Research Interests
- Orchid seed storage behaviour: My research focuses on the ex situ conservation of orchids seeds in seed bank conditions and the potential long term storage of the orchids of the Mediterranean region.
- Orchid seed germination behaviour: Regarding the germination behaviour of orchid species I focus on the study of individual factors on their germination, instead of complex media along, with the effect of in-situ conditions on the germination and quality of the produced seeds (e.g. effect of cross- and self-pollination on seed quality).
- Population dynamics of rare plant species: Through in-situ annual, long-term (>10 years), monitoring of target species e.g. Cephalanthera cucullata, Veronica oetaea, the study of their ecophysiology and the application of population matrix models we aim to assess the future survival of the species, suggest and implement conservation actions.
- Ex situ conservation of the seeds of the flora of Greece: With the NKUA Seed Bank team we aim to conserve seeds of the endemic and threatened plant species of the Greek flora the past 7 years during my collaboration with the NKUA Seed Bank we have targeted, collected and conserved in the seed bank aproximately 700 taxa represented by 800 collections.
Current major project (Scientific Responsible Emeritus Professor Costas A. Thanos): Conservig the flora of the Balkans: Native plants of Greece (Funded By: RBG, Kew)
Selected Publications
For a full list, please see my Google Scholar profile or my CV.
"Orchid embryo-to-seed (E:S) ratio as an indicator of germination behaviour and its ecological implications"
Oikonomidis S., Thanos C.A. (2024). Seed Science and Research, 34, pp. 218-227.
Although the seeds of various Orchidaceae members can be readily germinated on sterile nutrient media, numerous species exhibit complete asymbiotic germination failure. Also, while seed morphology in orchids has been previously linked to dispersal, associations with germinability have not been widely explored. We compiled seed morphometric and germination data for 203 orchid species globally, drawing from international literature and our lab's unpublished findings. Based on (a) final germination percentage and (b) pre-treatment duration, two distinct groups of asymbiotic germination behaviour emerged – termed compliant and defiant, respectively. Additionally, a statistically significant relationship between germinability and the embryo-to-seed (E:S) length ratio was observed. E:S values tended to be lower in species with defiant germination and higher in those with compliant germination. We further correlated seed morphometric and germination data with phylogenetically and ecologically significant parameters (subfamily, growth form, mycoheterotrophy level, climatic zone and habitat shadiness). Notably, lower E:S values and defiant germination predominate in orchids of shaded habitats, while compliant germination is more prevalent in open habitats. Lastly, considering the mycoheterotrophy continuum, we propose that the reduction in the E:S ratio is linked to the adaptation of various orchid lineages to shaded habitats through both an increased dispersal ability and their greater reliance on fungal symbiosis.
"Towards a standardised orchid germination protocol: determining the optimal duration of chemical scarification for orchid seeds by means of viability and permeability staining"
Oikonomidis S.,, Koutsovoulou K., Tsiftsis S., Thanos C.A. (2024). Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology, 158, pp. 563-571.
Complex nutrient media are used for the germination of orchids in the laboratory. These substrates are also suitable for the growth of microbes and thus the sterilization of both the medium and the seeds prior to sowing is mandatory. The surface disinfection of orchid seeds with chemical substances eliminates possible infections and enhances germination in several cases, by chemically scarifying their seed coats. However, long durations of chemical treatments may result in viability loss, and consequently, precisely determining the optimal treatment duration is essential for developing effective germination protocols. In this study, the double staining technique with Tetrazolium Chloride and Trypan Blue is tested as a proxy method to determine the optimal chemical treatment duration for 10 orchid taxa of Greece. Various durations of chemical treatment with 5% Ca(OCl)2 were carried out on independent seed samples which were subsequently tested, pairwise, for both germination and viability. The results in the corresponding experiments are extraordinarily similar and we conclude that the double viability staining is a quick and accurate technique in determining the permeability and optimal duration for chemical scarification prior to germination experiments. The storability potential of the taxa studied is discussed in comparison with previous data of the NKUA Seed Bank.
"The effect of pollen origin (self- and cross-pollination) on seed production and viability in Ophrys (Orchidaceae)"
Oikonomidis S., Koutsovoulou K., Kaltsis A., Constantinou C., Andreou M., Kadis C., Georghiou K., Thanos C.A. (2024). Botany Letters, 171: 500-508.
The pollination biology of the genus Ophrys has been extensively explored, primarily due to their utilisation of sexual deception to attract pollinators. Typically, members of this genus produce a low number of fruits per individual and are considered obligate crossers. However, instances of self-pollination in Ophrys are not uncommon, although the impact of pollen origin on seed production remains understudied. As a predominantly cross-pollinated genus we hypothesise that self-pollination in Ophrys has a negative effect on seed production. The results of the present work will support decision making for the conservation of the genus. We investigate the consequences of self- and cross-pollination on (a) empty seeds produced and (b) viability of sound seeds for three Ophrys species: Ophrys aesculapii, Ophrys ferrum-equinum, and Ophrys kotschyi native to the East Mediterranean region. Bagged individuals of these species were meticulously hand-pollinated with pollen sourced either from their own flowers or from neighbouring individuals. Significant differences were observed across all three species, both in terms of the number of empty seeds and the viability of the produced seeds, with significantly lower viability and higher number of empty seeds in seed collections from self-pollinated individuals. Despite being self-compatible, the three Ophrys species exhibited notable inbreeding depression, as evidenced by the outcomes of this study. Based on our results the implementation of controlled cross hand-pollination in wild population may contribute in the increase of the reproductive success of Ophrys spp. by increasing the quality and quantity of the produced seeds.
Get In Touch
I'm always open to discussing research, potential collaborations, or interesting ideas. Feel free to reach out!
Contact Information
- Email: soikonomidis@biol.uoa.gr
- Office: Office 74, Section of Botany, Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
- Phone: +30 6971634291