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The presence of vegetation in a channel may influence water movement in the channel and the surrounding land in several ways. One hypothesis is that increased abundance of the invasive plant Arundo donax in a watercourse contributes to increased flooding risk. To test this hypothesis, we determined Manning's coefficient for A. donax and subsequently used it in the HEC-RAS model to estimate the impact that A. donax has on flooding risks at three sites within two moderately sized northern California rivers. The mean value for Manning's coefficient for A. donax was 0.066, and it varied from 0.019 to 0.121 (n = 37). Model simulations showed that A. donax within a stream channel had a direct effect on flooded area, causing increases up to 10% above baseline conditions, which represent cross sections with no A. donax present. Storm size also affected A. donax's impact on the size of the flooded area. Using the maximum value for Manning's n for A. donax in the simulations resulted in an increase in the flooded a...

In California’s water-seeded rice systems, algal/cyanobacterial biomass can be a problem during rice establishment and can lead to yield reductions. Laboratory, enclosure, and field-scale experiments were established to evaluate the effects of fertilizer P management on algal/cyanobacterial growth. Two field-scale experiments evaluated the response of algal/cyanobacterial growth to three P management strategies: conventional surface applied, incorporated into the soil, and delaying P applications by 30 days. Results from these experiments indicated rice fields that received conventional surface-applied P fertilizer had 4–8 times more algal/cyanobacterial biomass and 3–11 times higher concentrations of soluble reactive phosphate (SRP) than those in which P fertilizer was incorporated or delayed. Laboratory experiments evaluated the ability of field water to support growth of Nostoc spongiaeforme. Results indicate that water from the incorporated or delayed P application fields was P limited for N. spongiaeforme growth. Water from the surface-applied fields was not P limited. Enclosure experiments evaluated the effects of delayed P applications on algal/cyanobacterial biomass and rice yields. Algal/cyanobacterial cover and biomass increased in enclosures which received added P. Soluble reactive phosphate concentrations were also significantly greater in these enclosures. Delaying the application by up to 28 days did not reduce rice yields in the enclosures. One management implication is that reducing SRP concentrations early in the season in rice field water will result in reduced algal/cyanobacterial biomass. Strategies to reduce water SRP include incorporating fertilizer P or delaying the P application by up to 30 days.

Chlorarachniophytes are unicellular marine algae with plastids (chloroplasts) of secondary endosymbiotic origin. Chlorarachniophyte cells retain the remnant nucleus (nucleomorph) and cytoplasm (periplastidial compartment, PPC) of the green algal endosymbiont from which their plastid was derived. To characterize the diversity of nucleus-encoded proteins targeted to the chlorarachniophyte plastid, nucleomorph, and PPC, we isolated plastid–nucleomorph complexes from the model chlorarachniophyte Bigelowiella natans and subjected them to high-pressure liquid chromatography-tandem mass spectrometry. Our proteomic analysis, the first of its kind for a nucleomorph-bearing alga, resulted in the identification of 324 proteins with 95% confidence. Approximately 50% of these proteins have predicted bipartite leader sequences at their amino termini. Nucleus-encoded proteins make up >90% of the proteins identified. With respect to biological function, plastid-localized light-harvesting proteins were well represented, as were proteins involved in chlorophyll biosynthesis. Phylogenetic analyses revealed that many, but by no means all, of the proteins identified in our proteomic screen are of apparent green algal ancestry, consistent with the inferred evolutionary origin of the plastid and nucleomorph in chlorarachniophytes.

A species' successful invasion into a new site depends on its ability to persist in the local environment. An experiment was conducted to examine the response of giant reed to intermittent periods of shading for 2 yr. Results indicate that giant reed persisted when exposed to significant shading (i.e., 90% reduction of full sun) and that shading also caused changes in a number of plant characteristics, such as stem height, internode length, leaf nitrogen, leaf chlorophyll content, specific leaf area, total leaf area per plant, and leaf life span. Estimates of leaf photosynthetic rates did not differ across shade levels. Giant reed's ability to persist and grow under intermittent low-light conditions implies that plants would be poised to take advantage of sun flecks and disturbances that create gaps within the resident plant community. Nomenclature: Giant reed, Arundo donax L. ABKDO. Management Implications: Giant reed (Arundo donax L.) occurs throughout the southern half of the United States, fr...

Cyanobacteria and algae grow in California rice fields where they form large mats that may smother seedlings or cause them to dislodge, resulting in reduced rice stand establishment and potential yield loss. The most troublesome species of cyanobacteria is Nostoc spongiaeforme. It is very difficult to control using currently accepted methods, i.e., aerial applications of copper sulfate. A non-copper algicide, the mono (N,N-dimethylalkylamine) salt of endothall has been suggested as an alternative method for controlling nuisance cyanobacterial and algal growths in California rice fields. The purpose of the experiments described here was to evaluate the effect of the mono (N,N-dimethylalkylamine) salt of endothall on growth of N. spongiaeforme and the green alga, Hydrodictyon reticulatum. In laboratory experiments, the mono (N,N-dimethylalkylamine) salt of endothall reduced N. spongiaeforme growth at 0.3 mg L−1. This effect was removed when rice straw was added to the growth medium, indicating that the rice straw may have introduced bacteria capable of degrading the mono (N,N-dimethylalkylamine) salt of endothall. In outdoor experiments, which used rice field water containing decomposing rice straw, the mono (N,N-dimethylalkylamine) salt of endothall concentrations between 0 and 5 mg L−1 had little effect on N. spongiaeforme. In contrast, H. reticulatum exhibited injury symptoms at 1 mg L−1 or greater. However, H. reticulatum recovered by the end of the 7-day exposure. It is not clear how this algicide will be useful in the management of N. spongiaeforme or H. reticulatum in California rice fields.

