千屈菜的经济价值及栽培技术

通过对千屈菜一年的栽培试验,就其观赏价值和药用价值作了初步探讨,提出了合理的栽培方法。     

Antitussive and bronchodilatory effects of Lythrum salicaria polysaccharide-polyphenolic conjugate

A high molecular mass polysaccharide-polyphenolic conjugate has been isolated from flowering parts of Lythrum salicaria by hot alkaline extraction. Its chemical analysis revealed 74% of carbohydrates and 17% of phenolics. Compositional analysis of carbohydrate part showed a high GalA content (49%), Rha (25%), Gal (13%) and Ara (9%) residues, and indicated thus rhamnogalacturonan associated with arabinogalactan in Lythrum conjugate. Antitussive activity tests, performed in three doses of Lythrum conjugate - 25, 50 and 75mg/kg of animal body weight, showed the reduction of the number of cough efforts even 5h after administration. However, their antitussive effects were lower in comparison with that of codeine, the strongest narcotic antitussive agent. The tests evaluating the influence of different doses on airways smooth muscle reactivity revealed more significant effect of Lythrum conjugate in comparison with that of salbutamol, a commercial bronchodilator used in a clinical practice. Measurements of specific airway resistance pointed at both, the dose-dependent bronchodilatory activity and possible participation of bronchodilation on antitussive effect of Lythrum conjugate. This study represents the first sight into pharmacodynamic properties of Lythrum polysaccharide-polyphenolic glycoconjugate.     

Response to enemies in the invasive plant Lythrum salicaria is genetically determined

Background and Aims

The enemy release hypothesis assumes that invasive plants lose their co-evolved natural enemies during introduction into the new range. This study tested, as proposed by the evolution of increased competitive ability (EICA) hypothesis, whether escape from enemies results in a decrease in defence ability in plants from the invaded range. Two straightforward aspects of the EICA are examined: (1) if invasives have lost their enemies and their defence, they should be more negatively affected by their full natural pre-invasion herbivore spectrum than their native conspecifics; and (2) the genetic basis of evolutionary change in response to enemy release in the invasive range has not been taken sufficiently into account.

Methods

Lythrum salicaria (purple loosestrife) from several populations in its native (Europe) and invasive range (North America) was exposed to all above-ground herbivores in replicated natural populations in the native range. The experiment was performed both with plants raised from field-collected seeds as well as with offspring of these where maternal effects were removed.

Key Results

Absolute and relative leaf damage was higher for introduced than for native plants. Despite having smaller height growth rate, invasive plants attained a much larger final size than natives irrespective of damage, indicating large tolerance rather than effective defence. Origin effects on response to herbivory and growth were stronger in second-generation plants, suggesting that invasive potential through enemy release has a genetic basis.

Conclusions

The findings support two predictions of the EICA hypothesis – a genetically determined difference between native and invasive plants in plant vigour and response to enemies – and point to the importance of experiments that control for maternal effects and include the entire spectrum of native range enemies.     

Impact and management of purple loosestrife (Lythrum salicaria) in North America

The invasion of non-indigenous plants is considered a primary threat to integrity and function of ecosystems. However, there is little quantitative or experimental evidence for ecosystem impacts of invasive species. Justifications for control are often based on potential, but not presently realized, recognized or quantified, negative impacts. Should lack of scientific certainty about impacts of non-indigenous species result in postponing measures to prevent degradation? Recently, management of purple loosestrife (Lythrum salicaria), has been criticized for (1) lack of evidence demonstrating negative impacts of L. salicaria, and (2) management using biocontrol for lack of evidence documenting the failure of conventional control methods. Although little quantitative evidence on negative impacts on native wetland biota and wetland function was available at the onset of the control program in 1985, recent work has demonstrated that the invasion of purple loosestrife into North American freshwater wetlands alters decomposition rates and nutrient cycling, leads to reductions in wetland plant diversity, reduces pollination and seed output of the native Lythrum alatum, and reduces habitat suitability for specialized wetland bird species such as black terns, least bitterns, pied-billed grebes, and marsh wrens. Conventional methods (physical, mechanical or chemical), have continuously failed to curb the spread of purple loosestrife or to provide satisfactory control. Although a number of generalist insect and bird species utilize purple loosestrife, wetland habitat specialists are excluded by encroachment of L. salicaria. We conclude that (1) negative ecosystem impacts of purple loosestrife in North America justify control of the species and that (2) detrimental effects of purple loosestrife on wetland systems and biota and the potential benefits of control outweigh potential risks associated with the introduction of biocontrol agents. Long-term experiments and monitoring programs that are in place will evaluate the impact of these insects on purple loosestrife, on wetland plant succession and other wetland biota.     

