EFFECT OF ULTRASONIC AND VACUUM TREATMENTS ON THE GERMINATION OF HIMANTOGLOSSUMROBERTIANUM (LOISELEUR) P. DELFORGEI (ORCHIDACEAE) SEEDS UNDER IN VITRO CONDITIONS

Abstract

Every year millions of orchid tubers are destroyed despite their conservation status as international conventions. Orchid species are consumed more frequently because of their tubers used for food production. H. robertianum is one of the main species utilized for food purposes due to its large tuber size and glucomannan content. As orchid seeds do not contain endosperms, there are challenges associated with their asymbiotic germination and reproduction. Seeds should be treated with appropriate chemical treatment with the right amount and duration for their asymbiotic germination, and thus seed dormancy could be eliminated. In these treatments, the aim is to weaken seed coat and facilitate water penetration. To eliminate seed dormancy appeared due to seed testa, physical methods such as ultrasonic and vacuum treatments can also be used. Sometimes these methods may be more reliable and effective than chemical methods. In this study, the effects of ultrasonic and vacuum treatments on the germination of Himantoglossum robertianum seeds, which have dormancy, were investigated. For this purpose, ultrasonic and vacuum treatments were performed at different durations, and their effects were assessed. Both treatments were found to increase the germination rate of the seeds significantly compared to the control groups. The highest germination rate was found in seeds treated with ultrasound for 3 minutes (20.5%) and with vacuum treated for 10 minutes (15.2%) when compared to controls' germination, which was 1.9% and 0.8%, respectively. Ultrasound and vacuum treatments increased the germination of H. robertianum seeds by promoting water uptake. According to these results, the methods can be used safely for the germination of orchid seeds.