In vitro reproduction of three Limodorum species (Orchidaceae): impacts of scarification methods and nitrogen sources on mature seed germination and seedling development

Abstract

Limodorum species are hard-to-cultivate, germinating with difficulty or not germinating at all on a number of media. The present work was focused on the effects of seed sterilization-scarification methods and of different nitrogen sources on in vitro seed germination and seedling development of Limodorum abortivum, L. brulloi and L. trabutianum. Our results showed that sodium hypochlorite solution with a 1% concentration of available chlorine was ineffective for both sterilization and scarification of Limodorum seeds, while a 5% concentration was found to be an effective sterilizing and scarifying solution for L. trabutianum. The positive effect of organic nitrogen in promoting asymbiotic germination in many terrestrial orchids was confirmed by this study for L. trabutianum and L. brulloi, which showed significantly higher germination percentages on Basal Medium modified than on Knudson C, which contains inorganic nitrogen. This is the first report of in vitro asymbiotic germination of mature seeds of L. brulloi and L. trabutianum, especially successful for L. trabutianum that showed high germination percentages (>63%) and an active seedling development. These results may be useful for conservation purposes, since L. brulloi is a narrow Italian endemics and L. trabutianum is threatened with extinction both in Italy and in France.

Keywords:

• Asymbiotic germination
• Limodorum
• mature seeds
• nitrogen source
• scarification methods

Acknowledgments

The authors thank G. Haile for help in germination tests; F. Petrucci and L. Bernardo for the collection of Limodorum trabutianum and L. brulloi seeds, respectively.