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.
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.