THE INFLUENCE OF pH AND LICHEN METABOLITES (VULPINIC ACID AND (+) USNIC ACID) ON THE GROWTH OF THE LICHEN PHOTOBIONTTREBOUXIA IRREGULARIS

The quantitative response to two lichen metabolites, vulpinic acid and (+) usnic acid, on biomass production by the photobiontTrebouxia irregularis, isolated from the lichenCladina mitis, was determined experimentally. The presence of usnic acid resulted in inhibition of photobiont growth, and the effect depended on the pH of the culture medium. The concentration effect of usnic acid was observed. The application of vulpinic acid almost completely inhibited the growth ofT. irregularisand no significant differences were found among samples at different medium pH values.     

Effect of lignin-related phenols and their methylated derivatives on the growth of eight white-rot fungi

When various lignin-related para-phenolic benzoic acids, para-phenolic cinnamic acids, para-phenolic phenylpropionic acids, the corresponding unsubstituted and 4-O-methylated derivatives, and 4-hydroxyl substituted benzaldehydes were tested on the growth of eight white-rot fungi, methylation of the 4-hydroxy substituent resulted, in most cases, in increased inhibition of fungal growth. This effect was most notable with monomethoxylated compounds. When the aromatic ring contained additional methoxyl substituents, the toxicity of the 4-O-methylated derivative was less pronounced. Marked inhibition of fungal growth was also observed with aromatic compounds lacking a para-substituent. Higher concentrations of aromatic aldehydes were manifestly more toxic than the corresponding carboxylic acid.J.A. Buswell is with the Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong. K.-E.L. Eriksson is with the Department of Biochemistry, The University of Georgia, Athens, Georgia, 30602, USA.     

PHYSIOLOGICAL EFFECT OF LICHEN SECONDARY METABOLITES ON THE LICHEN PARASITE MARCHANDIOMYCES CORALLINUS

It has been suggested that the host specificity exhibited by some lichenicolous fungi depends on their ability to tolerate the secondary chemistry of potential host lichens. For example, the lichen parasite Marchandiomyces corallinus is able to degrade the tissues of the lichen Flavoparmelia baltimorensis irrespective of the presence or absence of endogenous phenolic compounds. In contrast, the degradation of tissues from the lichen Lasallia papulosa is suppressed when endogenous phenolics are not removed. We have investigated the physiological basis of this inhibition in order to understand more about how lichen chemistry influences host preference in lichenicolous fungi. Results showed that the secondary compounds from L. papulosa inhibit the overall growth of M. corallinus , but not the catalytic activity of its tissue-degrading polysaccharidases. This effect is different from that shown by another lichen parasite, Nectria parmeliae , where lichen compounds specifically inhibited polysaccharidase activity. Compared with the compounds of L. papulosa , the endogenous phenolics of F. baltimorensis inhibited the growth of M. corallinus substantially less and exhibited little or no inhibition of polysaccharidases. For M. corallinus , host preference appears to be associated with physiological adaptation to the chemistry of F. baltimorensis .     

COENOGONIUM: A GREEN ALGAL LICHEN WITHOUT PHOTOSYNTHETIC DEPRESSION AT HIGH WATER CONTENTS

For experiments run at 350 ppm CO₂, the subtropical lichenCoenogoniumdoes not exhibit net photosynthetic depression at water contents above those at which initial maximal values are reached. This is in contrast to most lichens for which such a depression occurs. We infer that the results reflect the unusual morphology ofCoenogonium, in which the alga is the dominant symbiont, occurring as filaments at the lichen surface. This arrangement should minimize CO₂diffusion resistance to the algal surface. With light saturation occurring by 70 μmol photons m⁻²s⁻¹,Coenogoniiumhas one of the lowest light saturation values reported among lichens.     

中国砖孢发属地衣研究

简短回顾了砖孢发属地衣研究概况。在已知的8种亚洲砖孢发属地衣中,中国有七种,其中两种为台湾特有。根据150余份标本的形态与化学特征,承认中国大陆砖孢发属地衣5种,指出了个别异名,发现亚洲砖孢发(Okpogon asiaticus)存在两个化学型,提供了中国5种砖孢发地衣分布的新资料。研究结果表明,5种砖孢发地衣集中分布于我国云南、四川和西藏东部。作者认为中国西南地区是砖孢发属地衣在亚洲的一个分布中心。     

Extracts of the Brown Alga Dictyota dichotoma (Hudson) J.V. Lamouroux Alleviate Salt Stress in Rice (Oryza sativa L.) During Germination

