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Abstract

The Crassulaceae family mainly comprises herbaceous leaf succulents, some of which are used as ornamentals. The development of the embryo suspensor in Sedum reflexum L. was investigated using cytochemical methods, light and electron microscopy. The full development and functioning of the suspensor occurs during the late globular and heart-stage embryos. The suspensor consists of a large basal cell and a single row of 6-10 chalazal cells. The basal cell produces a branched haustorium which invades ovular tissues. The walls of the haustorium and the micropylar part of the basal cell form the wall ingrowths that are typical for transfer cells. The dense cytoplasm filling the basal cell is rich in profiles of endoplasmic reticulum, active dictyosomes, mitochondria, plastids, microtubules, bundles of microfilaments, microbodies and lipid droplets. The present work reveals that the suspensor structure in S. reflexum markedly differs from that found in other representatives of Crassulaceae. Ultrastructural analysis and cytochemical tests (including proteins, insoluble polysaccharides and lipids) indicate that in S. reflexum the embryo suspensor is involved mainly in absorption and transport of metabolites from the ovular tissues to the developing embryo proper via the chalazal suspensor cells.
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Abstract

The stigma of Ornithogalum sigmoideum is of dry and papillate type. The papillae are covered by a cuticle-pellicle layer, as revealed by staining. The activity of nonspecific esterase, acid phosphatase and peroxidase increases in the pellicle during the receptivity period. The style of O. sigmoideum is of the hollow type. Ultrastructural study of the cells lining the canal indicated that they are secretory cells and contain abundant endoplasmic reticulum, dictyosomes, mitochondria, plastids and ribosomes. After anthesis these organelles show degeneration at the end of the secretory phase. In canal cells, cytochemical tests showed the presence of acidic polyanions, insoluble and acidic polysaccharides, proteins and lipids. Before anthesis the canal cells are rich in polysaccharides, proteins and lipids. At maturity the cuticle is ruptured and secretory materials from the canal cells are released into the canal. In the unpollinated style of O. sigmoideum the exudates accumulated in the center of the canal; in pollinated pistils the same secretion materials were dispersed through the canal, which became wider.
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