A COMPARISON OF PERIPHYTIC ALGAL BIOMASS AND COMMUNITY STRUCTURE ON SCIRPUS VALIDUS AND ON A MORPHOLOGICALLY SIMILAR ARTIFICIAL SUBSTRATUM1

Chemically inert, cylindrical rods positioned in the littoral of two eutrophic Alberta lakes supported higher periphytic algal biomass (measured as total chlorophyll a) than nearby morphologically similar culms of Scirpus validus Vahl. during most of the summer. Upon initiation of macrophyte senescence, biomass on the two substrata became more similar. Experiments were conducted to investigate the basis for these observations. Whole extracts of intact vegetative Scirpus culms had no effect on periphyton photosynthesis, suggesting that the natural substrata do not produce water-soluble allelochemicals. Various modifications of the rod surfaces (roughening, wax coating, wax color) were used to test whether surficial properties of Scirpus culms influenced periphyton accumulation. Roughened rods supported levels of biomass similar to those of smooth rods, and both substrata developed structurally complex periphyton communities. Rods covered with paraffin wax had periphyton communities that were lower in biomass and structurally more simple than those on un-coated rods or on Scirpus culms. Coloring of the wax coating had no consistent effect on periphyton accumulation. We hypothesize that the hydrophobic cuticle on actively growing Scirpus culms retards the development of precursors for attachment by periphytic algae. Upon senescence of the culm and loss of epidermal integrity, colonization of culm surfaces by periphytic algae may occur in a manner similar to that on artificial substrata.     

Phenotypic Adaptations Help Rhodococcus erythropolis Cells during the Degradation of Paraffin Wax

During crude oil extraction, the reduction in temperature and pressure results in the precipitation of paraffin wax that contains 20–40 carbon chain hydrocarbons. The paraffin wax may accumulate inside production tubes, pipelines, and processing facilities, and also in tankers during petroleum transportation. There are few bacterial strains that are able to degrade solid substrates. In the present study, the biodegradation of paraffin is evaluated using Rhodococcus erythropolis cells. This bacterium is able to grow using paraffin wax from an oil refinery plant as the sole carbon source. The cells grow as a thick biofilm over the solid substrate, make scale‐like structures that increase the area of the initially smooth surface of paraffin, produce biosurfactants, and become more negatively charged than ethanol‐ or glucose‐grown cells. When paraffin wax is supplied as microparticles, to increase the cell–substrate contact area and to simulate paraffin precipitation, the cells also adjust the composition of the fatty acids of the phospholipids of the cellular membrane to decrease its fluidity and paraffin biodegradation increases considerably. The study suggests that the phenotypic adaptation of R. erythropolis cells may be used to degrade paraffin wax under real conditions.     

Production of branches from unsuccessful primary germ tubes of conidia of Erysiphe graminis f. sp. tritici on wheat leaves

Confusion exists regarding nomenclature and possible significance of outgrowths produced by conidial primary germ tubes (PGT) of Erysiphe graminis f. sp. tritici Em. Marchai on wheat leaves. Production of these outgrowths has been taken as a criterion of successful host-parasite relationship. However, such outgrowths have been observed to have developed from 12.3 % of the unsuccessful PGT on a resistant wheat and 9.2 % of the unsuccessful PGT on a susceptible wheat.It is proposed that these outgrowths may be called PGT branches which may develop whether the penetration by PGT is successful or not. In case the PGT penetration is successful, then such a PGT branch may be called a secondary hypha. These branches from unsuccessful PGT may also produce host responses in the form of halos in the host cell-walls or may also penetrate the host cells successfully and produce apparently healthy (normal) haustoria. Both PGT branches and the secondary hyphae may be called functional when they produce either host responses in the form of halos or penetrate successfully and produce haustoria, or produce both halos and haustoria.     

Genetic control of β-diketone and hydroxy-β-diketone synthesis in epicuticular waxes of barley

Summary Five eceriferum, (cer) mutants in barley which influence -diketone and hydroxy--diketone synthesis in spike and internode epicuticular waxes have been characterized. The mutation cer-u ⁶⁹ blocks the synthesis of hydroxy--diketones and leads to a compensatory increase in the amount of -diketones, indicating that -diketones are precursors of the hydroxy--diketones. Furthermore, highly lobed wax plates were observed for the first time on barley lemmas, in addition to the characteristic wax tubes. Both diketone classes are selectively and proportionally reduced in the spike wax of cer-i ¹⁶, which has shorter wax tubes. The three mutants cer-c ³⁶, -q ⁴², and -c,u ¹⁰⁸ synthesize neither diketone class and form no wax tubes. In contrast to the variable composition of most individual barley wax classes, only a single -diketone was identified, namely hentriacontan-14,16-dione.     

