David D. Biesboer

PERFORMANCE OF EROSION CONTROL PRODUCTS ON A HIGHWAY EMBANKMENT

Unprotected soil at construction sites often results in large rates of erosion. Five different erosion control treatments were tested on the slopes of a highway sedimentation basin to determine their impact on vegetative growth, runoff, and erosion. The treatments were a bare (no treatment) condition, a disk–anchored straw mulch, a wood–fiber blanket, a straw/coconut blanket, and a bonded–fiber matrix product (hydraulically applied). A minimum of three replicates was used for each treatment. Straw mulch was selected as the standard treatment for statistical analyses. The site was planted with native prairie seeds, and the establishment of vegetation was monitored over the growing season. Above–ground biomasses for the bare and straw–mulch treatments were statistically greater than those of the bonded–fiber matrix treatment. Statistically significant differences in above–ground biomass for the other treatments were undetected at the 10% level. Weedy grasses and forbs were the dominant plant species. Runoff and erosion data were collected using a rotating–boom rainfall simulator for spring and fall sets of runs corresponding to little and good vegetative growth, respectively. Runoff depths were generally larger from straw–mulch and bare plots. There were no statistically significant differences in relative runoff depth between the blankets and the bonded–fiber matrix product. Under conditions with little vegetation, erosion from the straw–mulch plots was roughly one–tenth of that from the bare soil plots; erosion from the blanket and bonded–fiber matrix plots was roughly one–tenth of that from the straw–mulch plots. There were no statistically significant differences in relative sediment yield between the blankets and the bonded–fiber matrix. Erosion from bare and straw–mulch treatments was greatly reduced by vegetative growth that occurred between the spring and fall runs.

Effects of a potential biocontrol agent, Euhrychiopsis lecontei, on Eurasian watermilfoil in experimental tanks

Eurasian watermilfoil (Myriophyllum spicatum L.) is a submersed macrophyte, exotic to North America where it is a major nuisance. One potential biological control agent is the native weevil Euhrychiopsis lecontei (Dietz) (Curculionidae). To determine the effects of known densities of the weevil on Eurasian watermilfoil in controlled conditions, we stocked weevils into outdoor 0.38 m3 tanks containing watermilfoil. Watermilfoil stems (20 cm long; 150 m−2 were planted in each tank and given 3 weeks to root and grow. Plants developed extensive roots and grew 10–15 cm prior to stocking. Weevils were then applied at four stocking densities (0, 6, 12 or 24 adults) to 16 tanks arrayed in a Latin square design. Plant length was measured and weevils were counted weekly in the tanks. Sediment nutrients, plant mass and nutrient content, and weevil densities were determined from a sample of plants prior to stocking and 3 and 4 weeks after stocking. After 4 weeks, all plant material was removed, biomass was determined and weevils were counted. Weevils survived in the stocked tanks and eggs appeared soon after introduction. There was an average of over 200 weevils (25 adults) in each of the stocked tanks at 4 weeks. Weevil stocking density resulted in a significant decline in watermilfoil biomass (P < 0.005) with biomass in the tanks stocked with 24 weevils reaching only 40% of the control. Root biomass also declined with weevil density (P < 0.005) and biomass in the high density tanks reached only 55% of the control. However, detached sunken and floating watermilfoil biomass increased with density of weevils and no change in total above ground biomass (sum of standing, floating and sunken watermilfoil) was found, indicating that effects were caused by plant damage rather than direct consumption. Periodic estimates of plant height, mass and root mass showed that effects on plants resulted from reductions in stems and roots from peak levels at Weeks 2 or 3 and were thus not simply a suppression of growth. Percent sugars and total nonstructural carbohydrates declined with stocking density in both roots and shoots. The total stock (g per plant) of sugars, starch and total nonstructural carbohydrates was reduced in the roots. Weevil densities of ≈ 300 m−2 can have rapid and substantial effects on Eurasian watermilfoil both above and below ground. Herbivory by weevils may have long term effects via disruption of plant carbohydrate stores that are essential for overwinter survival and subsequent regrowth.

