Effect of a cationic cellulosic polymer on gametophytes of Laminaria digitata (Laminariaceae, Phaeophyta): Improvement of dispersed `free-living' cultures

Abstract

As filament aggregation is responsible for heterogeneity of Laminariales gametophyte cultures, a project was conducted to obtain stable homogeneous `free-living' cultures of Laminaria digitatagametophytes. The alga was cultivated at 15 ^° Cunder low light and in the presence of a cationic cellulosic polymer, JR125. With 0.1%polymer in the culture medium, the filaments were dispersed and did not adhere to the culture vessel. The absence of any effect of the closely related, but uncharged, polymer LR-250 Natrasol on filament aggregation indicated that the cationic nature of the JR125 molecule was involved in gametophyte dissociation. In the presence of JR125, the gametophytes showed active vegetative growth; the doubling time, measured as chlorophyll concentration, was 5 days. The outer surface of the cell wall was clearly modified by the polymer treatment, as observed by transmission electron microscopy, while neither the inner cell wall or cell organelles were affected. Physiological studies indicated that JR125 treatment did not disturb cell physiology, there being no effecton respiration, photosynthetic activity, sensitivity to high-light stress or modification of pigment or fluorescence characteristics. We have therefore established the conditions for maintaining a stable culture of mixed male and female Laminaria digitata gametophytes in active vegetative growth. The presence of JR 125 in the medium yields a homogeneous culture without cell physiology becoming modified.