Planktic coccal and trichal green algae of Lake Volvi,Greece

In the course of three years' investigations (1983–1986) of Lake Volvi, N Greece, 62 species and varieties of chlorococcal algae and 6 species of ulotrichal algae (Chlorophyceae) were found. Although chlorophytes form the largest group of the phytoplankton assemblages of the lake, their biomass is relatively small or even negligeable in some periods of the year in comparison with domination cyanophytes, diatoms and cryptophytes. Morphological variation of diagnostic features is described and documented by original drawings in 53 taxa.     

Ecotoxicological contamination processes: Interaction with vegetation (a review)

Up-to-date crop production concentrates on the maximisation of plant matter production, both by optimum utilization of solar energy by plants and by the application of additional energy. Therefore a natural strategy is being developed aimed at combining the physiological functions of the assimilation organs with their external shaping and strengthening their variety in space and area. As demonstrated by many deposition studies, this effect is contradictory to the factors conditioning the low deposition capacity of plant covers. A high level of particle, gas and solution deposition increases the danger of food chain contamination and has a negative impact on plant production. Data concentrated on transport values of pollutants and their long-term dynamics in stands could be used for the selection of ideal crop types; therefore every effort should be directed towards selection and breeding.     

A new species ofAphidius [Hymenoptera] attacking the pea aphid,Acyrthosiphon pisum

Aphidius staryi Chen & Luhman n. sp. is described. The species was collected and introduced into California from Israel and Turkey byD. González. The new species is morphologically most similar toAphidius smithi, and keys toEady's urticae group.     

GROWTH PATTERN,REPRODUCTION, AND SELF-THINNING IN SEAWEEDS1

In unispecific plant stands, the logarithm of mean individual weight (w) depends on the logarithm of density (d) by the -3/4 power law (a slope of -1.5 and an intercept ranging from 2.3 to 5.0). The analysis of the w and d relationships in whole cohorts of two seaweed species from the Strait of Gibraltar shows deviations from the canonical equation. The kelp Phyllariopsis purpurascens (C. Agardh) Henry et South (Phaeophyta) growing at a 30-m depth has the lowest intercept value (0.6) recorded for any plant species and a slope not significantly different from -1.5. The slope value is in accordance with those found in species whose growth is not stopped by reproduction. Irradiance under a single layer of blades was lower than the photosynthetic light compensation point, and this could be due to overdispersion of the shoots and, in consequence, to the low intercept value of the self-thinning equation. The w to d relationships in Asparagopsis armata Harvey (Rhodophyta) show two different components: no dependence between these two variables (slope not significantly different from 0) at densities < 500 shoots·m^?2, and a slope more negative (-2.1) than proposed by the -3/2 power law at densities > 500 shoots·m^?2. The pattern at high densities could be due to intraspecific competition for light, whereas the slope ～0 at low densities could be related to inhibition of growth by reproduction (cystocarp and carpospore production). Therefore, rather than being considered exceptional, we suggest that a gradient of variability could be expected in the dependence of w on d when specific growth patterns and reproduction are considered.     

Effects of agents affecting Ca2+ homeostasis onTrichoderma viride growth and conidiation

Agents known to influence Ca²⁺ homeostasis affected significantly the vegetative growth and starvation-induced conidiation ofTrichoderma viride. Ca²⁺ in millimolar concentrations stimulated both growth and conidiation; a Ca²⁺ deprivation of the fungus by the chelation of extracellular Ca²⁺ (not Mg²⁺ or divalent trace metals) with EGTA (ethyleneglycolbis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) restricted both the vegetative growth rate and starvation-induced conidiation. Both processes were affected by either Ca²⁺ or EGTA with different efficiencies. Divalent cations (Sr²⁺, Ba²⁺, Co²⁺, Ni²⁺, Mg²⁺, Cd²⁺, Cu²⁺, Mn²⁺) and La³⁺ (inorganic Ca²⁺ blockers) in millimolar concentrations exerted complex (stimulatory, inhibitory, or biphasic) effects on growth and conidiation. In general, their effects on the two processes were mutually different either qualitatively, or quantitatively, or both. Organic Ca²⁺ antagonists (verapamil and dihydropyridines) inhibited the vegetative growth. The results show that Ca²⁺ is required for vegetative growth and conidiation, and that different Ca²⁺-dependent mechanisms may be involved in the two processes. Divalent cations could serve as a tool for investigating the relationship between growth and conidiation.     

Molecular evidence of a lignin peroxidase H8 homologue inFusarium oxysporum

We describe an evidence for the existence of a ligninase isoenzyme H8 in the deuteromyceteFusarium oxysporum on the genomic as well as on the RNA level.