“Natural” and NH3-induced variation in epicuticular needle wax morphology of Pseudotsuga menziesii (Mirb.) Franco

Summary Changes in epicuticular wax morphology of Pseudotsuga menziesii needles were studied with scanning electron microscopy throughout the growing season in current-year and older needles in 20 trees from two sites, Kootwijk and Garderen (The Netherlands). Fusion of crystalline wax rods leading to a reticulate structure and ultimately to degradation of the regular three-dimensional porous structure started several weeks after bud break and reached a high level at the end of the first growing season. The increase in amorphous (solid) wax showed a similar, but slightly slower development. In 1- and 2-year-old needles the degradation of crystalline wax and increase in amorphous wax had progressed only slightly further. The rates of change in crystalline wax morphology were very similar for sun-exposed and shaded needles, for the two sites, and for the two tree vitality classes included in the samples. The development of epiphyllous fungi also appeared to be largely needle age dependent. The effects of NH₃ on needle wax morphology were studied in young trees used in fumigation experiments. Short-term fumigation (approx. 5 weeks) did not affect wax morphology in current-year needles, but 1-year-old needles which had been exposed to different concentrations from bud break onwards showed a severe degradation of the crystalline wax, regardless of the NH₃ concentration used. In 2-yearold needles the effect of NH₃ could not be traced and was overshadowed by the natural ageing process. Ambient O₃, SO₂ and NO_x levels did not effect epicuticular wax morphology. It is suggested that the variation recorded for the two forest stands does not show effects of local pollution levels.     

Role of Pear Fruit Cuticular Wax and Surface Hydrophobicity in Regulating the Prepenetration Phase of Alternaria alternata Infection

The role of cuticular wax and the surface hydrophobicity of the fruit of the ‘Zaosu’ pear (Pyrus bretschneideri Rehd) in regulating the prepenetration phase of Alternaria alternata infection were analysed in vivo and in vitro. Results showed that cuticular wax on an intact fruit surface, as well as wax extracts mounted on silanized glass slides or onion epidermis, favoured the formation of short, differentiated germ tubes and large numbers of appressoria (APP) or infected hyphae (IH). Dewaxed fruits or no wax extract mounted on in vitro surfaces, however, enhanced germ tube elongation and inhibited or delayed the formation of infection structure. High surface hydrophobicity resulting from cuticular wax also stimulated infection structure formation, as contact angle (hydrophobicity) was positively correlated with APP formation but negatively correlated with germ tube elongation. Alternaria alternata cutinase enzyme activity was also induced by cuticular wax, both in vivo and in vitro. These findings suggest that the chemical composition and hydrophobicity of pear fruit cuticular wax are essential in facilitating fungal invasion by regulating the growth and differentiation of A. alternata during the prepenetration phase.     

Physical, chemical and spectral properties of leaf surfaces of Berberis aquifolium (Pursh.)

Abstract The leaves of Berberis aquifolium (Pursh.) exhibit either diffuse or specular (shiny) reflection, depending on the variety, but in no case are the leaves obviously glaucous. The dull-surfaced leaves were less wettable than the glossy ones. Using scanning electron microscopy it was determined that the diffuse reflection was due to tubular crystals of wax 250 nm in diameter. The crystals were primarily composed of 19-nonacosanol, a 29-carbon secondary alcohol, as determined by gas chromatography-mass spectrometry. The chemical constituents of the wax underlying the tubes appeared to be the same as those of the wax from glossy leaves, with 29-carbon and 31-carbon n-alkanes and n-heptacosanol as major constituents. The reflection spectra of dull-surfaced (diffuse reflection) or glossy (specular reflection) leaves were the same, as were those of leaves with different amounts of epicuticular wax. Removing the epicuticular wax with chloroform did not change the spectrum.     

