Mycosphaerella chaenomelis sp. nov.: The teleomorph ofCercosporella sp., the causal fungus of frosty mildew inChaenomeles sinensis, and its role as the primary infection source

A leaf spot disease called frosty mildew was observed onChaenomeles sinensis throughout Japan. Small brown spots with white tufts occurred followed by successive defoliation. On the fallen leaves, minute black dots are formed. The causal fungus was regarded as a new species ofMycosphaerella, M. chaenomelis, andCercosporella chaenomelis in anamorph. Pathogenicity of the fungus was confirmed only inC. sinensis by inoculation experiments. Colonies of the fungus grew well on potato sucrose agar, and grew at 10–30°C with an optimum temperature of 25°C. The fungus overwintered on the fallen diseased leaves in the form of pseudothecia, and ascospores served as the primary infection source from April to June.     

Nutrient and salt relations of <Emphasis Type="Italic">Pterocarpus officinalis</Emphasis> L. in coastal wetlands of the Caribbean: assessment through leaf and soil analyses

Pterocarpus officinalis L. is a dominant tree of freshwater coastal wetlands in the Caribbean and the Guiana regions. It is frequently associated with mangroves in areas with high rainfall and/or surface run-off. We hypothesized that P. officinalis is a freshwater swamp species that when occurring in association with mangroves occupies low-salinity soil microsites, or alternatively that it possesses mechanisms preventing accumulation of salt in photosynthetic tissues. To test this we compared the mineral composition of soils and leaves of several species in two Pterocarpus forests in Puerto Rico associated with coastal mangroves, Sabana Seca and Punta Viento. Results indicate that (1) Sabana Seca has low soil salinity values even in the P. officinalis and Laguncularia racemosa mixed zone. In Punta Viento, salinity in the mixed zone was higher than in the Pterocarpus forest, but much lower than in the mangrove area; (2) In both forests, leaves of P. officinalis showed much lower Na concentrations than mangrove species. The K/Na ratios were 16–20 times higher in P. officinalis, indicating preferential absorption of K against Na. The mangrove fern (Acrostichum aureum) growing side by side with P. officinalis and L. racemosa in Punta Viento also revealed high Na exclusion capacity. We found an asymmetric distribution of cations in the blade and rachis of the P. officinalis compound leaves in both sites. The rachis accumulates more Na and Ca, but less Mg than the leaf blade. This sequestration of Na in the rachis prevents salt damage of photosynthetic tissue in the leaf blade.     

Surculiseries rugispora gen. et sp. nov., a new endophytic mitosporic fungus from leaves ofBruguiera gymnorrhiza

Surculiseries rugispora gen. et sp. nov. is described as an endophytic fungus from leaves ofBruguiera gymnorrhiza in mangrove forests in the Iriomote Is., Okinawa, Japan. This fungus develops peculiar conditiongenous cells that resemble octopus legs with obvious sucker-like scars, and produces lentiform conidia with lines on surface. Sequence analysis of 18S rDNA places this new fungus in the family Xylariaceae and shows its close affinity to the genusAscotricha (anamorph:Dicyma).     

The Herbivore Assemblage, Herbivory and Leaf Chemistry of the Mangrove Kandelia obovata in Two Contrasting Forests in Hong Kong

The herbivore assemblage, intensity of herbivory and factors determining herbivory levels on the mangrove Kandelia obovata (previously K. candel, Rhizophoraceae) were studied over a 13-month period at two forests with contrasting growing conditions in Hong Kong. Mai Po was part of an eutrophic embayment in the Pearl River estuary and generally offered more favourable conditions for mangrove growth, whereas Ting Kok had a rocky substratum and oceanic salinity. Twenty-four insect herbivore species were recorded on K. obovata, with lepidopteran larvae that consume leaf lamina being the dominant species. While leaf litter production was similar at the two forests, herbivory level at Mai Po (mean = 3.9% in terms of leaf area loss) was more severe than that at Ting Kok (mean = 2.3%). Peak herbivory levels were found in summer at both locations (6.5% for Mai Po and 3.8% for Ting Kok). Young leaves of K. obovata at both locations were generally preferred by the herbivores from the period of late spring to summer. Concentrations of most feeding deterrents (ash, crude fibre, and total soluble tannins) were significantly higher in both young and mature leaves at Ting Kok, whereas leaf nutrients (total nitrogen and water) were the same at the two sites. Young leaves at Ting Kok contained about 30% more tannins than their counterparts at Mai Po. Significant differences in leaf chemistry also existed between young and mature leaves at either site. The differences were concomitant with the observed patterns of leaf herbivory on K. obovata, and suggest a potential relationship between environmental quality and plant defence against herbivory.     

