Distribution ofUrtica dioica L. andRubus fruticosus L. (+agg.) in relation to edaphic factors in cultivated poplar woods

Urtica dioica L. andRubus fruticosus L. (+agg.) are widely distributed in Belgian cultivated poplar woods. Using adjusted standardized residuals as an objective measure of preference of a species for ecoparameters, it seems possible to describe the distribution betweenUrtica andRubus as coincidental as regards ecological considerations. Both plant species behave obviously as antagonists.     

Resistance ofUrtica dioica to mycorrhizal colonization: a possible involvement ofUrtica dioica agglutinin

Roots of stinging nettle (Urtica dioica L.) were sampled at different sites around Basel (Switzerland) and examined under the microscope. They were completely devoid of mycorrhizal structures. Similarly, stinging nettle plants grown in the greenhouse in the presence of the arbuscular mycorrhizal fungusGlomus mosseae did not show any signs of mycorrhiza formation. Spread ofG. mosseae through the rhizosphere of stinging nettle plants was inhibited, and application of extracts of stinging nettle roots and rhizomes to hyphal tips ofG. mosseae reduced hyphal growth.Urtica dioica agglutinin, an antifungal protein present in the rhizomes of stinging nettle, inhibited hyphal growth in a similar way as the crude root extract. The possibility thatUrtica dioica agglutinin is at least partially responsible for the inability of stinging nettle to form the arbuscular mycorrhizal symbiosis withG. mosseae is discussed.     

The Effect of Nitrogen Supply to Urtica dioica L. Plants on the Distribution of Assimilate Between Shoot and Roots

In this study the influence of nitrogen nutrition on the patterns of carbon distribution was investigated with Urtica dioica. The nettles were grown in sand culture at 3 levels of NO^?₃, namely 3 (low), 15 (medium) and 22 (high) mM. These levels encompassed a range within which nitrogen did not affect total biomass production. The ratio of root: shoot biomass of the low nitrogen plants was, however, significantly higher than that of the nettles grown at medium and high N supply. Carbon allocation from one leaf of each pair of leaves was examined after a ¹⁴CO₂-pulse and a subsequent ¹⁴C distribution period of one night. Only the youngest two leaf pairs did not export assimilates. Carbon (¹⁴C) export to the shoot apex and to the roots, as measured at the individual nodes responded to the nitrogen status: At medium and high nitrogen supply the 3rd, 4th and 5th leaf pairs exported to the shoot apex, while lower leaves exported to the root. At low nitrogen supply only the 3rd leaf exported towards the shoot apex. The results illustrate the plastic response of carbon distribution patterns to the nitrogen supply, even when net photosynthesis, carbon export from the source leaves and biomass production were not affected by the nitrogen supply to the plant.     

Growth responses of Urtica dioica L. to different water table depth

The study has examined the effect of water table depth (WTD) on production, biomass allocation, allometric relationships and transpiration rate in Urtica dioica. The essential importance of WTD for occurence and spread of Urtica has been documented. Water table depths were: 60, 50, 40, 30, 20, and 10 cm below the soil surface. Thirty individuals of Urtica for each WTD, established from apical parts of young rhizomes, has been planted in containers and placed at WTD from the 8th May to the 24th July. The height of all individuals and the length and width of the largest leaf blade of each individual were measured after 42, 55 and 83 days. Transpiration rate was measured after 53 and 82 days. Above-ground biomass of all individuals was harvested on 24 of July and was separated into individual organs. Various biometric parameters were measured. Results showed that biomass, plant height, branching of stems and rhizomes and rhizomes length decreased in containers with a more shallow WTD. Particularly, allometric relationships between plant height and other characteristics such as basal diameter, length of longest branch and rhizome were affected by the water level. The biometric parameters were highly dependent on plant height. Transpiration strongly decreased with decreasing WTD. Therefore, the high water level in the soil suppresses growth of particular organs and water regime of Urtica plants/. Generally, long-term high water content in the soils of floodplains, particularly during floods, limits rapidly, particularly vegetative spread of Urtica in the wetland habitats.     