Synthesis of Novel Plant Growth Inhibitors Structurally Related to Abscisic Acid

When paraffin wax is dispersed in medium as emulsion, some kinds of bacteria and yeasts readily grow on it. This paper presents a study on microbial cell production from solid paraffin. In this study a paraffin wax which contains 91% of normal paraffins ranging from C₂₅ to C₃₇ with the melting point of 62.5°C was used as a substate, but no solvent was used for the dispersion of the wax.

As a result of this study, the following have been found out. (1) Many strains of liquid normal paraffin assimilating bacteria and yeasts can assimilate paraffin wax. (2) Dried cell yields on added hydrocarbons of Corynebacterium hydrocarboclastus S-12-B2 and Candida tropicalis S-315-Y1 are 70% and 56% respectively, when they are cultured by wax emulsion of 0.6% concentration. (3) When nonion surface-active agent (Plysurf A210G) was added as an emulsifing agent, highly concentrated wax emulsion was obtained, but the growth of microorganisms on it was slower. Further investigation is needed to obtain better strains of bacteria and yeasts and also to find out optimum culture conditions.     

Structural and dynamical characterization of tubular HIV‐1 capsid protein assemblies by solid state nuclear magnetic resonance and electron microscopy

The wild‐type HIV‐1 capsid protein (CA) self‐assembles in vitro into tubular structures at high ionic strength. We report solid state nuclear magnetic resonance (NMR) and electron microscopy measurements on these tubular CA assemblies, which are believed to contain a triangular lattice of hexameric CA proteins that is similar or identical to the lattice of capsids in intact HIV‐1. Mass‐per‐length values of CA assemblies determined by dark‐field transmission electron microscopy indicate a variety of structures, ranging from single‐wall tubes to multiwall tubes that approximate solid rods. Two‐dimensional (2D) solid state ¹³C? ¹³C and ¹⁵N? ¹³C NMR spectra of uniformly ¹⁵N,¹³C‐labeled CA assemblies are highly congested, as expected for a 25.6 kDa protein in which nearly the entire amino acid sequence is immobilized. Solid state NMR spectra of partially labeled CA assemblies, expressed in 1,3‐¹³C₂‐glycerol medium, are better resolved, allowing the identification of individual signals with line widths below 1 ppm. Comparison of crosspeak patterns in the experimental 2D spectra with simulated patterns based on solution NMR chemical shifts of the individual N‐terminal (NTD) and C‐terminal (CTD) domains indicates that NTD and CTD retain their individual structures upon self‐assembly of full‐length CA into tubes. 2D ¹H‐¹³C NMR spectra of CA assemblies recorded under solution NMR conditions show relatively few signals, primarily from segments that link the α‐helices of NTD and CTD and from the N‐ and C‐terminal ends. Taken together, the data support the idea that CA assemblies contain a highly ordered 2D protein lattice in which the NTD and CTD structures are retained and largely immobilized.     

THE FEMALE GAMETOPHYTE OF THREE SPECIES OF GRINDELIA AND OF PRIONOPSIS CILIATA (COMPOSITAE)

In the four species studied, Grindelia stricta ssp. blakei, G. arizonica, G. lanceolata, and Prionopsis ciliata (Haplopappus ciliatus), the female gametophyte develops according to the Polygonum (normal) type from the chalazal megaspore of a row of four. In most cases only two antipodal cells are formed, the micropylar one originally containing two nuclei. The number of nuclei increases in both cells; one or both antipodal cells typically grow laterally into the integument, often extending to near the surface of the ovule. This resembles the condition previously reported in Grindelia squarrosa. Since the four species of Grindelia have similar antipodal outgrowths, such outgrowths may be considered typical for this genus. The fact that Prionopsis resembles Grindelia in regard to outgrowths from the antipodal cells and differs in this respect from typical Haplopappus helps to justify its separation from Haplopappus, and perhaps its suggested merger with Grindelia.     

