Nuisance growth of Juncus bulbosus: the roles of genetics and environmental drivers tested in a large‐scale survey

1. Invasive species can transform aquatic ecosystems, and the nuisance growth of the freshwater macrophyte Juncus bulbosus has become a problem in many lakes and rivers in northern Europe. It affects biodiversity strongly and conflicts with human uses, not least compromising the generation of hydroelectricity. The causes of the proliferation of these massive stands of J. bulbosus are not finally resolved, however. 2. In this study, a wide range of catchment, lake and sediment parameters (n = 34) were assessed for 139 lakes in Southern Norway, with the aim of explaining the presence or absence of J. bulbosus and to assess potential drivers behind its prolific growth. 3. Juncus bulbosus was more often present in lakes with lower pH and phosphate concentrations, and a higher element ratio of dissolved inorganic nitrogen (DIN) to total phosphorus (DIN : TotP). 4. Despite the many parameters measured across substantial environmental gradients, none explained nuisance growth. Genetic screening (amplified fragment length polymorphism fingerprinting) of plants from a subset of lakes and additional river sites also showed no genetic differences between the various growth forms. A macrophyte trophic index, however, suggested that the most problematic growth occurred in the most oligotrophic lakes. 5. The lack of consistent patterns may reflect either factors not assessed in our survey, or that the current extension of stands represents a gradual cumulative response over time, not characterised effectively in our snapshot survey. Nevertheless, we can now exclude some putative causes of nuisance growth, including in particular genetics and N‐deposition.     

Characteristics of surface-water flows in the ridge and slough landscape of Everglades National Park: implications for particulate transport

Over the last one hundred years, compartmentalization and water management activities have reduced water flow to the ridge and slough landscape of the Everglades. As a result, the once corrugated landscape has become topographically and vegetationally uniform. The focus of this study was to quantify variation in surface flow in the ridge and slough landscape and to relate flow conditions to particulate transport and deposition. Over the 2002–2003 and 2003–2004 wet seasons, surface velocities and particulate accumulation were measured in upper Shark River Slough in Everglades National Park. Landscape characteristics such as elevation, plant density and biomass also were examined to determine their impact on flow characteristics and material transport. The results of this study demonstrate that the release of water during the wet season not only increases water levels, but also increased flow speeds and particulate transport and availability. Further, flow speeds were positively and significantly correlated with water level thereby enhancing particulate transport in sloughs relative to ridges especially during peak flow periods. Our results also indicate that the distribution of biomass in the water column, including floating plants and periphyton, affects velocity magnitude and shape of vertical profiles, especially in the sloughs where Utricularia spp. and periphyton mats are more abundant. Plot clearing experiments suggest that the presence of surface periphyton and Utricularia exert greater control over flow characteristics than the identity (i.e., sawgrass or spike rush) or density of emergent macrophytes, two parameters frequently incorporated into models describing flow through vegetated canopies. Based on these results, we suggest that future modeling efforts must take the presence of floating biomass, such as Utricularia, and presence of periphyton into consideration when describing particulate transport.     

Trade-offs between sexual and clonal reproduction in an aquatic plant: experimental manipulations vs. phenotypic correlations

That trade-offs result from the allocation of limited resources is a central concept of life history evolution. We quantified trade-offs between sexual and clonal reproduction in the aquatic plant, Butomus umbellatus, by experimentally manipulating sexual investment in two distinct nutrient environments. Increasing seed production caused a significant but nonlinear trade-off. Pollinating half of all flowers strongly reduced clonal bulbil production, but pollinating the remaining flowers did not cause any further trade-off. Trade-offs were not stronger under low nutrient conditions that clearly limited plant growth. Experimentally induced trade-offs were not reflected in negative phenotypic correlations between sexual and clonal allocation among plants within eight populations grown in a uniform greenhouse environment. Diminishing effects of increased sexual allocation plus a lack of accord between experimental manipulations and phenotypic correlations suggest that trade-offs between sexual and clonal reproduction are unlikely to constrain the evolution of reproductive strategy in this species.     