Algal extracts provide a safe regime for enhancing crop productivity under stressful conditions. The present study evaluated the efficiency of aqueous and ethanolic extracts of the brown alga Dictyota dichotoma in alleviation of salt stress on germination of rice seeds. Firstly, seeds were germinated using the aqueous extract of D. dichotoma at concentrations of 0, 5, 10, 20, and 50 g L⁻¹, prepared either at room temperature (RTE) or by boiling (BLE). The % germination of rice increased from 84% in non-treated seeds to 100% when treated with 20 g L⁻¹ BLE, although this treatment caused reduced uniformity of germination. Embryo growth was maximum at 20 g L⁻¹ of both extracts with superiority of BLE over RTE. In the second experiment, the effect of 20 g L⁻¹ aqueous and ethanolic extracts relative to a balanced nutrient supply on germination of seeds treated with 0, 40, 90, and 170 mM NaCl was investigated. Salinity reduced % germination with delayed onset but high uniformity of germination, whereas algal amendments counterbalanced the effect of salinity to a greater extent relative to the nutrient supply. Upon withdrawal of salt stress, seeds promptly recovered, with more efficient recovery of seeds exposed to 170 mM than from 90 mM NaCl. The lower recovery of salt-treated seeds compared with the control seed germination suggests that rice suffered from the toxic ion effect of salinity on embryo rather than from the osmotic effect. Extracts of D. dichotoma can enhance and also alleviate salinity stress on rice seed germination.

     

CYANOPHYTE CEPHALODIA IN THE LICHEN GENUS NEPHROMA

The lichens, Nephroma expallidum (Nyl.) Nyl. and N. arcticum (L.) Torss., consistently have at least two symbionts in a single thallus: a green alga in the algal layer and a blue-green alga in the internal cephalodia. The cephalodia originate from algal cells in contact with the lower surface of the lichen, in the zone of rhizine formation. The rhizines surround the epiphytic algal colony and form a second cortical layer; following dissociation of the original lower cortex, further growth of the two organisms results in the cyanophyte colony being enveloped by a compact layer of fungal tissue and positioned in the lichen medulla. The colony may eventually assume a superior or inferior position in relation to the lichen thallus, depending in part on the lichen species. Nephroma anticum may have two distinct morphological forms of blue-green algae in the same thallus and occasionally in the same cephalodium. It appears that the relationship that exists between the cephalodial algae and the lichen thallus is antagonistic and results, in some cases, in the exclusion of the green algal layer and death to the cephalodial cyanophytes.     

Bark pH and susceptibility to toxic air pollutants as independent causes of changes in epiphytic lichen composition in space and time

Abstract:The lichen composition on wayside Quercus robur in the Netherlands was related to bark properties (pH, EC, NH₄⁺, SO₄²⁻, NO₃⁻) and levels of air pollution (SO₂and NH₃). The pH of the bark and the susceptibility to toxic substances appear to be the two major primary factors affecting epiphytic lichen composition. These factors have independent effects on the lichen composition. Most of the so-called nitrophytic species appear to have a low sensitivity to toxic effects of SO₂; their only requirement being a high bark pH. An increased bark pH appears to be the primary cause of the enormous increase in nitrophytic species and the disappearance of acidophytic species over the last decade in the Netherlands. Measurements of ambient NH₃concentrations in air show that there is a nearly linear relationship between the NH₃concentration and the abundance of nitrophytes on Quercus. The abundance of nitrophytes was not correlated with SO₂concentrations. Most of the acidophytic species appear very sensitive to NH₃since in areas with concentrations of 35 μg m⁻³or more, all acidophytic species have disappeared. Current methods using species diversity to estimate or monitor SO₂air pollution need some modification, otherwise the air quality may be erroneously considered to be relatively good in areas with high NH₃levels.     

ULTRASTRUCTURE OF THE LICHEN COENOGONIUM INTERPLEXUM NYL.

Coenogonium interplexum Nyl. is a green to yellow-orange filamentous lichen commonly found on tree bark, rocks, and soil. The mycobiont is the ascomycetous fungus Coenogonium. The ultrastructure of the lichenized phycobiont, Trentepohlia, closely resembles that of the non-lichenized form, a filamentous subaerial green alga. The mycobiont has a typical fungal ultrastructure, and the cell wall sometimes appears thinner at points of contact with the phycobiont wall. Several branched fungal hyphae are usually randomly arranged around a Trentepohlia filament, and may in some cases completely ensheath the alga. Although no haustoria were observed, this relationship may still be termed a lichen since there is some modification of the alga and the lichen is structurally distinct from the two symbionts.     