The physico-chemical basis of leaf wettability in wheat

Summary Wild type wheat (Triticum aestivum L.) and three mutant lines that have reduced glaucousness on the flag leaf sheath have been examined for variations in glaucousness, contact angles, wax chemistry and wax morphology. On the sheath and culm, organs that are glaucous in the wild type, increasing glaucousness is correlated with increasing contact angles, an increasing proportion of -diketones plus hydroxy--diketones in the was and an increasing proportion of wax tubes. Organs that were non-glaucous in all four lines, namely both surfaces of the vegetative leaves and the adaxial surface of the flag leaf, had high contact angles, a dense covering of wax plates and waxes rich in primary alcohols but devoid of -diketones and hydroxy--diketones. The abaxial surface of the flag leaf was the most complex of the organ surfaces studied. In the wild type the glaucousness of the sheath continued onto this surface for 1–2 cm and this was correlated with the other characters studied as it was on the sheath. In the mutants, however, the tubes were absent. Flat ribbons of varying widths, a new wax structure in wheat, as well as various types of plates were found instead. These structures continued to the flag leaf tip and were also present on the abaxial surface of the wild type flag leaf. Changes in contact angle at the tip could not be correlated with the other measured parameters.     

Surface wax esters contribute to drought tolerance in Arabidopsis

Waxes are components of the cuticle covering the aerial organs of plants. Accumulation of waxes has previously been associated with protection against water loss, therefore contributing to drought tolerance. However, not much information is known about the function of individual wax components during water deficit. We studied the role of wax ester synthesis during drought. The wax ester load on Arabidopsis leaves and stems was increased during water deficiency. Expression of three genes, WSD1, WSD6 and WSD7 of the wax ester synthase/diacylglycerol acyltransferase (WS/DGAT or WSD) family was induced during drought, salt stress and abscisic acid treatment. WSD1 has previously been identified as the major wax ester synthase of stems. wsd1 mutants have shown reduced wax ester coverage on leaves and stems during normal or drought condition, while wax ester loads of wsd6, wsd7 and of the wsd6wsd7 double mutant were unchanged. The growth and relative water content of wsd1 plants were compromised during drought, while leaf water loss of wsd1 was increased. Enzyme assays with recombinant proteins expressed in insect cells revealed that WSD6 and WSD7 contain wax ester synthase activity, albeit with different substrate specificity compared with WSD1. WSD6 and WSD7 localize to the endoplasmic reticulum (ER)/Golgi. These results demonstrated that WSD1 is involved in the accumulation of wax esters during drought, while WSD6 and WSD7 might play other specific roles in wax ester metabolism during stress.     

Chemistry and micromorphology of compound epicuticular wax crystalloids (Strelitzia type)

Certain non-liliiflorous taxa within the monocotyledons (e.g.,Strelitzia, Heliconia, Typha) are characterized by compound epicuticular wax rodlets (Strelitzia type). Similar rodlets are also encountered on the surface of the dicotyledonous plantBenincasa hispida (Thunb.)Cogn. Chemical analysis of the surface wax from both sources showed that the rodlets are chemically distinct. The rodlets of the monocotyledons consist exclusively of aliphatic wax lipids, mainly wax esters. In contrast, the rodlets ofBenincasa are cheifly composed of triterpenol acetates and triterpenols. Formation of rodlets is therefore interpreted as ultrastructural convergency. It is concluded that taxonomical studies on wax crystalloids can be misleading when interpreted in terms of micromorphology of crystalloids only.     

Radiographic inspection of porosity in pure titanium dumbbell castings

Radiographic inspection of porosity in pure titanium dumbbell castings Background: Titanium frameworks are frequently indicated for implant supported prostheses; however, voids are usually encountered inside cast titanium. Objective: This study aimed to confirm the efficacy of a radiographic technique for inspection of porosity in commercially pure titanium castings with different diameter. Materials and methods: Sixty dumbbell rods (n = 20) with a central 1.5, 2.0 and 3.5 mm diameter were prepared by lost‐wax casting. Cast specimens were finished and polished and submitted to radiographic examination (90 kV, 15 mA, 0.6 s and 10–13 mm of distance) using periapical film. The radiographs were visually analysed for the presence of porosity in the extension of the dumbbell or in the central portion of the rods. Data were submitted to Pearson Chi‐square test (5%). Results: The tested radiographic method proved to be suitable for the evaluation of cast frameworks. Internal porosities were observed in most of the specimens (91.7%) (p = 0.0005); however, only 20% occurred on the central portion of the rods (p = 0.612). Conclusion: Internal porosities can be visualised through radiographs and occur mostly in small diameter structures. The radiographic evaluation of metal structures can improve the quality of frameworks and thereby potentially increase the longevity of the rehabilitation.     