Vegetation of tuscan ultramafic soils in relation to edaphic and physical factors

Vegetation and soil sampling were carried out in 80 plots located in five different ultramafic (serpentine) sites of Tuscany, central Italy. The physical and chemical features of each plot were determined and the species composition and cover recorded. The exchangeable fraction of soil metals was analysed because it gives a measure of their concentrations available to plants. The plots were classified by cluster analysis and ANOVA was used to compare the environmental variables of the groups of plots. Canonical correspondence analysis was used to detect the principal factors for gradients of species composition within the plant communities. A higher content of exchangeable metals was found under the more evolved and structured plant communities, suggesting that serpentine vegetation of Tuscany is not strongly limited by soil metals, such as chromium, cobalt, nickel and magnesium, typically associated with ultramafic soils. The low nutrient content of the soils and drought stress mainly due to topographical features, appear to have a more significant role in determining the typical scattered vegetation of the Tuscan ultramafics.     

Reversal of the Direction of Photosynthate Allocation in Urtica dioica L. Plants by Increasing Cytokinin Import into the Shoot

The natural cytokinin import from the root into the shoot of Urtica dioica plants was enhanced by supplying zeatin riboside (ZR) solutions of various concentrations to a portion less than 10 % of the root system after removal of their tips. After 6 h ZR pretreatment of the plants, ¹⁴CO₂ was supplied for 3 h to a mature (source) leaf or to an expanding leaf and the ¹⁴C-distribution in the whole plant was determined after a subsequent dark period of 14 h. ZR substantially increased ¹⁴C fixation by the expanding leaves and also enhanced export of carbon and transport to the shoot apex. The effect of the hormone treatment was, however, more pronounced when the ¹⁴CO₂ was supplied to a mature leaf. In the control plants these leaves exported carbon only to the roots: When the amount of the natural daily ZR input from the roots to the shoot was enhanced by 20%, the bulk of the ¹⁴C exported from a mature leaf moved to the shoot apex and only a minor portion of ¹⁴C was still detected in the root fraction. A several-fold increase of the natural daily ZR input into the shoot resulted in a flow of ¹⁴C only to the growing parts of the shoot. The results suggest control of the sink strength of the shoot apex by ZR in Urtica diocia.     

Quantification of the Daily Cytokinin Transport from the Root to the Shoot of Urtica dioica L.*

Cytokinins are predominantly root-born phytohormones which are distributed in the shoot via the xylem stream. In the hormone message concept they are considered as root signals mediating the transport of the photosynthates to the various sinks of a plant. In this paper the cytokinin relations of Urtica dioica L., the stinging nettle, are described, based on the daily flux from the roots to the shoot. Trans-zeatin-type cytokinins predominate in the various tissues of Urtica (Wagner and Beck, 1993), and accordingly trans-zeatin riboside and trans-zeatin are the forms transported by the xylem sap. The daily time-course of cytokinin concentration in root pressure exudates and in xylem sap collected from a petiole after pressurizing the root bed showed high concentrations in the morning, followed by a substantial drop to a level of 15–30% of the initial concentration which was then maintained during the afternoon. This time-course is interpreted as resulting from continuous synthesis and exudation of cytokinins into the xylem fluid of the roots whose cytokinin concentration is then modified by the dynamics of the transpiration stream. Loading of cytokinins into the xylem sap could be enhanced several times by increasing the flux rate of the xylem stream to the maximal transpiration rate when a maximum export rate was reached. The total daily cytokinin gain by the shoot depended on the nitrogen status of the plant. Roots of Urtica plants grown on a sufficient nitrogen supply had a significantly higher cytokinin content and exuded more cytokinins into the shoot than those of plants raised under nitrogen shortage. A positive correlation was found between the steady rates of cytokinin export measured during the afternoon and the shoot to root-ratios of biomass which, in turn, corresponded to the nitrogen status of the plants.     

