RESPONSE OF AUDOUINELLA-SAVIANA (MENEGHINI) WOELKERLING (NEMALIALES, RHODOPHYTA) CULTURES TO MONOCHROMATIC LIGHT

Audouinella saviana (Meneghini) Woelkerling was cultured at a constant temperature (24-degrees-C) and different irradiances (from 1 mumol to 30 mumol photons m-2 s-1) of blue (430-470 nm) and green (500-560 nm) light in order to study its adaptive response. Modifications in colou r, morphology and ultrastructure of the thalli, together with changes in pigment composition and in the spectral properties of chlorophyll a and R-phycoerythrin, were observed both by means of light and electro n microscopy (TEM, SEM) and spectrophotometric and spectrofluorimetric analyses. In this paper we report the adaptive response of the seawee d to blue and green radiation by focussing on the cell wall and on the photosynthetic apparatus, particularly on phycobilisomes in situ and on R-PE after extraction. PBSs were fully structured only under blue l ight at low irradiance whilst they were absent under green light, what ever the irradiance, in spite of the high R-PE content. This fact, tog ether with the spectral changes of R-PE, suggests adaptation at a mole cular level, presumably referable to changes in aggregation state.