LABORATORY STUDY OF HEAVY METAL PHYTOREMEDIATION BY THREE WETLAND MACROPHYTES

Detention ponds and constructed wetlands have proven to be effective in reducing peak stormwater runoff volume and flow, and recent interest has extended to utilizing them to improve stormwater runoff quality. A review of stormwater runoff studies indicated that lead, zinc, copper, cadmium, phosphorus, and chloride are contaminants of primary concern. In laboratory settings, the uptake of contaminants by three wetland plant species, Glyceria grandis, Scirpus validus, and Spartina pectinata, was examined and removal rates from nutrient solutions in flow and nonflow reactors were measured. The removal rates varied by plant species and target contaminant, and no one species was the best accumulator of all six contaminants. Belowground tissues of all three species accumulated higher concentrations of the four heavy metals and aboveground tissues accumulated higher concentrations of phosphorus and chloride. Plants grown in flow reactors showed significantly higher accumulation rates than those grown in nonflow reactors. Also, plants grown hydroponically accumulated higher concentrations of the six target contaminants than those grown in sand reactors. However, those grown in sand had a much greater increase of biomass and removed a greater mass of the six target contaminants. Removal rates measured in these experiments can be used to design detention ponds to maximize stormwater remediation.

Potential denitrification in submerged natural and impacted sediments of Lake Batata, an Amazonian lake

Lake Batata is one of many clear water lakes located on the floodplain of the Trombetas River in the northern Brazilian Amazon. Lake Batata is distinctly different from other lakes of this region because, for a period of 10 years, its waters received tremendous amounts of aluminum ore tailings from a bauxite mining operation. Approximately 30% of the sediments of the upper basin of the 2100 hectare lake were covered by tailings before dumping was curtailed. The goal of this research was to identify factors controlling denitrification in the natural and impacted sediments of Lake Batata. Rates of denitrification in sediments were estimated in the laboratory by the acetylene blockage method. Denitrification was measured under four conditions: without amendment; amended with glucose; amended with nitrate; and amended with glucose and nitrate. Denitrification was observed only in assays amended with nitrate suggesting that availability of nitrate is a principle factor for controlling denitrification in the sediments of Lake Batata. Effects of nitrate amendments are most pronounced when the water level is low, i.e. during the hydroperiods of draw-down and low-water.

Accumulation of non-utilizable starch in laticifers of Euphorbia heterophylla and E. myrsinites.

Starch biosynthesis and degradation was studied in seedlings and mature plants of Euphorbia heterophylla L. and E. myrsinites L. Mature embryos, which lack starch grains in the non-articulated laticifers, develop into seedlings that accumulate starch rapidly when grown either in the light or the dark. Starch accumulation in laticifers of dark-grown seedlings was ca. 47 and 43% of total starch in light-grown controls in E. heterophylla and E. myrsinites, respectively. In light-grown seedlings, starch was present in laticifers as well as parenchyma of stems and leaves, whereas in dark-grown seedlings starch synthesis was almost exclusively limited to laticifers. In 7-month-old plants placed into total darkness, the starch in chyma was depleted within 6 d, whereas starch in laticifers was not mobilized. The starch content of latex in plants during development of floral primordia, flowering, and subsequent fruit formation remained rather constant. The results indicate that laticifers in seedlings divert embryonal storage reserves to synthesize starch even under stress conditions (darkness) in contrast to other cells, and that starch accumulated in laticifers does not serve as a metabolic reserve. The laticifer in Euphorbia functions in the accumulation and storage of secondary metabolites yet retains the capacity to produce, but not utilize starch, a primary metabolite.

Influence of alkaloid precursors on the alkaloid content of Nicotiana alata root cultures

Abstract Root cultures of Nicotiana alata Link and Otto, growing in a Murashige and Skoog medium, contained the following alkaloid composition: nicotine (5 %), nornicotine (58%), anabasine (10%), and anatabine (27%), all with the ( S )-configuration with high enantiomeric excess. When the root growth was carried out in the presence of increasing concentrations of [2- 3 H]nicotinic acid (0.002–5 mM), there were profound changes in the amounts and composition of the alkaloids after three days incubation. High concentrations of nicotinic acid inhibited both alkaloid formation and the demethylation of nicotine to nornicotine. Anatabine production was stimulated with increasing nicotinic acid concentration. A second series of experiments with a fixed concentration of [2- 3 H]nicotinic acid and increasing amounts of 1-methyl-Δ 1 -pyrrolinium chloride indicated that this latter compound stimulated nicotine production and also inhibited its demethylation. In a third set of experiments it was found that increasing concentrations of [2- 14 C]-Δ 1 -piperideine promoted the production of [2′- 14 C]anabasine and also stimulated nornicotine production.

