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- Author or Editor: Jelena Milojević x
The pollen morphology of aromatic Tanacetum vulgare L. (Asteraceae), which has wide horticultural and medicinal uses, was examined using light microscopy and scanning electron microscopy. The investigation revealed that pollen grains are radially symmetrical, isopolar, spheroidal, tricolporate, and echinate–perforate. Average pollen length was 21.32 ± 1.12 μm, whereas average pollen width was 20.04 ± 0.98 μm (length:width ratio 0.94). Spine length was 2.72 ± 0.29 μm. Average distance from the spines was 7.15 ± 0.31 μm. Pollen exine consisted of 1–3 pores. Pori are elongated and also with a distinct margin. The porus latitude is smaller than the colpus latitude. One to three perforations were noticed on 1 μm2 of exine. Fluorescein diacetate was used to assess the viability of T. vulgare pollen. The effect of sucrose (1%, 5%, 10%, 20%, and 30%, w/v) on pollen germination and tube growth was evaluated. Overall, the inclusion of sucrose in the medium improved both pollen germination and tube growth. Also, pollen nucleus status was determined. Binucleate and trinucleate mature pollens were observed. Overall, the palynological features of this species may be helpful for further taxonomical and pharmaceutical investigations.
An efficient in vitro shoot regeneration method from leaf explants of apple cultivars Golden Delicious and Melrose by optimization of regeneration medium, explant type and orientation, dark pre-treatment, and gelling agent is presented. Murashige and Skoog’s regeneration medium containing 22 μM thidiazuron (TDZ) and 1.5 μM indole-3-butyric acid (IBA) (M2 medium) was superior for regeneration as well as for subsequent shoot multiplication in both cultivars, providing regeneration frequency of 95% or higher in the best combination with other factors. Pre-incubation in the dark proved to be an essential factor for regeneration. The use of agar as a gelling agent provides satisfactory regeneration frequency compared with media gelled with PhytagelTM. Leaf explants of cv. Melrose with adaxial surface in contact with M2 medium and those of cv. Golden Delicious orientated contrary regenerated the highest mean number of shoots per explant. Under optimal conditions, a maximal index of shoot-forming capacity of 11.44 and 6.30 for ‘Melrose’ and ‘Golden Delicious’, respectively, was achieved. Regenerated shoots were successfully rooted and acclimated ex vitro.
The effect of abscisic acid on the development of primary androgenic embryo and secondary somatic embryogenesis was investigated with the aim of improving multiplication rates and secondary somatic embryo quality in horse chestnut microspore and anther culture. The early embryo stage (globular) had a better response than late stages (heart, torpedo, and cotyledonary) in both types of cultures. Also, microspore culture had a high potential for mass secondary embryo production. The number of secondary somatic embryos was three times higher on hormone-free medium than on medium enriched with 0.01 mg·L−1 abscisic acid. However, most of the embryos on hormone-free medium had abnormal morphology. For this reason, abscisic acid was added to the media to improve embryo quality. The morphology of abscisic acid treated embryos was better than abscisic acid non-treated embryos. The optimal abscisic acid concentration for secondary somatic embryo induction and production of high-quality embryos was 0.01 mg·L−1. Overall, the effect of abscisic acid on the induction of secondary somatic embryogenesis and plant regeneration of androgenic embryos of this species may be helpful for the further synthesis of secondary metabolites in vitro and their application in the pharmaceutical industry.