Identification and characterization of a new group of root-colonizing fungi within the Gaeumannomyces–Phialophora complex

A new group of darkly pigmented root-infecting fungi was isolated from cereal roots obtained from six different locations in northeastern Germany. Similar random amplified polymorphic DNA(RAPD) patterns and restriction profiles of amplified rDNA were used as a basis for classifying the isolates in a separate group. The isolates demonstrating mycelial and infection characteristics typical of Gaeumannomyces graminis could be differentiated from the varieties of G. graminis as well as from Gaeumannomyces cylindrosporus / Phialophora graminicola using RAPD Polymerase chain reaction (PCR) and rDNA Restriction-fragment length polymorphism (RFLP) analysis. Phylogenetic analysis of the Internal transcribed spacer (ITS) regions suggests that the isolates form a distinct group (named group 'E') situated within the Gaeumannomyces – Phialophora complex between the branch of the G. graminis varieties and Gaeumannomyces incrustans / Magnaporthe poae . Isolates of group E produced lobed hyphopodia and were shown in biotests to be non-pathogenic to wheat, oats, Italian Ryegrass and Chewings Fescue, suggesting it is a benign parasite which colonizes cereals or grasses without destroying vascular tissue. Furthermore, curved phialospores could be found. Summarizing the results presented, this new group could be classified as a new species of Phialophora . Although isolates of group E were found at only six of the 32 investigated locations, they composed up to 50% of total isolates of the Gaeumannomyces – Phialophora complex at these sites. Because of the non-pathogenic behaviour, the new group may be of value as biological control agents for pathogenic fungi.     

Fitness consequences of nest infiltration by the mutualist‐exploiter Megalomyrmex adamsae

1. Fungus‐growing ants are obligate mutualists. Their nutrient‐rich fungus garden provides a valuable food store that sustains the ant hosts, but can also attract social parasites. 2. The ‘guest ant' Megalomyrmex adamsae Longino parasitises the fungus‐growing Trachymyrmex zeteki Weber queen just after nest founding. The parasitic queen infiltrates the incipient nest, builds a cavity in the fungal garden, and lays eggs that develop into workers and reproductive males and females. 3. This study compared young parasitised and non‐parasitised laboratory colonies by measuring garden growth and biomass, and the number of host workers and reproductives. Host queen survival and parasite colony growth were also monitored. 4. Parasitised Trachymyrmex colonies had reduced host worker and alate numbers, as well as lower garden biomass, compared with non‐parasitised control colonies, confirming that M. adamsae is a xenobiotic social parasite. Host queen survival was not significantly different between parasitised and control colonies. 5. This is the first study that experimentally infects host colonies with a xenobiotic social parasite to measure fitness cost to the host. The natural history of M. adamsae and the fungus‐growing ant mutualism are evaluated in the context of three general predictions of (Bronstein, Ecology Letters, 4 , 277–287, 2001a) regarding the cost of mutualism exploiters.     

The Response of the C3-CAM Tree, Clusia rosea, to Light and Water Stress: I. GAS EXCHANGE CHARACTERISTICS

Gas exchange measurements were undertaken on 2-year-old plantsof Clusia rosea. The plants were shown to have the ability toswitch from C₃-photosynthesis to CAM and vice versa regardlessof leaf age and, under some conditions, CO₂ was taken up continuously,throughout the day and night. The light response was saturatedby 120 µmol m^–2 s^–1 typical of a shade plant. Gas exchange patterns in response to light, water and VPD wereexamined. All combinations of daytime and night-time CO₂ uptakewere observed, with rates of CO₂ uptake ranging from 2 to 11µmol m^–2 s^–1 depending upon water status andlight. Categorization of this plant asC₃, CAM or an intermediateis impossible. Differing VPD affected the magnitude of changesfrom CAM to C₃-photosynthesis (0 to 0.5 and 0 to 6.0 µmolm^–2 s^–1 CO₂, respectively) when plants were watered.Under well-watered conditions, but not under water stress, highPPFD elicited changes from CAM to C₃ gas exchange. This is unusualnot only for a shade plant but also for a plant with CAM. Itis of ecological importance for C. rosea, which may spend theearly years of its life as an epiphyte or in the forest understorey,to be able to maximize photosynthesis with minimal water loss. Key words: Clusia rosea, CAM, C₃, stress     

Non-invasive determination of plant biomass with microwave resonators

Non-invasive and rapid determination of plant biomass would be beneficial for a number of research aims. Here, we present a novel device to non-invasively determine plant water content as a proxy for plant biomass. It is based on changes of dielectric properties inside a microwave cavity resonator induced by inserted plant material. The water content of inserted shoots leads to a discrete shift in the centre frequency of the resonator. Calibration measurements with pure water showed good spatial homogeneity in the detection volume of the microwave resonators and clear correlations between water content and centre frequency shift. For cut tomato and tobacco shoots, linear correlations between fresh weight and centre frequency shift were established. These correlations were used to continuously monitor diel growth patterns of intact plants and to determine biomass increase over several days. Interferences from soil and root water were excluded by shielding pots with copper. The presented proof of principle shows that microwave resonators are promising tools to quantitatively detect the water content of plants and to determine plant biomass. As the method is non-invasive, integrative and fast, it provides the opportunity for detailed, dynamic analyses of plant growth, water status and phenotype.     