In water-seeded rice systems, cyanobacteria (Nostoc spongiaeforme) hinder early-season crop growth by dislodging and reducing light to seedlings. Since algae are often phosphorus (P) limited, we investigated whether changing the timing of P fertilizer application could reduce algal growth without reducing crop yields or increasing mid-season water P concentrations to levels of concern for water quality. Water P and algae were monitored in 10 and 12 (respectively) side-by-side fields (16–60 ha in size) where P fertilizer was applied pre-plant or where P application was delayed until after rice plants had emerged above the surface of the floodwater (2–5 weeks after seeding). Early-season water P concentration and algal occurrence were higher (P < 0.001 and P = 0.018, respectively) when P fertilizer was applied pre-plant as opposed to delayed. In fields receiving a delayed P application, water P increased to as high as 1.68 mg L−1 immediately following application and subsequently declined by 0.054 mg L−1 day−1 (P = 0.029). A separate study evaluated the effect of P fertilizer timing on crop productivity and P uptake. Triple-super-phosphate was either not applied or was applied to the soil surface in the fall prior to the cropping season, immediately prior to planting, 35 days after seeding (DAS) and 49 DAS at a rate of 25 kg ha−1 P. P uptake and agronomic P use efficiency (APUE) were similar when P was applied at seeding or 35 DAS. However, relative to P application at seeding, yields were reduced by 6% and there was lower APUE when P was applied after harvesting the previous crop or at 49 DAS (P < 0.05). These results indicate that correctly timed, delayed fertilizer P applications can maximize rice yield while reducing early-season interference from algae. However, because delayed applications of P fertilizer also increased water P concentrations, drainage water must be managed carefully following application.

Arundo donax (giant reed) is a tall clonal invasive grass which has impacted many riparian ecosystems in the US. Experiments tested the hypotheses (1) that defoliation would affect A. donax stem growth and leaf production and (2) that leaf damage or removal would influence A. donax photosynthetic rates using a combination of field and laboratory settings. Leaf defoliation did not affect the height of stems or the number of leaves per stem for plants growing at a field site. Leaf damage did not influence the electron transport rate (ETR) for damaged or adjacent leaves, and defoliated stems maintained ETR which were similar to those of undamaged leaves. These findings suggest that moderate to low levels of leaf damage and/or defoliation alone may not significantly influence growth of A. donax stems and leaves and, therefore, may not reduce A. donax persistence in a particular habitat. Further, these results provide a benchmark against which to judge the effects of management approaches which affect A. donax...

Cyanobacteria and algae are problematic in California rice fields that are typically shallow and have high nutrient levels, providing ideal growing conditions. Nostoc spongiaeforme is a problem because extensive floating mats dislodge rice seedlings or smother them when the mats accumulate in windward areas. There is little published information on growth requirements for N. spongiaeforme. We grew N. spongiaeforme in BG-11 medium at 24 combinations of light (22, 87, 162, and 400 µM m−2 s−1) and temperatures (10°C, 15°C, 20°C, 25°C, 30°C, and 35°C). Results were summarized as a quadratic equation relating light and temperature to growth and indicate that optimal growth occurred at 26°C and 227 µM m−2 s−1 of light. Thus, N. spongiaeforme grows well at water temperatures and light levels similar to those measured in rice fields during the critical 30 days following initial flooding of the field.

Competitive abilities of Potamogeton pectinatus L. and Potamogeton gramineus L. were estimated using additive series experiments at across a gradient of total daily irradiance ranging from 1.2 to 9.7 mol m−2 day−1. Results for P. gramineus showed that its mean weight per plant was reduced more by the presence of other P. gramineus plants than by changes in the density of P. pectinatus. However, the difference was statistically significant only at the higher light levels examined. In the case of P. pectinatus, P. gramineus exerted a stronger impact on P. pectinatus plants than did other P. pectinatus plants. Coefficients representing interspecific competition were significantly greater than those representing intraspecific competition at higher light levels. These results indicate that P. gramineus was a stronger competitor when light levels were high. They further indicate that at low light levels, there was little evidence that competition was a strong force in determining either species performance. These results support a theory offered by Grime. However, it was possible to predict that P. gramineus would be a stronger competitor based on its light compensation point which was lower than the one for P. pectinatus. This demonstrates the utility of the R* approach proposed by Tilman. Aspects of both approaches may aid ecologists in understanding community structure.

Salvia miltiorrhiza Bge. is a well-known traditional Chinese herb. Its roots have been formulated and used clinically for the treatment of various diseases. However, little genetic information has so far been available and this fact has become a major obstacle for molecular studies. To address this lack of genetic information, an Expressed Sequence Tag (EST) library from whole plantlets of S. miltiorrhiza was generated. From the 12959 cDNA clones that were randomly selected and subjected to single-pass sequencing from their 5' ends, 10288 ESTs (with sizesor = 100 bp) were selected and assembled into 1288 contigs, leaving 2937 singletons, for a total of 4225 unigenes. These were analyzed using BLASTX (against protein databases), RPS-BLAST (against a conserved domain database) as well as the web-based KEGG Automatic Annotation Server for metabolic enzyme assignment. Based on the metabolic enzyme assignment, expression patterns of 14 secondary metabolic enzyme genes in different organs and under different treatments were verified using real-time PCR analysis. Additionally, a total of 122 microsatellites were identified from the ESTs, with 89 having sufficient flanking sequences for primer design. This set of ESTs represents a significant proportion of the S. miltiorrhiza transcriptome, and gives preliminary insights into the gene complement of S. miltiorrhiza. They will prove useful for uncovering secondary metabolic pathways, analyzing cDNA-array based gene expression, genetic manipulation to improve yield of desirable secondary products, and molecular marker identification.

Impact by two potential biological control agents, Tetramesa romana Walker and Rhizaspidiotus donacis (Leonardi), on the invasive weed, giant reed, Arundo donax L., was assessed in a quarantine greenhouse before release. Tetramesa romana alone and T. romana plus R. donacis significantly damaged A. donax by suppressing leaf and stem lengths and stimulated production of side branches during a 12-week period. R. donacis plus T. romana only slightly more impacted the plant than did T. romana alone, most likely because of the longer life cycle of R. donacis that may require a longer period of time to cause measurable damage. No negative interactions were observed between the two candidate biological control agents. Therefore, based on their potential to significantly damage A. donax under greenhouse conditions and their narrow host ranges, T. romana and R. donacis are suitable candidates for biological control of this invasive reed grass in North America.

Giant reed is an invasive plant of riparian habitats throughout California and the United States. Glyphosate is approved for controlling giant reed in California. Sources indicate that 1.5% to 5% glyphosate solutions are effective at controlling giant reed. There is little published data on the relative efficacy of different concentrations of glyphosate which can be used to select an appropriate application regime for California habitats. We conducted two field experiments to test the hypothesis that glyphosate concentrations of 1.5%, 3%, and 5% applied as foliar sprays were equally effective at killing giant reed plants. Leaf chlorophyll content and the proportion of living stems declined significantly following treatment with 1.5% or greater solutions of glyphosate. New stems were observed the spring following treatment for plants treated with 1.5% glyphosate. No new stems were observed for plants treated with either 3% or 5% glyphosate. A treatment that included “bending and breaking” stems pr...

