Morphological and physiological responses of Porphyra suborbiculata Kjellman (Bangiales, Rhodophyta) blades from five localities

Archeospore germlings of five strains of Porphyra suborbiculata from tropical to subtropical (Ilocos Norte, Philippines and Shangwei, China, respectively) and warmtemperate waters (Kagoshima and Enoshima, Japan and Tongyoung, South Korea) were cultured under two photoperiod regimes (14L:10D and 10L:14D) and different temperature conditions (5, 10, 15, 20, 25, and 30degreesC) at 60-80 mumol m(-2) s(-1) photon flux density in the laboratory. The blades of the Philippines and China strains grew at 15-30degreesC with optimum growth at 20-25degreesC under both photoperiods, while the strains from Japan and Korea tolerated a temperature range of 10-25degreesC under both photoperiods and grew best at 10-20degreesC under SD conditions. The specimens from the Philippines and China had varying blade shapes in culture while the Japanese and Korean strains had prominent round to ovoid blades and linear to lanceolate blades under long and short daylength conditions, respectively. Archeospore liberation was observed earlier in higher temperatures for all strains, regardless of photoperiod. Sexual reproduction occurred within the optimum growth conditions (20-25degreesC for the samples from the Philippines and China, and 10-20degreesC for the warm temperate samples) of all strains under both photoperiods. The Philippines specimens had blade spores that developed directly into "spoke-like conchosporangia" restrictively at 30degreesC, without observed fertilization. The appearance of 2-3-celled marginal denticulation generally occurred earlier at higher temperature under longday conditions. The Chinese strain had a smoothedged shape, denticulate cell margin and contrasting cell number (4-5 cells) at 25degreesC. Porphyra suborbiculata exhibits wide geographic distribution, and the temperature and photoperiod tolerance shown here could imply adaptation and differentiation within a species to varying environmental conditions.