Showing papers by "University of North Carolina at Wilmington published in 1990"
TL;DR: This article examined the concurrent validity of concept maps as vehicles for documenting and exploring conceptual change in biology and found significant and substantial changes in the complexity and prepositional structure of the knowledge base, as revealed in concept maps.
Abstract: This study examined the concurrent validity of concept maps as vehicles for documenting and exploring conceptual change in biology. Students (N = 91) who enrolled in an elementary science methods course were randomly assigned to one of two treatment groups. Subjects in both groups were administered a multiple-choice/free-response inventory which assayed their knowledge of “Life Zones in the Ocean,” and then were asked to construct a concept map on the same topic. Those in the experimental group subsequently received 45 minutes of computer-assisted instruction on marine life zones, while those in the control (“placebo”) group received an equivalent exposure to an unrelated topic (“Body Defenses”). Upon completing the instructional sequence, subjects were again administered the “Life Zones” inventory and asked to develop a postinstruction concept map on marine life zones. The data analysis employed a split plot factorial design with repeated measures. Differences among treatment groups were documented by analysis of variance and chi-square procedures. Subjects in the experimental group showed evidence of significant and substantial changes in the complexity and prepositional structure of the knowledge base, as revealed in concept maps. No such changes were found in the control group. Results suggest that concept mapping offers a valid and potentially useful technique for documenting and exploring conceptual change in biology.
276 citations
TL;DR: An alternative Gram staining technique has been developed by exploiting the phenomenon where fluorescence-labeled wheat germ agglutinin binds specifically to N-acetylglucosamine in the outer peptidoglycan layer of gram-positive bacteria.
Abstract: Fluorescence-labeled wheat germ agglutinin binds specifically to N-acetylglucosamine in the outer peptidoglycan layer of gram-positive bacteria. The peptidoglycan layer of gram-negative bacteria is covered by a membrane and is not labeled by the lectin. By exploiting this phenomenon, an alternative Gram staining technique has been developed.
114 citations
TL;DR: Results showed that although baseline conditional discrimination performances were under the control of reinforcement contingencies, and performances on symmetry trials varied with baseline responding for 3 of 4 subjects when contingencies were reversed, performances on transitivity probes remained consistent with the initial equivalence class.
Abstract: Following the emergence of two three-member equivalence classes (A1B1C1 and A2B2C2), 5 college students were exposed to one or more changes in the reinforcement contingencies controlling baseline conditional discriminations. AC relations were either reversed (i.e., C2 was reinforced and C1 punished when A1 was the sample; C1 was reinforced and C2 punished when A2 was the sample) or arranged randomly (i.e., C2 and C1 were reinforced and punished equally often in the presence of A1 and A2). In a third condition, the original AB and AC relations were reversed. Results showed that although baseline conditional discrimination performances were under the control of reinforcement contingencies, and performances on symmetry trials varied with baseline responding for 3 of 4 subjects when contingencies were reversed, performances on transitivity probes remained consistent with the initial equivalence class. These inconsistencies between probe and baseline performances were striking because conditional discriminations are thought to be the determinants of equivalence class performance. Similarly, the contrast between performances on symmetry and transitivity probes was of theoretical interest because equivalence classes are defined by congruent patterns of responding on probe trials.
113 citations
TL;DR: It is demonstrated that, as in humans, temporal-lobe limbic structures are essential for recognition only when the retention test exceeds the immediate memory span of a few seconds, and that the limbic system's selective contribution to learning and retention uncovered initially with objects applies equally to pictures.
Abstract: Three monkeys with complete ablations of temporal-lobe limbic structures and three unoperated controls were compared in an automated testing apparatus for their ability to remember pictures presented between 1 and 180 seconds previously, as well as to learn picture discriminations in which successive trials with a given pair were separated by either 20 seconds or 24 hours. The operated animals were not impaired in picture discrimination learning under either condition and they were not impaired in picture recognition memory up to about 10 seconds. At 10 seconds and beyond, however, the operated animals showed rapid deterioration of picture memory. The results demonstrate that the limbic system's selective contribution to learning and retention uncovered initially with objects applies equally to pictures, this contribution being essential for recognition memory but not for discrimination habits. The results demonstrate further that, as in humans, temporal-lobe limbic structures are essential for recognition only when the retention test exceeds the immediate memory span of a few seconds.
