Carbon isotope fractionation in tree ring early and late wood in relation to intra-growing season water balance

We determined the stable carbon isotope composition (δ^1.3C) of cellulose extracted from early and late wood in Douglas fir [Pseudotsuga menziexii (Mirb.) Franco] tree rings. Data were obtained for the period 1962 to 1981, at the start of which the trees were 20 years old. A water balance model was used to calculate daily stand transpiration and water deficit. The model incorporates site factors (soil water availability, slope and aspect) and environmental variables (solar radiation, air temperature and rainfall). There was far greater variability in late wood than in early wood δ^1.3C. In wet years, late wood δ^1.3C was significantly lighter (by as much as 2δ) than early wood δ^1.3C but in dry years this difference was reversed. Differences between spring and summer cumulative transpiration accounted for almost 60δ of the variability in differences between early and late wood δ^1.3C. We found excellent correspondence between summer cumulative transpiration and late wood δ^1.3C, with estimates of transpiration accounting for up to 93% of the variability in δ^1.3C. Correlations between early wood δ^1.3C and spring transpiration were generally poor (r2<0.4), but we were able to identify those exceptional years in which there had been a very dry spring. Our results indicate that, while tree ring δ^1.3C correlates reasonably well with basal area increment, it is a far better indicator of inter- and intra-annual variability in water availability than radial growth.     

Interactions between migratory endoparasitic nematodes and arbuscular mycorrhizal fungi in perennial crops: A review

The root-lesion nematodes are important pests attacking stone and pome fruit crops throughout the world. They play an important role in the development of orchard replant problems. Host resistance toPratylenchus vulnus, the nematode of concern in mediterranean environments, has been difficult to find, and even more, to transmit into commercial rootstocks. Alternative management measures using early mycorrhizal infection that would confer protection against the nematode at a stage when plants are most vulnerable are currently being explored. These measures are considered important, taking into account a widespread change towards production systems that use in vitro material propagated in treated substrates free of mycorrhizal and other beneficial microorganisms. The prophylactic effect against root-lesion nematodes would be linked to mycorrhizal dependency of the host plant. Increase in tolerance would seem to be related to mycorrhiza assisted nutrition rather than to a direct suppressive effect of AM over the root-lesion nematode. InCitrus, Prunus, Malus andCydonia rootstocks, the nematode has shown to have a negative effect over AM colonization in the root.     

Inhibition of polyamine biosynthesis and growth in plant pathogenic fungi in vitro

Polyamine (PA) biosynthesis inhibitors, difluoromethylornithine (DFMO), difluoromethylarginine (DFMA), methylglyoxal bis-(guanylhydrazone) (MGBG) and bis-(cyclohexylammonium) sulphate (BCHA) have been tested for their effects on colony diameters at different intervals after inoculation of four plant pathogenic fungi (Helminthosporium oryzae, Curvularia lunata, Pythium aphanidermatum and Colletotrichum capsici). All these inhibitors, except DFMA had strongly retarded the growth of four fungi in a dose- and species-dependent fashion, and H. oryzae and C. lunata were found to be most sensitive to the effects of PA inhibitors. P. aphanidermatum and C. capsici were relatively insensitive and required rather high concentrations of inhibitors to get greater inhibition of mycelial growth, except DFMA which had stimulatory effect on the growth of these two fungi. However DFMA had greatly suppressed the growth of H. oryzae and C. lunata. The effect was generally more pronounced with MGBG than with DFMO and BCHA, and 1 mM Put completely prevented the inhibitory effects of 1 and 5 mM DFMO. Analysis of free and conjugated PAs in two sensitive fungi (H. oryzae and C. lunata) revealed that Put was present in highest concentrations followed by Spd and Spm and their levels were greatly reduced by DFMO application, and such inhibitions were totally reversed by exogenously supplied Put; in fact, PA titers were considerably increased by 1 mM Put alone and in combination with 1 mM DFMO. These results suggest that PA inhibitors, particularly DFMO and MGBG may be useful as target-specific fungicides in plants.     

Comparative ultrastructure of aecial and telial infections of the autoecious rust fungus Puccinia tuyutensis

This study demonstrates morphological differences between aecial and telial stages of the autoecious rust Puccinia tuyutensis. The aeciospores possess verrucose ornamentation while the teliospores have smooth surfaces. The aecial and telial haustoria of this rust produced in the mesophyll of Cressa cretica differ morphologically in the following respects:(1) the haustorial mother cell of telial haustorium is more differentiated than that of aecial haustorium and its wall at the penetration site is composed of 4 layers; (2) the aecial haustorium is filamentous in appearance and slightly constricted at the point of entry into the host cell, while the telial haustorium is clavate and possesses a narrow neck with a densely staining neckband and swollen body; (3) the neck of the telial haustorium is always associated with numerous vesicles while that of the aecial haustorium is not. Vascular tissue of host leaves is heavily invaded by aecial haustoria but not by telial haustoria.     

