Pleomorphism of Scenedesmus quadricauda (Turp.) Bréb. (Chlorophyceae) in synchronized cultures

Summary

Cells of a pleomorphic Scenedesmus quadricauda strain are synchronized by 24 hour light-dark cycles (LD: 14, 10 regime). Synchronized cultures are diluted daily with fresh nutrient medium to the original cell density of ca. 0.4 × 10⁶ cells per ml. Using different temperatures and different media morphologically stable synchronized culture systems are established which yield either coenobia or unicells. In synchronized cultures grown at a temperature of 30 °C and with a medium containing 1800.5 mg per litre total inorganic salts only 4-celled coenobia are formed. When grown at a temperature of 20 °C with a medium containing 130.5 mg per litre total inorganic salts partially synchronized cultures develop which consist of 2-celled, 4-celled and 8-celled coenobia. Attempts to change the latter coenobia-yielding system into a unicell-yielding system by increasing the concentration of P from 1.14 up to 127.4 mg per litre and by increasing the concentrations of both P (up to 127.4 mg per litre) and N (from 11.7 up to 105.4 mg per litre) failed.

A completely synchronized morphologically stable unicell-yielding culture system is achieved at a temperature of 20 °C with high nutrient levels (i. e. 1800.5 mg per litre). This system becomes partly coenobial when subjected to short daylengths (e. g. LD: 3, 21 regime). Upon restoration of the original light-dark cycles (LD: 14, 10 regime) the coenobia disappear and the unicell-yielding system is re-established.