1986. Anatomy of the Sirelirzia reginae flower (Strelitziaceae). -Nord. J. Bot. 6 : 307-320. Copenhagen. ISSN Ol(37-055X.The Strelitzia reginae Ait. flower has many remarkable structural spezializations, the histology and cytology of which we have investigated. The chromoplasts of the sepals are conspicuously elongated and enclose numerous carotenoid tubules parallel to the long axis of the plastid. The petals have roundedpearshaped leucoplasts with a rhomboid protein crystal and aggregated plastoglobules. The blue colour is confined to the epidermal cells, which contain vacuoles with anthocyanin. Prominent papillar processes from the petal epidermis give rise to brilliance through refraction. Various reinforcements occur within the flower parts. The perianth leaves have permeating fibre ribs and thickened epidermal walls. The stigma and the free part of the style consist mainly of fibre cells (with protoplasm). The base of the style and the ovary are enclosed in the receptacle, the epidermal and hypodermal cells of which have thickened walls. -The ground tissue of the basal part of the receptacle appears aerenchymatous. There are also idioblasts containing raphides, druses, and tannin. The secretory cells of the stigma are long unicellular hairs outwards and columnar cells towards the canal between the three lobes. The stylar canal splits up into three individual arms, each leading to a locule. The epithelial cells are typical transfer cells. A composite secretion is deposited outside these cells. -The nectaries constitute three pockets between the carpels. Their secretory surface is greatly increased by folding of the epithelium and the presence of transfer cells.
The tapetal layer becomes distinct from the other layers of parietal cells about three days prior to the meiosis in the microspore mother cells. Differentiation of the tapetal cells includes an increased relative volume for dictyosomes, mitochondria and plas–tids, the appearance of autophagic vacuoles in the cytoplasm, and periplasmic spaces between the plasma membrane and the cell wall. About one day before the meiosis the basophilia in tapetal cells is elevated; there are numerous nonaggregated ribo–somes, nuclei are intensely stainable, and the rough ER is dilated. There is also a partial digestion of the cell walls around microspore mother cells and tapetal cells including the adaxial wall of the adjacent parietal cell layer. A wedge–shaped portion of the wall system between this parietal cell layer and tapetal cells is not lysed. A lamellation in the middle lamellar position is also spared. That lamellation remains prominent as the extratapetal lamellation. By the initiation of meiosis the surfaces of both tapetal and microspore mother cells are entirely free of cell walls. During that period the intense basophilia of tapetal cells recedes and there are many polyribosomes, an extensive system of rough ER, dictyosomes with vesicles containing fibrils, multivesicular bodies, and autophagic vacuoles. Microtubules occur close to the plasma membrane. The plasma membrane–glycocalyx differs in portions of the surface facing the extratapetal lamellation from the Iocular facing surface. We presume that the abaxial portion of tapetal cells with cavations containing glycocalyx–like filaments is a region of uptake and that the adaxial surface with detached glycocalyx is secretory.
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