The Ultrastructure of Tetrasporogenesis in the Marine Red Alga Chondria tenuissima (Good, et Woodw.) (Ceramiales, Rhodomelaceae) |
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| Authors: | TSEKOS, IOANNES SCHNEPF, EBERHARD MAKRANTONAKIS, A. |
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| Affiliation: | Botanical Institute, University of Thessaloniki Thessaloniki 54006, Greece and Zellenlehre, University of Heidelberg D-6900 Heidelberg 1, F.R.G. |
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| Abstract: | Tetraspore development has been studied in Chondria tenuissimausing light and electron microscopy. The transformation of tetrasporangialmother cells into mature tetrasporangia involves a series ofstructural changes, especially of dictyosomes and of the nucleus.The youngest stage of tetrasporogenesis consists of a uninucleatetetraspore mother cell with synaptonemal complexes present duringearly prophase of meiosis I. Mitochondria are aggregated aroundthe nucleus, dictyosome activity is low, and proplastids occurin the peripheral cytoplasm. The cleavage furrows are initiatedalmost concomitantly with commencement of meiosis. When thecleavage furrows are initiated, spherical bodies bounded bytwo membranes are found within the cytoplasm; they develop intovacuoles with fibrillar contents (fv1), which increase in sizeduring tetraspore development by fusing with each other andwith Golgi vesicles. The Golgi vesicles and the vacuoles withfibrillar contents (fv1) contribute material to the developingtetraspore wall. During the middle stage of tetraspore formationthe vacuoles with fibrillar contents (fv1) are dominant, dictyosomeactivity increases, as well as the number of plastids and mitochondria;starch formation also increases. Stacked cisternae of the endoplasmicreticulum are found within the peripheral part of the nucleus.The same nuclear structures are also observed in tetrasporangiaof the marine red alga Gastroclonium clavalum. The final stageis characterized by the disappearance of vacuoles with fibrillarcontents (fv1) and of the stacked ER within the nucleus, presenceof straight, large dictyosomes which produce cored vesicles,an abundance of starch grains and by the formation of fullydeveloped chlorqplasts. The cored vesicles contain Thiéry-positivematerial and contribute to the formation of vacuoles with fibrouscontents (fv2) as they are dominant in the tetraspores beforetheir liberation. Rhodophlyla, Chondria, tetrasporogenesis, ultrastructure, Golgi apparatus |
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