The effect of auxin and gibberellin on pollen germination and pollen tube growth of plum

During the two-year period, the effects of two plant hormones (auxin – NAA and gibberellin – GA3) on pollen germination and pollen tube growth were studied in vitro in three plum cultivars: ‘Nada’, ‘Čačanska Najbolja’ (from Serbia) and ‘Wangenheims Frühzwetschge’ (from Germany). The germination rate and growth of the pollen tubes were determined on a culture medium with 15% sucrose and 0.7% agar. Pollen germination in the control variant (without hormone application) was between 30.99% (‘Čačanska Najbolja’) and 57.35% (‘Wangenheims Frühzwetschge’). The length of the pollen tubes ranged from 189.8 µm (‘Čačanska Najbolja’) to 387.1 µm (‘Wangenheims Frühzwetschge’). Plant hormones had a significant influence on the increase in pollen germination and pollen tube length. Gibberellin had a stronger effect on pollen germination compared to auxin. Gibberellin-treated pollen had a 10-15% higher pollen germination compared to the control. The clearest effect of the plant hormones was seen in the length of the pollen tubes. In auxin-treated pollen, the length of the pollen tubes increased by 18-66% compared to the control, while in gibberellins-treated pollen, the length of the pollen tubes increased by 12-78% compared to the control. Therefore, treatment of trees with auxin and gibberellin can be recommended as a measure to improve the efficiency of fertilization and yield of plums.