Sirgi Saar will defend her doctoral thesis titled "Plant-soil interactions: the effects of root exudates and soil legacies on plant growth and litter decomposition" on 26 October at 13.15.
Professor Kristjan Zobel, University of Tartu, Institute Ecology and Earth Science
Research Fellow Marina Semchenko, University of Manchester (Suurbritannia)
Associate Professor Gordon McNickle, PhD, Purdue University (USA)
Description of the problem
Despite being sessile, plants display remarkable behaviour. Plants react to environmental cues through changes in traits altering their phenotype. Author of this thesis researched how plants recognise their relatives, distinguish them from unrelated plants and different species and what is the outcome of such recognition.
Result and benefit
It was found that kin recognition is mediated through compounds exuded by roots, which in turn are recognised by roots of other plants. As a result of kin recognition plants placed less roots towards cues of their relatives. Kin selection allows them to invest more in reproduction at an expense of competition. More roots were diverted towards non-relative conspecific cues from the same population that can be interpreted as aggressive occupation of space and resources whereas conspecific cues from different population elicited lesser response which may be explained with coevolution. Plants did not specifically react to the interspecific cues, suggesting that root exudates convey information about relatedness, community and species identity. Trait changes arising from kin recognition can affect nutrient cycling and growth of plants in next generation: plants grown in soil previously inhabited by kin groups that also included the root litter contained less nitrogen, compared to stranger groups, and root litter originating from related plants decomposed slower. This effect was probably caused by lower genetic diversity among relatives which makes them more susceptible to pathogen attack and requires reinforcement of defense-related root morphology and production of more recalcitrant roots. Lower nitrogen concentration in root litter of relatives and next generation plants shows that kin recognition can impact nutrient cycling in ecosystems. The practical application of kin recognition in plants can manifest in agriculture if plant varieties are bred to compete less with their neighbours and produce higher crop yield.