Insights into the chemical composition of <Emphasis Type="Italic">Equisetum hyemale</Emphasis> by high resolution Raman imaging

Equisetaceae has been of research interest for decades, as it is one of the oldest living plant families, and also due to its high accumulation of silica up to 25% dry wt. Aspects of silica deposition, its association with other biomolecules, as well as the chemical composition of the outer strengthening tissue still remain unclear. These questions were addressed by using high resolution (<1 μm) Confocal Raman microscopy. Two-dimensional spectral maps were acquired on cross sections of Equisetum hyemale and Raman images calculated by integrating over the intensity of characteristic spectral regions. This enabled direct visualization of differences in chemical composition and extraction of average spectra from defined regions for detailed analyses, including principal component analysis (PCA) and basis analysis (partial least square fit based on model spectra). Accumulation of silica was imaged in the knobs and in a thin layer below the cuticula. In the spectrum extracted from the knob region as main contributions, a broad band below 500 cm⁻¹ attributed to amorphous silica, and a band at 976 cm⁻¹ assigned to silanol groups, were found. From this, we concluded that these protrusions were almost pure amorphous, hydrated silica. No silanol group vibration was detected in the silicified epidermal layer below and association with pectin and hemicelluloses indicated. Pectin and hemicelluloses (glucomannan) were found in high levels in the epidermal layer and in a clearly distinguished outer part of the hypodermal sterome fibers. The inner part of the two-layered cells revealed as almost pure cellulose, oriented parallel along the fiber.     

Facilitating the restoration of aquatic plant communities in a Ramsar wetland

Human activities such as land clearing and intensive land use around water bodies, particularly wetlands, have a detrimental impact on water quality and quantity, aquatic plant communities, and associated wetland fauna. Lake Alexandrina and Lake Albert are internationally significant Ramsar wetlands located at the terminus of the Murray River, Australia's longest river system. Agriculture, water regulation, and extraction and droughts have had a detrimental impact on native plant communities in the lakes. We studied the influence of young (<1–3 years) and old (8–11 years) plantings of a native sedge (bulrush), Schoenoplectus tabernaemontani, to facilitate the establishment of aquatic plant communities in comparison with remnant and control sites. We also measured how planting structure (height, stand width, and stem density) changed with age in comparison with remnant sites. Results suggest that as plantings age they get substantially wider and have a greater maximum height, although do not reach similar stand widths by 11 years when compared to remnant areas. However, old plantings do not differ from remnant habitats in relation to aquatic plant species richness, counts of aquatic plants, and community composition. Young plantings have substantially less abundant and diverse plant communities, but are developing on a similar trajectory to old plantings. It is likely that planting sedges along lake shorelines causes a breakwater effect that facilitates the recolonization of wetland plants between the planted area and the water's edge. Management agencies should consider restoring native sedges to increase aquatic biodiversity, and potentially reduce erosion.     

Specific Volume and Free Space Relating to Mechanical Properties of Waxy Rice Cake

An interpretation was attempted of previous results that the method of reduced variables could not be applied to the relaxation curves of mochi cake. Temperature dependence of the apparent specific volume or the apparent density of mochi cake was determined. The correction factor by density Tρ/T₀ρ₀ was very small and ignored with usual materials. Ineffectiveness of WLF Eq. to the temperature dependence of relaxation modulus of mochi is attributed to the decrease of viscosity, which might be derived from free space on the mobility of polymer segments. It is suggested that free space corresponds to fine air bubbles mixed in mochi cake during its preparation which causes a decrease in viscosity and relaxation modulus.     