Arundo donax (giant reed) is an aggressive invasive weed of riparian habitats throughout the southern half of the United States from California to Maryland. Native to Asia, the species is believed to have been initially introduced into North America from the Mediterranean region although subsequent introductions were from multiple regions. To provide insight into the potential for biological control of A. donax, genetic variation in plants sampled from a wide geographical area in the United States was analyzed using Sequence Related Amplification Polymorphism (SRAP) and transposable element (TE)-based molecular markers. Invasive individuals from 15 states as well as four populations in southern France were genetically fingerprinted using 10 SRAP and 12 TE-based primer combinations. With the exception of simple mutations detected in four plants, A. donax exhibited a single multilocus DNA fingerprint indicating a single genetic clone. The genetic uniformity of invasive A. donax suggests that classical biological control of the species could be successful. A lack of genetic diversity in the invaded range simplifies identification of native source populations to search for natural enemies that could be used as biocontrol agents.

Arundo donax L. is a perennial reed and is an invasive weed of riparian systems in North America. A structural model (L-DONAX) of the species was constructed using L-system modelling in order to assist in understanding and demonstrating the complexities of the plant's development and structure. The model produces a realistic number of plant components from a single rhizome segment over the course of the first year of growth, using empirical relationships derived from outdoor experiments. Biomass production is also simulated, through the use of relationships found between aerial plant portion sizes and masses. L-DONAX demonstrates that control of A. donax clumps is likely to require more than annual biomass removal, due to the bulk of biomass being present underground, and the ability of remaining rhizome or stem segments to produce large clumps quickly. The model extrapolates to years of growth beyond the first, but is found to require some re-parameterisation to improve accuracy.

Management actions to control invasive aquatic species can have significant ecosystem-scale effects. We evaluated the water chemistry and nutrient effects of mechanical shredding to control water hyacinth (Eichhornia crassipes) in an agricultural slough and a tidal wetland on the Sacramento-San Joaquin River Delta, California. Shredding was conducted with two types of shredder boats in fall of 2003 and another boat in spring of 2004. Shredding measurably affected water quality, but specific effects varied as a function of shredding site and season. Significant increases were observed for total Kjeldahl nitrogen and total phosphorus for all experiments. Dissolved oxygen effects varied by site, decreasing after shredding at the agricultural slough but increasing at the tidal wetland. The increase in dissolved oxygen likely resulted from tidal incursions from the adjacent river. A year-long time series of dissolved oxygen data indicated a negative relationship between hyacinth abundance and dissolved oxygen concentrations. Hyacinth contained similar tissue concentrations of mercury to underlying sediments, suggesting that plant harvesting could aid mercury remediation efforts. Simple mass calculations indicated that Delta-wide shredding operations could cause between 0.1% and 9.6% increases in the overall abundance of carbon, nitrogen, and phosphorus in the Delta water column. Results suggest that local effects of management actions to control invasive aquatic plants will vary widely as a function of site-specific hydrology, but that estuary-wide effects would be limited.

Leaf carbon (C) content, leaf nitrogen (N) content, and C:N ratio are especially useful for understanding plant-herbivore interactions and may be important in developing control methods for the invasive riparian plant Arundo donax L. We measured C content, N content, C:N ratio, and chlorophyll index (SPAD 502 reading) for 768 leaves from A. donax collected over a five year period at several locations in California, Nevada, and Texas. Leaf N was more variable than leaf C, and thus we developed a linear regression equation for estimating A. donax leaf N from the leaf chlorophyll index (SPAD reading). When applied to two independent data sets, the equation (leaf N content % = -0.63 + 0.08 x SPAD) produced realistic estimates that matched seasonal and spatial trends reported from a natural A. donax population. Used in conjunction with the handheld SPAD 502 meter, the equation provides a rapid, non-destructive method for estimating A. donax leaf quality.

We sampled eight California rice fields every two days from May 1 to June 1, 2004 for algal biomass, species composition, and water quality parameters. Soil samples were collected prior to filling the fields with water and analyzed for selected nutrients. Algal abundance shifted from dominance by genera of green algae (Sphaeroplea, Tribonema, Ankistrodesmus, Tetraspora) and diatoms (Navicula) early in May to dominance by blue-green algae genera (almost totally Nostoc, with Anabaena and Phormidium also present) in late May-early June The same taxa occurred in all the fields at around the same time. The most abundant species consistent with the description “black algae” collected from these fields was Nostoc spongiaeforme. Results from multiple regression analysis showed that algal biomass was negatively related to total alkalinity and sulfate concentration, and positively related to the N: P ratio and the concentrations of ammonium, phosphate, sodium, and calcium. These variables explained 51% of ...

Arundo donax is a tall perennial reed. Once established, it spreads by producing new shoots (ramets) from rhizomes. We performed two separate experiments to test the hypotheses that temperature (7, 8, 14, 16, or 20 °C) and combinations of temperature and nitrate concentration (0, 0.3, 0.6,1.2, 2.4, 3.6, 4.8, and 6.0 mg/l nitrate) regulated the initiation of ramet production. No ramets emerged from rhizome sections at 7 or 8 °C, but ramets emerged at 14, 16, and 20 °C. Neither time to ramet emergence nor the number of ramets that emerged was influenced by nitrate level in the watering solution. We used the above results in combination with ramet emergence data from plants grown outdoors at Davis, California to develop degree-day equations for three separate ramet cohorts. When compared to ramet emergence from different plants in different years, there was very good agreement between predicted and actual ramet emergence indicating that these equations provide a realistic representation of processes involved in ramet emergence. This is an important step in developing integrated management plans for this species.

We developed an equation for estimating Arundo donax shoot dry weight from shoot length. The equation, shoot dry weight (g) = 14.254 (standard error = ±0.275) × shoot height 2 (m), was as effective at explaining a high proportion of total variation in shoot dry weight ( R 2 = 0.90) as more complicated equations containing additional morphometric parameters. Tested against two independent datasets, the equation provided accurate estimates of dry weight for shoots ranging from 0.3 to 7.06 m height (dataset 1, P R 2 = 0.87, N = 29; dataset 2, P R 2 = 0.82, N = 192). The equation provides aboveground biomass estimates from stem counts and heights more rapidly than harvest methods.