Plasticity of Lythrum salicaria and Phragmites australis growth characteristics across a European geographical gradient

Plants of Lythrum salicaria and Phragmites australis originating from localities across the European north–south geographical gradient were cultivated in parallel in an outdoor tub experiment. A strong correlation was found between growth and morphometric characteristics related to plant size (plant height, basal diameter, aboveground- and belowground plant biomass, etc.) and the position of the respective populations along the north–south gradient. Plants of both L. salicaria and P. australis from the southern localities grew taller and more vigorously and flowered later than plants from relatively more northern localities. From this point of view, the plants originating from south European populations were comparable to invasive North American plants. Our study indicates that explanation of the competitive success of populations invading new geographical areas may involve the role of geographic gradients within the species native range.     

Characterization of the polyphenolic composition of purple loosestrife (Lythrum salicaria)

Phenolic compounds of purple loosestrife (Lythrum salicaria L.) were analysed by the use of liquid chromatography-mass spectrometry (LC/MS) equipped with atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI). The presence of vitexin and orientin as well as their isomers, isovitexin and isoorientin, were confirmed using ion trap multiple stage LC/MS3 analysis. Several phenolic acids and tannins were also detected. Ellagitannins, vescalagin and pedunculagin, are reported from the plant for the first time.     

Fecundity and fitness in cross-compatible pollinations of tristylous North American Lythrum salicaria populations

As heterostyly and self incompatibility are linked in tristylous L. salicaria, all cross-compatible pollinations – those between anthers and styles of the same level – should produce viable seed. The rigor of this theory was tested using seed set and germination of cross-compatible pollinations in 18 naturalized L. salicaria populations in Minnesota/Wisconsin (n=342 genotypes; n=86 shorts, n=127 mids, and n=129 longs). Seed set for short-styled genotypes ranged from zero to 135 (36+38); mids–0–156, (53+39), and longs–0–151 (59+39). Mean seed set per capsule was not significantly different for mids and longs, but both were significantly greater than that of shorts (F=14, P<0.0001). Zero seed set frequently occurred in most compatible crosses, in contrast with theoretical expectations. The high percentage of populations deviating from normality must be due to incompatibility. An incompatibility system independent of heterostyly could cause this, where failed crosses result from matches of incompatibility specificities in pollen and pistil. This independence is questionable, however, given the non-significant difference in failed outcrosses for pooled χ² comparing within and between populations (χ²=0.395, P>0.5). A sporophytic incompatibility model is proposed with a minimum of three specificities. Zero seed set in compatible crosses is due to the addition of alleles from L. alatum, a distylous species that forms introgressive hybrids with L. salicaria. Reduced fecundity could increase the deficiency of shorts, and significantly greater seed germination of shorts could explain the continued presence of short-styled individuals in L. salicaria populations. Received: 3 February 2000 / Accepted: 25 March 2000     

Presence of Lythrum salicaria enhances the bodyguard effects of the parasitoid Asecodes mento for Filipendula ulmaria

