Pollen functional ability in two indigenous grapevine cultivars in Bosnia and Herzegovina
A large number of grapevine cultivars have functionally female flowers. The causes of male sterility in these cultivars in the spheres of microsporogenesis and pollen morphology are only partially tackled. This study examines microsporogenesis and pollen functional ability in two most economically important indigenous grapevine cultivars in Bosnia and Herzegovina by the evaluation of permanent histological sections and the use of a scanning electron microscope. When observed at the cytogenetic and embryological level, microsporogenesis in cvs. Blatina with sterile pollen and Žilavka with fertile pollen shows regularity, they coincide and there are no differences in the sequence of differentiation events, except in their timing and duration. In ‘Žilavka’, the development of pollen in the anther locule at all sequential events, including pollen release from the tetrad, formation of the structural elements of the exine, physiological and morphological preparations for pollen to be dispersed and its release from the anthers, progresses normally with typical – vital cytogenetic characteristics maintained. In ‘Blatina’, during pollen development in the anther locule upon release from the tetrads and during the formation of the structural elements of the exine, uncontrolled coverage of pollen by the exine occurs, ultimately resulting in the formation of inaperturate pollen – morphologically sterile pollen grains.