Trade-off between chemical and biotic antiherbivore defense in the South East Asian plant genus Macaranga.

The plant genus Macaranga is known for its manifold mutualistic associations with ants. The plants provide food for the ants and in turn get protection from herbivores. Depending on the strength of the plant-ant interaction, the plant's investment in ants and the biotic defense derived from them is more or less effective. We conducted a comparative study on tannin content in 12 Macaranga species that were selected based on their associations with ants (three nonmyrmecophytes and nine myrmecophytes, three of which start their ontogeny as nonmyrmecophytes). Different developmental stages were investigated in three Macaranga species. Extracts of every individual plant analyzed for tannins were also tested for their effects on larval growth employing larvae of the common cutworm (Spodoptera littoralis). The studied Macaranga species differed significantly in their tannin contents as well as in the effects of their leaf extracts on the growth of S. littoralis larvae. A correlation analysis shows a connection between tannin contents and larval growth. High tannin contents and, thus more effective chemical defense, were observed in nonmyrmecophytic Macaranga species associated only facultatively with ants as compared to obligate myrmecophytes. Our study supports the hypothesis of a trade-off between chemical and biotic defense in the genus Macaranga.

Adaptations to biotic and abiotic stress: Macaranga-ant plants optimize investment in biotic defence.

Obligate ant plants (myrmecophytes) in the genus Macaranga produce energy- and nutrient-rich food bodies (FBs) to nourish mutualistic ants which live inside the plants. These defend their host against biotic stress caused by herbivores and pathogens. Facultative, 'myrmecophilic' interactions are based on the provision of FBs and/or extrafloral nectar (EFN) to defending insects that are attracted from the vicinity. FB production by the myrmecophyte, M. triloba, was limited by soil nutrient content under field conditions and was regulated according to the presence or absence of an ant colony. However, increased FB production promoted growth of the ant colonies living in the plants. Ant colony size is an important defensive trait and is negatively correlated to a plant's leaf damage. Similar regulatory patterns occurred in the EFN production of the myrmecophilic M. tanarius. Nectar accumulation resulting from the absence of consumers strongly decreased nectar flow, which increased again when consumers had access to the plant. EFN flow could be induced via the octadecanoid pathway. Leaf damage increased levels of endogenous jasmonic acid (JA), and both leaf damage and exogenous JA application increased EFN flow. Higher numbers of nectary visiting insects and lower numbers of herbivores were present on JA-treated plants. In the long run, this decreased leaf damage significantly. Ant food production is controlled by different regulatory mechanisms which ensure that costs are only incurred when counterbalanced by defensive effects of mutualistic insects.

Molecular analysis of phylogenetic relationships among Myrmecophytic macaranga species (Euphorbiaceae).

Many species of the paleotropical pioneer tree genus Macaranga Thou. (Euphorbiaceae) live in association with ants. Various types of mutualistic interactions exist, ranging from the attraction of unspecific ant visitors to obligate myrmecophytism. In the latter, nesting space and food bodies are exchanged for protection by highly specific ant partners (mainly species of the myrmicine genus Crematogaster). As a first step toward elucidating the coevolution of ant-plant interactions in the Macaranga-Crematogaster system, we have initiated a molecular investigation of the plant partners' phylogeny. Nuclear ribosomal DNA internal transcribed spacer (ITS) sequences were analyzed for 73 accessions from 47 Macaranga species, representing 17 sections or informally described species groups. Three accessions from the putative sister taxon Mallotus Lour, were included as outgroups. Cladograms of the ITS data revealed Macaranga to be nested within Mallotus. ITS sequences are highly similar within section Pachystemon s.str., suggesting a relatively recent and rapid radiation of obligate myrmecophytes within this section. Forty-three accessions, mainly of ant-inhabited species, were additionally investigated by random amplified polymorphic DNA (RAPD) and microsatellite-primed PCR (MP-PCR) techniques. Phenetic analysis of RAPD and MP-PCR banding profiles generally confirmed the ITS results. Best resolutions for individual clades were obtained when ITS and RAPD/MP-PCR data were combined into a single matrix and analyzed phenetically. The combined analysis suggests multiple (four) rather than a single evolutionary origin of myrmecophytism, at least one reversal from obligate myrmecophytism to nonmyrmecophytism, and one loss of mutualistic specifity.