This paper reports significant effects of a co‐occurring plant species (Lythrum salicaria, Lythraceae) on the reproductive success of the perennial herb Filipendula ulmaria (Rosaceae). We studied 15 Filipendula populations in the Skeppsvik Archipelago; seven of which were monospecific and eight mixed with Lythrum. All the Filipendula populations studied harbored the chrysomelid beetle Galerucella tenella, and in 2005 seed set was strongly negatively correlated with the percentage leaf area consumed. Moreover, data from 2004 showed that 25–100% of the G. tenella larvae were parasitized by the hymenopteran parasitoid Asecodes mento, and we found a strong cascading top‐down effect of parasitism in 2004 on Filipendula seed set in 2005. In 2004, parasitism (at the population level) was negatively correlated with percentage leaf area consumed and positively correlated with seed set in 2005. The parasitoid Asecodes also parasitized G. calmariensis, which is monophagous on Lythrum. Mixed populations of Filipendula and Lythrum supported higher densities of their shared ‘bodyguard’Asecodes. Further, Y‐tube bioassays showed that floriferous Filipendula attracted more than twice as many gravid Asecodes females as floriferous Lythrum. Taken together, these findings suggest that coexistence of the two plants results in ‘associational resistance’ for Filipendula and ‘associational susceptibility’ for Lythrum. This scenario was supported for Filipendula since, for this species, we found lower leaf consumption followed by higher seed production in mixed than in monospecific populations. Considered together, our results show that bodyguards may increase the reproductive fitness of a perennial herb, and that the strength of the cascading ‘bodyguard’ effect can be strongly influenced by co‐occurring plants through ‘apparent competition’. This is the first paper to demonstrate that, in the wild, plant species may use odors to compete for ‘bodyguards’, thereby causing asymmetrical ‘apparent competition’ between the herbivores involved. Our data emphasize the need to consider community factors in studies of trophic interactions.     

Herbivory Differentially Affects Plant Fitness in Three Populations of the Perennial Herb Lythrum salicaria along a Latitudinal Gradient

Herbivory can negatively and selectively affect plant fitness by reducing growth, survival and reproductive output, thereby influencing plant population dynamics and evolution. Latitudinal variation in intensity of herbivory is common, but the extent to which it translates into corresponding variation in effects on plant performance is still poorly known. We tested the hypothesis that variation in the fitness-consequences of herbivory mirror differences in intensity of herbivory among three natural populations of the perennial herb Lythrum salicaria along a latitudinal gradient from southern to northernmost Sweden. We documented intensity of herbivory and examined its effect on survival, growth and reproductive output over two years by experimentally removing herbivores with insecticide. The intensity of herbivory and the effects of herbivory on plant fitness were strongest in the southern population, intermediate in the central population and weakest in the northern population. The mean proportion of the leaf area removed ranged from 11% in the southern to 3% in the northern population. Herbivore removal increased plant height 1.5-fold in the southern and 1.2-fold in the central population, the proportion plants flowering 4-fold in the southern and 2-fold in the central population, and seed production per flower 1.6-fold in the southern and 1.2-fold in the central population, but did not affect plant fitness in the northern population. Herbivore removal thus affected the relative fecundity of plants in the three populations: In the control, seed output per plant was 8.6 times higher in the northern population compared to the southern population, whereas after herbivore removal it was 2.5 times higher in the southern population. The results demonstrate that native herbivores may strongly affect the demographic structure of L. salicaria populations and thereby shape geographic patterns of seed production. They further suggest that the strength of herbivore-mediated selection varies among populations and decreases towards the north.     

Effects of Indoleamines and Short Photoperiods on the Encystment of Gonyaulax polyedra

At a temperature of 15^oC, Gonyaulax polyedra responds to short days (light ≤ 10 h) by transition to the stage of a resting cyst. At 20^oC, even an lightdark (LD) cycle of 6:18 is incapable of inducing this process. In otherwise cyst-inducing conditions (15^oC; 10 h of light per day), an interruption of the scotophase by 2 h of light (LDLD 8:2:2:12 or 2:2:8:12) prevented encystment. Cyst induction is, therefore, initiated by a photoperiodic mechanism rather than by light deficiency. In Gonyaulax, photoperiodism may be mediated by the action of indoleamines. Melatonin, which exhibits a circadian rhythmicity in this organism, leads to encystment when given 1 h before lights-off in LD 11:13 at 15^oC, i.e., under otherwise noninducing conditions. Again, at 20^oC, melatonin is inefficient. Some analogues of melatonin, in particular, 5-methoxytryptamine and N,N-dimethyl-5-methoxytryptamine, and, at high concentrations, their respective precursors, serotonin and bufotenin, are capable of inducing cyst formation at 20^oC and in LD 12:12, whereas A'-acetyl-serotonin does not show this effect.     