真红树和半红树植物叶片性状的比较研究

红树植物是一类生长在热带、亚热带海岸潮间带的乔木、灌木或草本植物,根据其分布特征可分为真红树植物植物和半红树植物。为了探究两者对海岸潮间带高盐、高光和缺氧等环境的生态适应策略的异同,该文选取5种真红树植物植物[卤蕨(Acrostichum aureum)、木榄(Bruguiera gymnorrhiza)、老鼠簕(Acanthus ilicifolius)、桐花树(Aegiceras corniculatum)、秋茄(Kandelia candel)]和4种半红树植物[银叶树(Heritiera littoralis)、水黄皮(Pongamia pinnata)、黄槿(Hibiscus tiliaceus)、杨叶肖槿(Thespesia populnea)]为研究对象,对叶片解剖和功能性状进行了对比研究。结果表明:(1)9种红树植物叶片的共同特征表现为均具有角质层、叶肉具有栅栏组织和海绵组织分化、气孔下陷等。(2)不同之处在于真红树植物植物叶片有蜡质层和内皮层、无表皮毛、气孔仅分布在下表皮,而半红树植物的叶片则较少有蜡质层,部分有表皮毛,无内皮层,气孔在上下表皮分布不完全一致。(3)真红树植物植物的气孔密度和比叶面积显著小于半红树植物(P<0.05),而叶片厚度、含水量、比叶重和鲜干重比则显著大于半红树植物(P<0.05)。以上结果说明真红树植物植物的叶片性状使其在维持盐度平衡及贮水保水能力方面强于半红树植物,从而能更好地适应海岸潮间带高盐环境。     

Variation in the δ<Superscript>13</Superscript>C of Two Mangrove Plants is Correlated with Stomatal Response to Salinity

To better understand the relationship between salinity and the carbon stable isotope composition (expressed as δ¹³C) of mangrove plants and to test whether the patterns of variation in δ¹³C of mangrove plants differ from those of nonhalophytes as response to salinity, the effect of salinity on leaf δ¹³C in two dominant mangrove species, Aegiceras corniculatum and Kandelia candel, was studied. Furthermore, to determine whether the variation in δ¹³C of mangrove species is adjusted by stomatal conductance, K. candel was selected as an example, and leaf gas-exchange characteristics of the seedlings were measured. It was observed that both mangrove species had a lower leaf δ¹³C under their optimum salinity (1.50% for Ae. corniculatum and 2.00% for K. candel). This variation in δ¹³C of mangrove plants was attributable largely to stomatal adjustment as for nonhalophytes in which a strong correlation between δ¹³C and relevant photosynthetic properties is observed. This result suggests that the different response pattern in δ¹³C was a consequence of the variation in stomata in relation to the different tolerance to salinity. The optimum salinity inferred by leaf δ¹³C provides a feasible method for comparing salt tolerance between mangrove plants belonging to different species, which is useful for mangrove restoration.     

Didymella fagi sp. nov. and its anamorphAscochyta fagi, causing the yellow leaf spot disease ofFagus crenata andQuercus mongolica var.grosseserrata in Japan

AnAscochyta fungus was obtained during a survey of leaf spot diseases ofFagus crenata in the mountains of Aomori prefecture in 1995. The pathogenicity of the fungus toF. crenata was confirmed by inoculation. Its teleomorph was first found on artificially infected leaves after the leaves were placed in an incubator at 5°C with a 12-h photoperiod (approximately 500lx, daylight strip lamps) for 4 mo. The fungus was found to be the causal agent of yellow leaf spots ofF. crenata andQuercus mongolica var.grosseserrata in the field. Comparison with similar fungi so far described from Fagaceae indicated that the anamorph isAscochyta fagi and the teleomorph is an undescribed species ofDidymella. The nameDidymella fagi is introduced for the teleomorph. Correlation between the two morphs has been proved by cultural, morphological and pathological studies.     

