Effects of different factors on the akinete germination of Pithophora oedogonia (Mont.) Wittrock

Abstract

The present study focuses on the effects of different kinds of visible light, the intensities of white light, temperature and p H on akinete germination in the green alga Pithophora oedogonia (MoNT.)WITTROCK. In addition, it was studied how different kinds of visible light applied during akinete formation influenced the subsequent germination in white light. Akinetes initiated to germinate 3 days earlier in blue and green light than in yellow, red and white light. The green light was most favourable to akinete germination, while red light had a poor effect. No photoreversible effect of red and green light was observed. Akinetes formed under green, blue and yellow light germinated quickly and showed a higher percentage of germination than those formed under red light. Germination of akinetes was initiated even when kept in total darkness. Germination of akinetes was favoured in white light a t intensities between 0.50 and 1.5 Klux. Maximum germination of akinetes occurred a t 25 "C, while progressively higher and lower temperature suppressed germination of akinetes a t different levels. Initiation of akinete germination was delayed a t a pH of 7 and 8. No germination of akinetes was observed a t a pH of 9 and 10.Very little information is available on the conditions which control spore germination in green algae. It has been reported that the presence of light is required for spore germinat,ion of Oedogonium foveolatum ( HOFFMANN 1965) and Chura sp. (PROCTOR 1967). AGRAWAL (1980) studied the effects of different kinds of light, intensities of white light, temperature and pH on the akinete germination of Stigeoclw~ium pmcheri. The present study reports the effects of variations in the type and intensity of light, temperature and p H on akinet,e germination in the green alga Pithophora oedogonia (MoNT.) W~TTROCK. In addition, it was studied how different kinds of visible light applied during akinete formation influenced t,he subsequent germination in white light. Materials and methodsThe alga was collected from a freshwater pond a t the University Campus. Clonal cultures were raised from single germinating akinete, maintained in BOLD'S basal medium (COX and BOLD 1966) a t 22 f 1 "C and illuminated with day light fluorescent tubes a t an intensity of 2 Klux for 16 hrs B day. The pH of medium was adjusted to 7.5. The alga reproduced itself by the formation of akinetes which appeared 5 days after inoculation of filaments and which required another 10 days for maturation. The akinetes harvested from basal medium were transferred to fresh medium end germinated directly into new filaments. The initiation of akinete germination was evident by a change in colour to light green and subsequent formation of a small protuberance. The emergence of protuberances originating from the wall of the akinete which subsequently developed into a germling was taken as a criterion for germination.The akinete germination was not synchronous in P. oedogonia. In control cultures about 21% of the akinetes initiated to germinate on the fifth d...

MOLECULAR PHYLOGENY AND TAXONOMY OF THE AEGAGROPILA CLADE (CLADOPHORALES, ULVOPHYCEAE), INCLUDING THE DESCRIPTION OF AEGAGROPILOPSIS GEN. NOV. AND PSEUDOCLADOPHORA GEN. NOV.1

“…Identification at the species level became basically impossible due to overlap of character states (Möbius 1895, van Oye 1922). Culture studies have shown that akinete formation and germination is controlled by a wide range of environmental conditions (Ernst 1908, Agrawal 1986, Stevens and Neilson 1987), that the size of akinetes is dependent on age (Brand 1904), that akinete and branch formation are the same reversible process (Mothes 1930), and that helicoid formation is inducible as a wounding response (Mothes 1930). Pankow and Täuscher (1980) concluded that species level identifications are not feasible due to the amount of redundant species descriptions and recognized only two species, synonymizing all taxa with either P. oedogonia (Montagne) Kützing or with P. roettleri .…”

Molecular phylogeny and taxonomic revision of the genus Wittrockiella (Pithophoraceae, Cladophorales), including the descriptions of W. australis sp. nov. and W. zosterae sp. nov.

“…In Pithophora , the size, shape, and arrangement of akinetes are not stable but are controlled by environmental conditions. Akinete germination is inducible by various external factors (Ernst , Agrawal , Stevens and Neilson ), and akinete and branch formation are the same, reversible process (Mothes ). It seems that in Wittrockiella akinetes can either transform into a sporangium or germinate into a branch, but more culture observations are needed.…”

Molecular phylogeny and taxonomic revision of the genus Wittrockiella (Pithophoraceae, Cladophorales), including the descriptions of W. australis sp. nov. and W. zosterae sp. nov

“…In Pithophora, the size, shape, and arrangement of akinetes are not stable but are controlled by environmental conditions. Akinete germination is inducible by various external factors (Ernst 1908, Agrawal 1986, Stevens and Neilson 1987, and akinete and branch formation are the same, reversible process (Mothes 1930). It seems that in Wittrockiella akinetes can either transform into a sporangium or germinate into a branch, but more culture observations are needed.…”