Effects of Indoleamines and Short Photoperiods on the Encystment of Gonyaulax polyedra

At a temperature of 15^oC, Gonyaulax polyedra responds to short days (light ≤ 10 h) by transition to the stage of a resting cyst. At 20^oC, even an lightdark (LD) cycle of 6:18 is incapable of inducing this process. In otherwise cyst-inducing conditions (15^oC; 10 h of light per day), an interruption of the scotophase by 2 h of light (LDLD 8:2:2:12 or 2:2:8:12) prevented encystment. Cyst induction is, therefore, initiated by a photoperiodic mechanism rather than by light deficiency. In Gonyaulax, photoperiodism may be mediated by the action of indoleamines. Melatonin, which exhibits a circadian rhythmicity in this organism, leads to encystment when given 1 h before lights-off in LD 11:13 at 15^oC, i.e., under otherwise noninducing conditions. Again, at 20^oC, melatonin is inefficient. Some analogues of melatonin, in particular, 5-methoxytryptamine and N,N-dimethyl-5-methoxytryptamine, and, at high concentrations, their respective precursors, serotonin and bufotenin, are capable of inducing cyst formation at 20^oC and in LD 12:12, whereas A'-acetyl-serotonin does not show this effect.     

The effect of a water gradient on the vesicular-arbuscular mycorrhizal status of Lythrum salicaria L. (purple loosestrife)

 The mycorrhizal status of Lythrum salicaria (Lythraceae) was assessed under growth room and field conditions. Growth room studies indicated that L. salicaria is facultatively mycorrhizal and capable of forming vesicular-arbuscular associations with six Glomus species, but not with Gigaspora margarita. Overall, hyphal and arbuscular colonization levels were significantly higher in the wet treatments than in the dry treatments (P<0.0001). However, taken individually, significant increases in arbuscular colonization (P<0.05) were found only in L. salicaria colonized with Glomus clarum, G. aggregatum, and G. versiforme and exposed to the wet treatments compared with the dry treatments, while significant increases in hyphal colonization were found in L. salicaria colonized with G. clarum, and G. versiforme exposed to the wet treatments. There was no overall effect of water availability on levels of vesicular colonization or differences in vesicular colonization levels within species under dry or wet conditions. In contrast, field studies along an existing water gradient revealed that hyphal and arbuscular colonization levels were significantly higher (P<0.05) in the dry and intermediate regions of the gradient than in the wet regions. Vesicular colonization was not significantly affected by the gradient. Total stem height was significantly affected by water availability, plot location and an interaction of the two (P<0.05), and was generally higher in the intermediate and wet plots. Accepted: 20 September 1995     

The implications of accepting untestedhypotheses: a review of the effectsof purple loosestrife (Lythrum salicaria)in North America

The acceptance of poorly tested hypotheses has adverse scientific consequences, and may have adverse ecological and social consequences. The hypothesis that purple loosestrife (Lythrum salicaria) has deleterious effects on North American wetlands is an example. We traced the history of purple loosestrife and its control in North America and found little scientific evidence consistent with the hypothesis that purple loosestrife has deleterious effects. The most commonly cited study of the effects of purple loosestrife on native flora and fauna produced inconclusive results. The general acceptance of this hypothesis, however, has resulted in the introduction of nonindigenous insects for biological control. Efforts to control purple loosestrife may be misplayed and may have long-term ecological consequences if loosestrife does not have the impact it is believed to have. The acceptance of this hypothesis using scientific justifications may affect future scientific credibil ity. Careful evaluation of the precautionary principle is necessary when considering the control of nonindigenous organisms.     

Biological control of the wetlands weed purple loosestrife (Lythrum salicaria) in the Pacific northwestern United States

Purple loosestrife (Lythrum salicaria) is an Eurasian perennial hydrophyte that has become naturalized in wetlands and in and along waterways throughout temperate North America. The ecological integrity of such areas is threatened by rapidly forming monotypic infestations that displace valued flora and diminish critical fish and wildlife habitat. The inability of physical, cultural, and chemical methods to provide adequate control of the weed has led to the development of an insect-based biological control program. The first field releases of the bud and leaf feeding beetles, Galerucella calmariensis and G. pusilla, and a root-mining weevil, Hylobius transversovittatus, were made in the United States and Canada in 1992. A total of 4740 Galerucella spp. adults were released in central Washington during 1992 and 1993 at eight sites and 471 H. transversovittatus egg inoculations were made in 1993 at three locations. Establishment of both Galerucella spp. was confirmed and Hylobius colonization was achieved.     