Acanthamoeba castellanii is a free-living amoeba found in soil, freshwater, and marine environments and an important predator of bacteria. Acanthamoeba castellanii is also an opportunistic pathogen of clinical interest, responsible for several distinct diseases in humans. In order to provide a genomic platform for the study of this ubiquitous and important protist, we generated a sequence survey of approximately 0.5 x coverage of the genome. The data predict that A. castellanii exhibits a greater biosynthetic capacity than the free-living Dictyostelium discoideum and the parasite Entamoeba histolytica, providing an explanation for the ability of A. castellanii to inhabit a diversity of environments. Alginate lyase may provide access to bacteria within biofilms by breaking down the biofilm matrix, and polyhydroxybutyrate depolymerase may facilitate utilization of the bacterial storage compound polyhydroxybutyrate as a food source. Enzymes for the synthesis and breakdown of cellulose were identified, and they likely participate in encystation and excystation as in D. discoideum. Trehalose-6-phosphate synthase is present, suggesting that trehalose plays a role in stress adaptation. Detection and response to a number of stress conditions is likely accomplished with a large set of signal transduction histidine kinases and a set of putative receptor serine/threonine kinases similar to those found in E. histolytica. Serine, cysteine and metalloproteases were identified, some of which are likely involved in pathogenicity.

The nucleotide sequences of wheat embryo 5.8-S and 5-S rRNAs have been determined with the use of several techniques, including classic analysis of oligonucleotides generated by ribo-nuclease T1 and resolution on gels of termiNatly labelled RNA partially degraded with ribonucleases or with chemical reagents. The sequence of wheat embryo 5.8-S rRNA was found to be p(C)-A-C- 5.8-S RNAs, the accommodation of this sequence by current secondary structural models, and the significance of the observed post-transcriptional modification pattern are discussed. The sequence . This sequence is compared to 5-S rRNA Sequences previously published for wheat and several other angiosperms.

We hypothesized that if aquatic plants were competing for nutrients then the spatial distribution and sizes of roots should change when competitors were present. Stukenia pectinatus, Potamogeton nodosus, and Hydrilla verticillata (monoecious type) were grown in either monocultures or mixtures in polyvinylchloride containers. Four 5 cm diameter minirhizotrons were mounted horizontally across the containers so that they were 2.5, 12.5, 22.5, or 32.5 cm below the surface of the sediment, and we inserted a specialized video camera in each minirhizotron tube and recorded root images at 21 locations in each tube. For two of three cases, adding plants of another species changed the root depth distribution and increased the volume of soil occupied by roots compared to monocultures. Additionally, smaller diameter roots were more abundant when competitors were present. This implies that the plants adjusted to the presence of competitors by producing more roots capable of nutrient uptake. These results impl...

Arundo donax L. is a tall perennial reed classified as an emergent aquatic plant. In California, it has invaded riparian zones, where it acts as a transformer species. Because plant growth and leaf quality influence the effectiveness of management techniques, we sought to determine if these characters varied temporally and spatially in a northern California population of A. donax. Tissue C and N content and C:N ratio varied during the growing season. Leaf N was higher in spring and in plants that were closer to a stream. It was significantly negatively related to the clump's distance from the stream but not related to its elevation relative to the stream. Plants near the stream produced taller stems with more leaves per stem than those more distant from the stream. RGR differed across time and space. It was highest in spring prior to the appearance of flowers on a few stems that were >1 year old within the clumps. Decline in RGR as the growing season progressed coincided with the appearance of branches and flowers on stems 1 year old). This implies that the decrease in stem growth reflected changes in nutrient availability within the entire A. donax clump and not just in the growing stems (

Biomass, akinete numbers, net photosynthesis, and respiration of Pithophora oedogonia were monitored over two growing seasons in shallow Surrey Lake, Indiana. Low rates of photosynthesis occurred from late fall to early spring and increased to maximum levels in late spring to summer (29–39 mgO2·g−1 dry wt·h−1). Areal biomass increased following the rise in photosynthesis and peaked in autumn (163–206g dry wt·m−2). Photosynthetic rates were directly correlated with temperature, nitrogen, and phosphorus over the entire annual cycle and during the growing season. Differences in photosynthetic activity and biomass between the two growing seasons (1980 and 1981) were apparently related to higher, early spring temperatures and higher levels of NO3-N and PO4-P in 1981. Laboratory investigations of temperature and light effects on Pithophora photosynthesis and respiration indicated that these processes were severely inhibited below 15°C. The highest Pmax value occurred at 35°C (0.602 μmol O2·mg−1 chl a·min−1). Rates of dark respiration did not increase above 25°C thus contributing to a favorable balance of photosynthetic production to respiratory utilization at high temperatures. Light was most efficiently utilized at 15°C as indicated by minimum values of Ik(47 μE·m−2·s−1) and Ic (6 μE·m−2·s−1). Comparison of P. oedogonia and Cladophora glomerata indicated that the former was more tolerant of temperatures above 30°C. Pithophora's tolerance of high temperature and efficient use of low light intensity appear to be adaptive to conditions found within the dense, floating algal mats and the shallow littoral areas inhabited by this filamentous alga.

Predicting aquatic plant growth based on sediment nutrients is problematic. Two experiments with sandy or silty sediments from Fall River, California were performed to identify the limiting nutrient for two abundant species of submersed plants in the river. Growth of Zannichellia palustris L. or Elodea canadensis Rich, was significantly enhanced by the addition of N or a combination of N and P to sandy sediments but not those that were silty. Root shoot ratios declined for plants growing with added nutrients. Plant tissue N concentrations increased as well. Tissue N:P ratios indicated that N rather than P limited growth. Results support the literature hypothesis that sediment N availability may limit growth and distribution of submersed rooted aquatic plants.