Inheritance of progeny sex ratio in Urtica dioica

Seed samples collected from female Urtica dioica plants in the field showed considerable inter-family variation in the sex ratio (faction of males). To investigate the inheritance pattern of the sex ratio trait, crosses were performed between individual male and female plants from different sex ratio families. Our results suggest, at least for the families studied here, that maternal parents strongly contribute to the variation in the primary sex ratio. Furthermore, progeny sex ratios from reciprocal crosses were significantly different and resembled the sex ratios produced by their maternal parents. We discuss the possible mechanisms underlying maternal control.     

Purification and characterization of polyphenol oxidase from nettle (Urtica dioica L.) and inhibitory effects of some chemicals on enzyme activity

Polyphenol oxidase (PPO) of nettle (Urtica dioica L.) was extracted and purified through (NH₄)₂SO₄ precipitation, dialysis, and CM-Sephadex ion-exchange chromatography and was used for its characterization. The PPO showed activity to catechol, 4-methylcatechol, L-3,4-dihydroxyphenylalanine (L-DOPA), L-tyrosine, p-cresol, pyrogallol, catechin and trans-cinnamic acid. For each of these eight substrates, optimum conditions such as pH and temperature were determined and L-tyrosine was found to be one of the most suitable substrates. Optimum pH and temperature were found at pH 4.5 and 30°C respectively and K_m and V_max values were 7.90?×?10^?4?M, and 11290?EU/mL for with L-tyrosine as substrate. The inhibitory effect of several inhibitors, L-cysteine chloride, sodium azide, sodium cyanide, benzoic acid, salicylic acid, L-ascorbic acid, glutathione, thiourea, sodium diethyl dithiocarbamate, β-mercaptoethanol and sodium metabisulfite were tested. The most effective was found to be sodium diethyl dithiocarbamate which acted as a competitive inhibitor with a K_i value of 1.79?×?10^?9?M. In addition one isoenzyme of PPO was detected by native polacrylamide slab gel electrophoresis.     

Effects of Nigella sativa L. and Urtica dioica L. on selected mineral status and hematological values in CCl4-treated rats

This study was designed to investigate the effects of Nigella sativa L. (NS), known as black seed, or/and Urtica dioica L. (UD), known as stinging nettle root, treatments on serum Na, K, Cl, and Ca levels and some hematological values of CCl₄-treated rats. Sixty healthy male Sprague-Dawley rats, weighing 250–300 g, were randomly allotted into 1 of 4 experimental groups: A (CCl₄-only treated), B (CCl₄+UD treated), C (CCl₄+NS treated), and D (CCl₄+UD+NS treated), each containing 15 animals. All groups received CCl₄ (0.8 mL/kg of body weight, subcutaneously, twice a week for 90 d starting d 1). In addition, B, C, and D groups also received the daily ip injection of 0.2 mL/kg NS and/or 2 mL/kg UD oils for 45 d starting d 46. Group A, on the other hand, received only 2 mL/kg normal saline solution for 45 d starting d 46. Blood samples for the biochemical analysis were taken by cardiac puncture from five randomly chosen rats in each treatment group at the beginning, d 45, and d 90 of the experiment. The CCl₄ treatment for 45 d significantly (p<0.05) increased the serum K and Ca and decreased (p<0.05) the red blood cell count (RBC), white blood cell count (WBC), packed cell volume (PCV), and Hb levels without changing (p>0.05) the serum Na and Cl levels. NS or UD treatments (alone or combination) for 45 d starting d 46 significantly (p<0.05) decreased the elevated serum K and Ca levels and also increased (p<0.05) the reduced RBC, WBC, PCV, and Hb levels. It is concluded that NS and/or UD treatments might ameliorate the CCl₄-induced disturbances of anemia, some minerals, and body’s defense mechanism in CCl₄-treated rats.     