Phosphorus,arbuscular mycorrhizal fungi and performance of the wetland plant Lythrum salicaria L. under inundated conditions

The role of arbuscular mycorrhizal (AM) fungi in aquatic and semi-aquatic environments is poorly understood, although they may play a significant role in the establishment and maintenance of wetland plant communities. We tested the hypothesis that AM fungi have little effect on plant response to phosphorus (P) supply in inundated soils as evidenced by an absence of increased plant performance in inoculated (AM+) versus non-inoculated (AM-) Lythrum salicaria plants grown under a range of P availabilities (0-40 mg/l P). We also assessed the relationship between P supply and levels of AM colonization under inundated conditions. The presence of AM fungi had no detectable benefit for any measures of plant performance (total shoot height, shoot dry weight, shoot fresh weight, root fresh weight, total root length or total root surface area). AM+ plants displayed reduced shoot height at 10 mg/l P. Overall, shoot fresh to dry weight ratios were higher in AM+ plants although the biological significance of this was not determined. AM colonization levels were significantly reduced at P concentrations of 5 mg/l and higher. The results support the hypothesis that AM fungi have little effect on plant response to P supply in inundated conditions and suggest that the AM association can become uncoupled at relatively high levels of P supply.     

Habitat and Population Effects on the Germination and Early Survival of the Invasive Weed, Lythrum salicaria L. (purple loosestrife)

In this study, we examined how environmental factors and differences among populations of Lythrum salicaria L. (Lythraceae; purple loosestrife) influenced the establishment of this species into both its preferred wetland habitat and secondary upland habitat. Seeds and seedlings from five parents from each of the three populations were planted in each wetland and upland of two sites in both disturbed and undisturbed plots. More seeds germinated in wetland than in upland sites (31% as compared to 11%) and, although a disturbance resulted in greater germination (23% as compared to 17% in undisturbed plots), there was no interaction with habitats. The results of a simultaneous greenhouse germination study in which seeds were planted under saturated and drained conditions suggest that the higher germination observed in wetland sites was due to the higher moisture present at such sites (79% vs. 45% in saturated and drained conditions, respectively). Disturbance enhanced both germination and growth of L. salicaria and this was especially so for seedlings. Dry weights of seedlings from disturbed plots were five times greater than those from undisturbed plots ( =9.2 vs. 1.8g in disturbed and undisturbed conditions, respectively). In addition to environmental factors, population differences are likely to play an important role in the spread of L. salicaria as we found differences between the populations in both life stages examined. One of the populations germinated equally well in both moisture treatments. In our seedling establishment experiment, one of the populations produced both the smallest plants and the most and earliest flowers, suggesting superior reproduction.     

The aerenchymatous phellem of Lythrum salicaria (L.): a pathway for gas transport and its role in flood tolerance

While the importance of cortical aerenchyma in flood tolerance is well established, this pathway for gaseous exchange is often destroyed during secondary growth. For woody species, therefore, an additional pathway must develop for oxygen to reach submerged tissues. In this paper we examine the potential for the aerenchymatous phellem (cork) of Lythrum salicaria L. to provide a pathway for gas transport from shoots to roots and assess its importance in flood tolerance. Plants in which the continuity of the aerenchymatous phellem between shoots and roots was broken showed a significant reduction in oxygen levels in roots, but no difference in carbon dioxide levels compared with controls that retained an intact phellem. These plants also had a greater total shoot height and shoot dry weight, and an increase in shoot/root dry mass ratios compared with controls. Total dry weight was not significantly affected by this treatment. This study is the first to show that the aerenchymatous phellem can provide a pathway for gaseous exchange between roots and shoots and can influence plant morphology and patterns of resource allocation. This suggests that this tissue may play a significant role in the flood tolerance of a woody plant.