Influence of light on the growth and maturation of the Conchocelis-thallus of Porphyra. I: Effect of photoperiod on the formation of monosporangia and liberation of monospores

During June 30-July 22, 1959 Conchocelis thalli of P. tenera Kjellman were cultured under 3 different light intensities (natural indoor light, light reduced in half by covering the culture vessel with a sheet of dark vinyl cloth, and light reduced to one quarter by covering the vessel with 2 sheets), with dark periods of 14 and 9 hours; temperature was kept at about 20-22°C. In natural indoor light, with a 14-hour dark period, the Conchocelis formed a large number of monosporangia and liberated many monospores. In weak light (about 50-100 lux) the process took several days longer for the liberation of monospores than in full light. Well-matured Conchocelis thallus, which had been cultured under a 14-hour dark period, was grown in different dark periods (18, 16, 12, and 9 hours) at 20-22°C. The change in dark period did not appear to affect the liberation of monospores. Conchocelis thalli of P. kuniedai Kurogi were cultured in dark periods of 20, 17, 14, 11, and 9 hours at 18-23°C during Aug. 2-Sept. 5. The greatest number of monospores was discharged with dark periods of 20 and 17 hours, and very few with dark periods of 11 and 9 hours. It appears then that the Conchocelis thallus of P. kuniedai also requires a short-day photoperiod for the libiration of monospores.