Physiological activity of Porphyra in relation to eulittoral zonation

Eulittoral seaweeds at different tidal elevations are exposed to various frequencies and durations of emergence. Their physiological activities (e.g. nutrient uptake) may be affected by water loss during emersion. We used three Porphyra species from different tidal elevations to test whether species at different vertical elevations on the shore respond differently to the increasingly non-marine environment, in terms of their physiological activities including nutrient uptake, tissue carbon, nitrogen and phycoerythrin contents. Simulated tidal cycles produced water losses of 0%, 40 ± 10% and 90 ± 5% tissue water. Emersion was stressful for all species regardless of their habitat. It was more stressful to nitrate and phosphate uptake for the sublittoral species P. yezoensis than eulittoral species, P. umbilicalis and P. leucosticta. Interestingly, tissue N for thalli that had been emerged and then re-submerged was significantly higher than those of continuously submerged individuals. During exposure, tissue N contents of all species declined but recovered quickly (e.g. within 30 min) after re-submergence. This result suggests that emersion-induced N release may constitute an undescribed biogeochemical pathway linking marine, terrestrial, and atmospheric N reservoirs.     

The control of aldolase in Lemna minor L. in relation to nitrogen deficiency

The loss of activity of aldolase which occurs when Lemna is deprived of nitrogen is shown to be due to the accumulation of a specific inhibitor of aldolase. The inhibitor has been purified 600-fold and has the properties of a low molecular weight protein. The inhibitor is not a proteolytic enzyme and the kinetics of the interaction between aldolase and the inhibitor are reported. The possible physiolgocal significance of the inhibition of aldolase is briefly discussed.     

Cytokinins in the perennial herb Urtica dioica L. as influenced by its nitrogen status

The effect of nitrogen on the cytokinin relations of Urtica dioica, the stinging nettle, has been investigated. The plants were grown in quartz sand and nutrient solutions providing levels of nitrate ranging from 1 to 22 mM. Nitrogen supply did not affect biomass production within the range of 3–15 mM NO ₃ ^- . However, the shoot: root ratio of biomass was significantly higher at 15 mM (standard plants) than at 3 mM (low-nitrogen plants) nitrate supply. The cytokinin patterns of the roots, stems and adult, as well as meristematic leaves of plants grown at these two levels of nitrate supply, were determined by means of high-performance liquid chromatography (HPLC) and immunoassays. Enzyme-linked immunosorbent assays (ELISAs) for zeatin riboside, dihydrozeatin riboside, isopentenyladenosine, benzyladenosine and o-hydroxybenzyladenosine enabled the quantification of 17 cytokinins, 13 of which were found in the various tissues of Urtica. trans-Zeatin and its conjugates were the predominant cytokinins in all examined samples. While the free base trans-zeatin and its O-glucoside were the major cytokinins in adult leaves, trans-zeatin riboside was prominent in the other tissues of at least the standard plants. Glucosides of the trans-zeatin type cytokinins were present only in lower amounts. However, considerable amounts of a compound, tentatively identified as cis-zeatin riboside-O-glucoside, were found, particularly in roots and meristematic leaves. Comparatively high amounts of trans-zeatin nucleotide as well as isopentenyladenosine phosphate were also demonstrated in these tissues. Analysis of the root-pressure exudates similarly showed trans-zeatin riboside and, at a lower concentration, trans-zeatin to be the only substantial components. In the low-nitrogen plants, shortage of nitrogen was manifest only in the roots; the nitrogen contents of the shoots did not respond to the nitrogen supply. Likewise, the total content of cytokinins in the shoots of the low-nitrogen plants equaled that of the standard-plant shoots, while it was lower by about 25% in the roots of the low-nitrogen plants. In the latter, the amounts of cytokinins exuded via the root-pressure fluid were also approximately 25% lower. Since the levels of only the trans-zeatin cytokinins in the roots showed a linear correlation with the shoot-to-root ratios, these cytokinins may play an important role in biomass partitioning in Urtica dioica.Abbreviations DHZ dihydrozeatin - ELISA enzyme-linked immunosorbent assay - -G glucoside - HPLC high-performance liquid chromatography - 2iP isopentenyladenine - 2iPA isopentenyladenosine - -N nucleotide (ribotide) - -OG O-glucoside - -R riboside - S/R shoot-to-root (ratio) - Z zeatin This work was supported by the Deutsche Forschungsgemeinschaft within the scope of the SFB 137. The authors wish to thank Mrs. A. Fischbach for skilful technical assistence and Dr. Paul Ziegler (Lehrstuhl für Pflanzenphysiologie, University of Bayreuth, FRG) for linguistic suggestions.     

