In situ studies of growth and pigmentation of the phaeophycean Nereocystis luetkeana

Abstract

1. Transplant studies of Nereocystis luetkeana indicate that the maximum rate of stipe elongation is a function of depth. 2. Salinity, temperature, nitrate concentrations and spectral irradiance were measured with depth and time, to learn which environmental factor or factors contributed to the pattern of stipe growth. Spectral irradiance showed the greatest and most consistent changes and is considered the principal factor affecting stipe elongation of Nereocystis luetkeana. 3. The depths at which stipes of Nereocystis luetkeana lengthened at a maximum rate corresponded to a decrease in the ratio of red to far-red wavelengths, suggesting the pattern of stipe growth may be a phytochrome-like response. 4. Photosynthetic pigments appear to respond to diurnal radiation with changes in concentration. Chlorophyll a and chlorophyll c in specimens collected at 4 m altered when the plants were kept at different constant depths for four hours. The chlorophylls of specimens from 2 m did not alter their concentrations. Carotenoids in Nereocystis luetkeana from neither 4 m nor 2 m changed in concentration in response to altered depths. © 1973 Biologischen Anstalt Helgoland.