Competitive relationships between two water plant species: Najas marina L. and Myriophyllum spicatum L.

The interrelationships between two submerged macrophytes, Najas marina and Myriophyllum spicatum, were investigated. Double-reciprocal analysis was used to distinguish between the possible types of negative relationships. Results have demonstrated that interspecific inhibition was more severe than the intraspecific one. The intensity of inhibition was negatively correlated with the density of the examined species. The mutual inhibitory effect and the pattern of the obtained results suggest that competitive relationships exist between Najas marina and Myriophyllum spicatum.     

The response of Ceratophyllum demersum L. and Myriophyllum spicatum L. to reduced, ambient, and enhanced ultraviolet-B radiation

The response of Ceratophyllum demersum and Myriophyllum spicatum to three levels of UV-B radiation – reduced (ca. 50% reduction), ambient and enhanced UV-B radiation, simulating 17% ozone depletion – is discussed. The research revealed that UV-B stimulated the production of UV-B absorbing compounds in C. demersum, but not in M. spicatum. The relative amount of UV-B absorbing compounds was about four times lower in C. demersum. Enhanced UV-B also affected respiratory potential in C. demersum (on average 3.7 mg O₂/gDM/h), but no effect on M. spicatum (on average 5.5 mg O₂/gDM/h) was detected. Increased need for energy revealed that UV-B radiation exerted stress in C. demersum. No changes in chlorophyll a and no disturbance to photochemical efficiency due to UV-B were observed in either species.     

Hydrostatic pressure as the controlling factor in the depth distribution of Eurasian watermilfoil,Myriophyllum spicatum L.

These experimental studies have shown that this plant will grow successfully at pressures encountered in water at depths as great as 17 m. When there were suitable levels of light, temperature, nutrients and aeration, the plants grown under constant hydrostatic pressure for three weeks showed variations in the measured amounts of new growth but no measure could be associated with the constant increased hydrostatic pressure. Sudden changes in pressure are thought to play a significant role in aquatic plant growth under experimental conditions.     

Induction of nitrate reductase by cytokinin and ethylene in Agrostemma githago L. embryos

In dark-grown, isolated embryos of Agrostemma githago, a transient period of nitrate-reductase (NR) (NADH: nitrate oxidoreductase, EC 1.6.6.1) activity occurred from 6 to 36 h after the start of imbibition. During this period, NR activity was enhanced by nitrate, 6-benzylamino-purine and ethylene. Ethylene and 6-benzylamino-purine acted synergistically, whereas ethylene had no effect on nitrate induction. Aminoethoxyvinyl-glycine, an inhibitor of ethylene biosynthesis, inhibited the cytokinin-induced increase of NR activity, but had no effect on the nitrate-induced increase. The inhibition by aminoethoxyvinylglycine was overcome completely by ethylene. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid had the same effect on NR activity as ethylene. Our data indicate that NR induction by cytokinins only occurs in the presence of ethylene, and that nitrate enhances NR activity through a mechanism which is distinct from the induction by hormones.Abbreviations ACC 1-aminocycloproparte-1-carboxylic acid - AVG aminoethoxyvinylglycine - BAP 6-benzylaminopurine - c.p. cotyledonary pair - NR nitrate reductase This article was finalized by the second author two weeks before his death. It was translated and adapted by Dr. G.J. de Klerk, Research School of Biological Sciences, Australian National University, Canberra. Reprint requests should be sent to Dr. de Klerk at his present address: Bulb Research Centre, Vennestraat 22, 2160 AB Lisse, The NetherlandsDeceased 4 September 1985     

两种狐尾藻属（小二仙草科）植物在中国的新记录

互花狐尾藻 Myriophyllum alterniflorum DC.和刺果狐尾藻M．tuberculatum Roxb．为中国首次记录。     

Vascular plants as bioindicators of regional warming in Antarctica

Monitoring selected populations of the only two native Antarctic vascular plant species (Colobanthus quitensis andDeschampsia antarctica) over a 27-year period has revealed a significant and relatively rapid increase in numbers of individuals and populations at two widely separated localities in the maritime Antarctic. There is strong evidence that this increase is a response to a warming trend in summer air temperatures, which has been evident throughout the region since the late 1940s, enhancing seed maturation, germination and seedling survival. This study provides the only known long-term monitoring data for any terrestrial organisms in Antarc-tica. Because their response to ameliorating conditions is more rapid than that of the dominant cryptogamic groups, Antarctic phanerogams may be useful bioindicators of climate change in West Antarctica.     

