Resistenza diPterocladia Capillacea(Gmel.) Born. Et Thur. A Variazione di Salinità

Abstract

Abstract Resistence of Pterocladia capillacea (Gmel.) Born, et Thur. to salinity variations. In the present paper the effects of salinity variations on P. capillacea are reported. Particularly, growth of apical segments, regenerations of intercalary segments, colour of thallus and, for some samples, respiration and photosynthesis are examined. The results obtained show that in sea water with reduced salinity (¾), there is a good adaptation. At salinity levels lower or higher the following phenomena are seen: a) the colour decreases; b) regeneration is inhibited; c) the growth of apical segments is abolished or reduced. Respiration and photosynthesis have been determined in the material cultured in distilled water and in high salinity medium (× 4). The results show that in the first condition the rate of O2 consumption remains constant for 48 hours, while O2 production decreases after an hour. In salinity × 4, O2 production compensate consumption after an hour. When intercalary segments (cultured in salinity ×4) are transferred to sea water photosynthesis is restored. On the contrary, when they are kept in sea water with high salinity for 23 hours, respiration decreases and photosynthesis is inhibited and is not restored by transferring the material to sea water with normal salinity for additional 24 hours. Analysis of pigments, carried out after 48 hours, has shown that in distilled water liposoluble pigments disappear while 30% phycoerytrin is still present. In salinity ×4, carotenoids and chlorophyll decrease to much lower quantities than phycoerythrin.