@phdthesis{EscalantePerez2010, author = {Escalante Perez, Maria}, title = {Poplar responses to biotic and abiotic stress}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-46893}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {In this study poplar trees have been examined under different stress conditions. Apart from the detailed descriptions above two main conclusions might be drawn: i) A small plant like Arabidopsis thaliana is highly susceptible to stress situations that might become life-threatening compared to a tree that has extremely more biomass at its disposal. Such an organism might be able to compensate severe stress much longer than a smaller one. It seems therefore reasonable that a crop like Arabidopsis reacts earlier and faster to a massive threat. ii) In poplar both tested stress responses seemed to be regulated by hormones. The reactions to abiotic salt stress are mainly controlled by ABA, which also has a strong impact upon cold and drought stress situations. The term commonly used for ABA is "stress hormone" and is at least applicable to all abiotic stresses. In case of herbivory (biotic stress), jasmonic acid appears to be the key-player that coordinates the defence mechanism underlying extrafloral nectary and nectar production. Thus the presented work has gained a few more insights into the complex network of general stress induced processes of poplar trees. Future studies will help to understand the particular role of the intriguing indirect defence system of the extrafloral nectaries in more detail.}, subject = {abiotic stress}, language = {en} } @article{WaeschkeHardgeHancocketal.2014, author = {W{\"a}schke, Nicole and Hardge, Kerstin and Hancock, Christine and Hilker, Monika and Obermaier, Elisabeth and Meiners, Torsten}, title = {Odour Environments: How Does Plant Diversity Affect Herbivore and Parasitoid Orientation?}, series = {PlOS ONE}, volume = {9}, journal = {PlOS ONE}, number = {1}, issn = {1932-6203}, doi = {10.1371/journal.pone.0085152}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-117687}, pages = {e85152}, year = {2014}, abstract = {Plant diversity is known to affect success of host location by pest insects, but its effect on olfactory orientation of non-pest insect species has hardly been addressed. First, we tested in laboratory experiments the hypothesis that non-host plants, which increase odour complexity in habitats, affect the host location ability of herbivores and parasitoids. Furthermore, we recorded field data of plant diversity in addition to herbivore and parasitoid abundance at 77 grassland sites in three different regions in Germany in order to elucidate whether our laboratory results reflect the field situation. As a model system we used the herb Plantago lanceolata, the herbivorous weevil Mecinus pascuorum, and its larval parasitoid Mesopolobus incultus. The laboratory bioassays revealed that both the herbivorous weevil and its larval parasitoid can locate their host plant and host via olfactory cues even in the presence of non-host odour. In a newly established two-circle olfactometer, the weevils capability to detect host plant odour was not affected by odours from non-host plants. However, addition of non-host plant odours to host plant odour enhanced the weevils foraging activity. The parasitoid was attracted by a combination of host plant and host volatiles in both the absence and presence of non-host plant volatiles in a Y-tube olfactometer. In dual choice tests the parasitoid preferred the blend of host plant and host volatiles over its combination with non-host plant volatiles. In the field, no indication was found that high plant diversity disturbs host (plant) location by the weevil and its parasitoid. In contrast, plant diversity was positively correlated with weevil abundance, whereas parasitoid abundance was independent of plant diversity. Therefore, we conclude that weevils and parasitoids showed the sensory capacity to successfully cope with complex vegetation odours when searching for hosts.}, language = {en} }