Photoperiod and temperature regulation of the life history of Porphyra columbina (Rhodophyta, Bangiales) from central Chile

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Abstract
The effects of temperature (10, 15, 20 °C) and photoperiod (8:16, 12:12, 16:8 (hours of light: hours of dark)) on the growth and reproduction of different stages in the life history of Porphyra columbina Montagne were assessed. The conchocelis phase had higher growth rates at 12 h light:12 h dark, 45 μmol m−2 s−1, and 15 °C. Under all the temperatures and photoperiods tested, the conchocelis phase could propagate either by monospores or vegetative fragmentation. Conchosporangia were formed only at 10 °C and 8 h light:16 h dark or at 15 °C and either 8 h light:16 h dark or 12 h light:12 h dark. Long photoperiods inhibited conchosporangia formation at all temperatures tested with the exception of 20 °C and 16 h light:8 h dark, where sporangia was formed once. Conchospores were released when the temperature was decreased (15 to 10 °C) maintaining the photoperiod. Conchospore germination occurred under the three photoperiods and temperatures tested. Growth of juvenile fronds was maximum at 15 °C and either 12 h light:12 h dark or 16 h light:8 h dark. Fronds formed carpospores and spermatia at 15 °C and 16 h light:8 h dark only. With optimum conditions the life history was completed in 60 days. Spermatia had three chromosomes (n = 3).