Currently at the Idaho National Engineering and Environmental Laboratory, a handheld device is being developed to measure fast neutrons and gamma rays using a single detector. The handheld detection system presented uses a single 12.7 mm (diameter) by 12.7 mm (length) liquid scintillator detector (BC501). The detection system can be made small and light. A small and light device can be used in several applications such as customs inspection, border security, and environmental radiation monitoring. The use of only one detector requires that the neutrons and gamma rays be distinguished by the shape of their pulses in the detector. Two methods of pulse shape discrimination (PSD) are presented: charge integration and zero crossing. Figures of merit were calculated for both methods for a threshold energy range of 50-600 keVee. Results show that the zero crossing method gives much better PSD for 100 keVee and lower, whereas the charge integration method leads. to better separation above 100 keVee. However, the neutrons and gamma rays are totally separated for energies of 100 keVee and above in both techniques. We are currently designing a miniaturized electronic system to be incorporated into the handheld device.

We report evidence of extensive substitutional editing of mitochondrial mRNAs in the dinoflagellate species Pfiesteria piscicida, Prorocentrum minimum and Crypthecodinium cohnii, based on a comparison of genomic and corresponding cDNA sequences determined for two mitochondrial DNA-encoded genes, cox1 (cytochrome oxidase subunit 1) and cob (apocytochrome b ). In the cox1 mRNA, we identify 72 substitutions at 40 sites in 39 codons, whereas in cob mRNA, we infer 86 editing events at 51 sites in 48 codons. Editing, which takes place in distinct clusters, changes , 2% of the total sequence, occurs predominantly at first and second positions of codons, and involves mostly (but not exclusively) A ! G (47%), U ! C (23%) and C ! U (17%) substitutions. In all but four of the 158 cases, editing changes the identity of the specified amino acid. At 21 (cox1 ) and 26 (cob ) sites, the same nucleotide change is observed at the same position in at least two of the species investigated. At about onethird of the sites, editing results in an amino acid change that increases similarity between the dinoflagellate Cox1 and Cob sequences and their homologs in other organisms; presumably editing at these sites is of particular functional significance. Overall, about half of the editing events either maintain or increase similarity between the dinoflagellate protein sequences and their non-dinoflagellate homologs, while a further onethird of the alterations are “dinoflagellate-specific” (i.e. they involve a change to an amino acid residue selectively conserved in at least two of the dinoflagellate species at a given position). The nature, pattern and phylogenetic distribution of the inferred edits implies either that more than one type of previously described editing process operates on a given transcript in dinoflagellate mitochondria, or that a mechanistically unique type of mitochondrial mRNA editing has evolved within the dinoflagellate lineage. q 2002 Elsevier Science Ltd. All rights reserved

A variation of the basic Cockroft-Walton (C-W) voltage multiplier circuit design may be used to generate multiple voltages at sufficient currents to drive the dynodes of a photomultiplier tube. In a battery-operated handheld device, the current draw on the batteries must be kept to a minimum. Several other parameters must be considered carefully during the design as well. Components must be chosen based on size restrictions, expected load current, expected output voltage range, and the maximum allowable ripple in the output voltage. A prototype surface mount C-W board was designed and tested to power two photomultipliers. The whole system, including the detectors, draws less than 15 mA of supply current with the outputs at 1000 Vdc.

Giant reed is an emergent aquatic plant that may be weedy in riparian habitats. Two herbicides approved for controlling giant reed in the US are glyphosate (N-(phosphonomethyl) glycine) and imazapyr (2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid). Foliar applications of these herbicides may be restricted in some areas, such as those, which are within the range of threatened or endangered species. We conducted two field experiments at sites in northern and central California. The first experiment evaluated the effects of three aquatic herbicides (glyphosate, imazapyr, and triclopyr [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid) injected into all of the stems within a giant reed (5 mL stem(-1)). In this experiment, leaf chlorophyll content, the proportion of living stems, and the number of new stems produced during the year after treatment declined (80%) following injection of either full strength glyphosate or imazapyr. The effects of injecting full strength triclopyr were considerably less. In a second experiment, different proportions (0, 10%, 25%, or 100%) of the stems within a plant were injected with full strength glyphosate. Results indicated that it was necessary to inject all of the stems within a clump to achieve the greatest reduction in the plant growth characteristics measured. These results imply that giant reed may be successfully controlled by injecting full strength glyphosate (5 mL stem(-1)) into all of the stems within a clump. While labor intensive and thus potentially more costly this method, offers a new method for managing giant reed in sensitive sites where foliar spray applications may be restricted.

A laboratory growth experiment indicated that the ribbon-leaved Potamogeton gramineus L. had a lower light compensation point for growth (LCP) than the thread-leaved P. pectinatus L. LCP and 95 % confidence intervals (CI) were 0.86 M m−2 day−1 (95% CI, −0.006 to 1.540) and 3.87 M m−2 day−1 (95% CI, 3.12 to 4.63), respectively. When germinated propagules of each species were planted in a P. gramineus stand in the Byrnes Canal, P. pectinatus exhibited lower survival than similar plants placed in the canal but outside the P. gramineus bed. Mean plant weight for P. pectinatus grown within the plant bed was less than 10 % of that for plants grown outside the P. gramineus bed. Neither survival nor mean dry weight of P. gramineus planted at the same sites differed among the sites. Estimates of light levels in the P. gramineus bed indicated that shading by P. gramineus reduced light to levels at or below the LCP for P. pectinatus but above the LCP for P. gramineus. These results suggest that P. pectinatu...

The ability to predict sprouting of aquatic macrophyte vegetative propagules is an important step in understanding their temporal distribution and abundance and in developing long-range management strategies. We examined the ability of degree-day based equations to predict monoecious hydrilla (HydriIIa verticillata L. f. Royle) tuber and turion sprouting in Clear Lake, Californai using sediment and water temperatures measured in the lake. Sediment temperature data were used to calculate accumulated degree-days. Sprouting of turions and tubers was estimated using previously developed equations relating sprouting to accumulated degree-days. There was good agreement between sprouting predictions and field data on the presence of hydrilla in weed rake samples. Small differences among water temperatures at the five sites and strong relationships between water and sediment temperatures indicate that sprouting should be similar in hydrilla beds found along the western and southern shores of upper Clear Lake. These results can be used to estimate optimal timing for surveys of hydrilla abundance and the application of hydrilla management techniques.

