Asymbiotic germination, initial development in vitro and acclimatization of Cyrtopodium paludicolum Hoehne, a Brazilian Savanna orchid species

Abstract

Cyrtopodium paludicolum is a terrestrial orchid species, native to Brazil, whose natural propagation is jeopardized by the intensive collection from the wild and is threatened by agricultural expansion in Cerrado areas. In light of that, this investigation aimed at studying the in vitro germination and early development of C. paludicolum as influenced by culture medium, sucrose and growth regulators as well as its micropropagation by using dark-grown stem segments. A protocol for its acclimatization is also detailed. The effects of Murashige & Skoog (MS), Knudson C (KC) and Vacin & Went (VW) media on the in vitro germination and initial development were tested. The influence of different concentrations of BA, NAA, and of sucrose on plant multiplication and growth were evaluated. The possibility of using etiolated stem segments for micropropagation was also assessed. Acclimatization was accomplished in two phases by using three different substrates. The results showed that VW was the best medium for germination whereas for seedling formation KC was the most advantageous since they were healthy and vigorous. Sucrose at 2% favored the greatest seedling growth and development. Shoot and root proliferation and development were best promoted in the presence of 2.28/2.28 and 0.57/0.57 µM BA/NAA, respectively. The use of etiolated stem segments for micropropagation was effective. Successful acclimatization was accomplished by initially growing plants in community pots containing a 3:1 (v/v) mix of Bioplant and dried Sphagnum moss followed by their transfer to individual pots containing a 2:1 (v/v) mix of Bioplant and Ouro Negro substrates.

Key words
Cerrado; culture media; growth regulators; protocorm development; sucrose