Influence of trace elements on akinete differentiation and germination in a blue green alga cyanobacterium nodularia spumigena
Yumnam, D.D.; Reddy, P.M.
Archiv fur Hydrobiologie, Supplementband 82(3): 371-380
ISSN/ISBN: 0365-284X Accession: 007460646
Trace elements were found to influence akinete formation and germination in Nodularia spumigena. Omission of one trace element at a time from the medium resulted in varied degrees of reduction of akinete production and germination indicating differential influence of each trace element on these two development processes. Deletion of Mo from the medium had no marked suppressive effect on akinete production. On the other hand, akinete formation was suppressed more in B, Cu or Zn deficient medium than in the medium lacking Mn or Co. It appears that B, Cu and Zn have a more important role than Mn and Co in the processes leading to akinete development. Akinetes seem to be better equipped with sufficient endogenous reserves of B and Zn as a greater majority of akinetes were found to be less dependent upon exogenously supplied B and Zn for germination than upon Mn, Co Cu and Mo. The pattern of germination relative to the position of heterocysts in the continguous akinetes in sporulated filaments revealed a centripetal sequence in the absence of B, Cu or Zn and a centrifugal sequence in the absence of Mn, Co or Mo. These observations suggest heterocyst mediated preformation of increasing (B, Cu and Zn) or diminishing (Mn, Co and Mo) concentration gradients of trace elements towards heterocysts in the sporulated filaments. Further, the evidenced differential accumulation of the trace elements in the cells of the sporulating filaments grown in the presence of the medium containing nitrate indicates that the heterocyst mediated gradient formation of the micronutrients is independent of the nitrogen-fixing activity of the heterocysts.