91 citations
TL;DR: It is indicated that the DNMS and DMS tasks, when applied to children, may provide insight into the functional maturation of brain areas responsible for memory, rule-learning, and behavioral inhibition.
Abstract: Children 12 to 36 months old were tested on DMS, DNMS, and object discrimination tasks in a WGTA with procedures that closely followed those used previously with monkeys Mastery of DNMS showed a clear developmental progression The youngest children (12-15 months old) required extensive training, and they failed to reach criterion until they were 15-18 months old The differentially slower learning of the youngest children cannot be attributed to "performance" deficits (perceptual, motivational, or associational inabilities) or the inability to make 2-part responses, because a test of object discrimination showed that even 12-month-old children can perform with accuracy in the WGTA testing situation Analysis of learning curves along with additional tests of memory provided evidence that the youngest children are (1) less proficient in learning the novelty-reward rule and (2) less proficient in memory for a particular stimulus item Furthermore, we found that a task that we think requires learning two rules, a DMS task, was even more difficult for children to master These results together with data collected on brain-damaged humans and monkeys indicate that the DNMS and DMS tasks, when applied to children, may provide insight into the functional maturation of brain areas responsible for memory, rule-learning, and behavioral inhibition
67 citations
TL;DR: Haemolymph ion analyses and transepithelial potential differences indicate that chloride is actively transported out of the brine shrimp while sodium is very close to electrochemical equilibrium across the body wall, suggesting that the metepipodites of theBrine shrimp appear to possess cells with many functional similarities to the teleost branchial chloride cells.
Abstract: Silver staining of the adult brine shrimp, Artemia salina , revealed that only the metepipodites of the phyllopodia were significantly permeable to chloride and/or silver ions. The metepipodites stained in a reticulated pattern, possibly indicating areas in the cuticle over cells specialized for chloride secretion. Crude homogenates of metepipodites had very high Na+/K+-ATPase enzyme specific activity (ESA) which increased in proportion to the salinity of the external medium and, thus, in proportion to the need for outward salt transport in these strongly hypoosmoregulating animals. Metepipodite ESA as a percentage of whole-body ESA increased from 7.6% in 50% sea water (SW) to 25.0% in 400%SW. Gut and maxillary gland also had high Na+/K+-ATPase ESAs, implicating these organs in osmoregulatory processes as well. The time courses of increases in phyllopodial and gut ESAs in brine shrimps transferred from 100% SW to 400 % SW are consistent with the induction of new Na+/K+-ATPase; 4–7 days was required for significant increases to occur. Haemolymph ion analyses and transepithelial potential differences, measured in brine shrimp acclimated in all the SW media, indicate that chloride is actively transported out of the brine shrimp while sodium is very close to electrochemical equilibrium across the body wall. Thus, the metepipodites of the brine shrimp appear to possess cells with many functional similarities to the teleost branchial chloride cells.
64 citations
TL;DR: Sediment samples were collected at stations along cross-shelf transects in Onslow Bay, North Carolina, during two cruises in 1984 and 1985 as discussed by the authors.
