Ripening and dehiscence of the anther in some Crocus(Iridaceae) species

Abstract The anther development was examined in some Crocus species, by light and scanning electron microscopy. Epidermal cells develop a longitudinal stomium which is connected to the interlocular septum by cells with wide intercellular spaces.Endothecial cells are mono or bilayered, and they develop annular wall thickenings.Middle layer cells degenerate shortly after the microspore release. Tapetal cells are secretory with orbicules, and they form the tapetal membrane. The stomium disjoins from the interlocular septum after the lysis of the middle lamellae in the abscission region. The stomial cells break long before the flower opening, and in C. boryithey show signs of programmed cell death. Following the flower opening, the locular walls shrink tangentially, with flattening of epidermal cells and shortening of endothecial cells, and they bend up to turn inside out, exposing the pollen grains. The results are discussed in relation to the dehiscence mechanism

Megasporogenesis and Development of Embryo Sac in Crocus Sativus L.

SUMMARYCytological observations during megasporogenesis and embryo sac development of Crocus sativus L. are reported. During meiotic divisions irregular assortment of chromosomes was observed; consequently, megaspores resulted numerically variable (4–6) and they were genetically unbalanced. The megaspore tetrads-hexads showed chalazal heteropolarity, however, the microphylar pole resulted more active than the chalazal one in promoting megaspore development. This was attributed to the nutritional factors liberated from degenerated micropylar spores. Independently on the number of produced megaspores the micropylar ones (M1, M2, M3), generally, degenerated, the chalazal spores (M4–M6) persisting; therefore, besides single embryo sacs, megaspores close to embryo sac or development of two embryo sacs could be observed. Frequently, the megasporogenesis or development of the persistent megaspore were not completed; consequently, ovules lacking embryo sac or showing immature embryo sac occurred. The mature embry..

Karyotype and Meiotic Behaviour of the Triploid Crocus Sativus L.

SUMMARYThe karyotype and microsporogenesis of triploid Crocus sativus were studied. The high percentage of trivalents observed at metaphase I (on average, 7.3 trivalents per cell) together with the karyotype configuration confirm autotriploidy. Some considerations about the presence of one unique chromosome in the karyotype and about the origin of triploidy are presented

Penetration and Toxicity of Nanomaterials in Higher Plants

Nanomaterials (NMs) comprise either inorganic particles consisting of metals, oxides, and salts that exist in nature and may be also produced in the laboratory, or organic particles originating only from the laboratory, having at least one dimension between 1 and 100 nm in size. According to shape, size, surface area, and charge, NMs have different mechanical, chemical, electrical, and optical properties that make them suitable for technological and biomedical applications and thus they are being increasingly produced and modified. Despite their beneficial potential, their use may be hazardous to health owing to the capacity to enter the animal and plant body and interact with cells. Studies on NMs involve technologists, biologists, physicists, chemists, and ecologists, so there are numerous reports that are significantly raising the level of knowledge, especially in the field of nanotechnology; however, many aspects concerning nanobiology remain undiscovered, including the interactions with plant biomolecules. In this review we examine current knowledge on the ways in which NMs penetrate plant organs and interact with cells, with the aim of shedding light on the reactivity of NMs and toxicity to plants. These points are discussed critically to adjust the balance with regard to the risk to the health of the plants as well as providing some suggestions for new studies on this topic