Spore Germination And Protonema Development Of Sphagnum In China

Sphagnum L.(Sphagnaceae,Sphagnopsida)are dominant species and “ecological engineers” in peatlands,with important ecological,economic and scientific values.They are also a key bryophyte group in urgent need of protection.Spore germination and protonema development are key stages in the life cycle of Sphagnum,which are not only the basis for growth and development but also have great significance for ex-site protection,the establishment of a culture system,and the acquisition of enough sterile materials.There are about 47 species of Sphagnum in China,however,systematic research on spore germination and protonema development of Sphagnum is still lacking.This study established an in vitro sterile culture system using the spores of 19 Sphagnum species(covering all five subgenera of Sphagnum: subg.Rigida,subg.Sphagnum,subg.Actifolia,subg.Subsecunda,and subg.Cuspidata)collected from the field in China,and explore the rules of Sphagnum spore germination.The main results are as follows:1.The germination type and development rule of Sphagnum spores are relatively stable within the genus.After spore germination,multicellular filamentous protonemata grow,and then the apical cells expand and divide to form a single layer of thallus protonemata,from which cormus grow.A large number of filamentous protonemata also grow from the base of filamentous protonemata and thallus protonemata.The Sphagnum type is known in all 19 species in this study.2.All Sphagnum species in this study germinated within 3–6 days.S.compactum is the first to develop thallus protonemata,and S.fallax is the earliest to develop cormus.S.lindbergii is the last to develop thallus protonemata and cormus.3.Rhizoids are produced during the growth and development of Sphagnum.All species produce rhizoids at the protonema stage.A few species including S.capillifolium,S.squarrosum,S.inundatum,S.angustifolium and S.flexuosum also grow rhizoids from the stems during the cormus stage,but rhizoids usually only exist on the stems near the base,and most of them would gradually disappear with the growth of the plant.With the development of Sphagnum,some chloroplasts in the filamentous protonemata degenerate,and the cell walls grow obliquely,gradually becoming transparent rhizoids.4.The development time of spore germination,thallus protonemata,and cormuses in Sphagnum has certain rules among subgenera.The spores in the subg.Subsecunda germinate within 3 to 5 days,and all spores grow thallus protonemata on the ninth day.The cormus develops within 40 to 47 days after spore inoculation,and the development time of each stage is relatively close,which is the most stable and regular among all subgenera in this study.5.The Knop culture medium is suitable for exploring spore germination and protonema development of Sphagnum,and the Hoagland culture medium is suitable for the vegetative growth of Sphagnum.The author systematically studied the spore germination and protofilament development of all subgenera of the Sphagnum.The results of the present study provide a scientific basis for the conservation of Sphagnum diversity,artificial planting,and establishment of Sphagnum germplasm resource banks.The present study also provids material guarantees for genome sequencing and research on the biological and reproductive mechanisms of Sphagnum.