Abstract: Sediment samples were collected at stations along cross-shelf transects in Onslow Bay, North Carolina, during two cruises in 1984 and 1985. Station depths ranged from 11 to 285 m. Sediment chlorophyll a concentrations ranged from 0·06 to 1·87 μg g −1 sediment (mean, 0·55), or 2·6–62·0 mg m 2 . Areal sediment chlorophyll a exceeded water column chlorophyll a a at 16 of 17 stations, especially at inshore and mid-shelf stations. Sediment ATP concentrations ranged from 0 to 0·67 μg g −1 sediment (mean, 0·28). Values for both biomass indicators were lowest in the depth range including the shelf break (50–99 m). Organic carbon contents of the sediments were uniformly low across the shelf, averaging 0·159% by weight. Photography of the sediments revealed extensive patches of microalgae on the sediment surface. Our data suggest that viable benthic microalgae occur across the North Carolina continental shelf. The distribution of benthic macroflora on the North Carolina shelf indicates that sufficient light and nutrients are available to support primary production out to the shelf break. Frequent storm-induced perturbations do not favour settling of phytoplankton, an alternative explanation for the presence of microalgal pigments in the sediments. Therefore, we propose that a distinct, productive benthic microflora exists across the North Carolina continental shelf.
64 citations
TL;DR: The data are consistent with the hypothesis that bone growth is influenced by the cardiovascular changes associated with tail suspension, and the skull and mandible dry and ash weights were significantly higher in suspended rats than in control rats.
Abstract: Rats, age 28 days, experiencing tail suspension in modified metabolic cages for 1, 2, and 3 wk were compared with littermate controls. Food and water consumption, urinary and fecal Ca excretion, and serum Ca were measured; hearts, fore- and hindlimb bones, skulls, and mandibles were removed for determination of wet, dry, and ash weights and Ca concentration and for histological examination. Weight gain and Ca intake and excretion were the same for both groups; both displayed net Ca gain. Suspended rats had significantly lower wet, dry, and ash weights of femora and tibiae. Dry weights of the humeri and radii/ulnae were moderately higher, and the skull and mandible dry and ash weights were significantly higher in suspended than in control rats. Cortical thickness of the femur, but not humerus, was less in suspended rats. The data are consistent with the hypothesis that bone growth is influenced by the cardiovascular changes associated with tail suspension.
62 citations
01 Jan 1990
TL;DR: There have been tremendous changes in wetlands bordering the Cape Fear estuary since the first permanent European settlement in the 1720s as mentioned in this paper, and these changes resulted in the average high tide being 56.5 cm higher than in 1885.
Abstract: There have been tremendous changes in wetlands bordering the Cape Fear estuary since the first permanent European settlement in the 1720’s. First, tidal freshwater swamps were cleared of cypress (Taxodium distichum) and gum (Nyssa sylvatica), diked, managed for rice production and finally abandoned around 1908. During the past 100 years the main channel through the estuary has been widened and deepened, increasing the tidal range at Wilmington, North Carolina by 53 cm. This produced a high tide 26.5 cm above previous levels. Also during the last century relative sea level has risen 30 cm. Today these increases result in the average high tide being 56.5 cm higher than in 1885. Wetlands inhabiting abandoned rice fields and swamps previously not subject to tidal flooding and/or to salinities above that of fresh water are now being affected. The intrusion of saline water into these wetlands has led to the conversion of freshwater tidal swamps into brackish marshes in the middle reaches of the estuary. Swamps in the upper reaches are gradually disintegrating and being replaced by oligohaline tidal marshes. Tropical and extratropical storms have the potential for pushing more saline water farther into the estuary and may accelerate conversion of swamp to marsh.
31 citations
TL;DR: It was clear that 17-alpha-methyltestosterone retarded growth when administered at moderate and high dosage levels, and its strong androgenic properties were reflected by a precocious maturation of the testes of treated males.
29 citations
TL;DR: Information for genome size, organization and complexity is used to develop a nuclear genome profile for Gracilaria blodgettii and Gracilariopsis lemanieformis which are characterized by commercial grade agars having high gel strengths and elevated melting temperatures (99 °C).