Two species of the genus Myriophyllum L. (Haloragaceae) newly recorded in China

Myriophyllum alterniflorum DC. and M. tuberculatum Roxb. of the Haloragaceae, are reported as new records in China.     

Response of Pinus sylvestris L. to recent climatic events in the French Mediterranean region

Exceptional climatic events from 2003 to 2005 (scorching heat and drought) affected the whole of the vegetation in the French Mediterranean region and in particular the Scots pine (Pinus sylvestris L.), one of the most important forest tree species in this area. To understand its response to these extreme conditions, we investigated its radial growth, branch length growth, architectural development and reproduction for the period 1995–2005, and linked these variables to climatic parameters. We used four plots situated in southeastern France and presenting different levels of site quality and potential forest productivity. The results show that: (1) the climatic episode 2003–2005 was highly detrimental to the growth (bole and branches), crown development, and cone production but favored the production of male flowers; (2) these variables depend on climatic factors of both the current and previous years; (3) the 2003 scorching heat impact was strong but was mainly apparent from 2004; it was part of a 6-year-long unfavorable cycle beginning in 2000, characterized by high minimum and maximum temperatures and very dry springs; (4) in spite of a significant effect of site quality, the Scots pine’s response to extreme climatic conditions was homogeneous in the French Mediterranean area; and (5) the stress induced by poor site conditions generally resulted in the same consequences for tree growth, architecture, and reproduction as in unfavorable climatic conditions.     

Ecological life histories of the three aquatic nuisance plants,Myriophyllum spicatum,Potamogeton crispus and Elodea canadensis

The life histories of Myriophyllum spicatum L., Elodea canadensis Michx., and Potamogeton crispus L., serious aquatic nuisances in many regions of the world, are reviewed to provide insights into the life style of successful aquatic nuisance plants. Specifically, their distribution and spread in North America; their life cycle, productive and reproductive potential; and their ecosystem relationships are reviewed. Hopefully this review will improve a manager's ability to deal with aquatic nuisance problems. It also provides suggestions for basic research needed to develop more effective management practices.It was found that all three species possess a number of adaptations, including an ability to rapidly propagate vegetatively, an opportunistic nature for obtaining nutrients, a life cycle that favors cool weather, and a number of mechanisms which enhance photosynthetic efficiency, which allow them to proliferate.These three species do provide benefits to the ecosystem through their roles in materials cycling and energy flow. Therefore, management of these species should take an integrated approach which recognizes these benefits.The life history information available about the three species varies tremendously; however, a better understanding of resource gain and allocation is needed to manage all three species. Specifically, more research is needed to provide a better understanding of: 1) the role bicarbonate plays in photosynthesis, 2) the role roots play in supplying CO₂ to the plabts, 3) resource accumulation and allocation under different temperature and light regimes, 4) resource allocation on a seasonal basis, and 5) nutrient cycling under different management regimes.     

The discovery of Myriophyllum exalbescens Fernald (Haloragaceae) in Europe and the typification of M.spicatum L. And M.verticillatum L.

Myriophyllum exalbescens Fernald, hitherto regarded as a North American endemic, has been fund to occur widely as a native plant in northern Europe, where it has occasionally been distinguished as a subspecies or variety of M.spicatum L.under the epithet squamosum Linnacus original concept of M.spicalum appears to have included M.exalbescens (and also M. Alterniflorum DC.) but selection of Burser VII(1)79 at UPS as lectotvpe ensures the continued use of the epithet spicatum for the native Eurasian weed species to which it is customarily applied. .M.verlicillalum L., the name of a morphologically similar species, is also lectotypified in a way that preserves its current usage. Distinguishing features of M.exalbescens and M.spicatum are provided along with details of the synonymy and presently known distribution in Europe of M.exalbescens .     

Inter-relationships between Najas marina L. and three other species of aquatic macrophytes

The ability of Najas marina L. to thrive in the presence of the submerged hydrophytes (Myriophyllum spicatum L. and Potamogeton lucens L.) and of an emerged hygrophyte (Scirpus litoralis Schard.) was investigated in Tel Aviv, Israel. Najas plants were unaffected by the presence of Potamogeton lucens and Scirpus litoralis, but were significantly suppressed by Myriophyllum. Bilateral negative relationships exist between Najas and Myriophyllum and these seem to be of an allelophatic nature, depending more on the nature of the accompanying species rather than on their mass.     