The purpose of this study was to develop equations that predict emergence from vegetative propagules for four species of aquatic plants. We established artificial propagule banks by growing monoecious and dioecious Hydrilla verticillata (L.f.) Royle, Potamogeton pectinatus L., Potamogeton nodosus Poiret in outdoor tanks in Davis, California. Dioecious H. verticillata, P. pectinatus, P. nodosus and Vallisneria americana L. were grown in similar tanks in Lewisville, Texas. Emergence of undisturbed propagules was monitored the following spring. In California, P. pectinatus tubers, P. nodosus winter buds, and axillary turions formed by monoecious H. verticillata began to sprout at about the same time in mid-February, while dioecious H. verticillata tubers did not begin to emerge until mid-August. The distinct separations of emergence times for propagules in the Texas experiment were similar to those observed in California, and V. americana showed the earliest emergence time. Using sediment temperature data from each location, we calculated degree-days using the single triangle method. We fit a single logistic equation relating cumulative emergence to accumulated degree-days for each species-propagule combination from the two locations.

We compared seasonal changes in tissue C, tissue N, C:N ratio, and total phenolic acids for five species of submersed plants from Fall River, California. Mean tissue C differed among the five species and was between 35 and 40%, except for Ranunculus aquatilis, which was 26%. Mean tissue N differed among species; Ranunculus aquatilis had the lowest mean value (2.71%) and Zannichellia palustris had the highest (3.74%). Mean C:N ratio was between 9.7 and 12.7. Among the five species examined, mean phenolic acid content was greatest for Myriophyllum sibiricum and it was nearly seven times that for the species with the lowest phenolic acid content, Elodea canadensis. Regression analysis indicated positive relationships between phenolic acid content and tissue C for two species, Callitriche hermaphroditica and Ranunculus aquatilis. Regression equations relating phenolic acid content to tissue N were not statistically significant. For Elodea canadensis, the equation describing phenolic acid content as a...

Resource allocation reflects a plant's response to its environment and affects its overall growth and performance in a particular habitat. We measured ash, C, N, and caloric content for various parts of Hydrilla verticillata (L.f.) Royle, Potamogeton nodosus Poir., P. gramineus L., and P. pectinatus L. Mean ash content of vegetative propagules ranged from 2.96 to 5.46%, lower than values previously reported for aquatic plant shoots. Potamogeton propagule C and N contents were greater than those of Hydrilla propagules. Mean propagule caloric content ranged from 3753 to 4198 cal g−1 and construction costs from 1.00 to 1.12 g glucose g−1. They were similar to or slightly greater than those for shoots or leaves. Construction costs for leaves of eight aquatic species averaged 1.02 g glucose g−1. Vegetative propagules had sink strengths similar to those of shoots. H. verticillata, P. pectinatus, and P. gramineus were grown in a greenhouse with different levels of N in the water column. In this experiment, P. pectinatus and H. verticillata roots had higher construction costs than shoots whereas P. gramineus did not. Only the costs for P. pectinatus shoots and roots were affected by the N level in the water column. Construction costs for aquatic plant vegetative propagules, shoots, and roots were lower than similarly calculated values published for roots, stems and leaves of terrestrial plants, in agreement with expectations based on the structural characteristics of leaves and stems of aquatic plants.

Vegetative propagules ofPotamogeton pectinatus, P. gramineus, andHydrilla verticillata were exposed to aerobic or anaerobic atmospheres for 7, 14, or 21 days in the dark at 18°C or 7°C. There were no differences in the proportion of propagules sprouting due the presence or absence of oxygen. However, propagules exposed to an anaerobic atmosphere at 18°C sprouted sooner than those exposed to an aerobic atmosphere. This effect was less apparent when exposure to anaerobic conditions was at 7°C. In field experiments,Potamogeton gramineus winter buds were buried at 4 depths in Byrnes Canal sediment. Those buried for 25 days at 25 cm (where sediment redox potential is < 50 mV and conditions are likely hypoxic) showed discoloration consistent with sulfide deposition, and they sprouted more rapidly than winter buds buried at 5 or 15 cm. As the duration of burial in Byrnes Canal sediment increased, propagule sprouting time decreased. Predicting the timing of propagule sprouting in habitats with fluctuating water levels may benefit from information on seasonal changes in the oxygen status of the sediments.

To provide insights into the occurrence, evolution, and phylogenetic distribution of discontinuous mitochondrial and chloroplast large subunit ribosomal RNAs (LSU rRNAs) among green algae, we surveyed 12 taxa representing three classes of green algae: the Chlorophyceae, Pleurastrophyceae, and Micromonadophyceae (sensu Mattox and Stewart 1984). We present evidence that discontinuous mitochondrial and chloroplast LSU rRNAs are quite widespread among green algae. Mitochondrial LSU rRNAs appear discontinuous in zoosporic chlorophycean lineages displaying a clockwise or directly opposed configuration in their flagellar apparatus, as well as in chlorococcalean autosporic taxa phylogenetically related to them, but are continuous among zoosporic green algal lineages with a counterclockwise flagellar apparatus configuration, as well as among chlorococcalean autosporic taxa phylogenetically related to them. Chloroplast LSU rRNAs appear discontinuous in all of the lineages investigated. Discontinuous mitochondrial LSU rRNA represents a molecular trait that might have originated at or near the base of Chlorophyceae, whereas discontinuous chloroplast LSU rRNA might have developed very early in the evolutionary history of the green algal group itself. We suggest, therefore, that the presence of discontinuous mitochondrial but not chloroplast LSU rRNA can be used as an additional character in assessing phylogenetic affiliations among green algae.

Hydrilla verticillata (L. f.) Royle tubers from monoecious plants andPotamogeton gramineus L. winter buds were sprouted and allowed to grow in the dark for 120 days. We measured plant length and counted the number of leaves at 2–3 day intervals.Hydrilla grew most rapidly during the first 16–17 days andPotamogeton grew most rapidly during the first 16–25 days. Measurement of propagule carbon content over time indicated that cessation of rapid growth coincided with depletion of tuber carbon by one-half forHydrilla. ForPotamogeton, growth was reduced after 16 to 25 days while the winter bud C half-life was 37 days. Calculations indicated thatHydrilla mobilized 49% andPotamogeton 39% of the initial propagule carbon to support growth. In a second experiment, in which plants were grown in substrate the plants grew taller and produced slightly more leaves per plant.Potamogeton removed from darkness after specified time periods, and allowed to grow for 21 days in a greenhouse recovered from 20–30 days in the dark. Similarly treatedHydrilla plants recovered from up to 80 days in the dark.Potamogeton had mobilized 79% of initial C by the time it was unable to recover from the dark treatment. Combined results for both species indicate that the majority of propagule C was utilized in the first 16 to 30 days following sprouting. In conjunction with an understanding propagule sprouting requirements, this information will be useful in the timing of application for management techniques.