Abstract: DNA reassociation kinetics were used to determine inter- and intraspecific variation in genome organization and complexities in species ofGracilaria andGracilariopsis. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repeated sequences varied from 13–95%. Three geographic populations ofGracilaria tikvahiae were similar with 13–27% repeated sequences.Gracilaria sp. cultivars G-1 and G-6 with 35% and 95% repeated sequences, respectively, were distinct from each other andG. tikvahiae. No pattern of genome organization and complexity was found which permitted a distinction betweenGracilaria andGracilariopsis. Comparison of the percent of unique and repetitive sequences (U/R) indicated a wide range of ratios, withGracilaria tikvahiae populations having the highest values (2.7–7.3) andGracilaria sp. cultivar G-6,G. blodgettii andGracilariopsis lemanieformis the lowest (0.05–1.80). Unique component complexities varied one order of magnitude, from 108 forGracilaria takvahiae to 107 forGracilaria sp. cultivar G-6,G. blodgettii andGracilariopsis lemanieformis. Information for genome size, organization and complexity is used to develop a nuclear genome profile forGracilaria blodgettii andGracilariopsis lemanieformis which are characterized by commercial grade agars having high gel strengths (> 700 g cm−2) and elevated melting temperatures (99 °C).
TL;DR: The heuristic solution is compared to the optimal solution for 192 randomly generated problems to investigate the effects of problem size, due date coefficient of variation, and due date lightness on the quality of the heuristic.
TL;DR: This paper examined the impact of the recent feminization of the sociological profession on gender differences in patterns of publication in leading sociology journals and found that women are better represented in the leading journals in an absolute sense, but continue to be underrepresented relative to men.
Abstract: This paper examines the impact of the recent feminization of the sociological profession on gender differences in patterns of publication in leading sociology journals. Our findings show that women are better represented in the leading journals in an absolute sense, but continue to be underrepresented relative to men. Moreover, while women are better represented in the leading journals than in the past, they more often occupy marginal locations within the structure of the discipline. Finally, we discuss the likely implications of the feminization of sociology on the production of knowledge within the discipline as a whole.
TL;DR: In this article, an optimal thickness design and optimal closed-loop and open-loop distributed control functions for a symmetric, cross-ply laminate are determined for a rectangular laminate made of an advanced composite material.
TL;DR: It is shown that the recognition problem for cographs, transitive orientation, maximum node weighted clique, minimum node coloring, minimum weight domination set, minimum fill-in, isomorphism for cograph are in the class NC, and a NC algorithm for parity graph recognition is presented.
TL;DR: In this paper, the Rayleigh-Ritz variational method is used with a multiconfiguration-interaction function to obtain the nonrelativistic energies and wave functions of the triply excited 2${\mathit{p}}^{2}$np $^{4}$S.
Abstract: The Rayleigh-Ritz variational method is used with a multiconfiguration-interaction function to obtain the nonrelativistic energies and wave functions of the triply excited 2${\mathit{p}}^{2}$np $^{4}$S\ifmmode^\circ\else\textdegree\fi{} (n=2,3,4) and 2${\mathit{p}}^{2}$3p $^{2}$S\ifmmode^\circ\else\textdegree\fi{} states and also the doubly excited 1s2pmp $^{4}$P (m=2,3,4), 1s2${\mathit{p}}^{2}$ $^{2}$P, [(1s2p${)}^{3}$P,3p${]}^{2}$P, and [(1s2p${)}^{1}$P,3p${]}^{2}$P states for atomic systems with nuclear charges from Z=3 to 10. The relativistic and mass polarization corrections are evaluated via first-order perturbation theory, and the resulting relativistically corrected energies are used to compute transition wavelengths for 2${\mathit{p}}^{2}$np $^{4,2}$S\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\rightarrow}1s2pmp $^{4,2}$P. The fine structure of the 1s2pnp $^{4,2}$P states is also calculated with first-order perturbation theory. The nonrelativistic wave functions are used to compute the electric-dipole transition probabilities for 2${\mathit{p}}^{2}$np $^{4,2}$S\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\rightarrow}1s2pmp $^{4,2}$P; this information is then used to compute the lifetimes for the 2${\mathit{p}}^{2}$np $^{4,2}$S\ifmmode^\circ\else\textdegree\fi{} states and the branching ratios for the transitions to the 1s2pmp $^{4,2}$P levels. Intermediate-coupling effects for the 2${\mathit{p}}^{3}$ $^{4}$S\ifmmode^\circ\else\textdegree\fi{}${,}^{2}$D\ifmmode^\circ\else\textdegree\fi{}${,}^{2}$P\ifmmode^\circ\else\textdegree\fi{} and the 1s2${\mathit{p}}^{2}$ $^{4}$P${,}^{2}$D${,}^{2}$P${,}^{2}$S states are investigated for the case of Z=10 and are shown to be small. Comparisons with experimental wavelength and lifetime measurements are made.