A newHalophytophthora species,H. porrigovesica, from subtropical and tropical mangroves

A new oomycete was found from intertidal fallen leaves of mangroves in Japan and Thailand and is described here asHalophytophthora porrigovesica. This species is characterized by having an epapillate, ovate zoosporangium with a lens-shaped dehiscence plug-like material at the apex, and by forming an expanding long cylindrical vesicle prior to zoospore release. A key to 14 species and 2 varieties ofHalophytophthora including the new species is proposed. The subtropical (Iriomote is., Japan) strains and tropical (Thailand) strains were different in physiological properties and especially in the asexual reproduction. The subtropical strains showed a lower optimal temperature and wider range of suitable temperature and salinity for zoosporangium formation, whereas the tropical strains showed a higher optimal temperature and narrower range of temperature and salinity. These differences are explained as adaptations of the strains to the environmental conditions of their respective habitats. From the subtropical mangroves, six strains of the new species have been isolated only from submerged leaves ofSonneratia alba, while several strains have been isolated from tropical mangroves from the leaves of three species of mangrove trees,S. alba, Bruguiera gymnorrhiza andAvicennia alba. This indicates a change of taxon selectivity (host specificity) with the geographical distribution.     

Soil Respiration and Belowground Carbon Allocation in Mangrove Forests

Mangrove forests cover large areas of tropical and subtropical coastlines. They provide a wide range of ecosystem services that includes carbon storage in above- and below ground biomass and in soils. Carbon dioxide (CO₂) emissions from soil, or soil respiration is important in the global carbon budget and is sensitive to increasing global temperature. To understand the magnitude of mangrove soil respiration and the influence of forest structure and temperature on the variation in mangrove soil respiration I assessed soil respiration at eleven mangrove sites, ranging from latitude 27°N to 37°S. Mangrove soil respiration was similar to those observed for terrestrial forest soils. Soil respiration was correlated with leaf area index (LAI) and aboveground net primary production (litterfall), which should aid scaling up to regional and global estimates of soil respiration. Using a carbon balance model, total belowground carbon allocation (TBCA) per unit litterfall was similar in tall mangrove forests as observed in terrestrial forests, but in scrub mangrove forests TBCA per unit litter fall was greater than in terrestrial forests, suggesting mangroves allocate a large proportion of their fixed carbon below ground under unfavorable environmental conditions. The response of soil respiration to soil temperature was not a linear function of temperature. At temperatures below 26°C Q10 of mangrove soil respiration was 2.6, similar to that reported for terrestrial forest soils. However in scrub forests soil respiration declined with increasing soil temperature, largely because of reduced canopy cover and enhanced activity of photosynthetic benthic microbial communities.     

Feeding clusters and olfaction in the mangrove snail Terebralia palustris (Linnaeus) (Potamididae: Gastropoda)

Large numbers of the snail Terebralia palustris (Linnaeus) (Potamididae; Gastropoda) are frequently observed feeding in a cluster on a single fallen mangrove leaf, yet none are present on leaves nearby. Consequently, we investigated the food-finding ability of T. palustris in a Kenyan mangrove forest using field experiments. We estimated the attractive effect of different cues and analysed the paths (video-recorded) of snails when approaching a food-related odour. This intertidal snail can potentially use both air-borne and water-borne odours to locate food. T. palustris is attracted to conspecifics feeding on leaves, while intact leaves as well as non-feeding snails are not attractive. Moreover, the guiding stimulus appears to be compounds released when the leaves are damaged.T. palustris also seems able to discriminate between different food items; it is more strongly attracted to green mangrove leaves than senescent or fallen ones or mangrove propagules, probably because green leaves release a greater amount of attractive cues.Feeding snails thus recruit more snails to feed on the same leaf. The ecological implications of this behaviour are discussed: a large number of snails on the same leaf counteracts the ability of crabs to remove the leaf being eaten by the snails.     

