Occurrence of specific behaviour of growing pollen tubes in the ovary of the 'Pozna Plava' plum cultivar

Plum cultivar 'Pozna Plava' was developed at the Fruit Research Institute, Cacak, and released as a new cultivar in 2008. This plum cultivar bears poorly and irregularly, resulting in very low fruit set. Therefore, the occurrence of specific behaviour of growing pollen tubes in the ovary was studied over a three-year period, in three pollination variants (self-, cross- and open). The cross-pollination was performed using the pollen of 'Cacanska Najbolja', 'Hanita' and 'Presenta' plum cultivars. Growth of pollen tubes was observed by means of fluorescent microscopy. The analysis was conducted taking into consideration whether or not the pollen tube has penetrated into the nucellus. Presence of specific behaviour of growing pollen tubes in the ovary was observed in all pollination variants. Atypical pollen tube growth was recorded in the locyle of the ovary as well as in the region of the obturator, the micropyle and the embryo sac. The largest percentage of atypical pollen tube growth in all pollination variants, before and after the penetration into the nucellus was recorded in the obturator and micropyle region. In the open pollination variant, the ovaries showing this specific behaviour of growing pollen tubes, were noted in only one year. Cross- and self-pollination variant showed the existence of specific behaviour of growing pollen tubes in all regions of the ovule, including the embryo sac (except in self-pollination). Only in cross-pollination variant, correlation-regression analysis has shown that specific behaviour of growing pollen tubes did affect the pollen tube penetrating into the nucellus