Decomposer-plant interactions

• Main Author: Endlweber, Kerstin
• Format: Others
• Language: English; en
• Published: 2007
• Online Access: http://tuprints.ulb.tu-darmstadt.de/857/1/Dissertation_Kerstin_Endlweber.pdf; Endlweber, Kerstin <http://tuprints.ulb.tu-darmstadt.de/view/person/Endlweber=3AKerstin=3A=3A.html> : Decomposer-plant interactions. [Online-Edition] Technische Universität, Darmstadt [Ph.D. Thesis], (2007)

This study investigated the effect of Collembola on plant growth and competition between plant species. The competitive relationship between plants is determined by differences in root morphology and foraging strategy. In the first experiment the effect of Collembola on the competitive relationship between Cirsium arvense and Epilobium adnatum was analysed. Collembola neither affected plant biomass nor plant nutrient concentration. However, they induced the production of longer, thinner roots and enhanced the number of root tips with the effect being more pronounced in E. adnatum. The inoculation of plant roots with mycorrhizal fungi is an important factor improving plant nutrition. The second experiment focused on changes in the competitive relationship between Lolium perenne and Trifolium repens due to Collembola grazing on mycorrhizal fungi. Collembola reduced the competitive superiority of L. perenne over T. repens. However, the reduction was independent of the rate of mycorrhizal inoculation. Similar to the first experiment Collembola induced the production of longer, thinner roots and increased the number of root tips, particularly in L. perenne. The results suggest that Collembola affect root morphology by damaging plant roots while grazing in the rhizosphere and by creating nutrient rich patches in soil. In a third experiment feeding preferences of Collembola were investigated using analysis of stable isotopes and compound specific analysis of fatty acids. Collembola were introduced to a system consisting of a maize plant (C4 plant), growing in soil mixed with 15N labelled C3 litter. Collembola preferentially incorporated plant-born carbon and nitrogen. The concentration of C and N in Collembola tissue increased when either litter or plants were available, whereas the combination of both resources caused no further increase in nutrient concentrations. Collembola preferentially incorporated fatty acid originating from plant material, whereas the fatty acid composition of Collembola was not affected by the availability of litter. Damaging or feeding on plant roots induces plant defence as well as the production of plant hormones. In a fourth experiment induction of plant defence and phytohormone production in Arabidopsis thaliana by Collembola were investigated employing DNA microarrays. Gene expression patterns were correlated with changes in rosette growth. Collembola initially reduced growth of A. thaliana with the deceleration being compensated during further development. The temporary deceleration probably was caused by the induction of plant defence by Collembola thereby reducing plant investment in growth. The enhanced production of the growth promoting hormone auxin presumably facilitated the compensational growth during further development. The results of this study suggest that Collembola influence plant growth mainly via two mechanisms: (i) Collembola affect nutrient availability and distribution by grazing on microorganisms in rhizosphere and thus enhance plant nutrition and growth; (ii) while grazing in the rhizosphere, Collembola induce plant secondary metabolism and thus increase plant defence against herbivores. The subsequent deceleration in plant growth is compensated by the increased production of growth promoting hormones in presence of Collembola. Further, the compensational growth is facilitated by the increased nutrient availability and the production of a more expansive root system induced by Collembola.