Activité néformatrice d'acides ribonucléiques extraits de tumeurs végétales

RNAs extracted from crown-gall tumors, induced by Agrobacterium tumefaciens (strain B6) on stems of Datura stramonium L., have been isolated by the phenol method and purified through Biogel P 60 columns. These RNAs have been transformed into complexes with l -amino acids by incubation in a medium containing: Tris HCI buffer, pH 7.6, ATP, MgCl₂, a mixture of l -amino acids and a polypeptide synthetase purified from Alcaligenes faecalis. The inoculation of stems of Datura plants with these complexes induces the development of nodular outgrowths, whereas other complexes made from RNAs isolated from healthy Datura plants, from Agrobacterium tumefaciens, Escherichia coli and Alcaligenes faecalis do not cause any hyperplasia under our experimental conditions. The analysis of the results obtained, supported by histological studies of the outgrowths, suggests that these neoformations should be of tumoral nature.     

Chemical composition of epicuticular wax crystals on the slippery zone in pitchers of five <Emphasis Type="Italic">Nepenthes</Emphasis> species and hybrids

Plants of the carnivorous genus Nepenthes efficiently trap insects in leaf pitchers, mostly employing epicuticular wax crystals on the pitcher walls to make them slippery for the prey. In the present study, the compositions and micromorphologies of the wax crystals of five Nepenthes species and hybrids were analysed in order to test whether the chemical principles underlying this ecological function are widespread within the genus. Three wax layers could be distinguished within the Nepenthes pitcher cuticles: (1) the outermost part of the crystals forming the platelets visible in standard scanning electron microscopy, (2) the bottom portion of the epicuticular wax crystals, and (3) an intracuticular wax layer. The composition of the intracuticular wax differed significantly from that of the neighbouring epicuticular layer. The compositions of corresponding wax mixtures from all five Nepenthes species and hybrids were very similar, with almost equal amounts of very long chain aldehydes and primary alcohols. While triacontanal (C₃₀ aldehyde) was prevailing in the epicuticular crystals of Nepenthes albomarginata and Nepenthes x intermedia, Nepenthes x superba and Nepenthes x henriana were found to have especially high percentages of dotriacontanal (C₃₂ aldehyde). Nepenthes “khasiana” had an intermediate aldehyde composition with almost equal amounts of both chain lengths.     

Synthesis of oleyl oleate wax esters in Arabidopsis thaliana and Camelina sativa seed oil

Seed oil composed of wax esters with long‐chain monoenoic acyl moieties represents a high‐value commodity for industry. Such plant‐derived sperm oil‐like liquid wax esters are biodegradable and can have excellent properties for lubrication. In addition, wax ester oil may represent a superior substrate for biodiesel production. In this study, we demonstrate that the low‐input oil seed crop Camelina sativa can serve as a biotechnological platform for environmentally benign wax ester production. Two biosynthetic steps catalysed by a fatty alcohol‐forming acyl‐CoA reductase (FAR) and a wax ester synthase (WS) are sufficient to achieve wax ester accumulation from acyl‐CoA substrates. To produce plant‐derived sperm oil‐like liquid wax esters, the WS from Mus musculus (MmWS) or Simmondsia chinensis (ScWS) were expressed in combination with the FAR from Mus musculus (MmFAR1) or Marinobacter aquaeolei (MaFAR) in seeds of Arabidopsis thaliana and Camelina sativa. The three analysed enzyme combinations Oleo3:mCherry:MmFAR1?c/Oleo3:EYFP:MmWS, Oleo3:mCherry:MmFAR1?c/ScWS and MaFAR/ScWS showed differences in the wax ester molecular species profiles and overall biosynthetic performance. By expressing MaFAR/ScWS in Arabidopsis or Camelina up to 59% or 21% of the seed oil TAGs were replaced by wax esters, respectively. This combination also yielded wax ester molecular species with highest content of monounsaturated acyl moieties. Expression of the enzyme combinations in the Arabidopsis fae1 fad2 mutant background high in oleic acid resulted in wax ester accumulation enriched in oleyl oleate (18:1/18:1 > 60%), suggesting that similar values may be obtained with a Camelina high oleic acid line.