GRAVITY AND LIGHT CONTROL OF THE DEVELOPMENTAL POLARITY OF REGENERATING PROTOPLASTS ISOLATED FROM PROTHALLIAL CELLS OF THE FERN CERATOPTERIS-RICHARDII

A procedure has been developed for isolating protoplasts from prothall i of Ceratopteris richardii which can be cultured and are capable of r egeneration. Protoplasts were isolated from 2-week-old gametophytes in a medium containing wall-digesting enzymes in 0.5 M sucrose, followed by purification of the released protoplasts by floating them up into a 0.5 M sorbitol layer. Regeneration occurred over a period of 10-24 d ays, and, under optimal osmotic conditions, followed the developmental pattern seen during spore germination, in that the first division gav e rise to a primary rhizoid. Thus, prothallial protoplasts are compara ble to germinating spores as suitable models for studies of developmen tal polarity in single cells. As in germinating spores, the polarity o f development in regenerating protoplasts is influenced by the vectors of gravity and unilateral light. However, the relative influence of l ight in fixing this polarity is greater in regenerating protoplasts, w hile in germinating spores, the influence of gravity is greater.