Optimal scarification times for seeds of two Mediterranean orchids

A critical step during the in vitro sexual propagation of Mediterranean orchids is the treatment of seeds with a disinfecting solution thatalso serves to scarify the seeds. If the seeds are not properly disinfected, microorganisms grow within the culture vessel, thus reducingthe efficacy of the process in terms of the extra time and materials required. On the other hand, a long period of disinfection may damagethe embryo. The literature is inconclusive with respect to the proper combination of disinfectant strength and duration of the treatment. Theobjective of this research is to determine the optimal scarification times for two orchid species with thin and thick seed coats, respectively.Seeds of Anacamptis laxiflora (Lam.) and Himantoglossum robertianum (Loisel.) were treated with 0.5% NaClO solution for 5, 15, 25, 35, 45,55, 65, 75 and 85 minutes and sown in modified organic Malmgren medium. Logistic regression models were fitted to the results. We foundthat the longer the chemical treatment, the lower the percentage infection and higher the percentage germination, within the range oftimes tested. A chemical treatment of 85 minutes in 0.5% NaClO results in satisfactory percentage germination for both seeds with relativelypermeable seed coats such as A. laxiflora (Lam.) and those with relatively impermeable seed coats such as H. robertianum (Loisel.).