Delayed Chemical Defense: Timely Expulsion of Herbivores Can Reduce Competition with Neighboring Plants.

Time delays in plant responses to insect herbivory are thought to be the principal disadvantage of induced over constitutive defenses, suggesting that there should be strong selection for rapid responses. However, observed time delays between the onset of herbivory and defense induction vary considerably among plants. We postulate that strong competition with conspecifics is an important codeterminant of the cost-benefit balance for induced responses.

Traumatic insemination and female counter-adaptation in Strepsiptera (Insecta).

In a few insect groups, males pierce the female's integument with their penis during copulation to transfer sperm. This so-called traumatic insemination was previously confirmed for Strepsiptera but only in species with free-living females. The more derived endoparasitic groups (Stylopidia) were suggested to exhibit brood canal mating.

The clonal dependence of turion formation in the duckweed Spirodela polyrhiza--an ecogeographical approach.

Formation of turions, the vegetative perennation organs, plays an important role in the survival strategy of Spirodela polyrhiza (L.) Schleiden. Turion formation [quantified as number of turions formed per frond; specific turion yield (SY)] was investigated in 27 clones collected from a wide geographical range.

Evolutionary classification of toxin mediated interactions in microorganisms.

A trade-off between the parameters of Lotka-Volterra systems is used to give verifications of relations between intrinsic growth rate and limiting capacity and the stability type of the resulting dynamical system. The well known rock-paper-scissors game serves as a template for toxin mediated interactions, which is best represented by the bacteriocin producing Escherichia coli bacteria. There, we have three strains of the same species.

Contents of vitamin C, carotenoids, tocopherols, and tocotrienols in the subtropical plant species Cyphostemma digitatum as affected by processing.

The subtropical plant species Cyphostemma digitatum, Vitaceae, is used in central Yemen in traditional medicine, as a culinary herb, and as a source of food flavoring. The contents of vitamin C, vitamin E, and carotenoids and changes caused by common processing were investigated. Carotenoids were determined by reversed phase C30-high-performance liquid chromatography (HPLC) with diode array detection at 470 nm, while tocopherols and tocotrienols were analyzed by using normal phase HPLC with fluorescence detection (excitation, 292 nm; emission, 330 nm).

Modification of chromate toxicity by sulphate in duckweeds (Lemnaceae).

Two duckweed species, Spirodela polyrhiza and Lemna minor, were used to measure the toxicity of chromate (100 microM) at three levels of sulphate (13 microM, low sulphate=LS; 410 microM, normal sulphate=NS; 10,000 microM, high sulphate=HS). Growth rates calculated on the basis of dry weight, chlorophyll and carotenoid content were all reduced by chromate. This inhibition was the strongest under LS conditions and the weakest under HS conditions.

Genetic diversity of Ranunculus acris L. (Ranunculaceae) populations in relation to species diversity and habitat type in grassland communities.

Correlates between genetic diversity at intra- and interpopulation levels and the species diversity in plant communities are rarely investigated. Such correlates may give insights into the effect of local selective forces across different communities on the genetic diversity of local plant populations. This study has employed amplified fragment length polymorphism to assess the genetic diversity within and between 10 populations of Ranunculus acris in relation to the species diversity (richness and evenness) of grassland communities of two different habitat types, 'seminatural' and 'agriculturally improved', located in central Germany.