Ontogenetic Changes in Dna Content in Roots of the Water Fern Azolla Filiculoides

Abstract

The DNA content of the apical cell and various other cells in the roots of Azolla filiculoides was determined by two‐wavelength cytospectrophotometry. DNA content decreased markedly with increasing age of the apical cell; there was a similar but less pronounced trend in the other cell populations studied. These findings suggest the possibility of DNA amplification in very young roots with rapidly dividing cells.

Development and Cell Cycle Activity of the Root Apical Meristem in the Fern Ceratopteris richardii

“…The proximal merophytes and the RCI showed a slower incorporation frequency compared to the RAC at the earlier exposure times (Figure 7D, upper panel). A similar observation was reported in Marsilea and Azolla, where the RAC displays a higher cell division frequency compared to the merophytes [93,94]. Additionally, the RAC of Ceratopteris and Marsilea constantly produces merophytes at both proximal and distal planes, while Azolla's RAC has only the capacity to generate proximal merophytes [25,93,94].…”

“…A similar observation was reported in Marsilea and Azolla, where the RAC displays a higher cell division frequency compared to the merophytes [93,94]. Additionally, the RAC of Ceratopteris and Marsilea constantly produces merophytes at both proximal and distal planes, while Azolla's RAC has only the capacity to generate proximal merophytes [25,93,94]. Several questions regarding the functionality of these cell units regard unanswered: how merophytes do function to generate all different lineages in the proximal body?…”

“…At the last time registered (30 days of growth), we still observed a small change in root length. While this modest root growth was found to be statically significant in our results (Figure 5B), we propose it may not be caused due to an active meristematic growth but to remaining developmental processes, such as cell elongation, as it has been described for in the roots of other fern species [93][94][95].We observed the cessation of root growth, following a decrease in growth rate, in the earliest SBRs compared to recently-emerged roots. Hou and Hill [40] found a similar outcome while Ceratopteris plants growing in liquid media, which lead us to conclude that media firmness has little to none effect on root growth.…”

A Novel Pattern of Apical Cell Polyploidy, Sequential Polyploidy Reduction and Intercellular Nuclear Transfer in the Red Alga Polysiphonia

“…Autofluorescence from pigments and reflection from storage granules as well as the internal positioning ofthe nucleus within spores at this stage ofdevelopment make precise determination of ploidy levels impossible. However, the nuclei of the two cells of the bipolar germling that results from the first spore division are clearly polyploid; the nuclei 1 Evidence for the existence of a polyploid nucleus in the root apical cell ofthe water fern Azolla has just appeared (Kurth and Gifford, 1985). of the determinant basal cell and the indeterminant apical cell generally have the same level of nuclear DNA (Fig.…”

DNA content variation in monilophytes and lycophytes: large genomes that are not endopolyploid

“…Endopolyploidy has also been documented in areas of meristematic growth, such as in the root and shoot apical meristems. For example, endopolyploidy has been found in the root apical meristems of Marsilea strigosa (D'Amato and Avanzi 1965), Ceratopteris thalictroides, Polypodium aureum, and two species of Blechnum (Avanzi and D'Amato 1967), Azolla filiculoides (Kurth and Gifford 1985), and in the shoot apical meristems of Equisetum arvense (D'Amato and Avanzi 1968) and Pteris cretica (Michaux 1970). However, many of these claims could not be corroborated in further studies (for example: Gifford et al 1979;Polito 1980;Gifford and Polito 1981;Kurth 1982;Kurth 1982, 1983;Freeberg and Gifford 1984).…”