Alfalfa (Medicago sativa L.) seed yield in relation to phosphorus fertilization and honeybee pollination

This investigation was conducted at the Agricultural and Veterinary Training and Research Station, King Faisal University, Al-Ahsa, Saudi Arabia, during the alfalfa growing season in 2014. The study aimed to evaluate the impact of phosphorus fertilization and honeybee pollination on alfalfa seed production. The experiment was divided into 9 treatments of open pollination, honeybee pollination, and non-pollination with three different levels (0, 300 or 600 kg P₂O₅/ha/year) of triple super phosphate. All vegetative growth attributes of Hassawi alfalfa were significantly higher in the non-insect pollination plots, while the yield and yield component traits were significantly higher with either open pollination or honeybee pollination in parallel with the increasing level of phosphorus fertilizer up to 600 kg P₂O₅/ha/year in light salt-affected loamy sand soils. There was no seed yield in Hassawi alfalfa without insect pollination. Therefore, placing honeybee colonies near the fields of Hassawi alfalfa and adding 600 kg P₂O₅/ha/year can increase seed production.     

Quantification by ELISA of Cytokinins in Root-Pressure Exudates of Urtica dioica Plants Grown under Different Nitrogen Levels

ELISAs for [9R]iP, [9R]Z and (diH) [9R]Z have been worked out which, in combination with HPLC., allow the quantitative determination of cytokinins of the isopentenyladenin-, zeatin- and dihydrozeatin-type in samples of plant material. The three ELISAs are optimally applicable in the range from 0.5 to 20 pmoles of cytokinins per assay but reliable measurements can still be performed down to 0.05 pmoles. The assay has been applied to root pressure exudates obtained from Urtica dioica plants grown under controlled conditions and at different nitrogen (nitrate) levels. The predominant cytokinins of the xylem exudate were Z, Z-nucleotide, iP, [9R]iP and iP-nucleotide, while (diH)Z was present to a minor extent. The concentrations of these compounds were found to range between 0.2 and 3 pmoles per ml exudate. Interestingly, no effect of the different nitrogen nutrition on the pattern and concentration of cytokinins in the xylem exudate could be established.     

Thermodynamic Analysis of Chitooligosaccharide Binding to Urtica dioica agglutinin by Isothermal Titration Calorimetry

UDA (Urtica dioica agglutinin) contains two hevein like domains with two non-identical interacting sites and is specific for chitooligosaccharides. The binding of chitooligosaccharides to UDA was studied by Isothermal Titration Calorimetry. Each site is composed of three subsites, each binding to a sugar residue. Thermodynamic parameters obtained show that while chitobiose has two independent non-interacting sites, chitotriose, chitotetrose and chitopentose have two interacting sites on each monomer of UDA. Values of binding enthalpy (H) increase almost by a factor of 7 in going from chitobiose to chitotriose indicating the existence of three subsites in the combining site of UDA. The binding constant for chitotetrose and chitopentose increase without any further enhancement in the values of H indicating that for oligomers larger than chitotriose interaction is favoured entropically.     

Distribution of heterochromatin on the mitotic chromosomes of Musca domestica L. in relation to the activity of male-determining factors

In the housefly, male sex is determined by a dominant factor, M, located either on the Y, on the X, or on any of the five autosomes. M factors on autosome I and on fragments of the Y chromosome show incomplete expressivity, whereas M factors on the other autosomes are fully expressive. To test whether these differences might be caused by heterochromatin-dependent position effects, we studied the distribution of heterochromatin on the mitotic chromosomes by C-banding and by fluorescence in situ hybridization of DNA fragments amplified from microdissected mitotic chromosomes. Our results show a correlation between the chromosomal position of M and the strength of its male-determining activity: weakly masculinizing M factors are exclusively located on chromosomes with extensive heterochromatic regions, i.e., on autosome I and on the Y chromosome. The Y is known to contain at least two copies of the M factor, which ensures a strong masculinizing effect despite the heterochromatic environment. The heterochromatic regions of the sex chromosomes consist of repetitive sequences that are unique to the X and the Y, whereas their euchromatic parts contain sequences that are ubiquitously found in the euchromatin of all chromosomes of the complement. Received: 20 February 1998; in revised form: 11 May 1998 / Accepted: 23 May 1998     