Sterols and triterpenols in latex and cultured tissues of Euphorbia pulcherrima

Abstract The sterol and triterpenol constituents of Euphorbia pulcherrima latex and cultured callus tissues were examined by GLC and mass spectrometry. Latex extracts from different varieties contained sitosterol, β-amyrin, germanicol, cycloartenol, β-amyrin acetate, and germanicol acetate. Capillary GC profiles of these varieties indicated that the triterpene content was essentially identical for examined latices. Cultured tissues derived from petioles and stem internodes synthesized only sitosterol in significant quantities, although trace amounts of several sterols that occur in latex were also detected in cultured tissues. This study supports the interpretation that the pattern of triterpene synthesis in the laticifer of the normal plant is a highly controlled and stable phenomenon among varieties of this species.

The detection of cells with a laticifer-like metabolism in Asclepias syriaca L. suspension cultures

Plant cell suspension cultures of Asclepias syriaca L. are morphologically homogeneous, that is, most cells in a suspension population are thin-walled, parenchyma-like cells. However, metabolic specialization of certain cells may occur in culture without morphological specialization. This study shows that a small number of suspension cells may synthesize secondary metabolites normally synthesized by a secretory cell, the non-articulated laticifer. The laticifer cell is an elongate, non-septate cell that is present in most intact plant tissues of Asclepias syriaca but which has not been observed to develop in vitro.

Nonreciprocal Hybridization Failure in Crosses between Annual Wild-Rice Species (Zizania palustris X Z. aquatica: Poaceae)

Natural interspecific hybridization has been proposed to account for morphological variation in the annual members of the genus Zizania, commonly known as wild-rice, although isozyme data, as reported in a single study, have disclosed no evidence of introgression. Experimental hybridizations were conducted in all possible combinations among the five varieties of the two annual species of wild-rice. Meaningful intraspecific variation in crossability was not detected, which is in agreement with morphological and isozyme data. A unilateral interspecific crossability barrier was found between the two annual species. Pistillate florets of Z. palustris typically failed to produce viable fruits when pollinated by Z. aquatica. The reciprocal interspecific cross was successful at a low level of crossability. This evidence further strengthens the taxonomic separation of the two annual species previously defined by spikelet morphology, ultrastructure, and isozyme varia- tion. Examination of pollinated stigmas of the infertile types of crosses disclosed that pollen tubes had penetrated the entire length of the stigma. The crossing barrier is therefore not due to a pollen/ stigma interaction that severely interferes with pollen tube growth. Interspecific F, hybrids ex- pressed the spikelet morphology of the Z. aquatica parent exclusively, although other morphological characters were typically expressed as intermediate to those of the parent species. The potential for natural hybridization between Z. aquatica and Z. palustris is discussed.

Anatomical distinctions between the pistillate spikelets of the species of wild-rice (Zizania, Poaceae)

The most reliable macromorphological characters that can be used to discriminate between the annual species of the genus Zizania are found in the pistillate spikelet. One aspect of this morphology is a textural dimorphism. The pistillate lemmas and paleas of Z. aquatica are chartaceous (papery) whereas those of Z. palustris are coriaceous (leathery). Pistillate lemmas and paleas of the two perennial species, Z. texana and Z. latifolia, are also chartaceous. To determine the anatomical basis for the nature of this character, pistillate lemmas and paleas were either fixed, treated with hydrofluoric acid, and sectioned; or fresh material was sectioned on a freezing microtome. Those with a chartaceous texture were found to have a single layer of thin-walled, subepidermal fibers whereas those with a coriaceous texture had at least two layers of thick-walled, subepidermal fibers. THE PISTILLATE SPIKELET in Zizania L. exhibits a dimorphism that is of primary importance in the diagnosis of the two annual species. The systematic significance of this character has been extensively discussed elsewhere and spikelet morphology has gained recent wide acceptance as a diagnostic for the two annual species of Zizania (Dore, 1969; Dore and McNeill, 1980; Terrell and Wergin, 1981; Gould and Shaw, 1983; Aiken, 1986; Aiken et al., in press). The three varieties of Z. aquatica L. have chartaceous (papery) pistillate lemmas and paleas covered uniformly with prickle hairs. Both of the perennial species, Z. texana Hitchc., known from only one locality, and Z. latifolia (Griesb.) Stapf, the Asiatic wild-rice, also exhibit this morphology. By contrast, the lemmas and paleas of the two varieties of Z. palustris L. are coriaceous (leathery) with prickle hairs