In vitro Performance of Fresh and Stored Plum (Prunus domestica L.) Pollen

In this study, the in vitro performance of fresh and pollen stored for three months at different constant temperatures was investigated in three plum cultivars (‘Valerija’, ‘^a~anska Lepotica’,
‘Valjevka’). Pollen was collected from flowers in the late balloon phase and, after drying, stored for
three months at four different constant temperatures (+4°C, -20°C, -80°C, -196°C). Pollen tube length
as well as the nuclear presence in the pollen tube and its migration were examined. In vitro pollen tube length was tested after a 24-hour germination period, after which the pollen tube was stained with
Hoechst 33258 to observe the nuclear presence within it. The longest average pollen tube length in
all tested cultivars was observed with fresh pollen. With the pollen stored at low temperatures, a longer pollen tube was obtained compared to pollen stored at +4°C. In all cultivars, mature pollen grains at the binucleate stage contained a vegetative nucleus (VN) and a generative nucleus (GN). Although at each storage temperature a higher percentage of GN was achieved in pollen tubes compared
to fresh ones, nevertheless, regular movement of nuclei, primarily VN rather than GN or sperm nucleus (SN), was found in the highest percentage in all tested cultivars.