Keratinolytic fungi in sewage sludge

Sewage sludge from the Upper Silesia Region of Poland were surveyed for keratinolytic fungi. Out of 100 Petri dishes examined, 89 were positive for these micro-organisms. Altogether, 185 fungal appearances belonging to 10 species were observed. Trichophyton terrestre with its teleomorph Arthroderma quadrifidum, T. ajelloi with A. uncinatum, Microsporum gypseum with Arthroderma sp., and Chrysosporium keratinophilum with Aphanoascus keratinophilus prevailed in the sludges. The sewage treatment technologies together with the sludge structure, humidity and pH were found to be critical factors determining the occurrence of keratinolytic fungi in the sludge environment. The qualitative and quantitative composition of keratinolytic fungi could be a useful tool in evaluation of sludge treatment processes.     

Fungal biodiversity in the air of Turin

The qualitative fungal composition of Turin 's atmospheric environment was surveyed, carrying out a twelve-month study and collecting with a single stage volumetric sieve sampler on Dermasel agar supplemented with 0.4 g l^–1 cycloheximide and 0.05 g l^–1 chloramphenicol. We isolated 165 species and 2 varieties of mesophilic fungi from 58 genera and 26 thermotolerant species from 12 genera. Penicillium, Aspergillus, Acremonium, Chrysosporium, Scopulariopsis, Malbranchea, Paecilomyces, Phialophora and Cladosporium were in sequence the genera most rich in mesophilic species; Aspergillus, Penicillium, Chrysosporium and Scopulariopsis the most rich in thermotolerant species. Many of the species isolated are rarely or never recorded in the atmospheric environment. Cycloheximide can thus be said to select among airborne fungi, giving a characteristic picture.Abbreviation CH Cycloheximide - cfu colony forming unit     

腺苷三磷酸和环腺苷单磷酸对丝状真菌纤维素酶合成的调节

以虫荧光素酶法检验了四株丝状真菌在葡萄糖—无机盐液体培养过程中的胞内ATP含量。结果表明,只有当胞内ATP浓度低于10~(-S)mg/ml时,真菌才开始合成胞外纤维素酶(FPA)。以不同浓度的各种碳源培养时,菌体胞内ATP含量只要超过10~(-1)mg/ml,FPA的合成即发生阻遏。菌体胞内ATP含量与FPA合成呈显著负相关。以高效液相色谱(HPLC)法检测了菌体培养液中的cAMP含量。在非阻遏条件下,外源cAMP可以提高FPA的合成水平。但外源cAMP不能解除已经发生的酶合成阻遏。菌体ATP和cAMP水平是调节真菌纤维素酶合成的重要因子。     

Effect of increased CO2 concentration and temperature on the phyllosphere mycoflora of winter wheat flag leaves during ripening

The impact of elevated carbon dioxide (CO₂, 600/700 μmol mol^-1) and temperature (+ 4°C) on phyllosphere fungi colonising flag leaves of mini crops of winter wheat cv. Mercia between anthesis and harvest was determined in a computer-controlled environment facility in 1993 and 1994. In both years the total fungal populations (cm² leaf) were found to have increased due to exposure to either elevated CO₂ and elevated CO₂+ temperature treatments. This was mainly due to significant increases in populations of Cladosporium spp. (C. cladosporioides and C. herbarum) on the flag leaves during ripening. Other phyllosphere component species such as white and pink yeasts were not markedly affected by treatments. The range of fungal species found in such controlled environment chambers was narrower than that commonly found on flag leaves of field grown crops. Common and important colonisers of leaves and ripening ears such as Aureobasidium pullulans, Epicoccum nigrum and Fusarium spp. were seldom isolated.     

Ammonia fungi of iriomote Island in the southern Ryukyus,Japan and a new ammonia fungus,Hebeloma luchuense

Species composition and fruiting season of ammonia fungi were investigated in Iriomote Island of the southern Ryukyus, Okinawa Prefecture, Japan.Castanopsis andPinus forests were surveyed and 10 species of ammonia fungi were collected, including one new agaric species,Hebeloma luchuense sp. nov. This new fungus is characterized by having a rooting, squamulose-scaly stipe and cortinate veil and forms ectomycorrhizae withCastanopsis cuspidata var.sieboldii. Although the general mushroom season in theCastanopsis forest in Iriomote island was very short and restricted to summer, ammonia fungi were observed to fruit throughout the year in urea-treated plots.     

捕食真菌及其相关丝孢菌中国的新记录

本文报道了来自我国云南及长白山地区的捕食真菌及其相关丝孢菌的8个新记录种,即纺锤孢指隔孢(Dactylella atractoides),狭长孢指隔孢(D. stenomeces)、顶毛孢单顶孢(Monacrosporium acrochaeturn),泡环单顶孢(M. aphrobrochum),异孢单顶孢(M. heterobrochum),瘤捕单顶孢(M. phymatopagum),三叉霉(Tridentaria sp.)及龟头轮枝孢(Verticillium balanoides).