Abstract

 

The morphology and ultrastructure of the pollen exine were studied using scanning electron microscopy (SEM) in 14 hazelnut genotypes (Corylus avellana L.). Pollen measurements were performed in a dry stage at magnifications ranging from 500 × to 15,000 ×, during which the following parameters were analyzed: pollen grain height and width (µm), estimated pollen grain volume (µm³), type and ultrastructure of the exine, and the frequency of microexcrescences per 10 µm². Pollen samples were collected for analysis at two locations in the Banja Luka region (Bosnia and Herzegovina), and the following cultivars were analyzed: Multiflorum, Tankoljuskasti, Tonda Gentile Romana, Merveille de Bollwiller, Avellino, Ludolph Zellernuss, Apolda, Hall's Giant, Romai I, Romai II, Istarski okrugli, Imperial de Trebizonde, Gustav Zellernuss, Jean's. The research results have indicated that the pollen grains were of the triporate type, subspheroidal in shape, with dimensions ranging from 19.91 µm in Imperial de Trebizonde to 32.29 µm in Tonda Gentile Romana. The lowest pollen volume was determined for the Tankoljuskasti cultivar (5417.40 µm3), and the highest for the Tonda Gentile Romana cultivar (12645.70 µm3). Measurements of exine ultrastructure have indicated the presence of certain differences among the observed cultivars. The available literature states that the pollen exine in cultivated hazelnut cultivars is uniform and characterized by a verrucate-type exine. In this study, differences were identified at the level of microexcrescences in the Gustav Zellernuss and Tonda Gentile Romana cultivars, in which clustering of microexcrescences positioned on shallow reticula was observed. The question of genotypic specificities of hazelnut exine ultrastructure remains open in this study, and future research should focus on the characteristics of interspecies hybrids resulting from the crossing of different species within the genus Corylus (Corylus avellana L., Corylus pontica Koch., and Corylus maxima Mill.).

 

Key words: Palynology, Microexcrescences.