Laboratory studies on vegetative regeneration of the gametophyte of Bryopsis hypnoides Lamouroux (Chlorophyta, Bryopsidales)

Vegetative propagation from thallus segments and protoplasts of the gametophyte of Bryopsis hypnoides Lamouroux (Chlorophyta, Bryopsidales) was studied in laboratory cultures. Thallus segments were cultured at 20 degrees C, 20 mu mol photons m-(2) s(-1), 12:12 h LD); protoplasts were cultured under various conditions, viz. 15 degrees C, 15 mu mol photons m(-2) s(-1), 10:14 h LD; 20 degrees C, 20 mu mol photons m(-2) s(-1), 12:12 h LD; and 25 degrees C, 25 mu mol photons m(-2) s(-1), 14:10 h LD. Microscope observation revealed that the protoplast used for regeneration was only part of the protoplasm and the regeneration process was complete in 12 h. The survival rate of the segments was 100% and the survival rate of protoplasts was around 15%, regardless of culture conditions. Protoplasts were very stable in culture and were tolerant of unfavorable conditions. Cysts developed at the distal end or middle portion of gametophytic filaments under low illumination (2 - 5 mu mol photons m(-2) s(-1)), the key induction factor. Cysts formed several protoplast aggregations inside or the cyst as a whole detached directly from the matrix and all the units were able to develop directly into new gametophytes. Regeneration directly from protoplasts and thallus segments were also discovered in the field. A relatively completed life history of B. hypnoides is established with newly discovered propagation methods, namely protoplast regeneration.