Use ofCladophora glomerata to monitor heavy metals in rivers

Methods were developed for the use ofCladophora glomerata to monitor heavy metal concentrations in flowing waters. At least under conditions without marked fluctuations in ambient metal concentration, there was no detectable difference in the metal concentrations of young plants between terminal 2-cm lengths of filament and whole plants. In order to establish the relationship between metal concentration in plant and that in water, 60 algal and water samples were analyzed from sites in northern England for Fe, Cu, Zn, Cd and Pb. Other environmental variables were measured at the time in order to assess their influence on metal accumulation. There were highly significant correlations for each of the five metals between concentrations in alga and water. The regression equations relating metal in alga to metal in water permit an unknown environmental metal concentration to be estimated from the algal concentration. Multiple stepwise regression analyses were used to indicate environmental factors which may influence metal accumulation; for instance, Fe appears to have a positive influence on Cu accumulation. In generalCladophora accumulates much less metal than bryophytes, but the slope relating metal in alga to metal in water is steeper, particularly for Pb. This means thatCladophora is especially useful where there is a need for a sensitive indicator of differences between sites or sampling occasions.     

The effects of various soils,different provenances and air pollution on root tip chromosomes in Norway spruce

The classification of chromosomal aberrations was used to characterize different factors affecting chromosomes in the root meristem of Norway spruce [Picea abies (L.) Karst.] trees. It is important to know the most significant factor affecting the chromosomes in the root meristem of plants at natural sites. The results suggest that an intensive site effect is more significant than the soil or the provenance of the individual. This cytogenetic plant test system was also used to investigate 5-year-old spruce trees exposed in environmental chambers to elevated concentrations of carbon dioxide (750 cm³m^–3) and ozone (0.08 cm³m^–3) as single variables or in combination, and then transferred to a field for observation of a memory effect. The fumigated variants showed an increased number of chromosomal aberrations compared to the controls, which carried on as a memory effect in the root meristems far beyond the fumigation period.     

Comparative capitular morphology and anatomy of Coreopsis L. and bidens L. (compositae), including a review of generic boundaries

The capitular and floral morphology and anatomy ofBidens L. andCoreopsis L. were studied. All the North American species ofCoreopsis were studied. Selected species ofBidens from North and South America andCoreopsis from South America were included. The results were compared with previous observations on African species ofBidens (incl.Coreopsis). Emphasis was given to character states of the ray florets, paleae, stylearm apices, outer phyllaries, achenes, and pollen grains. Some of the character states are unique features ofCoreopsis, e.g., globular and elongately conical receptacles, deltoid outer phyllaries, truncate and indistinctly 3–5-dentate, 3–4-lobed ray florets, narrowly spathulate paleae, subulate paleae with linear-filiform upper half, hairy and apically 3-cleft paleae, truncate, convex or shallowly conical stylearm apices with the sweeping hairs limited to the area above the stigmatic surfaces and the orbicular to circular achenes. The cylindric setaceous pappus bristles so commonly encountered inBidens are unknown inCoreopsis. The pappus bristles inCoreopsis are paleaceous but similar, though thicker ones are also found in African species ofBidens (incl.Coreopsis) with winged achenes. Twin-celled hairs (setulae) with differing degrees of wall thickness are found on the achenes ofCoreopsis sect.Pseudoagarista (Mexico and South America),Coreopsis sect.Pugiopappus (California), AfricanBidens with winged achenes (e.g.,B. prestinaria, B. macroptera) and some North AmericanBidens (e.g.,B. aristosa). Similar sclerotic parenchyma make up the achenial wings of species in both genera. These may be interpreted as homologous structures, indicating the underlying similarity of these taxa and their derivation from a common ancestral stock.     

Endosulfan induces oxidative stress and changes on detoxication enzymes in the aquatic macrophyte Myriophyllum quitense

Endosulfan (1) is a chlorinated insecticide still in use in both developed and emerging countries. Although its toxicity on animals has been studied in the last years, scarce information is available on its effects on plants. In this study, we exposed the aquatic macrophyte Myriophyllum quitense to environmentally relevant concentrations of endosulfan (microg/L) (1) for a short time, simulating exposures that might occur after either accidental spills or toxic run-off from agricultural areas. The main goal was to evaluate changes in both detoxication and antioxidant enzymatic systems of this plant upon exposure to endosulfan (1). Thus, we measured the activities of catalase (CAT), soluble and membrane associated glutathione-S-transferases (s- and m-GSTs) and glutathione reductase (GR), as well as the hydrogen peroxide (H2O2) content. Results showed that endosulfan (1) exerts oxidative stress on M. quitense, which was evidenced by the increase of CAT activity and the H2O2 content in exposed plants. At 5 microg/L endosulfan (1), we found a generalized induction of activities of tested enzymes, indicating that this xenobiotic activates the protection system of this plant, increasing its capacity to scavenge reactive oxygen species. On the other hand, we did not find significant changes at 0.02 microg/L endosulfan (1), which is the maximal concentration allowed for freshwater. We conclude that runoff events, which can produce significant amounts of endosulfan (1) in aquatic environments during short time, can result in oxidative stress on M. quitense, and probably on similar macrophytes.     