QUANTITATIVE VARIATION IN VULPINIC AND PINASTRIC ACIDS PRODUCED BY TUCKERMANNOPSIS PINASTRI (LICHEN-FORMING ASCOMYCOTINA,PARMELIACEAE)

Tuckermannopsis pinastri is a lichen species found commonly on rocks and tree branches in boreal and alpine habitats in the northern United States. Members of this species produce three yellow-pigmented phenolic compounds: usnic, pinastric, and vulpinic acids. The objective of our study was to quantify the variation in concentration of the latter two of these compounds in relation to substrate factors, chlorophyll content, and thallus size. Using high-performance liquid chromatography, we analyzed 120 thalli of T. pinastri collected randomly from a single large population located at Spruce Knob, West Virginia. Although individuals were sampled from both tree and rock substrates that differed markedly in light intensity, these environmental factors were not correlated with observed variations in vulpinic or pinastric acid concentrations. Instead, compound concentrations were correlated most closely with thallus size, with small rather than large thalli having the highest concentrations of the two compounds. Small thalli did not have higher concentrations of chlorophylls than large thalli, however, which suggests that the rate of production of secondary compounds by the fungus in T. pinastri is independent of algal biomass. Inasmuch as lichen secondary compounds serve a defensive role against microorganisms and herbivores, our results suggest that small, juvenile thalli are better defended than more mature thalli.     

THE EFFECT OF OXYGEN DEPRIVATION ON INORGANIC NITROGEN UPTAKE IN AN ANTARCTIC MACROLICHEN

Snow meltwater containing 36 ng ml⁻¹NO₃⁻-N (raised here to between 95–101 ng ml⁻¹NO₃⁻-N) and 112 ng ml⁻¹NH₄⁺-N was sprayed onto illuminatedUsnea sphacelataat 2°C in a 2-1 capacity transparent perspex chamber force-ventilated with either air or O₂- (and CO₂-) free N₂. The NO₃-concentration in meltwater recirculated through a layer ofU. sphacelatafell toc. 8 ng ml⁻¹after 1·25 h. Although the pattern of decline was broadly comparable in both air and N₂, the initial rate of decline was lower in N₂. When undepleted meltwater was continuously sprayed onto the lichen and the effluent collected for analysis, the lichen was found to retain 55% of the wet deposited NO₃⁻in air but only 27% under N₂. Up to 90% of NH₄⁺supplied in a continuous spray of meltwater was retained by the lichen but this was affected little by O₂and CO₂deprivation.     

EFFECTS OF PHENOLIC INHIBITORS ON GROWTH AND METABOLISM OF GLUCOSE-UL-14C IN PAUL'S SCARLET ROSE CELL-SUSPENSION CULTURES

ABSTRACT Paul's Scarlet rose cell-suspension cultures were incubated in varying concentrations of the following phenolic inhibitors; chlorogenic acid, cinnamic acid, p-coumaric acid, ferulic acid, and scopoletin. All test compounds except chlorogenic acid were completely inhibitory at a 10⁻³m concentration, resulting in death of the cells prior to completion of the growth cycle. To assess the cellular effects of two commonly named plant inhibitors, ferulic and cinnamic acids, these compounds were provided to cultures during incubation of cells with glucose-UL-¹⁴C. Incubation of cells with glucose-UL-¹⁴C in the presence of 10⁻⁴m ferulic acid resulted in increased incorporation of ¹⁴C into the soluble lipid fraction along with decreased incorporation of ¹⁴C into protein, organic acids, and soluble amino acids. Treatment of the cells with 10⁻⁵m cinnamic acid during the incubation period resulted in a significant decrease in incorporation of ¹⁴C into protein. These alterations in the flow of carbon into cellular constituents when cells are treated with cinnamic and ferulic acids explain, at least in part, why these compounds inhibit growth, seed germination, and seedling development.     

LEAD INHIBITION OF CHLOROPHYCEAN MICROALGAE1

The effects of lead on the growth of 9 microalgae representing 4 chlorophycean genera were investigated in axenic laboratory cultures. Variations in sensitivity to lead existed among the algae tested with availability of phosphate often limiting growth. Under conditions in which phosphate was growth limiting at pH 6.2, Chlorella pyrenoidosa Chick, C. ellipsoidea Gerneck, C. vulgaris Beij. Scenedesmus sp. (IUCC 1591).Sc. Obtusiusculus Chodat and Selenastrum capricornutum Printz first showed toxicity at 0.5 mg·l^?1 pb. Two planktonic Scenedesmus spp. And an Ankistrodesmus sp. Were more tolerant, developing toxicity at 1 mg· l^?1 Pb. The relationship of phosphate supply to Pb toxicity was investigated with S. capricornutum and Sc. Obtusiusculus. Al pH 8.0, Selenastrum developed toxicity at 3 mg·l^?1 pb either with or without phosphate. When phosphate supply was growth-limiting, 6 times as much pb (i.e., 3 vs. 0.5 mg l^?1 was required to demonstrate toxicity with Selenastrum at pH 8.0 as opposed to pH 6.2 Sc. Obtusiusculus was inhibited at 0.5 mg· l^?1 pb in phosphate-limiting medium and developed toxicity at 1 mg·l^?1 in media containing phosphate. Control of colonial morphology with Sc. Obtusiusculus was inhibited. Phosphate availability as well as pH would seem to be important factors determining lead toxicity with some algae.     

INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS. III. INHIBITORS OTHER THAN TANNINS

We obtained considerable evidence in earlier work that inhibition of nitrification begins during old-field succession and increases to a maximum in the climax (Rice and Pancholy, 1972, 1973). Moreover, we found that tannins and tannin derivatives appear to be important inhibitors of nitrification. In the present project, other potential phenolic inhibitors of nitrification were identified in acetone extracts of entire plants of most herbaceous species and leaves of tree species important in an intermediate stage of succession and the climax in three vegetation types in Oklahoma. Attempts were made also to identify potential inhibitors in acetone extracts of soil from the top 15 cm of the oak-pine climax. Seventeen potential inhibitors were identified from the eleven important species of plants surveyed. These were mostly phenolic acids and flavonoids, but one coumarin compound, scopolin, was found in high amounts in several species. The potential inhibitors were most common in green tops or green leaves, but roots, dead tops (of previous year), and dead leaves had high amounts of some compounds. Caffeic and ferulic acids were prominent in dead leaves or dead tops, and one flavonoid, myricetin, occurred in sizeable amounts in dead tops of Sorghastrum nutans. The aglycones of most of the compounds were tested against nitrification in soil suspensions, and all completely inhibited oxidation of NH⁺₄ to NO⁻₂ by Nitrosomonas at concentrations as low as 10⁻⁶ to 10⁻⁸ M. Oxidation of NO⁻₂ to NO⁻₃ by Nitrobacter, however, was affected much less severely by these inhibitors. The greater resistance of Nitrobacter is not significant biologically because inhibition of the first step carried out by Nitrosomonas effectively inhibits the entire process of nitrification. The 3-glucoside of quercetin, isoquercitrin, inhibited the activity of Nitrosomonas completely at the same concentration as quercetin. We found a compound in large quantities in the oak-pine climax soil which appeared in all tests to be a flavonoid aglycone, but we were never able to identify it to our satisfaction. This substance was extremely inhibitory to germination and seedling growth of ‘Crimson Giant’ radish seeds. These have hard seed coats and germinate very rapidly so most inhibitors do not affect their germination at all. It is likely that some, if not all, of the nitrification inhibitors identified may be important in inhibition of nitrification in the later stages of succession and in the climax along with the tannins.     

ERUMPENT CEPHALODIA,AN APPARENT CASE OF PHYCOBIAL INFLUENCE ON LICHEN MORPHOLOGY1,2,3

On the upper surface of some specimens of the lichen Lobaria cf. crosa (Eschw.) Nyl. there are shrub-like growths which have a morphology similar to that of a free-living fruticose lichen, Polychidium umhausense (Auersw.) Henss., and contain a cyanophyte phycobiont, Nostoc. A few growths also contain scattered colonies of a chlorophyte phycobiont, in which case the lichen tissue locally assumes the foliose form characteristic of the parent Lobaria thallus. The differentiation of dorsiventral lichen cortices and the formation of a lax medulla and distinct algal layer are correlated with the presence of the green phycobiont. The lichen substances atranorin, gyrophoric acid, and 4-0-methylgyrophoric acid occur in both, the foliose L. erosa thallus and the fruticose tissue. It is suggested that the fruticose structures are erumpent cephalodia which are derived from the outgrowth of internal, cephalodia and should not be considered, to be epiphytic colonies of the lichen Polychidium.     

Some chemical and biological properties of culture filtrate ofNostochopsis lobatus

The blue-green algaNostochopsis lobatus released amino acids (glycine, serine, arginine and glutamic acid), sugars (glucose, fructose and sucrose), organic acids (oxaloacetic acid and oxalic acid) and protein in the culture medium. The quantity of extracellular amino acids and protein increased with age of culture from 30 to 120 d. All culture filtrates ofN. lobatus were highly toxic to spore formation and germination ofWestiellopsis prolifica and growth and conjugation ofSpirogyra decimina, while old-age culture filtrates inhibited total chlorophyll, heterocyst and akinete formation in the same alga and total chlorophyll and zoospore formation inChaetophora attenuata. The toxicity ofN. lobatus culture filtrate persists following high temperature treatment and at extremes of pH.     

