Embryo Development in the Lady's Slipper Orchid, Paphiopedilum delenatii, with Emphasis on the Ultrastructure of the Suspensor

• Background and Aims Owing to large-scale collecting, the lady's slipper orchid, Paphiopedilum delenatii, is under threat of extinction. Asymbiotic germination provides a useful way to re-establish plants in the wild and for commercial propagation. A detailed study of embryo development would...

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Bibliographic Details
Published in:Annals of botany 2006-12, Vol.98 (6), p.1311-1319
Main Authors: LEE, YUNG -I, YEUNG, EDWARD C, LEE, NEAN, CHUNG, MEI-CHU
Format: Article
Language:English
Subjects:
Cuticular material
Cytoplasm
Embryogenesis
embryology
Embryonic cells
Embryos
Fluorescence
lady's slipper orchid
Mitochondria
Orchidaceae - embryology
Orchidaceae - ultrastructure
Original
Paphiopedilum
Plant cells
Plastids
Seeds
Seeds - embryology
Seeds - ultrastructure
suspensor
Testa
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Summary:• Background and Aims Owing to large-scale collecting, the lady's slipper orchid, Paphiopedilum delenatii, is under threat of extinction. Asymbiotic germination provides a useful way to re-establish plants in the wild and for commercial propagation. A detailed study of embryo development would provide information on subsequent germination events and aid in the propagation of the species. • Methods Developing capsules were collected for histochemical and ultrastructural studies by using both light and transmission electron microscopy. • Key Results The suspensor of this species consists of three vacuolated cells. During the early globular stage of embryo development, structural differentiation occurs, revealing an abundance of smooth endoplasmic reticulum cisternae and wall ingrowths within the suspensor cells. These features are not present in cells of the embryo proper. Furthermore, the results of Nile red staining demonstrate that a cuticular layer is present only in the embryo proper, but absent from the suspensor. Cuticular material is also present in the inner walls of the seed coat, and persists through seed maturation. • Conclusions The morphological features of the transfer cell and the absence of cuticular material in the suspensor cell wall corroborate the hypothesis that the suspensor is the major nutrient uptake site for the developing embryo in the lady's slipper orchid. The absence of an endosperm and presence of cuticular material in the inner walls of the seed coat enclosing the embryo proper further support the notion that nutrient uptake by the embryo is confined to the micropylar end of the seed through the suspensor.
ISSN:0305-7364
1095-8290
DOI:10.1093/aob/mcl222