Extrafloral nectar production of the ant-associated plant, Macaranga tanarius, is an induced, indirect, defensive response elicited by jasmonic acid.

Plant species in at least 66 families produce extrafloral nectar (EFN) on their leaves or shoots and therewith attract predators and parasitoids, such as ants and wasps, which in turn defend them against herbivores. We investigated whether EFN secretion is induced by herbivory and/or artificial damage, and thus can be regarded as an induced defensive response. In addition, we studied the underlying signaling pathway. EFN secretion by field-grown Macaranga tanarius increased after herbivory, artificial leaf damage, and exogenous jasmonic acid (JA) application. Artificial damage strongly enhanced endogenous JA concentrations. The response in EFN production to artificial damage was much less pronounced in those leaves that were treated with phenidone to inhibit endogenous JA synthesis. Quantitative dose-response relations were found between the increase in nectar production and both the intensity of leaf damage and the amounts of exogenously applied JA. The amount of endogenously produced JA was positively correlated with the intensity of leaf damage. Increased numbers of defending insects and decreased numbers of herbivores were observed on leaves after inducing EFN production by exogenous JA treatment. Over 6 weeks, repeatedly applied JA or artificial damage resulted in a ten-fold reduction in herbivory. These results demonstrate that EFN production represents an alternative mechanism for induced, indirect defensive plant responses that are mediated via the octadecanoid signal transduction cascade.

Why do young women use sunbeds? A comparative psychological study.

Many people are keen on getting a skin tan despite being aware of warnings of health hazards. The present study investigates differences between women regularly using sunbeds and a control group of non-users in the areas of self-concept, narcissistic regulatory modalities, social assertiveness and generalized self-efficacy. Thirty women users of suntan salons and 34 women who never used one were investigated with standardized psychological questionnaires. In addition, their knowledge about the hazards of using sunbeds and attitudes to tanning were recorded. Statistical evaluation shows that sunbed users demonstrate more object devaluation: that is, other persons are devalued so that they are not even considered worthy of affection. Furthermore, they also display greater anxiety in their feelings and relationships with others. The results of this pilot study support the hypothesis that a tanned skin, by helping sunbed users to achieve their ideal of beauty, enables them to devalue other people and thus possibly to protect themselves from close relationships. As medical information about the hazards of ultraviolet irradiation fails to make an adequate impression on them, public relations campaigns must be undertaken in order to make them aware of the underlying motives of their behaviour.

Antiphlogistics in periodontology.

In 146 individuals with inflammatory periodontal disease the authors verified the therapeutical effect of Sanchelin (the mixture of sanguinarine and chelerythrine in 0.05% concentration) in gel (4% hydrogel carboxymethylcellulose) applied into pockets and in aqueous solution administered in the intrapapillar route. The effect of Sanchelin in solution was compared with the effect of 2% hydrocortison in the same way of administration. The clinical condition of periodontium and the quality of oral hygiene was evaluated by means of indexes and papillae were examined histologically. The authors demonstrated that Sanchelin in gel is an effective drug in treatment of inflammatory periodontal disease. They observed lesser effectivity when intrapapillar administration of Sanchelin in solution was used.

Nucleoli of lymphocytes in the peripheral blood of patients with periodontal disease (preliminary report).

A group of 104 patients with various grades of severity of the periodontal disease and a control group of healthy volunteers were examined. On the basis of an examination of the nucleoli, the activity of the RNA synthesis in the lymphocytes of peripheral blood was established. Patients with a very advanced periodontal disease showed a statistically highly significant increase in the ratio of active and reversibly inactivated lymphocytes. Thus, the significance of immune factors in the development of the periodontal disease was confirmed.