on the involvement of ethylene in constitutive aerenchyma formation in Juncus effusus. Plants of J. effusus and maize were treated with ethylene and inhibitors of ethylene action to determine the consequences for aerenchyma formation. Neither treatment with high ethylene concentrations nor with ethylene inhibitors resulted in changes in root aerenchyma in J. effusus. By contrast, ethylene increased aerenchyma development in maize unless ethylene action inhibitors were applied simultaneously. Similarly, root elongation was insensitive to ethylene treatment in J. effusus, but was affected negatively in maize. The data show that aerenchyma in J. effusus is highly constitutive and, in contrast to the inducible aerenchyma in maize, is not obviously controlled by ethylene.     

Isolation and characterization of 16 polymorphic microsatellite loci for Euchiloglanis kishinouyei

A total of 16 novel polymorphic microsatellite marker loci were isolated from a genomic library of Euchiloglanis kishinouyei and further characterized using a sample from a wild population consisting of 40 individuals. The number of alleles among loci ranged from three to 17 and the observed and expected heterozygosities ranged from 0·030 to 0·950 and 0·163 to 0·980, respectively. The average polymorphic information content (PIC) of all loci was 0·450.     

Seed coat morphology and its systematic significance in Juncus L. (Juncaceae) in Egypt

The seed morphology of nine taxa of Juncus from Egypt has been investigated using light and scanning electron microscopy, to determine the importance of seed coat features as taxonomic characters. Macro- and micromorphological characters, including seed shape, color, size, seed appendages, epidermal cell shape, anticlinal boundaries, and outer periclinal cell wall and secondary cell wall sculpture are presented. Four types of seed appendages are recognized: (i) seeds with two appendages; (ii) seeds without appendages; (iii) seeds with minutely a piculate at one end; and (iv) seeds with minutely a piculate at both ends. Two types of anticlinal cell wall boundaries,(i) raised-channeled, straight and (ii) raised, straight or sinuous, and three different shapes of outer periclinal cell wall are described: (i) flat; (ii) concave; and (iii) flat to slightly concave. The secondary sculpture of the cell wall varies from striate to microreticulate or reticulate, and smooth to finely folded. Seed characters provide useful data for formulating the taxonomy of Juncus both on the subgeneric and sectional level. A key for the identification of the investigated taxa based on seed characters is provided.     

Seed coat morphology and its systematic significance in Juncus L. (Juncaceae)in Egypt

The seed morphology of nine taxa of Juncus from Egypt has been investigated using light and scanning electron microscopy,to determine the importance of seed coat features as taxonomic characters.Macro-and micromorphological characters,including seed shape,color,size,seed appendages,epidermal cell shape,anticlinal boundaries,and outer periclinal cell wall and secondary cell wall sculpture are presented.Four types of seed appendages are recognized:(i)seeds with two appendages;(ii)seeds without appendages;(iii)seeds with minutely a piculate at one end;and(iv)seeds with minutely a piculate at both ends.Two types of anticlinal cell wall boundaries,(i)raised-channeled,straight and(ii)raised,straight or sinuous,and three different shapes of outer periclinal cell wall are described:(i)flat;(ii)concave;and(iii)flat to slightly concave.The secondary sculpture of the cell wall varies from striate to microreticulate or reticulate,and smooth to finely folded.Seed characters provide useful data for formulating the taxonomy of Juncus both on the subgeneric and sectional level.A key for the identification of the investigated taxa based on seed characters is provided.     

Decreasing the Abundance of Juncus effusus on Former Agricultural Lands with Noncalcareous Sandy Soils: Possible Effects of Liming and Soil Removal

More and more agricultural land in the Netherlands is becoming available for ecological restoration projects. However, nutrient levels in the top layer of the soils are high because the agricultural lands have been heavily fertilized for decades. As drainage ditches are no longer maintained when agricultural use ends, the agricultural lands usually become much wetter. As a result, former agricultural soils tend to develop extensive monotonous stands of Juncus effusus , which have little value from an ecological point of view. In this article, we present the results of field measurements/observations and experiments to examine the relationship between nutrient availability and J. effusus growth. In addition, we present and discuss results of experiments to study the potential beneficial effects of liming. Our findings show that the growth of J. effusus on moist or wet soils seems to be strongly determined by the Olsen-P concentration in the soil. The restoration of diverse, species-rich vegetation types on former agricultural lands with a noncalcareous sandy soil will in most cases not be possible within a reasonable time span without topsoil removal. Liming might be a valuable additional measure to enhance the quality of the soil after topsoil removal, and to prevent mobilization of P to groundwater or surface water. If removal of the topsoil is considered to create P limitation, it is important to study P concentrations at various depths to establish the amount of soil that has to be removed.     

