Studies on the regeneration of the Calli induced from epidermal cells of leaves of Lepisorus thunbergianus. II. Chromosomal stability in sporophytes and gametophytes regenerated.

Abstract

1. Cytogenetic characteristics were investigated in the leaf calli and the regenerated plants, i.e., whole sporophytes and cordate gametophytes from these calli, of the fern Lepisorus thunbergianus.2. No chromosomal abnormality was found to occur in the young leaf tips used as explants for the present tissue clutures. The karyomorphological features of these explants were identical with those of the native sporophytes of L. thunbergianus (diploid, 2n=50) in the previous report by Takei (1982b).3. In the calli induced from the diploid explants (2n=50), two different chromosome numbers were observed as follows: 2n=50 and 2n=100. The former chromosome number was observed in about 85% of the callus cells, i.e., all the aggregated green cells and many of the large-sized globular cells, and the latter one was observed only in some of the large-sized globular callus cells.4. The uniform chromosome numbers, 2n=50, were observed in cells of the whole sporophytes regenerated from the leaf calli showing a low variability in chromosome number. These sporophytes were also found to show a stability in karyotypic feature, for example, arm-ratio, chromosome length and staining density of chromatin. These features were identical with those of the leaf tips used as explants.5. The regenerated cordate gametophytes were found to be karyomorphologically and microspectrophotometrically uniform. The chromosome numbers and the microspectrophotometrical values of the nuclear DNA showed that these gametophytes were the same diploid (n=50) as the regenerated sporophytes or as the leaf tips used as explants. In addition to this, these gametophytes were observed to possess identical characteristics in arm-ratio, length, staining density, etc. of the metaphase chromosomes with those of the regenerated sporophytes or of the explants.6. All the cytological results of the present investigrations indicate that the chromosomal stability was maintained throughout the process of the regeneration of the new plants (i.e., whole sporophytes and cordate gametophytes) from the calli originating in young leaf tissues of L. thunbergianus (diploid, 2n=50).