Coal Dust Pollution Effects on Wetland Tree Species in Richards Bay,South Africa

In this study, the effects of coal dust on four, sympatric, wetland tree species in Richards Bay Harbour were investigated. We tested the hypothesis that leaf micromorphology influenced dust accumulation and that coal dust occluded stomata and reduced photosynthetic performance of three mangroves, Avicennia marina, Bruguiera gymnorrhiza and Rhizophora mucronata, and a mangrove associate, Hibiscus tiliaceus. To investigate leaf micromorphology, leaf blade material of the four species was prepared following standard procedures and viewed under scanning electron microscopy. Gas exchange and chlorophyll fluorescence measurements were made at saturating light (>1000 μmol m⁻² s⁻¹) and high temperature (>25 °C) on leaves that were either covered or uncovered with coal dust. There was no evidence of occlusion of stomata by dust. Dust accumulation in A. marina and H. tiliaceus was exacerbated by the presence of a dense mat of trichomes on the undersurface of the leaves, as well as by the sticky brine secreted by salt glands in the former species.Coal dust significantly reduced CO₂ exchange, Photosystem II (PS II) quantum yield and electron transport rate (ETR) through PS II in A. marina and H. tiliaceus but not in the other two mangroves. Reduction in photosynthetic performance was attributed to reduction in light energy incident on the photosynthetic tissues.     

Bioindicator capacity of trees towards dryland salinity

To investigate plant–soil reactions towards site salinity we chose Ruprechtia triflora as the dominant tree species in its natural habitat in dry forests of Paraguay. We applied freezing point osmometry to measure tree leaves and soil samples identically on the basis of colligative solute properties. In order to substantiate the first field findings, the relation of tree and soil in terms of salinity was further investigated under controlled conditions in the greenhouse. R. triflora shows extreme osmotic adaptability. In three independent greenhouse experiments with NaCl application, Ruprechtia seedlings and later Eucalyptus dunnii seedlings from E Australia (for inter-species comparison) showed highly significant responses to their soil salinities. We conclude that tree leaves can serve as bioindicator for soil salinity within the tree’s rhizosphere.     

Mycopappus quercus sp. nov., causing frosty mildew inQuercus acutissima

The causal fungus of frosty mildew inQuercus acutissima was taxonomically studied. Brown spots with conical white to yellowish tufts of the causal, fungus developed on the leaves, followed by successive defoliation. The fungus was regarded as a new species ofMycopappus, M. quercus, from the morphology of the multicellular propagules. The ascogenous stage and true conidia of the fungus were not observed, although sclerotia were formed on the fallen diseased leaves.     

Mycosphaerella buna sp. nov. with aPseudocercospora anamorph isolated from the leaves of Japanese beech

A species ofMycosphaerella with aPseudocercospora anamorph was collected on overwintered fallen leaves of Japanese beech,Fagus crenata. Based on comparison of morphology withMycosphaerella species on Fagaceae, the fungus was newly described asMycosphaerella buna. ThePseudocercospora anamorph derived from a single ascospore of the fungus was morphologically identical to an endophytic anamorph isolated from asymptomatic living leaves of Japanese beech. Contribution No. 150, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba     

Breakdown of fresh and dried <Emphasis Type="Italic">Rhizophora mucronata</Emphasis> leaves in a mangrove of Southwest India

Patterns of fungal colonization, mass loss and biochemical changes during the decomposition of predried and fresh (naturally fallen) leaves of Rhizophora mucronata were studied in a southwest mangrove of India. Dried and fresh leaves in litter bags were introduced at the mid-tide zone and retrieved after 1, 2, 4, 8, 10, 12 and 14 weeks. On incubation in the laboratory, a total of 5 ascomycetes and 18 anamorphic fungi were recorded. The majority of anamorphic taxa were natural inhabitants of the phyllosphere of senescent leaves. Following two weeks of exposure, they were largely replaced by marine fungi (ascomycetes and anamorphic fungi). More taxa were recovered from dried than from fresh leaves, and predrying accelerated the initial rate of mass loss. Ergosterol levels were much lower than those reported from vascular plant detritus exposed in other aquatic habitats. Both ergosterol and nitrogen levels peaked after between 4 weeks and 8 weeks of exposure; ergosterol levels subsequently declined, while nitrogen remained stable in predried leaves and fell in fresh leaves. The dynamics of remaining mass for the first 8 weeks of exposure were best described by a double-exponential decay model. The decay rate then appeared to accelerate, and the second phase was best described by a single exponential decay model. The apparent breakpoint coincided with an increase in the salinity of the mangrove swamp.     