Holocene environmental changes and the seal (Phocidae) fauna of the Baltic Sea: coming,going and staying

• 1 The occurrence of different species of seal (Phocidae) during the Holocene in north‐eastern Europe was influenced by a changing geological situation over the last 12 000 years, characterized by alternating freshwater, brackish and marine stages and by spatially and temporally limited opportunities for migration of marine species into the Baltic basin. The patterns of immigration by ringed seal Phoca hispida, harp seal Phoca groenlandica, grey seal Halichoerus grypus and harbour seal Phoca vitulina are reviewed here in order to understand present distributions and population sizes. Furthermore, the future of their populations is analysed.
• 2 Phoca hispida immigrated into the Baltic basin during its brackish Yoldia Stage at the Late Glacial/Early Holocene boundary and has persisted in some disjunct populations until now. A second immigration followed at the beginning of the Littorina Transgression – which resulted in the present stage of the Baltic Sea, obviously caused by the strong cooling event that occurred 6200 calibrated ¹⁴C years BC. Its present status is not threatened, but global warming will restrict suitable habitat.
• 3 Phoca groenlandica had a mid‐Holocene intermezzo in the Baltic Sea. Its later disappearance was probably caused by hunting of subadult animals by humans.
• 4 Halichoerus grypus and Phoca vitulina also immigrated at the beginning of the present stage of the Baltic Sea. Whereas H. grypus has been common from this beginning point until modern times, the population of P. vitulina persisted at a low level for millennia. Only since the 18th century has its population increased and spread over the whole Baltic Sea.

     

Gene Activity Patterns and Cellular Differentiation

Puffing in giant chromosomes ot Diptera is considered to reflectthe pattern of active gene loci in these chromosomes. In anyone tissue only a relatively small portion of the total bands(about 10 to 20%) have been observed to form a puff at sometime or another in larval development. These patterns of "potentiallyactive" loci are tissue specific, though greatly overlapping.The actual rate of activity at these loci is controlled independentlyof each other and independently in each tissue by factors ofthe extranuclear metabolism. Puffing at some loci seems to berelated to specific cellular functions, such as secretion ofthe salivary glands. The activity of others may be related tomore basic metabolic processes. In relation to larval development,puffing patterns may change with changing cell functions orwith developmental processes in the cells themselves. In salivaryglands ofChironomus activity of DNAase and of acid phosphataseseems to change in relation to cell breakdown at the end ofthe pupal molt. Changes of acid phosphatase activity begin earlyin the last larval ins tar, but the enzyme is bound to lysosomesuntil metamorphosis. This suggests that the genes specificallyactive during metamorphosis have to interact with a longtermcontrol-system of development. The induction of metamorphosisis a sequential process, gene activations being among the firststeps in this sequence. The activation of these genes by ecdysoneis independent of protein synthesis. It is only the reactionof these genes that leads to the subsequent events in the cell,including the subsequent puff activations. This is shown bythe fact that they depend on early RNA synthesis as well ason protein synthesis. These results on puffing are discussedwith regard to the general problem of the relationships betweenpatterns of gene activity and differentiation.     

Economic Mass Cultivation of Paramecium tetraurelia on a 200-Liter Scale1

ABSTRACT. A new and inexpensive medium is described for axenic mass cultivation of Paramecium tetraurelia stock 51s and the double mutant pawn A/pawn B. Skim milk powder is the major carbon and nitrogen source in this medium. Growth characteristics (proliferation rate, final cell density, and cell size) are similar to those observed with other axenic culture media. Cultures were run in one-liter erlenmeyer flasks, a 20-liter, and a 250-liter airlift bioreactor. The yield of a large bioreactor is 750 g (wet wt.) Paramecium or 5 × 10⁹ cells. This easy, economical culture technique will greatly facilitate the use of Paramecium as a model organism for extensive biochemical studies.     

The Effect of Temperature and Light on Gas Exchange and Acid Accumulation in the C3-CAM Plant Clusia minor L

Gas exchange and organic acid accumulation of the C₃-CAM intermediateClusia minor L. were investigated in response to various day/nighttemperatures and two light regimes (low and high PAR). For bothlight levels equal day/night temperatures between 20°C and30°C caused a typical C₃ gas exchange pattern with all CO₂uptake occurring during daylight hours. A day/ night temperatureof 15°C caused a negative CO₂ balance over a 24 h periodfor low-PAR-grown plants while high-PAR-grown plants showeda CAM gas exchange pattern with most CO₂ uptake taking placeduring the dark period. However, there was always a considerablenight-time accumulation of malic acid which increased when thenight-time temperature was lowered and had its maximum (54 mmolm^–2) at day/night temperature of 30/15°C. A significantamount of malic acid accumulation (23 mmol m^–2) in low-PAR-grownplants was observed only at 30/15°C. Recycling of respiratoryCO₂ in terms of malic acid accumulation reached between 2·0and 21·5 mmol m_–2 for high-PAR-grown plants whilethere was no significant recycling for low-PAR-grown plants.Both low and high-PAR-grown plants showed considerable night-timeaccumulation of citric acid. Indeed under several temperatureregimes low-PAR-grown plants showed day/night changes in citricacid levels whereas malic acid levels remained approximatelyconstant or slightly decreased. It is hypothesized that lowand high-PAR-grown plants have different requirements for citrate.In high-PAR-grown plants, the breakdown of citrate preventsphotoinhibition by increasing internal CO₂ levels, whereas inlow-PAR-grown plants the night-time accumulation of citric acidmay function as an energy and carbon saving mechanism. Key words: C. minor, C₃, CAM, citric acid, light intensity