The developmental patterns of the fern protonema of
Pteris vittata and regeneration patterns of isolated single cells, which were cultured under various light conditions, were investigated.
Branchings were induced when the 5-cell stage protonemata, which were germinated under 700lux white light, were transferred to 3, 000lux white light, or replaced to the former condition after transferring to continuous blue light, red light, or darkness. When the protonema grown in white light was cut to the component cells, each cell regenerated mainly from its anterior region. Intra- and intercellular gradients were observed in regeneration patterns. These gradients disappeared in the protonemata transferred to 3, 000lux white light, blue, red, or dark conditions.
Regeneration time was shorter in the cells which were isolated from the gametophytes transferred to blue or 3, 000lux white light, and longer in the cells which were isolated from the protonemata kept in darkness or red. The original apical cell, isolated from the branched protonema which had already ceased the growth, required a long time for regeneration, and initiated regeneration from the posterior or the middle regions of that cell.
These results show that branching seems to depend on the disappearance of apicobasal gradient of physiological activity to which polar regeneration patterns are owing.
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