Cytological studies in the genus azolla

Abstract

The somatic chromosome numbers (2n) were 48, 40, 44, 44 and 66 respectively in A. mexicana, A. filiculoides, A. pinnata Aftrica, A. pinnata Cuttack, India and A. pinnata (green isolate, Vietnam). The karyotype study revealed that chromosomes were small and asymmetrical. The total chromatin length (TLC) was employed as an index of species delimitation. Basing on absolute length (AL) the chromosomes were grouped into different sets and karyotypic formula was established for each species. Meiotic behaviour of microspore mother cells (SMC) of all species was almost similar except A. pinnata (Vietnam) and A. filiculoides. In all cases microspore mother cells (SMC) exhibited many common features. Usually quarterets of SMC were observed on pressing. Vacuolisation put the cytoplasm more clear during early prophase and gradual granulation brought more stainability in later stages. Marginal orientation of chromatic materials was noticed. Multivalents were observed in A. pinnata (Vietnam). In A. filiculoides, deformed spindle and unequal spore formation were noticed in some of the SMC. In A. pinnata (Vietnam) almost all spores were much smaller in size. A. mexicana, A. pinnata (India), A. filiculoides and A. pinnata (Africa) were considered to be true diploids whereas A. pinnata (green isolate, Vietnam) was a triploid. © 1989, Japan Mendel Society, International Society of Cytology. All rights reserved.