Locating The Sites of Active Plastids in Coralline Algae

Abstract

Coralline algae (Corallinales) are ecologically important producers found amongst a variety of marine habitats across the globe. Their secreted calcium carbonate cell walls and the distribution of some families at deep water depths calls for a closer examination into coralline anatomy and physiology. This study located plastids across crustose and articulated morphologies using laser scanning confocal microscopy and scanning electron microscopy. Phycocyanobilin and chlorophyll a fluorescence was highest in cortical and meristematic regions in both crusts and fronds, sometimes in two fluorescent bands. These findings challenged conventional definitions for Calliarthron medulla and cortex layers and were re-defined accordingly. Extending this work across the taxon of Corallinales may provide a unifying definition for medulla and cortex, and plastid roles in medullary cells may reveal more efficient photosynthesis adaptations than previously thought.