Title : The anatomical and morphological structure of generative and vegetative spheres of Conophytum aequale L. Bolus (Aizoaceae, Ruschioideae) in oder to study the evolutionary adaptation to arid conditions and searching criteria for genus systematization and phylogeny
Abstract:
Genus Conophytum is unusually large group of leaf succulents of Southern Africa’s arid flora and considered taxonomically complex. Species number still varies up to 290. There is not enough data of floral anatomy and morphology of these species, although its structure helps to determine genus relationship with other genera and its place among Aizoaceae. Conophytum have a number of structural features caused by adaptation to arid conditions. Vegetative body, so-called "corpuscle“, formed by leaf pair in result of congenital merging and its degree is species-specific. Flower’s ovary completely submerged in the thickness of corpuscle and just perianth, column and stamens come out. This arrangement is an example of evolutionary adaptation to arid conditions. Object of my detailed research is C.aequale L. Bolus in flowering stage. For permanent microscopic preparations were made series of microtome sections of 10-15 µm thickness made from paraffin-embedded material, which subsequently stained with Hematoxylin by Delafield and Safranin by Curtis. Leaf pair not completely merged, forming a two-lobed corpuscle of heart shape. Xeromorphic leaves are smooth, internodes strongly shortened. Outer wall of epidermis has a crystalline layer, which covered with a thin layer of cuticle and epicuticular wax, and cells look like papillae. Along epidermis is more or less evenly distributed cells containing metabolic products. Flower of C.aequale has a double perianth, multi-petal corolla of staminodial origin, 5-membered calyx, a multi-stamen androecium, a 5-nested gynoecium, and a lophomorphic nectar ring. Forming of petal-stamen tube is typical for Conophytum, but length of tube and column is several times longer than size of the ovary.
Ovary completely submerged in thickness of corpuscle reliably protected from external environment. Bright, multi-petaled corolla protruding outward attracts pollinators, while the calyx loses its protective function and becomes very thin, almost filmy, unlike other members of Ruschioideae, which sepals can be thickened and very hard. In fact, calyx of C.aequale looks like an elongated vagina with petal-stamen tube inside. Sepals separated just outside of corpuscle and have only 2-3 mm long. Petal-stamen tube is sandwiched between the leaves, so has flattened ellipse shape, and only leaving out gradually acquire a spherical shape. Inferior ovary and five carpels are congenitally merged together to form a syncarpous gynoecium. Placentation is basal-parietal. In apical part of each nest, a false median septum (FMS) develops, dividing its cavity in half so that visually, not 5 but 10 nests observed in the cross section. Lower edge of FMS is located in area where ventral margins of carpels open and their cavities connected to each other by ventral slits. Above the margins of carpels close again to form ventral canals, which also involve FMS. Apical parts of carpels formed ovary roof in form of pentagon, which gradually turns into very long column. Between ovary roof and petal-stamen tube a lofomorphic nectaries ring lies. Ovary of C.aequale is homologous to previously studied Lampranthus haworthii and Delosperma echinatum ovaries, which proved that formation of epigyny in Ruschioideae occurs due to the invagination of receptacle. In ovary wall of C.aequale, loops of receptacle bundles also found, indicating its invagination. Also occurs deformation of carpels, when their ventral parts moved in basal-parietal position, dorsal parts shortened, but apical parts are only slightly deformed (FMS remain in apical position, unlike in L.haworthii where its moved to central position). Ovary of C.aequale occupies an intermediate position because degree of placentas displacement is intermediate between basal (Delosperma) and parietal (Lampranthus) type of placentation.
What will audience learn from my presentation:
• This research helps to learn more about group of succulent plant Ruschioideae, its variability and systematisation.
• In this research investigated in detail morphology and anatomy of genus Conophytum allows noted a number of adaptations to arid conditions and water stress.
• Studying of flower structure of Ruschioideae species, showed that evolutionary adaptations went on the way of inferior ovary forming, i.e. an epigyny, goes by invagination of the receptacle, changing the type of placentation from central-angular to basal-parietal, and formation of elongated ventral canals.
• The mechanisms of epigyny formation may serve as a clear criterion for the systematization and fhylogeny of complex taxonomic groups.