Lower marine fungi (labyrinthulomycetes) and the decay of mangrove leaf litter

This paper deals with the association of members of the Labyrinthulomycetes (Thraustochytriales and Labyrinthulales) with decaying or decayed leaves at an intertidal mangrove at Morib, Malaysia. Representatives of both orders of these obligately marine unicellular eukaryotes of unresolved taxonomic affinities (Chamberlain & Moss, 1998) were consistently isolated from leaves at all stages of decay from the recently fallen to those in an advanced stage of decay, but not from either green or senescent yellow leaves attached to trees. Baiting experiments using -irradiated leaf discs of Sonneratia and Rhizophora spp. immersed in the aquatic environment of the mangrove, revealed that leaf material was colonised by both labyrinthulids and thraustochytrids within 24 hours of immersion at the test site and these organisms were isolated from the leaf material throughout the 14 day study period. In vitro experiments using axenic cultures of three thraustochytrid genera inoculated onto sterile discs of Sonneratia leaves and incubated for 14 days caused loss of both biomass and structural integrity of the leaf material. Freeze fracture, followed by scanning electron microscopy of leaves inoculated with a thraustochytrid and a strain of Labyrinthula, revealed that penetration of the leaf occured after 4 days and that the thraustochytrid was associated with localised degradation of internal leaf tissues. Cellulase production by an isolate of Schizochytrium aggregatum was detected. The results of all the above investigations are discussed with reference to the role of members of the Labyrinthulomycetes in nutrient cycling in the mangrove.     

Effects of temperature and water activity on <Emphasis Type="Italic">Lecanicillium</Emphasis> spp. conidia germination and growth,and mycosis of <Emphasis Type="Italic">Pissodes strobi</Emphasis>

Selecting entomopathogenic fungal isolates for use as biocontrol agents requires an assessment of their growth and virulence characteristics as affected by environmental conditions. Here we demonstrate a wide temperature and moisture range for colony growth, effective conidial germination and virulence against Pissodes strobi Peck (white pine weevil) of several isolates of Lecanicillium Gams and Zare, an entomopathogenic fungus distributed worldwide and indigenous to forests on Vancouver Island, British Columbia, Canada. In order to examine the potential Lecanicillium as a biological control agent, the pathogenicity of isolates collected from different geographical locations on P. strobi cadavers was assessed, and colony growth at different temperatures was evaluated. Colony growth was evident between 5 and 30°C, with optimal growth occurring at 25°C. Various combinations of water activity (0.55, 0.76, 0.85 and 0.99 a _w) and temperature (10, 15, 20, and 25°C) were also used to evaluate environmental impacts on conidial germination and cumulative mycosis of adult P. strobi. Certain Lecanicillium isolates displayed xerophilic (0.85 a _w) or psychrophilic (10°C) growth optima. Ultimately, identifying the abiotic limits of this entomopathogenic fungus will be used to determine which isolates have potential for future in situ biocontrol trials.     

Effects of salinity and flooding on seedlings of cabbage palm (Sabal palmetto)