TL;DR: Ascospores ellipsoid to ovoid, 12-17 x 5.5-7.0 pm, 1-septate, septa often appearing angular, colorless, smooth, often 1-2 orange guttules per cell, sometimes germi?
Abstract: 70 x 8-10 pm, 8-spored, unitunicate, apex trun? cate, containing a non-amyloid apical ring, as? cospores biseriate in the middle, uniseriate above and below, filling the ascus. Ascospores ellipsoid to ovoid, 12-17 x 5.5-7.0 pm, 1-septate, septa often appearing angular, colorless, smooth, often 1-2 orange guttules per cell, sometimes germi? nating in the centrum, L/W 2.3. Centrum con? tents appearing slightly brown, orange oily drops emitted from crushed perithecia. Paraphyses not
TL;DR: In this paper, a predictive model of logistic form using 14-day means of daily actual evapotranspiration fit the data well (R2= 0.83) and tested well against soil CO2 data acquired in the coastal plain at Rocky Point, NC.
Abstract: Soil carbon dioxide content, temperature, and moisture were measured biweekly for one year at Pigeon Mountain, GA. Levels of soil CO2 ranged from 0.04% to 2.4% and were highest during the growing season, lowest during the winter. Soil temperature correlated positively with soil CO2, accounting for 90% of CO2 variation. Soil moisture variations decreased CO2 concentration at times of high soil water content when CO2 was flushed downward, and also at times of low soil moisture content when CO2 production was inhibited. A predictive model of logistic form using 14-day means of daily actual evapotranspiration fit the data well (R2= 0.83). The model also tested well against soil CO2 data acquired in the coastal plain at Rocky Point, NC. If actual evapotranspiration rates are known, the model permits estimation of soil CO2 without preliminary field work, and can be used for studies of karst denudation, which require soil CO2 data for seasonal and regional comparison of solution rates.
TL;DR: Polysiphonia breviarticulata, a species previously known only from the Adriatic, the Mediterranean, and the Canary Islands, was reported for the first time from the Western Atlantic in Dominica and North Carolina as discussed by the authors.
Abstract: Polysiphonia breviarticulata, a species previously known only from the Adriatic, the Mediterranean, and the Canary Islands, is reported for the first time from the Western Atlantic in Dominica and North Carolina. In the latter region it has grown in bloom quantities as drifting, planktonic plants that are a nuisance on beaches and a serious impediment to fishermen whose nets become fouled with the plants.
TL;DR: A potent agglutinin of rabbit and sheep red blood cells, obtained from the red alga Gracilaria tikvahiae, was purified by ammonium sulfate fractionation, ion exchange, gel filtration, and hydroxylapatite chromatography and suggested that the agglUTinin has affinity for N-acetylneuraminic acid as well as glycoconjugates containing N- acetylneursic acid.
TL;DR: Calcul par la methode de rotation complexe du point de selle pour ces resonances de Feshbach (2≤z≤6) avec formation d'ions dans les etats 1s2s 3 S and 1s3p 3 P 0 apres autoionisation.
Abstract: The saddle-point complex-rotation method is used to compute the energies and autoionization widths of the 1s3s3p $^{4}$P\ifmmode^\circ\else\textdegree\fi{} and 1s3p3p $^{4}$P Feshbach resonances for the lithiumlike ions with nuclear charges from Z=2 to 6. These doubly core-excited quartet states rapidly autoionize, emitting low-energy electrons via the continua associated with the 1s2s $^{3}$S and 1s2p $^{3}$P\ifmmode^\circ\else\textdegree\fi{} states of the residual ion. The radiative decay rates of these initial states are shown to be small relative to their autoionization rates, so that the lifetimes of these resonances are essentially determined by their widths due to autoionization. A detailed study of the closed-channel component of the 1s3p3p $^{4}$P resonance is made in order to investigate the degree to which the saddle-point solution approximates this component of the resonance wave function.
