Life history, in culture, of the obligate epiphyte Porphyra moriensis (Bangiales, Rhodophyta)

Abstract

The life history of the obligate epiphyte Porphyra moriensis Ohmi, collected from the type locality in Japan, was demonstrated in culture. Conchocelis filaments were cultured at temperatures between 5 and 30 °C under photon irradiances of 10–80 μmol m⁻²s⁻¹ and photoperiods of 10L:14D or 14L:10D. Conchosporangial branches developed at 5–20 °C under both photoperiods, and were abundant when the conchocelis was cultured at 20 °C, 20 μmol m⁻²s⁻¹, 14L:10D and 15 °C, 40 μmol m⁻²s⁻¹, 10L:14D. No folióse thalli survived at 25 or 30 °C and conchocelis failed to survive at 30 °C. Released conchospores attached very poorly to synthetic strings and glass slides but settled very well on Chorda filum thalli and thereafter germinated to develop into foliose thalli. Thalli grew well at 15 °C and 14L:10D or 10L:14D and at 20 °C and 10L:14D. No archeospores were observed on the thallus under any culture conditions. Spermatangial and zygotosporangial sori were formed in patches along the upper margins of mature thalli. Anatomical examination revealed that the mature spermatangial packets were 128 (a/4, b/4, c/8) and zygotosporangia were 16 (a/2, b/2, c/4) according to the Hus formula. Released zygotospores gave rise to conchocelis filaments. Neither monospores nor protothalli were produced by the conchocelis in culture. The life history of this plant is a simple biphasic cycle, with the thallus stage appearing to require attachment to Chordafilum.