Borowitzka, MA & Larkum, AWD 1977, 'CALCIFICATION IN THE GREEN ALGA HALIMEDA. I. AN ULTRASTRUCTURE STUDY OF THALLUS DEVELOPMENT1', Journal of Phycology, vol. 13, no. 1, pp. 6-16.
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Borowitzka, MA & Larkum, AWD 1977, 'CALCIFICATION IN THE GREEN ALGAHALIMEDA.I. AN ULTRASTRUCTURE STUDY OF THALLUS DEVELOPMENT1', Journal of Phycology, vol. 13, no. 1, pp. 6-16.
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ABSTRACTThe ultrastructure of 4 species of the calcareous, siphonaceous algaHalimeda (H. cylindraceaDecaisne,H. discoideaDecaisne,H. macrolobaDecaisne andH. tuna(Ellis & Solander) Lamour) has been studied, and the observed changes during growth and development are related to changes in the degree of calcification. A distinct gradient in the types and quantities of cell organelles exists in a growing apical filament. As these filaments grow, branch, and eventually develop into a mature segment, changes in the organization of organelles such as mitochondria and chloroplasts are observed. Calcification begins when the chloroplasts reach structural maturity and when the peripheral utricles adhere (fuse). This adhesion of the peripheral utricles isolates the intercellular space (ICS) in which calcification occurs from the external seawater. Calcification begins in the outermost (pilose) cell wall layer of the walls facing into the ICS. The cell walls at the thallus exterior undergo extensive changes after utricular fusion; the pilose layer is lost, the cuticles of adjacent utricles fuse forming a ridge at their junction, and multiple cuticles are formed.The aragonite (CaCO3) crystals which are initially precipitated within the pilose wall layer, rapidly increase in size and number, eventually filling much of the ICS. Only the initial nucleation of aragonite is associated with the pilose wall layer, the later precipitation of aragonite is totally independent of the pilose layer. In older segments secondary deposition of CaCO3also occurs around existing aragonite needles.
BOROWITZKA, MA, LARKUM, AWD & DAY, R 1977, 'SEASONAL ASPECTS OF PRODUCTIVITY OF CORAL-REEF ALGAL TURF COMMUNITIES', JOURNAL OF PHYCOLOGY, vol. 13, pp. 8-8.
LARKUM, AWD & BOROWITZKA, MA 1977, 'DEEP-WATER RED ALGAE OF SOUTHERN GREAT BARRIER REEF', JOURNAL OF PHYCOLOGY, vol. 13, pp. 38-38.
Larkum, AWD & Weyrauch, SK 1977, 'PHOTOSYNTHETIC ACTION SPECTRA AND LIGHT‐HARVESTING IN GRIFFITHSIA MONILIS (RHODOPHYTA)', Photochemistry and Photobiology, vol. 25, no. 1, pp. 65-72.
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Abstract— In cells of the red alga Griffithsia monilis the action spectrum of photosynthetic oxygen production at low light intensity shows that the phycobilins (including allophycocyanin) are the major light‐harvesting pigments. As the light intensity is increased carotenoids and chlorophyll a contribute proportionately more to the spectrum, since the phycobilin activity becomes light‐saturated. When action spectra are performed against a background light of various monochromatic wavelengths it can be shown that chlorophyll a increases in its light‐harvesting activity. Nevertheless light absorbed at a single wavelength (487 nm) by phycoerythrin (and possibly a carotenoid) still shows the highest photosynthetic activity. Fluorescence measurements at 77K indicate that a chlorophyll a fluorescence is small and that the amount of chlorophyll all (f 693) is very low. A model is proposed in which the phycobilins, in phycobilisomes, pass on absorbed light energy to either photosystem, whereas light absorbed by chlorophyll is passed on mainly to photosystem I.
