Culture studies of the marine brown alga Petalonia Fascia (O.F. Müll.) Kuntze

Abstract

The morphological life cycle of the marine brown alga Petalonia fascia (O.F. Müll.) Kuntze has been investigated in artificial sea water under unialgal culture. The zoospores produced from the plurilocular sporangia of sporophytes developed directly into protonemata, plethysmothalli, and Ralfsia-like thalli. The appearance and fertility of various morphological types of thalli of P. fascia might be controlled by iodine concentrations, light and temperature. The last two factors, Interrelated with each other, were discussed. Protonemata and/or plethysmothalli survived in the most extreme experimental culture conditions, such as lowest and highest temperatures, intensities of light, and total iodine deficiency. However, Ralfsia-like thalli and sporophytes required more suitable environments. -- Optimum concentrations of inorganic micronutrient requirements (I, Br, Mo, Fe, Mn, Cu, Zn, and Co) and growth-regulating substances (indoleacetic acid and vitamin B12) for the growth, development, and/or reproduction of P. fascia were determined. Iodine appears to be an essential element for growth, morphogenesis and reproduction of P. fascia and it cannot be replaced by bromine. There is an antagonistic effect between iron and manganese in the growth of the experimental alga. -- The low concentrations of indoleacetic acid stimulate growth and accelerate zoospore production of P. fascia. This plant hormone may counteract the zinc deficiency. Vitamin B12 is a good stimulant for the growth of this alga, but it does not substitute for cobalt.