Plant regeneration was studied in petal cultures of three Sedum species: S. aizoon, S. spectabile and S. gracile. The course of morphogenesis was examined by light and electron microscopy. Histological examination revealed that morphogenesis took place as direct organogenesis, indirect organogenesis or somatic embryogenesis, depending on the species and the concentrations of growth regulators in the medium. Initial petals and explants from cultures were studied to determine the origin of organogenesis. Petal histology showed that all cells at the time of culture initiation were differentiated. Epidermal and parenchymatous cells were highly vacuolated and the parenchyma contained chloroplasts with starch grains. TEM revealed that cell dedifferentiation occurred in culture under the influence of BAP and IBA. In petal culture the first cell division started subepidermally on day 2 of culture initiation. Epidermal cells underwent regular anticlinal divisions on day 3 of culture initiation, as confirmed by histology and SEM. Direct formation of adventitious buds in petals was observed in meristematic cells dedifferentiated from the epidermis and parenchyma. In indirect organogenesis, callus tissue resulted from division of dedifferentiated parenchyma cells. Somatic embryos were formed directly from subepidermal parenchymatous cells.
The aim of the work was to determine how the induction of androgenesis in selected genotypes of Salix viminalis is affected by thermal factors and medium composition. Anthers isolated from male clones of S. viminalis were pre-cultured at 4, 27 and 32°C for two to eight days in liquid Kyo medium with and without the addition of mannitol and on solid MS or WPM medium. The solid media were supplemented with different concentration of disaccharidesand various combinations of growth regulators including kinetin, 2iP, IAA and IBA. Multi-nucleate microspores indicative of androgenesis were observed in anthers pre-cultured for seven days at 4°C in liquid Kyo medium containing mannitol. The rate of androgenesis was higher when the anthers were transferred to solid modified MS medium containing high concentrations of sucrose and kinetin. In studied genotypes of basket willow early uninucleate microspores underwent sporophytic divisions. Ultrastructural observations showed differences in cellular arrangement of pre-stressed microspores. In Salix viminalis, microspores without starch grains and decreased number of lipid bodies were potentially androgenic cells.
In this paper we focus on anatomic structure of the outer cellular layers of the fruit of Sorbus torminalis. We have confirmed the theory of existing of multilayered epidermis providing developmental, histogenetic evidence. The studies were made from blooming time (ovules) to fully ripen fruits, using various histological techniques and microscope types. The multilayered epidermis is derived from successive tangential divisions of cells of initially single-layered epidermis commencing about two weeks after full bloom. The subsequent epidermal layers result from division of cells of epidermal meristem. The mature fruits – about 12 weeks after full bloom – are covered with four – to five-layered epidermis; each layer with its own cuticle. The lenticels developed beneath stomata from phellogen which is not in continuity with the epidermal meristem. Measurements of cuticular membranes thicknesses during development were also made.
The pollen–stigma interaction plays an important role in reproductive process and has been continuously studied in many interspecific and intergeneric crossing experiments. The aim of this study was to investigate stigma receptivity (SR) of willow in order to determine the most suitable period for its pollination with poplar pollen and improve the effectiveness of Salix × Populus crosses. Tissue samples were examined histologically using light, epifluorescent, scanning, and transmission electron microscopy. Willow SR was determined by stigma morphological traits, test of pollen germination rate, Peroxtesmo test of peroxidase and esterase activity on stigma surface as well as papilla ultrastructure at anthesis. We have ascertained that the SR duration in willow is short, lasting from 1 to 2 DA. The poplar pollen germination rate on willow stigmas on 1 DA ranged from 26.3 to 11.2%.