Effects of cold stratification and GA₃ on germination of <i>Arbutus unedo</i> seeds of three provenances

Abstract

Background: Arbutus unedo is a valuable Mediterranean shrub as an ornamental plant as well as fruit tree. Fresh fruits of A. unedo are a good source of antioxidants, of vitamins C, E and carotenoids and also are characterized by the high content of mineral elements.

Materials and Methods: The effects of gibberellic acid (GA₃) and cold stratification (CS) on seed germination performance were investigated in A. unedo seeds collected from three provenances in the Northern part of Greece. Seeds of each provenance were soaked in solutions of GA₃ (500, 1000 or 2000 ppm) for 24 h and subsequently were subjected to CS at 3 – 5ºC for 0, 1, 2, and 3 months.

Results: Non-stratified seeds of the three A. unedo provenances which were not treated with GA₃ solutions exhibited very low germination. However, seed germination was significantly improved after a one-month period of CS. Similarly, the non-stratified seeds of all three provenances became non-dormant after the treatment with 2000 ppm GA₃ and they germinated at high percentages. However, in untreated seeds with GA₃, after a one-month CS period the seeds of the Pieria provenance exhibited higher germination percentage than that of Rodopi provenance seeds. Furthermore, in non-stratified seeds, the Pieria provenance seeds treated with GA₃ germinated at higher percentages and more rapidly than those of the other two provenances.

Conclusion: The results indicated that untreated seeds exhibited very low germination at 20/25ºC. However, in all three provenances seed germinability was significantly improved by a one-month period of CS or treatment of seeds with 2000 ppm GA₃. Furthermore, there was a considerable variability among seed provenances in response to the treatments which were applied.

Keywords: pre-germination treatment, seed dormancy, strawberry tree, Mediterranean species