Effect of external oxygen demand on radial oxygen loss by Juncus roots in titanium citrate solutions

Radial oxygen loss (ROL) from the roots of two semiaquatic rushes, Juncus effusus L. and Juncus inflexus L., was studied in reducing titanium citrate buffer, using both closed incubations and a flow-through, titrimetric system. In closed experiments, roots released oxygen at a constant rate over a wide range of external oxygen demands, with the ROL rate only depending on sink strength at low demands, and no oxygen release into oxidized solutions. In the titrimetric experiments, roots continued to release oxygen at constant rates when provided with a constant external oxygen demand. ROL was higher in J. effusus (9·5 ± 1 × 10^?7 mol O₂ h^?1 root^?1) than in J. inflexus (4·5 ± 0·5 × 10^?7 mol O₂ h^?1 root^?1). Light and dark changes around the shoots did not affect the ROL rate in J. inflexus, whereas in J. effusus ROL was ≈ 1·75 times higher in the light than in the dark, presumably due to changes in stomatal aperture. These results suggest that ROL is controlled by the external oxygen demand at low to moderate reducing intensities, but that structural limitations to oxygen diffusion rates prevent ROL from continuing to increase at higher external oxygen demands.     

光照对蔺草生长和草茎开花率的影响

蔺草草茎长度和是否开过花是决定其品质的两个重要方面。试验表明,不同光周期及光照强度对蔺草的生长和草茎开花率会产生显著影响。生育前期,延长日照显著促进开花,遮光处理降低蔺草的分蘖、草茎长度、减少草茎开花率和每花序小花数。中后期对蔺草进行一定遮光处理后,草茎长度增加,开花率下降。试验表明,光照是造成蔺草开花逆转和影响草茎品质的重要生态因子之一。     

New taxa and combinations in neotropical Juncus (Juncaceae)

Juncus arequipensis andJ. breviculmis are described as new species, andJ. ramboi subsp.colombianus as a new subspecies.Juncus arcticus Willd. var.mexicanus (Willd.), var.montanus (Engelm.), and var.andicola (Hook.) are proposed as new combinations.     

~(14)-C菲在“植物-火山石-营养液-空气”系统中的迁移和转化

利用放射性同位素示踪技术 ,研究14 C 菲在“植物 火山石 营养液 空气”封闭系统中的迁移转化 .结果表明 ,菲在该系统中降解较快 ,实验进行到 2 3d时 ,营养液中的放射性含量仅为施入时的 2 5 % .实验结束 (46d)时 ,14 C放射性在该系统各部分间的分布顺序为根 (38.5 5 % ) >挥发性有机代谢产物 (VOCs ,17.6 8% ) >火山石(14 .35 % ) >CO2 (11.42 % ) >茎 (2 % ) ;植物体内的放射性物质主要以结合态 (根 4.6 8% ;茎叶 0 .6 8% )与植物组织结合和以极性代谢产物 (根 2 3 .14 % ;茎 0 .78% )形式存在 .     

Isolation and characterization of microsatellite loci from two inbreeding bark beetle species (Coccotrypes)

We developed 14 microsatellite markers in Coccotrypes carpophagus and 14 in C. dactyliperda. These loci will be used for studying genetic structure and the level of inbreeding in populations in the Canary Islands and Madeira. As a result of long‐term inbreeding, genetic variability is relatively low in these bark beetle species. We found one to five alleles per locus in 29 C. carpophagus and 41 C. dactyliperda from various localities. Eleven of the markers developed for C. carpophagus amplified in C. dactyliperda and seven of the markers developed for C. dactyliperda amplified in C. carpophagus.     

The embryology and systematic relationships of Prionium serratum (Juncaceae: Juncales)

Although Prionium is included in Juncaceae, rbcL sequence data indicate that Juncaceae is paraphyletic, with most genera closer to Cyperaceae than to Prionium. Cyperaceae and Juncales have embryological synapomorphies: thus embryology is used to test the monophyly of Juncaceae. The embryology of Prionium is described and its systematic position discussed. Material was prepared using standard methods of paraffin embedding. Additional embryological data were extracted from the literature. The anther in Prionium is tetrasporangiate, and the wall has an epidermis, an endothecium and middle layer, and an irregularly bilayered, glandular secretory tapetum. Microsporogenesis is probably simultaneous; pollen is ulcerate with a granular exine, in tetrahedral and cross tetrads, and trinucleate at release. The trilocular ovary contains many crassinucellate ovules probably having a Polygonum-type embryo sac. Endosperm is helobial and the embryo is of the Onagrad type, Juncus variation. The seed is testal-tegmic and germination is epigeal. The embryology of Prionium is most like that of Juncaceae, which shares several synapomorphies with Cyperaceae. Some of the characters in Cyperaceae may be interpreted as specialized forms of those found in Juncaceae. Embryology supports the monophyly of Cyperaceae and Juncales, but not Juncaceae; thus the position of Prionium remains unresolved.     

Economic use of totorilla (Juncus arcticus, Juncaceae) in Ecuador

Juncus arcticus var. andicola is native to the Andean region. Its stems are used to make handicrafts by the rural mestizo population of Cotopaxi province in Ecuador. These products are sold at traditional markets along the Andes of Ecuador. The plant is of great economic importance in the modest lives of the artisans. Totorilla has been cultivated by this rural population. It is cultivated in pools and sometimes wild populations are managed. The area of production is 1.5 ha. One woven item can be made from a 0.35 m² totorilla stand area. A 100 m² yielded 850 woven items annually, bringing in a gross income of U.S. $1275 per year, corresponding to 66% of the official minimum salary in Ecuador. The plant also provides a good source of cattle fodder during periods of drought.