Sabal palmetto (Walt.) Lodd. ex Schultes (cabbage palm) dominates the coastal limit of many forests in North Florida and Georgia, United States. Changes in saltwater flooding due to sea level rise have been credicted with pushing the coastal limit of cabbage palms inland, eliminating regeneration before causing death of mature trees. Localized freshwater discharge along the coast causes different forest stands to experience tidal flooding with waters that differ in salinity. To elucidate the effect of such variation on regeneration failure under tidal flooding, we examined relative effects of flooding and salinity on the performance of cabbage palm seedlings. We examined the relationship between seedling establishment and degree of tidal inundation in the field, compared the ability of seedlings to withstand tidal flooding at two coastal sites that differed in tidal water salinity, and investigated the physiological responses of cabbage palm seedlings to salinity and flooding in a factorial greenhouse experiment. Seedling survival was inversely correlated with depth and frequency of tidal flooding. Survival of seedlings at a coastal site flooded by waters low in salinity [c. 3 parts per thousand (ppt)] was greater than that at a site flooded by waters higher in salinity (up to 23 ppt). Greenhouse experiments revealed that leaves of seedlings in pots flushed twice daily with salt solutions of 0 ppt and 8 ppt exhibited little difference in midmorning net CO₂ assimilation rates; those flushed with solutions of 15 ppt and 22 ppt, in contrast, had such low rates that they could not be detected. Net CO₂ assimilation rates also declined with increasing salinity for seedlings in pots that were continuously inundated. Continuous root zone inundation appeared to ameliorate effects of salinity on photosynthesis, presumably due to increased salt concentrations and possibly water deficits in periodically flushed pots. Such problems associated with periodic flushing by salt water may play a role in the mortality of cabbage palm seedlings in the field. The salinity range in which plant performance plummeted in the greenhouse was consistent with the salinity difference found between our two coastal study sites, suggesting that variation in tidal water salinity along the coast plays an important role in the ability of cabbage palm seedlings to withstand tidal flooding.     

Tannin Dynamics of Propagules and Leaves of Kandelia candel and Bruguiera gymnorrhiza in the Jiulong River Estuary, Fujian, China

Changes in the total phenolics, condensed tannins (CT), protein-precipitable phenolics content and protein precipitation capacity were determined on a series of mangrove leaves from two true viviparous mangrove species (Kandelia candel and Bruguiera gymnorrhiza) at various stages of development and decomposition in the Jiulong River Estuary, Fujian, China. Similar measurements were also done for the propagules at different developmental stages. The results showed that the total phenolics, extractable condensed tannins, total condensed tannins, protein-precipitable phenolics content and protein precipitation capacity in young leaves were higher than those in mature and senescent leaves. Tannin dynamics during leaf decomposition varied with species, and the rapid loss of phenolics observed during decomposition can be ascribed to leaching and degradation. Protein-bound CT and fibre-bound CT tended to increase with leaf decomposition, with CT binding more strongly to protein than to fibre. Protein-bound CT was higher than fibre-bound CT with the exception of mature leaves. Total phenolics, extractable CT and protein-precipitable phenolics contents in flower tissues were relatively lower than those in hypocotyls at different developmental stages. Protein precipitation capacity fluctuated with the development of propagules. Increases in nitrogen in decaying litter, and declines in contents of total phenolics and total condensed tannins of detritus support the general conclusion that decomposing mangrove detritus can be a more palatable heterotrophic substrate than living leaves.     

Studies on life history characteristics of <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> O. F. Müller (Rotifera) in relation to temperature,salinity and food algae

Effects of temperature (18, 24, and 30°C), salinity (5–40 ppt, five intervals) and algal foods (Synechococcus sp., Chlorella pyrenoidosa, Isochrysis zhanjiangensis, Dunaliella salina and Tetraselmis cordiformis) on the life table demography of six geographical Brachionus plicatilis sensu stricto clones, which had been identified according to the prevalent taxonomy and biometric analysis of B. plicatilis sensu lato, were studied. The results showed that temperature, salinity and temperature × salinity significantly influenced the life history parameters. Genotype (clone) had no effect on the population growth rate but did influence the net reproductive rate, generation time and lifespan. All rotifer clones showed the expected increase in population growth rate with increasing temperature. B. plicatilis s. s. attained a higher population growth rate at low–medium salinities (5–20 ppt) than at high salinities (25–40 ppt). The equivalent spherical diameter (ESD) of food algae, salinity and ESD × salinity had significant effects on the life history parameters. In this case, genotype had no effect on population growth rate, net reproductive rate and generation time but did influence lifespan. The population growth rate of B. plicatilis s. s. evaluated against particle retention spectrum of algae at two salinities resulted in bell-shaped curves. Dunaliella salina with an ESD = 7.7 μm was considered to be the best food for B. plicatilis s. s. while Synechococcus appeared to be an inadequate food algae.