TL;DR: This work considers the problem of contouring a bivariate quadratic polynomial, defined as a triangular Bezier patch, and develops a simple, yet completely robust algorithm for describing contours as piecewise rational quadRatic Beziers curves.
TL;DR: The novel anxiolytic CGS 9896 produced effects that closely resembled those of the benzodiazepine anxIOlytic, chlordiazepoxide, while buspirone decreased both avoidance and timeout responding.
Abstract: Concurrent performances were studied in rats under conditions where responses on one lever postponed shock on a Sidman avoidance schedule and responses on another lever produced periods of signaled timeout from avoidance on a variable-interval schedule. Chlorpromazine decreased rates of responding on both the timeout and avoidance levers to about the same extent. The effects of chlordiazepoxide and CGS 9896 depended upon the event maintaining responding. Both drugs increased responding on the timeout lever at doses that concurrently decreased responding on the avoidance lever. Thus, the novel anxiolytic CGS 9896 produced effects that closely resembled those of the benzodiazepine anxiolytic, chlordiazepoxide. Like chlorpromazine, buspirone decreased both avoidance and timeout responding. Despite the documented anxiolytic properties of buspirone, its actions here were unlike those of the other anxiolytic drugs tested. Nonetheless, the differentiation between drugs obtained with the timeout from avoidance procedure indicates its utility for behavioral pharmacology.
TL;DR: In this article, the authors examined the use of price bundling as a marketing technique for recreation services and applied it to an actual case involving the visitor accommodations at a state department of parks.
Abstract: This article examines the use of price bundling as a marketing technique for recreation services. The use of conjoint analysis allows the researcher to determine consumers’ part‐worth utilities for various service attributes. This information can then be used to design a service bundle or package and determine the price to be charged. This approach to service design is applied to an actual case involving the visitor accommodations at a state department of parks. Consumers are segmented in order to enhance the analysis and provide management with more useful information. The limitations of the study and methodology are discussed along with strategic implications for park managers. Finally, suggestions are provided for future research in this area.
TL;DR: Estimates of nuclear DNA base pair composition by determination of thermal denaturation temperatures (Tm) indicated guanine + cytosine (G + C) levels of 35–56% for 17 species of marine green algae.
Abstract: Estimates of nuclear DNA base pair composition by determination of thermal denaturation temperatures (Tm) indicated guanine + cytosine (G + C) levels of 35–56% for 17 species of marine green algae. Tm values were found to be reproducible with coefficients of variation among samples and replicates of generally less than 1 percent. G + C% values in four species of Enteromorpha varied within a narrow range of 53–56%, whereas values for three species of Ulva showed substantially greater variation, ranging from 35–55%. Ulva fasciata collections from two geographically separate North Carolina sites had mean G + C composition of 44.8 and 35.6 respectively, suggesting that these populations may be genetically distinct. Enteromorpha linza, which has been treated as a species of Ulva, had a G + C composition of 53.2, typical of the Enteromorpha species investigated. Nuclear DNA base pair composition data for species of Cladophorales and Caulerpales are given as well.
TL;DR: In this paper, an optimal control problem with a prescribed performance index for parabolic systems with time delays is investigated, and a necessary condition for optimality is formulated and proved in the form of a maximum principle.
Abstract: An optimal control problem with a prescribed performance index for parabolic systems with time delays is investigated. A necessary condition for optimality is formulated and proved in the form of a maximum principle. Under additional conditions, the maximum principle gives sufficient conditions for optimality. It is also shown that the optimal control is unique. As an illustration of the theoretical consideration, an analytic solution is obtained for a time-delayed diffusion system.
