Comparison of determined and undetermined meristems of Selaginella willdenovii Baker

Three types of meristems from Selaginella willdenovii were compared. Undetermined dorsal branch junction meristems were aseptically cultured for 0, 1, 3, 5, and 7 days on Knop's medium prior to fixation. Root tips and shoot tips, which have meristems already determiend developmentally, were excised from intact plants and fixed immediately. The cellular ultrastructure of each meristem was studied showing some differences in chloroplast structure, microtubule deposition, vesicle formation, degree of vacuolation, and invaginations of the plasma membrane. Some of these features, such as microtubule deposition and vesicle formation and vacuolation could be attributed to the different developmental states of the meristems.