Toxicity of 2,3,5,6-tetrachlorophenol to willow trees (Salix viminalis)

Chlorinated phenols have been intensively investigated from an eco-toxicological point of view, however almost nothing is known about toxicity of tetrachlorophenol (TeCP) to higher terrestrial plants. This article applied the willow tree acute toxicity test to study the toxicity of 2,3,5,6-TeCP to willows Salix viminalis (S. viminalis) at neutral and acidic conditions (roughly pH 7 and 4) with inhibition of transpiration as toxic endpoint. At neutral pH the EC₅₀ was >10 mg L^?1 while the EC₅₀ at acidic conditions was 0.32 ± 0.17 mg L^?1, clearly indicating that toxicity is exerted by the non-ionic chemical fraction. Standard tests running at neutral pH are therefore not capturing the full toxicity of weak acids and bases.     

The occurrence of lichen phenolics in the xylem sap of Quercus pyrenaica,their translocation to leaves and biological significance

Oak branches supporting the epiphytic lichens Evernia prunastri and Ramalina calicaris do contain both evernic and everninic acids which are acropetally translocated, via xylem, to reach the leaves. However, lichen phenolics have not been found in the mesophyllic cells and thus the photosynthetic ability of is not affected.     

N-Methylated Analogs of hIAPP Fragments 18–22, 23–27, 33–37 Inhibit Aggregation of the Amyloidogenic Core of the Hormone

Amylin (hIAPP) aggregation leads to the formation of insoluble deposits and is one of the factors in the development of type II diabetes. The aim of this research was to find N-methylated analogs of the aggregating amylin fragments 18–22, 23–27, and 33–37, which would not themselves be susceptible to aggregation and would inhibit the aggregation of the amyloidogenic cores of the hormone. None of the analogs of fragment 18–22 containing one or two N-methylated amino acid residues showed any tendency to aggregate. Only the peptide H−F(N−Me)GA(N−Me) IL−OH ( 6 ) derived from the 23–27 hIAPP hot spot did not form fibrous structures. All analogs of the 33–37 amylin fragment were characterized by the ability to form aggregates, despite the presence of N-methylated amino acids in their structures. N-Methylated peptides 1 – 5 demonstrated inhibitory properties against the aggregation of fragment 18–22. Aggregation of the amyloidogenic core of 23–27 was significantly inhibited by N-methylated peptides 1 – 3 derived from the (18–22) H−HSSNN−OH fragment and by the H−F(N-Me)GA(N−Me)IL−OH ( 6 ) fragment derived from the 23–27 amylin hot spot. Fragment (33–37) H−GSNTY−NH₂ was found to be inhibited in the presence of N-methylated peptides 1 – 3 derived from the 18–22 fragment and by the double methylated peptide H−F(N−Me)GA(N−Me)IL−OH ( 6 ). Research on the possibility of using N-methylated analogs of amyloidogenic amylin cores as inhibitors of hormone aggregation is ongoing, with a focus on finding the minimum concentration of N-methylated peptides capable of inhibiting the aggregation of hIAPP hot spots.     

Differential susceptibility ofSclerotium cepivorum Berk. to some synthesized visnagin sulfonamide derivates

Twenty-five visnagin sulfonamide derivatives were testedin vitro against sclerotial germination, growth and cellulolytic activity ofSclerotium cepivorum Berk. The effectiveness of the derivatives depends on the concentration and the substituent introduced to the title compounds. The introduction of SO₂Cl₂ to C₉ of visnagin induced high toxicity than introducing SO₂NH₂. Compounds with sulfonyl piperidine or sulfonyl morpholine gave small toxicity only at 30 and 75 μg cm⁻³. Addition of N-aryl ring to visnagin-9-sulfonamide rendered the title compound to be more toxic. The substitution of the N-aryl ring bym-CH₃,m-Cl orp-Cl enhanced the toxicity, while its substitution witho-CH₃,p-CH₃,p-Br,o-OCH₃ orm-OCH₃ caused a drop in the toxicity as compared to compounds with unsubstituted aryl ring. Visnagin sulfonamide derivatives having azole rings were strongly inhibitory for sclerotial germination, growth, sclerotial formation and cellulolytic activity, even when applied at 4 μg cm⁻³. The most toxic one was that having dimethyl isoxazole. The cleavage of γ-pyrone ring led to a decline in the toxicity as compared with the other sulfonamide derivatives. Communicated by J. ŠPAK