Seasonal variation of neutral lipids in Pinus sylvestris L. sapwood and heartwood

Summary The lipid levels and fatty acid composition of three fractions (free fatty acids, triacylglycerols and sterol/triterpenoid esters) extracted from the sapwood and heartwood of three stems of Pinus sylvestris were determined to investigate both seasonal changes in sapwood and possible metabolic changes related to heartwood formation. Seasonal changes were observed only in the amount of the free fatty acids in the sapwood: the level of free fatty acids was greatest at the beginning and end of the growing season. In the January and March samples the amount of the free fatty acid fraction in the sapwood was very small. The amount of the other fractions remained at the same level throughout the study. Marked seasonal changes in the fatty acid composition occurred only in the free fatty acid fraction of the sapwood: the saturation grade increased during the winter.     

Variability and structure of natural populations of Hordelymus europaeus (L.) Jess. ex Harz and Leymus arenarius (L.) Hochst. as revealed by morphology and DNA markers

Seven populations of Hordelymus europaeus and four populations of Leymus arenarius from Poland were subjected to examination of 36 morphological characters. This study showed that both species are relatively uniform and that morphological variation of their populations represents a continuum. Of those, three populations of either species were selected for analysis with molecular markers – RAPDs and AFLPs. These populations differed with respect of geographical location as well as syntaxa and habitat. RAPD-PCR was performed for individual plants and clearly grouped them according to the population origin. For either H. europaeus or L. arenarius - the studied populations differed in degree of their intrinsic variation while none of them as a whole was significantly different from the remaining ones. In AFLP analysis the studied populations were represented by DNA pools of several individual plants. Also this approach allowed discrimination among the population samples of both H. europaeus and L. arenarius. Both RAPDs and AFLPs were accordant in indication that H. europaeus exceeds L. arenarius with respect to variation accumulated at the DNA level. It is the sixth paper of the series: Biodiversity of wild Triticeae (Poaceae) in Poland. The first is: M. Mizianty (2005). Variability and structure of natural populations of Elymus caninus (L.) L. based on morphology. Pl. Syst. Evol. 251: 199-216. The second: M. Mizianty, and M. Szklarczyk (2005). Systematic significance of Elymus caninus morphological characters revealed by AFLP analysis. In: L. Frey (ed.) Biology of grasses. W. Szafer Institute of Botany, Polish Academy of Sciences. Kraków, pp 9–21. The third: M. Mizianty et al. (2006). Variability and structure of natural populations of Elymus caninus (L.) L. and their possible relationship with Hordelymus europaeus (L.) Jess. ex Harz revealed by AFLP analysis. Pl. Syst. Evol. 256: 193–200. The fourth: M. Mizianty (2006). Variability and structure of natural populations of Hordeum murinum L. based on morphology. Pl. Syst. Evol. 261: 139–150. The fifth: B. Paszko Variability and structure of natural populations of Brachypodium pinnatum and B. sylvaticum based on morphology. Acta Soc. Bot. Pol. (in press).     

The morphological background to imbibition in seeds ofPinus sylvestris L. of different provenances

An examination was made of the structure of the coats of Scots pine (Pinus sylvestris L.) seeds of different provenance and the contribution of this factor to differences in imbibition. The seed coat layers derived from the integument, the sarcotesta, sclerotesta and endotesta did little to restrict imbibition, even though the sclerotesta of the northern provenance seeds was composed of a double multicellular layer and the sarcotesta contained large numbers of pigmented, phenol-bearing cells. In addition to the micropyle, the sclerotesta was found to possess structural openings at the chalazal end and at the ridge joining the two halves of the seed, but being covered by the pigmented cells of the sarcotesta, these did not allow water to enter any more than did the micropyle itself. Imbibition was chiefly regulated by the lipophilic covers surrounding the endosperm, which are mainly of nucellar origin, especially by the megaspore membranes nearest to the endosperm, the outer and inner exine. The nucellar cap covering the micropylar end of the endosperm proved to be impermeable to water, and its edge extended between the exine layers, which further enhanced the importance of the endosperm covers as regulators of imbibition.