Subterranean vegetative propagules are important life cycle stages for some species of rooted aquatic plants. Sediments contain numerous compounds resulting from anaerobic degradation of organic matter, including acetic acid. Tubers, turions, and winter buds of Hydrilla verticillata (L.f.) Royle, Potamogeton gramineus L., and Potamogeton pectinatus L. were exposed to acetic acid concentrations from 0 to 696 mmol l−1 for 1–8 days. Hydrilla verticillata propagules were more sensitive to acetic acid exposure than those of either Potamogeton species. Monoecious H. verticillata propagules did not sprout at acetic acid concentrations of 17 mmol l−1 or over, even at the shortest exposure time. Potamogeton gramineus winter buds and P. pectinatus tubers were less inhibited between 17 and 87 mmol l−1 if the exposure time was short (2 days or less). Sediment type did not influence the differential response to acetic acid, but the presence of sediments ameliorated the effects of acetic acid somewhat. More than two-thirds of P. pectinatus tubers sprouted after a 24 h exposure to 696 mmol l−1 at 4°C, at higher temperatures sprouting was greatly reduced. Hydrilla verticillata tubers did not sprout following exposure to 17 mmol l−1 at any temperature (4, 13, 19, and 25°C) examined.

Spirogyra Link (1820) is an anabranched filamentous green alga that forms free-floating mats in shallow waters. It occurs widely in static waters such as ponds and ditches, sheltered littoral areas of lakes, and stow-flowing streams. Field observations of its seasonal distribution suggest that the 70-μm-wide filament form of Spirogyra should have a cool temperature and high irradiance optimum for net photosynthesis. Measurements of net photosynthesis and respiration were marie at 58 combinations of tight and temperature in a controlled environment facility. Optimum conditions were 25°C and 1500 μmol photons m−2 s−1, at which net photosynthesis averaged 75.7 mg O2 gdm−1 h−1. Net photosynthesis was positive at temperatures from 5° to 35°C at most irradiances except at combinations of extremely low irradiances and high temperatures (7 and 23 μmol photons m−2 s−1 at 30°C and 7, 23, and 35 μmol photons m−2 s−1 at 35°C). Respiration rates increased with both temperature and prior irradiance. Light-enhanced respiration rates were significantly greater than dark respiration rates following irradiances of 750 μmol photons m−2 s−1 or greater. Polynomials were fitted to the data to generate response surfaces; such response surfaces can be used to represent net photosynthesis and respiration in ecological models. The data indicate that the alga can tolerate the cool water and high irradiances characteristic of early spring but cannot maintain positive net photosynthesis under conditions of high temperature and low light (e.g. when exposed to self-shading).

Potamogeton pectinatus, P. gramineus, and monoeciousHydrilla verticillata were grown in greenhouse experiments at 2 photoperiods, 5 levels of sediment nutrients, and from initial propagules of 3 different size classes to determine how these factors influenced growth and production of vegetative propagules.Potamogeton pectinatus weight increased with increasing tuber size and soil fertility, but differences between plants grown at two photoperiods were small. Mean weight of tubers was greater for plants grown under a 10-h photoperiod and from tubers in the medium or large size class. Tuber production by plants grown from small tubers under a 10-h photoperiod was much less and was about the same as that for all plants grown under the 16-h photoperiod whatever the initial tuber size.Potamogeton gramineus weight was greater for plants grown on more fertile soils at the 16-h photoperiod. Plant weights at the 10-h photoperiod were less affected by soil fertility. Plants from larger winter buds weighed more. Winter buds were only produced under the 10-h photoperiod. ForH. verticillata, there were several significant interactions. In general, plants from larger tubers weighed more if they grew on more fertile soils or at the 16-h photoperiod. Plants grown at the short photoperiod produced more tubers with increasing soil fertility and with increasing propagule size. These results imply that propagule size may be important in determining aquatic plant persistence in an area through its effects on growth and propagule production.

Cryptophyte and chlorarachniophyte algae are transitional forms in the widespread secondary endosymbiotic acquisition of photosynthesis by engulfment of eukaryotic algae. Unlike most secondary plastid-bearing algae, miniaturized versions of the endosymbiont nuclei (nucleomorphs) persist in cryptophytes and chlorarachniophytes. To determine why, and to address other fundamental questions about eukaryote–eukaryote endosymbiosis, we sequenced the nuclear genomes of the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans. Both genomes have

A restriction-fragment-length polymorphism (RFLP) in mitochondrial DNA (mtDNA) was detected between varieties of fall rye (Secale cereale L.) by Southern hybridization with rrn18, the gene encoding the mitochondrial 18S ribosomal RNA. Restriction mapping showed that the RFLP is based on differing numbers of genomic contexts (one vs three) for a recombining-repeat element (the "18S/5S repeat"). From examination of other Secale species, we conclude that the one-context state arose relatively recently, putatively by deletion of two of an ancestral set of three distinct genomic loci containing the mitochondrial 18S/5S repeat. This is consistent with our earlier conclusion that the 18S/5S repeat has probably existed in at least two genomic copies throughout much of the history of the grass family (at least 40 million years). Interestingly, the intervarietal difference in the number of distinct rrn18 loci is not accompanied by a major difference in the number of rrn18 copies per unit mass of mtDNA. This suggests the existence of a mechanism that can compensate rather precisely for differences in mitochondrial gene dosage, perhaps by over-replication or stabilization of specific subgenomic molecules.

Potamogeton gramineus L. winter buds were present in the Byrnes Canal in northern California from August through October. Density (number m−2) of winter buds increased during this period and was inversely related to photoperiod. Density varied from year to year (1985–1991) and maximum average density of 761 m−2 was recorded in 1986. In greenhouse experiments, winter buds were present on plants after 8–10 weeks of growth at a 10 h photoperiod, but not at a 14 photoperiod. Plants grown at a 10 h photoperiod but with the dark period interrupted with either 20 or 60 min of dim light at 13 μM m−2 s−1 did not produce winter buds. Similar plants grown at a 10 h photoperiod with no interruption of the dark period produced winter buds. Plants grown with interruption of the dark period displayed dry matter allocation patterns similar to plants grown at a 16 h photoperiod. This information confirms earlier reports with other species about the importance of photoperiod for initiating vegetative propagule formation, and will improve capabilities for predicting vegetative reproduction by rooted aquatic plants.

