Tree ferns biotechnology: From spores to sporophytes

Abstract

Tree ferns are typical for rain forest of tropical and subtropical climate and play a very crucial role in the ecology of lands of origin and some of the -species are economically very important due to various utilization by autochthons or citizens. Majority of tree ferns are illegally collected from natural sites, which has resulted in the decrease of their population, though they are listed on both the National and International Red Books and are protected by CITES (Convention on International Trade in Endangered Species). Two fern generations, gametophyte (haploid) and sporophyte (diploid), have the same genome but are fundamentally different organisms, however, both are photosynthetically independent and are very strong autotrophs for the majority of their life. Gametophyte life starts when spores imbibe water, their coat break and unequal first cell division takes place, and prothallial and rhizoidal initials are formed. This generation lacks the typical vascular character with limited number of meristematically active cells (1-4) in notch which are responsible for its somatic growth, produce tiny size with fast growth and with limited life span. The major function of this generation is to generate and to comfort the next generation, namely, sporophyte. Due to these facts, the formation of the sexual organs, both archegonia and antheridia, occurs on the bottom surface of the body. Such location of sexual organs helps to carry on the water path for sperms to the egg cells to make fertilization. In nature, gametophyte biological function is limited and completed when the first leaf of the sporophyte starts photosynthetic activity. Until now, there is only limited information concerning perennial growth of gametophyte through vegetative proliferation which increased its life span and formation of both sex organs in favorable condition for life. The aim of the present chapter is to summarize only published results dealing with the application of biotechnology methods, which are restricted only to tree ferns which have originated from various climatic conditions, different continents and countries. According to our best knowledge, the number of studied species is limited to ca. 20. This chapter will analyze particular stages in vitro cultured events initiated by sowing spores in or on liquid or solidified media. Favorable growth conditions of gametophyte result in formation of generative organs and sporophytes production. Sporophytes in the early stages appeared to be a good source for explants which could be used for tree fern multiplication with the biotechnology methods.