13: Lycoris sanguinea Maxim. (Amaryllidaceae)

The life-history characteristics of Lycoris sanguinea Maxim., a bulbous perennial of the Amaryllidaceae, are described here. Its geographical range is in the warm-temperate to cool-temperate zone of Honshu, Shikoku and Kyushu, Japan, extending further to the Korean Peninsula and China. Its growth form and seasonality are very unique, that is, the productive and reproductive phases are separate, which has been observed in other Lycoris species as well. In late March to mid-April for approximately 2 months, only radical leaves appear above ground; these leaves wither and disappear in late April to early May when the canopy of the deciduous trees casts heavy shade on the ground layer; then, in mid- to late-July when the forest floor becomes even darker, only scapes appear above ground, with two to six orange-red flowers borne on the umbels, occasionally forming large clumps here and there on the forest floor. Lycoris sanguinea is a typical insect-pollinated polycarpic perennial that is pollinated by small bees, such as Amegilla florae , and small butterflies, such as Thymelicus leoninus leoninus and Thymelicus sylvaticus sylvaticus . The seed output per plant is not very high, and 6–20 black spherical seeds, each approximately 6 mm in size, are produced.     

A comparative analysis of embryo-sac development in three closely-related Gagea species (Liliaceae), with some considerations on their reproductive strategies

Abstract

Embryo-sac development in Gagea bohemica, G. chrysantha and G. granatellii conforms to the Euphorbia dulcis-type (=Fritillaria-type), and all three species are proterandrous. G. bohemica and G. chrysantha are embryologically closer to each other than to G. granatellii and both develop seven- and eight-nucleate female gametophytes (although with clearly different proportions). G. granatellii, however develops only seven-nucleate embryo-sacs. All the species share, in various ways, cytological and micromorphological aberrations in both male and female gametophytes. Pollen grains are mostly morphologically regular in G. bohemica and G. chrysantha, while in G. granatellii malformed pollen is dominant. The studied plants of G. bohemica and G. chrysantha produced a very low amount of seeds, while G. granatellii produced no seeds at all.     

Tissue culture and plant regeneration of the salt marsh monocots <Emphasis Type="Italic">Juncus roemerianus</Emphasis> and <Emphasis Type="Italic">Juncus gerardi</Emphasis>

Summary Tissue culture and plant regeneration protocols for the salt marsh plants Juncus roemerianus Scheele and Juncus gerardi Loisel, were developed. J. roemerianus callus was induced from mature seeds cultured on Murashige and Skoog (MS) medium supplemented with 2.22 μM 6-benzylaminopurine (BA), 5.37 μM α-naphthaleneacetic acid (NAA), 2.26 μM 2,4-dichlorophenoxyacetic acid (2,4-D), and 50 ml l⁻¹ coconut water (callus induction medium). The callus was subcultured on MS medium containing 2.22 μM BA, 5.37 μM NAA, and 9.05 μM 2,4-D for callus maintenance. Shoot regeneration occurred 2 wk after transferring the callus onto shoot regeneration medium, which consisted of MS medium containing BA or thidiazuron. A high frequency of shoot regeneration was obtained when the medium contained 13.3 μM BA. Regenerated shoots were transferred to MS medium supplemented with 10.7 μM NAA for root production. Rooting did not occur in the shoots regenerated on the thidiazuron-containing media. The callus induction medium for J. roemerianus was also effective in inducing callus of J. gerardi from young inflorescences. The same medium was also used for callus maintenance. Shoot regeneration occurred 10 d after transferring the callus onto MS medium supplemented with 0.44 μM BA and 0.57 μM indole-3-acetic acid. Root regeneration occurred after transferring the shoots onto MS medium plus 0.44 μM BA and 14.8 μM indole-3-butyric acid. The regenerated plants of both J. roemerianus and J. gerardi grew vigorously in potting soil in the greenhouse. J. roemerianus regenerants also grew well in a saltwater-irrigated field plot. Tissue culture-produced plants of J. roemerianus and J. gerardi can be used for planting in created or restored wetlands.