Plants of Hydrilla verticillata (L.f.) Royle were grown under two photoperiods (11 or 15 h) in a greenhouse. Under the 11 h photoperiod, Hydrilla produced geotropic shoots after 34 days, tubers were first observed at 48 days, and turions after 76 days. During this study, Hydrilla plants grown under the 11 h photoperiod produced 317 tubers, and those grown under the 15 h photoperiod produced two tubers. C and N were directed from other plant structures, especially shoots and roots, into newly formed tubers and turions. C was allocated to new tubers at a rate that was about 43 times that for N. After 12 weeks, about 15 times more C and N were allocated to tuber production than to turion production. Nutrient use efficiency for N increased significantly in both photoperiods. N use efficiency was not a good indicator of the onset of tuber or turion production.

This paper describes a program which simulates growth of the aquatic plant, Potamogeton pectinatus L. (sago pondweed), and plant consumption by the herbivorous fish, Ctenopharyngodon idella Val (triploid grass carp), under environmental conditions characteristic of a northern California irrigation system. In the program, plant growth is driven by temperature and light intensity, and grass carp feeding and growth by water temperature. The program uses data on these variables collected from the Byrnes Canal using data loggers which recorded temperature and light at 0.5-h intervals on 115 days during the summer of 1989. Less extensive data sets from two other canals were used to construct realistic simulation scenarios for canals with warmer or cooler water temperatures. The program provided reasonable predictions of plant growth, plant consumption by the fish, and fish growth. Simulations showed that using triploid grass carp in northern California irrigation systems that typically have cool water temperatures (12 to 24°C) would require more fish (50 or 250 kg vegetated ha−1 depending on the management objectives) than previous simulations for lakes in the U.S. would suggest. Evaluation of two management strategies indicated that stocking grass carp at 50 kg vegetated ha−1 in the first year, and retrieving and releasing them in subsequent years would be economically competitive with current management practices.

SUMMARY 1. Data on sample means (x|) and variances (s2) of propagule abundance for five typos of aquatic plants growing in a variety of habitats were collected. The data set consisted of 379 values for x| and s2, based on 4942 individual sample units (sediment samples), drawn from the literature or from data collected as part of this study. 2. Regression analysis relating log s2 to log x| yielded an equation which was solved for the number of sample units (n) required to achieve a given degree of precision. For precise estimates [standard error (SE) = 20% of x|], values of n between twenty-seven and 234 are required when propagule density is low (

We sampled areas of two canals (Solano Irrigation District, California) that were dominated by Potamogeton gramineus L. The ratios of variance to mean for winter bud abundance in the Byrnes Canal indicated that winter buds were not randomly distributed. Clumping was detected at a patch size of 7.2 cm diameter in both 1985 and 1989. Applying two quadrat variance methods to data from the Weyend Canal also indicated that winter buds were clumped. The radius of the patch size was 1.65 m. Patch edges were not sharply defined, and the spaces between patches were not empty. Geostatistical analysis yielded an experimental semivariogram for winter bud abundance, using the spherical equation, with a sill of 49776, a nugget of 32378, and a range of influence of 57 m.

Potamogeton pectinatus L., grown in greenhouse cultures, was harvested from three photoperiod treatments (16 h, 10 h, and 16 h switched to 10 h after four weeks) at weekly intervals. Plant weight increased over time, and those plants grown at a 16 h photoperiod showed the greatest increase. Plants began to produce tubers after 70 to 77 days at all photoperiods. Plants grown at the 16 h photoperiod and those initially grown at 16 h and switched to the 10 h photoperiod allocated less biomass to new tubers (ca. 5%) than those grown at the 10 h photoperiod (ca. 30%). Plants grown at the 10 h photoperiod had decreased weights of stems and leaves. Plants grown at the long photoperiod produced tubers after attaining dry weights between 0.8 and 1.0 g. Plants grown at the short photoperiods produced tubers regardless of plant weight, but the frequency of tuber production increased for larger plants. Changes in the pigment and protein content of leaves were not associated with the onset of tuber production.

Field experiments may be useful for researchers and managers concerned with aquatic plants. Since experimental design and statistical analysis are closely related, this paper discusses statistical and practical considerations for conducting and evaluating field experiments with aquatic plants. Special emphasis is given to the analysis of variance, assumptions required for its use, and concepts related to it (e.g., statistical power, means comparison procedures, treatment structure, pseudoreplication, etc.). The paper concludes with a brief introduction to papers in the literature which illustrate the use of field experiments for studying aquatic plants.

Because relatively little information is available about mtDNA in the euglenid protozoa, distant relatives of the kinetoplastid protozoa, we investigated mitochondrial genome structure and expression in Euglena gracilis. We found that isolated E. gracilis mtDNA comprises a heterodisperse collection of short molecules (modal size approximately 4 kbp) and that the mitochondrial large subunit (LSU) and small subunit (SSU) rRNAs are each split into two pieces. For the two halves of the SSU rRNA, we identified separate, non-contiguous coding modules that are flanked by a complex array of (primarily direct) A + T-rich repeats. The potential secondary structure of the bipartite SSU rRNA displays the expected conserved elements implicated in ribosome function. Label from [α-(32)P]GTP was incorporated in the presence of guanylyltransferase into each of the separate SSU and LSU rRNA fragments, confirming that these RNAs are primary transcripts, separately expressed from non-contiguous rRNA modules. In addition to authentic genes for SSU rRNA, we discovered numerous short fragments of protein-coding and rRNA genes dispersed throughout the E. gracilis mitochondrial genome. We propose that antisense transcripts of gene fragments of this type could have been the evolutionary precursors of the guide RNAs that mediate U insertion/deletion editing in the kinetoplastid relatives of the euglenids. To the extent that E. gracilis mtDNA is a representative euglenid mitochondrial genome, it differs radically in structure and organization from that of its kinetoplastid relatives, instead more closely resembling the mitochondrial genome of dinoflagellates in many of its features, an apparent evolutionary convergence.