NONEQUILIBRIUM RATES OF PHOTOSYNTHESIS AND RESPIRATION UNDER DYNAMIC LIGHT SUPPLY1

To identify processes that might account for differences in growth rates of rhodophytes under constant and dynamic light supply, we examined nonequilibrium gas exchange by measuring time courses of photoinduction, loss of photoinduction, and respiration rates immediately after the light–dark transition. Using the rhodophyte species Palmaria palmata (Huds.) Lamour and Lomentaria articulata (Huds.) Lyngb., we compared the effects of growth-saturating constant photon flux density (PFD) (95 μmol photons · m^?2· s^?1) to those of a dynamic light supply modeled on canopy movements in the intertidal zone (25 μmol photons · m^?2· s^?1 background PFD plus light flecks of 350 μmol photons · m^?2· s^?1, 0.1 Hz). The time required for P. palmata and L. articulata to be fully photoinduced was not affected by the dynamics of light supply. L. articulata required only 6 min of illumination with either fluctuating or constant light to be completely induced compared to 20 min for P. palmata. The latter species also lost photoinduction more rapidly than did L. articulata in the dark. There was no significant decline in photoinduction state for either species at the background PFD. The time courses of respiration after illumination with constant and fluctuating light were significantly different for P. palmata but not for L. articulata when the total photon dose was equal. In general, gas exchange of P. palmata appeared to be particularly sensitive to the temporal distribution of light supply whereas that of L. articulata was sensitive to the amplitude of variations, being photoinhibited at high PFD. These results are discussed in terms of the different mechanisms of inorganic carbon acquisition in the two species.     

Aplysia punctata added to list of laboratory-cultured Aplysia

The marine opisthobranch molluscAplysia punctata was cultured at the Laboratoire de Biologie Marine in Concarneau, France.A. punctata veligers settled and underwent metamorphosis on the algaLomentaria articulata, but not onUlva spp., Palmaria marina, Laminaria spp. andFucus spp.Research supported by grants from The Arts Foundation and the Lerner Fund for Marine Research of the American Museum of Natural History. We wish to thank Director Yves Legal, College de France for his support and cooperation.     

THE USE OF PLASTID DNA RESTRICTION ENDONUCLEASE PATTERNS IN DELINEATING RED ALGAL SPECIES AND POPULATIONS1

Plastid DNA band patterns generated by electrophoresis of endonuclease digests demonstrate remarkable conservation of DNA sequences at the species and subspecies level in flowering plants. Generally, patterns are identical or near-identical from different populations belonging to the same species. This methodology has now been applied to red algae to ascertain its value in systematic studies. Plastid DNA from nine bangiophycean and florideophycean red algae was isolated and cut with restriction endonucleases that recognize different 6-base pair sequences. The patterns generated upon the electrophoretic separation of digestion fragments show that within a species patterns are identical, but not within higher taxa. The proper identification of one Gracilaria population of uncertain taxonomic affinity was clearly established by this method of plastid DNA analysis. Differences between species in plastid DNA sequences were confirmed by probing blots of restriction fragments with known gene sequences. A number of heterologous plastid DNA probes were found to be sufficiently homologous to be useful in studying red algal DNA. Unexpectedly, supercoiled circular plasmids ranging in size from ca. 1.5–8 kb were found in some red algal species but not in others. The position of these plasmids in agarose gels following electrophoresis is uniform within a species but differs between different species of the same genus, contributing further patterns for taxonomic analysis.     

INDETERMINATE GROWTH OF PERICARPS IN THREE MEMBERS OF THE RHODYMENIALES (RHODOPHYTA)12

Pericarps generally are thought of as structures having determinate growth, serving as a protective covering for the developing gonimoblast. In laboratory culture, the pericarps of Champia parvula (C. Agardh) Harvey, Lomentaria baileyana (Harvey) Farlow and Lomentaria sp. exhibited indeterminate growth. These tissues could be excised and grown as separate female plants. The new plants were indistinguishable from the parent tissue, were fertile, and produced viable carpospores.