Jihočeská Univerzita, Přírodovědecká fakulta, Katedra botaniky
Abstract
Knowledge of nuclear cytology in algae remains to be much improved, compared to that in higher plants and animals. Especially, The Euglenophyceae, the Cryptophyceae, the Dinophyceae and the Zygnematophyceae contain many species with ectremely high chromosome numbers of over one hundred (Sarma 1982). Since Strasburger’s (1875) first report for the process of cell division in Spirogyra orthospira, studies on the nuclear cytology (Godward 1954, 1961; Godward and Newnham 1965) and the cytototaxonomy of Spirogyra were carried out (Tatuno and Iiyama 1971, Vedajanani and Sarma, 1978, Abhayavardhani and Sarma, 1983). However, chromosome numbers of this genus were determined for only forty-four identified species (Chaudhary and Agrawal 1996, Kim et al. 2009). Chromosome numbers in Spirogyra ranged from n = 2 in three Japanese species (Tatuno and Iiyama, 1971) to n = 94 in S. nitida (Abhayavardhani and Sarma, 1983). Polyploidization (endomitosis) is a major evolutionary process in plants where hybridization and chromosome doubling induce enormous genomic stress and can generate genetic and epigenetic modifications (Stebbins, 1971), in which it promotes rapid speciation (Levin, 1983). In contrast, ploidal changes in algae have been studied, i.e. Nichols (1980) reported that polyploidization is known in most major algal taxa, especially in the green algae (chlorophyta). In this study was used culture collections from various habitats. These cultures provided ecological preferences of single taxa and ploidal variants. Cell morphology was obtained from both field material and cultures. In this context, the traditional characters was compared with cellular DNA-contents and chromosome numbers. We supposed that additional species complexes will be delimited and that polyploidy is widespread among Spirogyra. Special attention was paid to the different karyological methods