TL;DR: A limestone outcrop along the north shore of Lake Waccamaw, North Carolina, was found to contain ca. 0.1 % of phosphate by weight as discussed by the authors, which may explain the lake's near eutrophic state.
Abstract: A limestone outcrop along the north shore of Lake Waccamaw, North Carolina, is found to contain ca. 0.1 % phosphate by weight. Weathering processes have probably driven steady inputs of phosphate from this source throughout the lake's history, accounting for its near eutrophic state. The sediments of Lake Waccamaw are enriched with phosphate, particularly in the littoral zone near the outcrop. Chemical and biological processes apparently remove phosphate from solution rapidly, making detection of a soluble phosphate signal near the outcrop difficult. Management of nutrient inputs and water quality in Lake Waccamaw requires consideration of the effects of this in-lake source of phosphate. Other sources of phosphate, particularly in the lake's drainage basin, may be less important than previously thought.
TL;DR: In vitro studies of salinity tolerance of saprolegniaceous fungi have demonstrated that some representatives exhibit substantial resistance to salt stress, and an Aphanomyces sp.
Abstract: An Aphanomyces sp. recovered from and thought to be a pathogen of Atlantic menhaden was subjected to salinity stress to see if its behavior suggested that it was a salt-resistant isolate. Respiration during prolonged salinity exposure as well as hyphal morphology suggested a degree of salinity tolerance generally greater than previously reported for this or other saprolegniaceous fungi. Furthermore, zoo? spores were shown to germinate during salinity stress if exogenous nutrients are present. In vitro studies of salinity tolerance of saprolegniaceous fungi have demonstrated that some representatives exhibit substantial resistance to salt stress. Te Strake (1959) described vegetative growth of several species at salinities as high as 22.5 parts per thousand (ppt), while Harrison and Jones (1971) observed growth of Saprolegnia
TL;DR: It appears that agar from Gracilaria verrucosa Strain G-16 has some 4-0-methylgalactose branching side groups, but probably only minimal amounts of C6 methylation.
Abstract: We recently published several studies regarding the role of environmental factors on agar quality and chemistry from Gracilaria verrucosa (tentative species identification) Strain G-16 (Bird, 1988, Bird etal., 1989; Chiles etal., 1989). Despite observing a high gelling temperature (42-53 °C), we reported that we did not observe any evidence of C2 or C6 methylation based on 3C NMR. Since then, it has been suggested that the spectra provided evidence of C4 methylation of the galactose repeating unit (Lahaye, personnel communication). Lahaye etal. (1988) and Karamanos et al. (1989) have published assignments for 4-0methyl-L-galactose in the agar from Gracilaria verrucosa, and suggested that it represents a side group linked to 0-6 of the 3-0-linked galactopyranose units in agar. A re-examination of our spectral data suggests that assignments for agar from Gracilaria verrucosa Strain G-16 are similar to those of Lahaye etal. (1988) and Karamanos etal. (1989). In alkali-modified agars from plants grown in 8 different culture environments, there are discernable shifts at 98.4, 79.4, 72.6, 70.7 and 69.5 ppm, corresponding to C 1, C4, C5, C3 of the galactose repeating unit and C6 of the anhydrogalactose repeating unit, respectively. There is also a shift at 61.8 ppm, corresponding to the C4 methylation. However, our alkali-modified agars showed either a negligible or barely discernable shift at 59.1 ppm, which corresponds to the C6 methylation. Evidence for C6 methylation is not apparent until NMR data are examined from agars extracted based on their solubility in decreasing concentrations of hot alcohol in water (Chiles et al., 1989). It appears that agar from Gracilaria verrucosa Strain G-16 has some 4-0-methylgalactose branching side groups, but probably only minimal amounts of C6 methylation. This suggestion is especially supported by a comparison of the extremely weak shifts at 59.1 for C6 methylation compared to those at 61.8 for C4 methylation (Bird et al., 1989; Chiles et al., 1989).