麻叶荨麻化学成分研究

对荨麻属植物麻叶荨麻(Urtica cannabina L．)化学成分进行初步研究,从其叶提取物的石油醚、乙酸乙酯和正丁醇部分分离得到3个化合物。经理化常数和波谱分析,分别鉴定为：β-谷甾醇(β-sitosterol,1),黄芩素-7-O-α-L-广鼠李糖苷(scutellarein-7-O-α-L-rhamnoside,2),芹菜素-6,8-二-C-β-D-葡萄糖苷(apigenin-6,8-di-C-glycoside,又名vicenin-2,3)。以上3个化合物均为首次由该种植物中获得。     

Nitrate nutrition ofDeschampsia flexuosa (L.) Trin. in relation to nitrogen deposition in Sweden

Summary Current and maximally induced nitrate reductase activity (NRA), total-N, nitrate, K, P, Ca, Mg, Mo and sucrose in leaves ofDeschampsia flexuosa was measured three times during the vegetation period in forests along a deposition gradient (150 km) in south Sweden, in north Sweden where the nitrogen deposition is considerably lower, and at heavily N-fertilized plots. In addition, the interaction between nitrogen nutrition and light was studied along transects from clearings into forest in both south and north Sweden. Plants from sites with high nitrogen deposition had elevated current NRA compared to plants from less polluted sites, indicating high levels of available soil nitrate at the former. Current NRA and total N concentration in grass from sites with high deposition resembled those found at heavily N-fertilized plots. Under such circumstances, the ratio current NRA: maximally induced NRA as well as the concentration of nitrate was high, while the concentration of sucrose was low. This suggests that the grass at these sites was already utilizing a large portion of its capacity to assimilate nitrate. Light was found to play an important role in the assimilation of nitrate; leaf concentration of sucrose was found to be negatively correlated with both nitrate and total N. Consequently, grass growing under dense canopies in south Sweden is not able to dilute N by increasing growth. The diminished capacity of the grass to assimilate nitrate will increase leaching losses of N from forests approaching N saturation.     

Short-term temporal variation in sporulation dynamics of arbuscular mycorrhizal (AM) fungi and physico-chemical edaphic properties of wheat rhizosphere

In this study, we investigated the pattern of short-term temporal variation in the arbuscular mycorrhizal (AM) fungi and physico-chemical edaphic properties of some wheat growing areas of the Bundelkhand region, Central India. Rhizospheric soil samples were collected every month from December 2007 to May 2008 from four wheat growing sites around Jhansi (Bundelkhand region). AM fungal root colonization, sporulation and physico-chemical edaphic properties during this period were determined and compared to evaluate the dynamics of response of wheat towards the AMF along crop maturation. Maximum AMF root colonization recorded was 54.3% indicating that AMF, particularly in low phosphorus (P) soils, can be important even in case of less responsive crop like wheat. In the two out of four sites studied, the AMF spore density increased with the increase in soil temperature. Absence of this type of pattern in remaining two sites indicated that site-specific environmental and agricultural conditions may affect the degree of wheat response to AMF. It also suggested that AMF communities inhabiting agroecosystems may exhibit considerable temporal sporulation patterns. The maximum AMF colonization was observed during February–March 2008, whereas maximum AMF sporulation was noticed during March–April 2008. Statistically significant negative correlation of AMF spore density with pH, organic carbon (OC) and available P was observed in the one of the sites studied. Overall assessment of the data indicated that season and location significantly affected the interaction of AM fungi with winter wheat necessitating the further need to understand the ecology of AMF populations with reference to specific host species under different micro-climatic conditions of Bundelkhand region.