Pei Zuchang’s scientific contributions

Mitochondrial distribution and abundance were assessed during the growth of apical and subapical cells in the red algae Colaconema caespitosum (J. Agardh) Jackelman, Stegenga and Bolton and Antithamnion cruciatum (C. Agardh) N?geli after staining with 3,3?-dihexyloxacarbocyanine iodide [DiOC6(3)] and 2,4?-dimethylaminostyryl-Nethylpyridinium iodide (DASPEI). In fully elongate apical cells of C. caespitosum there were 100-120 mitochondria. During apical cell enlargement and division there is a doubling and then halving of the mitochondrial numbers. Apical cells prior to cytokinesis in young filaments are smaller than in mature filaments (ca. 50 and 100 ?m long, respectively) and have fewer mitochondria (ca. 100 and 120 mitochondria per cell, respectively). In older vegetative cells mitochondria tend to aggregate at opposite ends of the cells with some mitochondria associated with the central nucleus or at points of apparent branch initiation. There is a greater density of mitochondria in apical cells of smaller versus larger plants (one mitochondrion per 6.3 ?m3 and 9.8 ?m3, respectively), suggesting that apical cells of younger plants may be more metabolically active. Male and female gametophytic thalli of Antithamnion cruciatum had similar numbers of mitochondria in apical cells of indeterminate axes, as did gametophytic and sporophytic thalli. There were about 40-50 mitochondria in fully elongated apical cells with about half this number in newly divided apical and subapical cells. Apical cells of determinate branches had more mitochondria (60-77) than indeterminate branches (60-70 vs. 40-50). In both species and in all cell types mitochondrial numbers were highly correlated with cell size.

The shape, number and distribution of mitochondria were examined during monosporogenesis in Audouinella botryocarpa using fluorescence microscopy and staining with DiOC sub(6) (3) and DASPEI. Mitochondria are variable in shape and range from spherical to ovoid or irregular. There is an increase mitochondrial number during sporogenesis from about 75 to 200, and mitochondrial number is closely correlated with sporangial size (r = 0.90). Mitochondria are evenly distributed in monosporangial initials. At least ten, large mitochondrial complexes occur early in sporangial development, and these are evenly scattered throughout the cell. Subsequently, these complexes decrease and become restricted to the central portion of monosporangia. Just prior to spore release about one half of the mitochondria remain aggregated in this region. Patterns of mitochondrial distribution and abundance likely reflect changes in metabolic demands and in nuclear/cytoplasmic interactions during sporogenesis.

Mitochondrial distribution was examined during monospore germination in Audouinella botryocarpa (Harvey) Woelkerling using fluorescence microscopy and staining with DiOC sub(6) (3) and DASPEI. Mitochondria varied in shape from spherical to ovoid or irregular. In released monospores mitochondria were evenly distributed. During germination many mitochondria became concentrated where the single germination tube emerged, and large mitochondrial complexes developed. This dense aggregation of mitochondria became associated with tip growth of the germ tube, and was retained through at least several apical cell divisions of the sporeling. In addition, many mitochondria remained in the spore and formed large complexes associated with the transverse wall of the developing filament. They were retained during the apical cell division of the sporeling and subsequently declined in size and number.